perlapi - autogenerated documentation for the perl public API

- NAME
- DESCRIPTION
- ``Gimme'' Values
- Array Manipulation Functions
- Callback Functions
- Character classes
- Cloning an interpreter
- CV Manipulation Functions
- Embedding Functions
- Functions in file pp_pack.c
- Global Variables
- GV Functions
- Handy Values
- Hash Manipulation Functions
- Magical Functions
- Memory Management
- Miscellaneous Functions
- Numeric functions
- Optree Manipulation Functions
- Pad Data Structures
- Stack Manipulation Macros
- SV Flags
- SV Manipulation Functions
- Unicode Support
- Variables created by `xsubpp` and `xsubpp` internal functions
- Warning and Dieing
- AUTHORS
- SEE ALSO

# NAME

perlapi - autogenerated documentation for the perl public API

# DESCRIPTION

This file contains the documentation of the perl public API generated by embed.pl, specifically a listing of functions, macros, flags, and variables that may be used by extension writers. The interfaces of any functions that are not listed here are subject to change without notice. For this reason, blindly using functions listed in proto.h is to be avoided when writing extensions.

Note that all Perl API global variables must be referenced with the `PL_` prefix. Some macros are provided for compatibility with the older, unadorned names, but this support may be disabled in a future release.

The listing is alphabetical, case insensitive.

# ``Gimme'' Values

GIMME
  A backward-compatible version of `GIMME_V` which can only return `G_SCALAR` or `G_ARRAY`; in a void context, it returns `G_SCALAR`. Deprecated. Use `GIMME_V` instead.

              U32     GIMME

GIMME_V
  The XSUB-writer's equivalent to Perl's `wantarray`. Returns `G_VOID`, `G_SCALAR` or `G_ARRAY` for void, scalar or list context, respectively.

              U32     GIMME_V

G_ARRAY
  Used to indicate list context. See `GIMME_V`, `GIMME` and the perlcall manpage.

G_DISCARD
  Indicates that arguments returned from a callback should be discarded. See the perlcall manpage.

G_EVAL
  Used to force a Perl `eval` wrapper around a callback. See the perlcall manpage.

G_NOARGS
  Indicates that no arguments are being sent to a callback. See the perlcall manpage.

G_SCALAR
  Used to indicate scalar context. See `GIMME_V`, `GIMME`, and the perlcall manpage.

G_VOID
  Used to indicate void context. See `GIMME_V` and the perlcall manpage.

# Array Manipulation Functions

AvFILL
  Same as `av_len()`. Deprecated, use `av_len()` instead.

              int     AvFILL(AV* av)

av_clear
  Clears an array, making it empty. Does not free the memory used by the array itself.

              void    av_clear(AV* ar)

av_delete
  Deletes the element indexed by `key` from the array. Returns the deleted element. If `flags` equals `G_DISCARD`, the element is freed and null is returned.

              SV*     av_delete(AV* ar, I32 key, I32 flags)

av_exists
  Returns true if the element indexed by `key` has been initialized.

  This relies on the fact that uninitialized array elements are set to `&PL_sv_undef`.

              bool    av_exists(AV* ar, I32 key)

av_extend
  Pre-extend an array. The `key` is the index to which the array should be extended.

              void    av_extend(AV* ar, I32 key)

av_fetch
  Returns the SV at the specified index in the array. The `key` is the index. If `lval` is set then the fetch will be part of a store. Check that the return value is non-null before dereferencing it to a `SV*`.

  See Understanding the Magic of Tied Hashes and Arrays in the perlguts manpage for more information on how to use this function on tied arrays.

              SV**    av_fetch(AV* ar, I32 key, I32 lval)

av_fill
  Ensure than an array has a given number of elements, equivalent to Perl's `$#array = $fill;`.

              void    av_fill(AV* ar, I32 fill)

av_len
  Returns the highest index in the array. Returns -1 if the array is empty.

              I32     av_len(AV* ar)

av_make
  Creates a new AV and populates it with a list of SVs. The SVs are copied into the array, so they may be freed after the call to av_make. The new AV will have a reference count of 1.

              AV*     av_make(I32 size, SV** svp)

av_pop
  Pops an SV off the end of the array. Returns `&PL_sv_undef` if the array is empty.

              SV*     av_pop(AV* ar)

av_push
  Pushes an SV onto the end of the array. The array will grow automatically to accommodate the addition.

              void    av_push(AV* ar, SV* val)

av_shift
  Shifts an SV off the beginning of the array.

              SV*     av_shift(AV* ar)

av_store
  Stores an SV in an array. The array index is specified as `key`. The return value will be NULL if the operation failed or if the value did not need to be actually stored within the array (as in the case of tied arrays). Otherwise it can be dereferenced to get the original `SV*`. Note that the caller is responsible for suitably incrementing the reference count of `val` before the call, and decrementing it if the function returned NULL.

  See Understanding the Magic of Tied Hashes and Arrays in the perlguts manpage for more information on how to use this function on tied arrays.

              SV**    av_store(AV* ar, I32 key, SV* val)

av_undef
  Undefines the array. Frees the memory used by the array itself.

              void    av_undef(AV* ar)

av_unshift
  Unshift the given number of `undef` values onto the beginning of the array. The array will grow automatically to accommodate the addition. You must then use `av_store` to assign values to these new elements.

              void    av_unshift(AV* ar, I32 num)

get_av
  Returns the AV of the specified Perl array. If `create` is set and the Perl variable does not exist then it will be created. If `create` is not set and the variable does not exist then NULL is returned.

  NOTE: the perl_ form of this function is deprecated.

              AV*     get_av(const char* name, I32 create)

newAV
  Creates a new AV. The reference count is set to 1.

              AV*     newAV()

sortsv
  Sort an array. Here is an example:

          sortsv(AvARRAY(av), av_len(av)+1, Perl_sv_cmp_locale);

  See lib/sort.pm for details about controlling the sorting algorithm.

              void    sortsv(SV ** array, size_t num_elts, SVCOMPARE_t cmp)

# Callback Functions

call_argv
  Performs a callback to the specified Perl sub. See the perlcall manpage.

  NOTE: the perl_ form of this function is deprecated.

              I32     call_argv(const char* sub_name, I32 flags, char** argv)

call_method
  Performs a callback to the specified Perl method. The blessed object must be on the stack. See the perlcall manpage.

  NOTE: the perl_ form of this function is deprecated.

              I32     call_method(const char* methname, I32 flags)

call_pv
  Performs a callback to the specified Perl sub. See the perlcall manpage.

  NOTE: the perl_ form of this function is deprecated.

              I32     call_pv(const char* sub_name, I32 flags)

call_sv
  Performs a callback to the Perl sub whose name is in the SV. See the perlcall manpage.

  NOTE: the perl_ form of this function is deprecated.

              I32     call_sv(SV* sv, I32 flags)

ENTER
  Opening bracket on a callback. See `LEAVE` and the perlcall manpage.

                      ENTER;

eval_pv
  Tells Perl to `eval` the given string and return an SV* result.

  NOTE: the perl_ form of this function is deprecated.

              SV*     eval_pv(const char* p, I32 croak_on_error)

eval_sv
  Tells Perl to `eval` the string in the SV.

  NOTE: the perl_ form of this function is deprecated.

              I32     eval_sv(SV* sv, I32 flags)

FREETMPS
  Closing bracket for temporaries on a callback. See `SAVETMPS` and the perlcall manpage.

                      FREETMPS;

LEAVE
  Closing bracket on a callback. See `ENTER` and the perlcall manpage.

                      LEAVE;

SAVETMPS
  Opening bracket for temporaries on a callback. See `FREETMPS` and the perlcall manpage.

                      SAVETMPS;

# Character classes

isALNUM
  Returns a boolean indicating whether the C `char` is an ASCII alphanumeric character (including underscore) or digit.

              bool    isALNUM(char ch)

isALPHA
  Returns a boolean indicating whether the C `char` is an ASCII alphabetic character.

              bool    isALPHA(char ch)

isDIGIT
  Returns a boolean indicating whether the C `char` is an ASCII digit.

              bool    isDIGIT(char ch)

isLOWER
  Returns a boolean indicating whether the C `char` is a lowercase character.

              bool    isLOWER(char ch)

isSPACE
  Returns a boolean indicating whether the C `char` is whitespace.

              bool    isSPACE(char ch)

isUPPER
  Returns a boolean indicating whether the C `char` is an uppercase character.

              bool    isUPPER(char ch)

toLOWER
  Converts the specified character to lowercase.

              char    toLOWER(char ch)

toUPPER
  Converts the specified character to uppercase.

              char    toUPPER(char ch)

# Cloning an interpreter

perl_clone
  Create and return a new interpreter by cloning the current one.

  perl_clone takes these flags as parameters:

  CLONEf_COPY_STACKS - is used to, well, copy the stacks also, without it we only clone the data and zero the stacks, with it we copy the stacks and the new perl interpreter is ready to run at the exact same point as the previous one. The pseudo-fork code uses COPY_STACKS while the threads->new doesn't.

  CLONEf_KEEP_PTR_TABLE perl_clone keeps a ptr_table with the pointer of the old variable as a key and the new variable as a value, this allows it to check if something has been cloned and not clone it again but rather just use the value and increase the refcount. If KEEP_PTR_TABLE is not set then perl_clone will kill the ptr_table using the function `ptr_table_free(PL_ptr_table); PL_ptr_table = NULL;`, reason to keep it around is if you want to dup some of your own variable who are outside the graph perl scans, example of this code is in threads.xs create

  CLONEf_CLONE_HOST This is a win32 thing, it is ignored on unix, it tells perls win32host code (which is c++) to clone itself, this is needed on win32 if you want to run two threads at the same time, if you just want to do some stuff in a separate perl interpreter and then throw it away and return to the original one, you don't need to do anything.

              PerlInterpreter*        perl_clone(PerlInterpreter* interp, UV flags)

# CV Manipulation Functions

CvSTASH
  Returns the stash of the CV.

              HV*     CvSTASH(CV* cv)

get_cv
  Returns the CV of the specified Perl subroutine. If `create` is set and the Perl subroutine does not exist then it will be declared (which has the same effect as saying `sub name;`). If `create` is not set and the subroutine does not exist then NULL is returned.

  NOTE: the perl_ form of this function is deprecated.

              CV*     get_cv(const char* name, I32 create)

# Embedding Functions

cv_undef
  Clear out all the active components of a CV. This can happen either by an explicit `undef &foo`, or by the reference count going to zero. In the former case, we keep the CvOUTSIDE pointer, so that any anonymous children can still follow the full lexical scope chain.

              void    cv_undef(CV* cv)

load_module
  Loads the module whose name is pointed to by the string part of name. Note that the actual module name, not its filename, should be given. Eg, ``Foo::Bar'' instead of ``Foo/Bar.pm''. flags can be any of PERL_LOADMOD_DENY, PERL_LOADMOD_NOIMPORT, or PERL_LOADMOD_IMPORT_OPS (or 0 for no flags). ver, if specified, provides version semantics similar to `use Foo::Bar VERSION`. The optional trailing SV* arguments can be used to specify arguments to the module's `import()` method, similar to `use Foo::Bar VERSION LIST`.

              void    load_module(U32 flags, SV* name, SV* ver, ...)

nothreadhook
  Stub that provides thread hook for perl_destruct when there are no threads.

              int     nothreadhook()

perl_alloc
  Allocates a new Perl interpreter. See the perlembed manpage.

              PerlInterpreter*        perl_alloc()

perl_construct
  Initializes a new Perl interpreter. See the perlembed manpage.

              void    perl_construct(PerlInterpreter* interp)

perl_destruct
  Shuts down a Perl interpreter. See the perlembed manpage.

              int     perl_destruct(PerlInterpreter* interp)

perl_free
  Releases a Perl interpreter. See the perlembed manpage.

              void    perl_free(PerlInterpreter* interp)

perl_parse
  Tells a Perl interpreter to parse a Perl script. See the perlembed manpage.

              int     perl_parse(PerlInterpreter* interp, XSINIT_t xsinit, int argc, char** argv, char** env)

perl_run
  Tells a Perl interpreter to run. See the perlembed manpage.

              int     perl_run(PerlInterpreter* interp)

require_pv
  Tells Perl to `require` the file named by the string argument. It is analogous to the Perl code `eval "require '$file'"`. It's even implemented that way; consider using load_module instead.

  NOTE: the perl_ form of this function is deprecated.

              void    require_pv(const char* pv)

# Functions in file pp_pack.c

packlist
  The engine implementing `pack()` Perl function.

              void    packlist(SV *cat, char *pat, char *patend, SV **beglist, SV **endlist)

pack_cat
  The engine implementing `pack()` Perl function. Note: parameters next_in_list and flags are not used. This call should not be used; use packlist instead.

              void    pack_cat(SV *cat, char *pat, char *patend, SV **beglist, SV **endlist, SV ***next_in_list, U32 flags)

unpackstring
  The engine implementing `unpack()` Perl function. `unpackstring` puts the extracted list items on the stack and returns the number of elements. Issue `PUTBACK` before and `SPAGAIN` after the call to this function.

              I32     unpackstring(char *pat, char *patend, char *s, char *strend, U32 flags)

unpack_str
  The engine implementing `unpack()` Perl function. Note: parameters strbeg, new_s and ocnt are not used. This call should not be used, use unpackstring instead.

              I32     unpack_str(char *pat, char *patend, char *s, char *strbeg, char *strend, char **new_s, I32 ocnt, U32 flags)

# Global Variables

PL_modglobal
  `PL_modglobal` is a general purpose, interpreter global HV for use by extensions that need to keep information on a per-interpreter basis. In a pinch, it can also be used as a symbol table for extensions to share data among each other. It is a good idea to use keys prefixed by the package name of the extension that owns the data.

              HV*     PL_modglobal

PL_na
  A convenience variable which is typically used with `SvPV` when one doesn't care about the length of the string. It is usually more efficient to either declare a local variable and use that instead or to use the `SvPV_nolen` macro.

              STRLEN  PL_na

PL_sv_no
  This is the `false` SV. See `PL_sv_yes`. Always refer to this as `&PL_sv_no`.

              SV      PL_sv_no

PL_sv_undef
  This is the `undef` SV. Always refer to this as `&PL_sv_undef`.

              SV      PL_sv_undef

PL_sv_yes
  This is the `true` SV. See `PL_sv_no`. Always refer to this as `&PL_sv_yes`.

              SV      PL_sv_yes

# GV Functions

GvSV
  Return the SV from the GV.

              SV*     GvSV(GV* gv)

gv_fetchmeth
  Returns the glob with the given `name` and a defined subroutine or `NULL`. The glob lives in the given `stash`, or in the stashes accessible via @ISA and UNIVERSAL::.

  The argument `level` should be either 0 or -1. If `level==0`, as a side-effect creates a glob with the given `name` in the given `stash` which in the case of success contains an alias for the subroutine, and sets up caching info for this glob. Similarly for all the searched stashes.

  This function grants `"SUPER"` token as a postfix of the stash name. The GV returned from `gv_fetchmeth` may be a method cache entry, which is not visible to Perl code. So when calling `call_sv`, you should not use the GV directly; instead, you should use the method's CV, which can be obtained from the GV with the `GvCV` macro.

              GV*     gv_fetchmeth(HV* stash, const char* name, STRLEN len, I32 level)

gv_fetchmethod
  See gv_fetchmethod_autoload.

              GV*     gv_fetchmethod(HV* stash, const char* name)

gv_fetchmethod_autoload
  Returns the glob which contains the subroutine to call to invoke the method on the `stash`. In fact in the presence of autoloading this may be the glob for ``AUTOLOAD''. In this case the corresponding variable $AUTOLOAD is already setup.

  The third parameter of `gv_fetchmethod_autoload` determines whether AUTOLOAD lookup is performed if the given method is not present: non-zero means yes, look for AUTOLOAD; zero means no, don't look for AUTOLOAD. Calling `gv_fetchmethod` is equivalent to calling `gv_fetchmethod_autoload` with a non-zero `autoload` parameter.

  These functions grant `"SUPER"` token as a prefix of the method name. Note that if you want to keep the returned glob for a long time, you need to check for it being ``AUTOLOAD'', since at the later time the call may load a different subroutine due to $AUTOLOAD changing its value. Use the glob created via a side effect to do this.

  These functions have the same side-effects and as `gv_fetchmeth` with `level==0`. `name` should be writable if contains `':'` or `' ''`. The warning against passing the GV returned by `gv_fetchmeth` to `call_sv` apply equally to these functions.

              GV*     gv_fetchmethod_autoload(HV* stash, const char* name, I32 autoload)

gv_fetchmeth_autoload
  Same as gv_fetchmeth(), but looks for autoloaded subroutines too. Returns a glob for the subroutine.

  For an autoloaded subroutine without a GV, will create a GV even if `level < 0`. For an autoloaded subroutine without a stub, `GvCV()` of the result may be zero.

              GV*     gv_fetchmeth_autoload(HV* stash, const char* name, STRLEN len, I32 level)

gv_stashpv
  Returns a pointer to the stash for a specified package. `name` should be a valid UTF-8 string. If `create` is set then the package will be created if it does not already exist. If `create` is not set and the package does not exist then NULL is returned.

              HV*     gv_stashpv(const char* name, I32 create)

gv_stashsv
  Returns a pointer to the stash for a specified package, which must be a valid UTF-8 string. See `gv_stashpv`.

              HV*     gv_stashsv(SV* sv, I32 create)

# Handy Values

Nullav
  Null AV pointer.

Nullch
  Null character pointer.

Nullcv
  Null CV pointer.

Nullhv
  Null HV pointer.

Nullsv
  Null SV pointer.

# Hash Manipulation Functions

get_hv
  Returns the HV of the specified Perl hash. If `create` is set and the Perl variable does not exist then it will be created. If `create` is not set and the variable does not exist then NULL is returned.

  NOTE: the perl_ form of this function is deprecated.

              HV*     get_hv(const char* name, I32 create)

HEf_SVKEY
  This flag, used in the length slot of hash entries and magic structures, specifies the structure contains an `SV*` pointer where a `char*` pointer is to be expected. (For information only--not to be used).

HeHASH
  Returns the computed hash stored in the hash entry.

              U32     HeHASH(HE* he)

HeKEY
  Returns the actual pointer stored in the key slot of the hash entry. The pointer may be either `char*` or `SV*`, depending on the value of `HeKLEN()`. Can be assigned to. The `HePV()` or `HeSVKEY()` macros are usually preferable for finding the value of a key.

              void*   HeKEY(HE* he)

HeKLEN
  If this is negative, and amounts to `HEf_SVKEY`, it indicates the entry holds an `SV*` key. Otherwise, holds the actual length of the key. Can be assigned to. The `HePV()` macro is usually preferable for finding key lengths.

              STRLEN  HeKLEN(HE* he)

HePV
  Returns the key slot of the hash entry as a `char*` value, doing any necessary dereferencing of possibly `SV*` keys. The length of the string is placed in `len` (this is a macro, so do not use `&len`). If you do not care about what the length of the key is, you may use the global variable `PL_na`, though this is rather less efficient than using a local variable. Remember though, that hash keys in perl are free to contain embedded nulls, so using `strlen()` or similar is not a good way to find the length of hash keys. This is very similar to the `SvPV()` macro described elsewhere in this document.

              char*   HePV(HE* he, STRLEN len)

HeSVKEY
  Returns the key as an `SV*`, or `Nullsv` if the hash entry does not contain an `SV*` key.

              SV*     HeSVKEY(HE* he)

HeSVKEY_force
  Returns the key as an `SV*`. Will create and return a temporary mortal `SV*` if the hash entry contains only a `char*` key.

              SV*     HeSVKEY_force(HE* he)

HeSVKEY_set
  Sets the key to a given `SV*`, taking care to set the appropriate flags to indicate the presence of an `SV*` key, and returns the same `SV*`.

              SV*     HeSVKEY_set(HE* he, SV* sv)

HeVAL
  Returns the value slot (type `SV*`) stored in the hash entry.

              SV*     HeVAL(HE* he)

HvNAME
  Returns the package name of a stash. See `SvSTASH`, `CvSTASH`.

              char*   HvNAME(HV* stash)

hv_clear
  Clears a hash, making it empty.

              void    hv_clear(HV* tb)

hv_clear_placeholders
  Clears any placeholders from a hash. If a restricted hash has any of its keys marked as readonly and the key is subsequently deleted, the key is not actually deleted but is marked by assigning it a value of &PL_sv_placeholder. This tags it so it will be ignored by future operations such as iterating over the hash, but will still allow the hash to have a value reassigned to the key at some future point. This function clears any such placeholder keys from the hash. See Hash::Util::lock_keys() for an example of its use.

              void    hv_clear_placeholders(HV* hb)

hv_delete
  Deletes a key/value pair in the hash. The value SV is removed from the hash and returned to the caller. The `klen` is the length of the key. The `flags` value will normally be zero; if set to G_DISCARD then NULL will be returned.

              SV*     hv_delete(HV* tb, const char* key, I32 klen, I32 flags)

hv_delete_ent
  Deletes a key/value pair in the hash. The value SV is removed from the hash and returned to the caller. The `flags` value will normally be zero; if set to G_DISCARD then NULL will be returned. `hash` can be a valid precomputed hash value, or 0 to ask for it to be computed.

              SV*     hv_delete_ent(HV* tb, SV* key, I32 flags, U32 hash)

hv_exists
  Returns a boolean indicating whether the specified hash key exists. The `klen` is the length of the key.

              bool    hv_exists(HV* tb, const char* key, I32 klen)

hv_exists_ent
  Returns a boolean indicating whether the specified hash key exists. `hash` can be a valid precomputed hash value, or 0 to ask for it to be computed.

              bool    hv_exists_ent(HV* tb, SV* key, U32 hash)

hv_fetch
  Returns the SV which corresponds to the specified key in the hash. The `klen` is the length of the key. If `lval` is set then the fetch will be part of a store. Check that the return value is non-null before dereferencing it to an `SV*`.

  See Understanding the Magic of Tied Hashes and Arrays in the perlguts manpage for more information on how to use this function on tied hashes.

              SV**    hv_fetch(HV* tb, const char* key, I32 klen, I32 lval)

hv_fetch_ent
  Returns the hash entry which corresponds to the specified key in the hash. `hash` must be a valid precomputed hash number for the given `key`, or 0 if you want the function to compute it. IF `lval` is set then the fetch will be part of a store. Make sure the return value is non-null before accessing it. The return value when `tb` is a tied hash is a pointer to a static location, so be sure to make a copy of the structure if you need to store it somewhere.

  See Understanding the Magic of Tied Hashes and Arrays in the perlguts manpage for more information on how to use this function on tied hashes.

              HE*     hv_fetch_ent(HV* tb, SV* key, I32 lval, U32 hash)

hv_iterinit
  Prepares a starting point to traverse a hash table. Returns the number of keys in the hash (i.e. the same as `HvKEYS(tb)`). The return value is currently only meaningful for hashes without tie magic.

  NOTE: Before version 5.004_65, `hv_iterinit` used to return the number of hash buckets that happen to be in use. If you still need that esoteric value, you can get it through the macro `HvFILL(tb)`.

              I32     hv_iterinit(HV* tb)

hv_iterkey
  Returns the key from the current position of the hash iterator. See `hv_iterinit`.

              char*   hv_iterkey(HE* entry, I32* retlen)

hv_iterkeysv
  Returns the key as an `SV*` from the current position of the hash iterator. The return value will always be a mortal copy of the key. Also see `hv_iterinit`.

              SV*     hv_iterkeysv(HE* entry)

hv_iternext
  Returns entries from a hash iterator. See `hv_iterinit`.

  You may call `hv_delete` or `hv_delete_ent` on the hash entry that the iterator currently points to, without losing your place or invalidating your iterator. Note that in this case the current entry is deleted from the hash with your iterator holding the last reference to it. Your iterator is flagged to free the entry on the next call to `hv_iternext`, so you must not discard your iterator immediately else the entry will leak - call `hv_iternext` to trigger the resource deallocation.

              HE*     hv_iternext(HV* tb)

hv_iternextsv
  Performs an `hv_iternext`, `hv_iterkey`, and `hv_iterval` in one operation.

              SV*     hv_iternextsv(HV* hv, char** key, I32* retlen)

hv_iternext_flags
  Returns entries from a hash iterator. See `hv_iterinit` and `hv_iternext`. The `flags` value will normally be zero; if HV_ITERNEXT_WANTPLACEHOLDERS is set the placeholders keys (for restricted hashes) will be returned in addition to normal keys. By default placeholders are automatically skipped over. Currently a placeholder is implemented with a value that is `&Perl_sv_placeholder`. Note that the implementation of placeholders and restricted hashes may change, and the implementation currently is insufficiently abstracted for any change to be tidy.

  NOTE: this function is experimental and may change or be removed without notice.

              HE*     hv_iternext_flags(HV* tb, I32 flags)

hv_iterval
  Returns the value from the current position of the hash iterator. See `hv_iterkey`.

              SV*     hv_iterval(HV* tb, HE* entry)

hv_magic
  Adds magic to a hash. See `sv_magic`.

              void    hv_magic(HV* hv, GV* gv, int how)

hv_scalar
  Evaluates the hash in scalar context and returns the result. Handles magic when the hash is tied.

              SV*     hv_scalar(HV* hv)

hv_store
  Stores an SV in a hash. The hash key is specified as `key` and `klen` is the length of the key. The `hash` parameter is the precomputed hash value; if it is zero then Perl will compute it. The return value will be NULL if the operation failed or if the value did not need to be actually stored within the hash (as in the case of tied hashes). Otherwise it can be dereferenced to get the original `SV*`. Note that the caller is responsible for suitably incrementing the reference count of `val` before the call, and decrementing it if the function returned NULL. Effectively a successful hv_store takes ownership of one reference to `val`. This is usually what you want; a newly created SV has a reference count of one, so if all your code does is create SVs then store them in a hash, hv_store will own the only reference to the new SV, and your code doesn't need to do anything further to tidy up. hv_store is not implemented as a call to hv_store_ent, and does not create a temporary SV for the key, so if your key data is not already in SV form then use hv_store in preference to hv_store_ent.

  See Understanding the Magic of Tied Hashes and Arrays in the perlguts manpage for more information on how to use this function on tied hashes.

              SV**    hv_store(HV* tb, const char* key, I32 klen, SV* val, U32 hash)

hv_store_ent
  Stores `val` in a hash. The hash key is specified as `key`. The `hash` parameter is the precomputed hash value; if it is zero then Perl will compute it. The return value is the new hash entry so created. It will be NULL if the operation failed or if the value did not need to be actually stored within the hash (as in the case of tied hashes). Otherwise the contents of the return value can be accessed using the `He?` macros described here. Note that the caller is responsible for suitably incrementing the reference count of `val` before the call, and decrementing it if the function returned NULL. Effectively a successful hv_store_ent takes ownership of one reference to `val`. This is usually what you want; a newly created SV has a reference count of one, so if all your code does is create SVs then store them in a hash, hv_store will own the only reference to the new SV, and your code doesn't need to do anything further to tidy up. Note that hv_store_ent only reads the `key`; unlike `val` it does not take ownership of it, so maintaining the correct reference count on `key` is entirely the caller's responsibility. hv_store is not implemented as a call to hv_store_ent, and does not create a temporary SV for the key, so if your key data is not already in SV form then use hv_store in preference to hv_store_ent.

  See Understanding the Magic of Tied Hashes and Arrays in the perlguts manpage for more information on how to use this function on tied hashes.

              HE*     hv_store_ent(HV* tb, SV* key, SV* val, U32 hash)

hv_undef
  Undefines the hash.

              void    hv_undef(HV* tb)

newHV
  Creates a new HV. The reference count is set to 1.

              HV*     newHV()

# Magical Functions

mg_clear
  Clear something magical that the SV represents. See `sv_magic`.

              int     mg_clear(SV* sv)

mg_copy
  Copies the magic from one SV to another. See `sv_magic`.

              int     mg_copy(SV* sv, SV* nsv, const char* key, I32 klen)

mg_find
  Finds the magic pointer for type matching the SV. See `sv_magic`.

              MAGIC*  mg_find(SV* sv, int type)

mg_free
  Free any magic storage used by the SV. See `sv_magic`.

              int     mg_free(SV* sv)

mg_get
  Do magic after a value is retrieved from the SV. See `sv_magic`.

              int     mg_get(SV* sv)

mg_length
  Report on the SV's length. See `sv_magic`.

              U32     mg_length(SV* sv)

mg_magical
  Turns on the magical status of an SV. See `sv_magic`.

              void    mg_magical(SV* sv)

mg_set
  Do magic after a value is assigned to the SV. See `sv_magic`.

              int     mg_set(SV* sv)

SvGETMAGIC
  Invokes `mg_get` on an SV if it has 'get' magic. This macro evaluates its argument more than once.

              void    SvGETMAGIC(SV* sv)

SvLOCK
  Arranges for a mutual exclusion lock to be obtained on sv if a suitable module has been loaded.

              void    SvLOCK(SV* sv)

SvSETMAGIC
  Invokes `mg_set` on an SV if it has 'set' magic. This macro evaluates its argument more than once.

              void    SvSETMAGIC(SV* sv)

SvSetMagicSV
  Like `SvSetSV`, but does any set magic required afterwards.

              void    SvSetMagicSV(SV* dsb, SV* ssv)

SvSetMagicSV_nosteal
  Like `SvSetSV_nosteal`, but does any set magic required afterwards.

              void    SvSetMagicSV_nosteal(SV* dsv, SV* ssv)

SvSetSV
  Calls `sv_setsv` if dsv is not the same as ssv. May evaluate arguments more than once.

              void    SvSetSV(SV* dsb, SV* ssv)

SvSetSV_nosteal
  Calls a non-destructive version of `sv_setsv` if dsv is not the same as ssv. May evaluate arguments more than once.

              void    SvSetSV_nosteal(SV* dsv, SV* ssv)

SvSHARE
  Arranges for sv to be shared between threads if a suitable module has been loaded.

              void    SvSHARE(SV* sv)

SvUNLOCK
  Releases a mutual exclusion lock on sv if a suitable module has been loaded.

              void    SvUNLOCK(SV* sv)

# Memory Management

Copy
  The XSUB-writer's interface to the C `memcpy` function. The `src` is the source, `dest` is the destination, `nitems` is the number of items, and `type` is the type. May fail on overlapping copies. See also `Move`.

              void    Copy(void* src, void* dest, int nitems, type)

CopyD
  Like `Copy` but returns dest. Useful for encouraging compilers to tail-call optimise.

              void *  CopyD(void* src, void* dest, int nitems, type)

Move
  The XSUB-writer's interface to the C `memmove` function. The `src` is the source, `dest` is the destination, `nitems` is the number of items, and `type` is the type. Can do overlapping moves. See also `Copy`.

              void    Move(void* src, void* dest, int nitems, type)

MoveD
  Like `Move` but returns dest. Useful for encouraging compilers to tail-call optimise.

              void *  MoveD(void* src, void* dest, int nitems, type)

New
  The XSUB-writer's interface to the C `malloc` function.

              void    New(int id, void* ptr, int nitems, type)

Newc
  The XSUB-writer's interface to the C `malloc` function, with cast.

              void    Newc(int id, void* ptr, int nitems, type, cast)

Newz
  The XSUB-writer's interface to the C `malloc` function. The allocated memory is zeroed with `memzero`.

              void    Newz(int id, void* ptr, int nitems, type)

Poison
  Fill up memory with a pattern (byte 0xAB over and over again) that hopefully catches attempts to access uninitialized memory.

              void    Poison(void* dest, int nitems, type)

Renew
  The XSUB-writer's interface to the C `realloc` function.

              void    Renew(void* ptr, int nitems, type)

Renewc
  The XSUB-writer's interface to the C `realloc` function, with cast.

              void    Renewc(void* ptr, int nitems, type, cast)

Safefree
  The XSUB-writer's interface to the C `free` function.

              void    Safefree(void* ptr)

savepv
  Perl's version of `strdup()`. Returns a pointer to a newly allocated string which is a duplicate of `pv`. The size of the string is determined by `strlen()`. The memory allocated for the new string can be freed with the `Safefree()` function.

              char*   savepv(const char* pv)

savepvn
  Perl's version of what `strndup()` would be if it existed. Returns a pointer to a newly allocated string which is a duplicate of the first `len` bytes from `pv`. The memory allocated for the new string can be freed with the `Safefree()` function.

              char*   savepvn(const char* pv, I32 len)

savesharedpv
  A version of `savepv()` which allocates the duplicate string in memory which is shared between threads.

              char*   savesharedpv(const char* pv)

StructCopy
  This is an architecture-independent macro to copy one structure to another.

              void    StructCopy(type src, type dest, type)

Zero
  The XSUB-writer's interface to the C `memzero` function. The `dest` is the destination, `nitems` is the number of items, and `type` is the type.

              void    Zero(void* dest, int nitems, type)

ZeroD
  Like `Zero` but returns dest. Useful for encouraging compilers to tail-call optimise.

              void *  ZeroD(void* dest, int nitems, type)

# Miscellaneous Functions

fbm_compile
  Analyses the string in order to make fast searches on it using `fbm_instr()` -- the Boyer-Moore algorithm.

              void    fbm_compile(SV* sv, U32 flags)

fbm_instr
  Returns the location of the SV in the string delimited by `str` and `strend`. It returns `Nullch` if the string can't be found. The `sv` does not have to be fbm_compiled, but the search will not be as fast then.

              char*   fbm_instr(unsigned char* big, unsigned char* bigend, SV* littlesv, U32 flags)

form
  Takes a sprintf-style format pattern and conventional (non-SV) arguments and returns the formatted string.

          (char *) Perl_form(pTHX_ const char* pat, ...)

  can be used any place a string (char *) is required:

          char * s = Perl_form("%d.%d",major,minor);

  Uses a single private buffer so if you want to format several strings you must explicitly copy the earlier strings away (and free the copies when you are done).

              char*   form(const char* pat, ...)

getcwd_sv
  Fill the sv with current working directory

              int     getcwd_sv(SV* sv)

strEQ
  Test two strings to see if they are equal. Returns true or false.

              bool    strEQ(char* s1, char* s2)

strGE
  Test two strings to see if the first, `s1`, is greater than or equal to the second, `s2`. Returns true or false.

              bool    strGE(char* s1, char* s2)

strGT
  Test two strings to see if the first, `s1`, is greater than the second, `s2`. Returns true or false.

              bool    strGT(char* s1, char* s2)

strLE
  Test two strings to see if the first, `s1`, is less than or equal to the second, `s2`. Returns true or false.

              bool    strLE(char* s1, char* s2)

strLT
  Test two strings to see if the first, `s1`, is less than the second, `s2`. Returns true or false.

              bool    strLT(char* s1, char* s2)

strNE
  Test two strings to see if they are different. Returns true or false.

              bool    strNE(char* s1, char* s2)

strnEQ
  Test two strings to see if they are equal. The `len` parameter indicates the number of bytes to compare. Returns true or false. (A wrapper for `strncmp`).

              bool    strnEQ(char* s1, char* s2, STRLEN len)

strnNE
  Test two strings to see if they are different. The `len` parameter indicates the number of bytes to compare. Returns true or false. (A wrapper for `strncmp`).

              bool    strnNE(char* s1, char* s2, STRLEN len)

sv_nolocking
  Dummy routine which ``locks'' an SV when there is no locking module present. Exists to avoid test for a NULL function pointer and because it could potentially warn under some level of strict-ness.

              void    sv_nolocking(SV *)

sv_nosharing
  Dummy routine which ``shares'' an SV when there is no sharing module present. Exists to avoid test for a NULL function pointer and because it could potentially warn under some level of strict-ness.

              void    sv_nosharing(SV *)

sv_nounlocking
  Dummy routine which ``unlocks'' an SV when there is no locking module present. Exists to avoid test for a NULL function pointer and because it could potentially warn under some level of strict-ness.

              void    sv_nounlocking(SV *)

# Numeric functions

grok_bin
  converts a string representing a binary number to numeric form.

  On entry start and *len give the string to scan, *flags gives conversion flags, and result should be NULL or a pointer to an NV. The scan stops at the end of the string, or the first invalid character. Unless `PERL_SCAN_SILENT_ILLDIGIT` is set in *flags, encountering an invalid character will also trigger a warning. On return *len is set to the length of the scanned string, and *flags gives output flags.

  If the value is <= UV_MAX it is returned as a UV, the output flags are clear, and nothing is written to *result. If the value is > UV_MAX `grok_bin` returns UV_MAX, sets `PERL_SCAN_GREATER_THAN_UV_MAX` in the output flags, and writes the value to *result (or the value is discarded if result is NULL).

  The binary number may optionally be prefixed with ``0b'' or ``b'' unless `PERL_SCAN_DISALLOW_PREFIX` is set in *flags on entry. If `PERL_SCAN_ALLOW_UNDERSCORES` is set in *flags then the binary number may use '_' characters to separate digits.

              UV      grok_bin(char* start, STRLEN* len, I32* flags, NV *result)

grok_hex
  converts a string representing a hex number to numeric form.

  On entry start and *len give the string to scan, *flags gives conversion flags, and result should be NULL or a pointer to an NV. The scan stops at the end of the string, or the first invalid character. Unless `PERL_SCAN_SILENT_ILLDIGIT` is set in *flags, encountering an invalid character will also trigger a warning. On return *len is set to the length of the scanned string, and *flags gives output flags.

  If the value is <= UV_MAX it is returned as a UV, the output flags are clear, and nothing is written to *result. If the value is > UV_MAX `grok_hex` returns UV_MAX, sets `PERL_SCAN_GREATER_THAN_UV_MAX` in the output flags, and writes the value to *result (or the value is discarded if result is NULL).

  The hex number may optionally be prefixed with ``0x'' or ``x'' unless `PERL_SCAN_DISALLOW_PREFIX` is set in *flags on entry. If `PERL_SCAN_ALLOW_UNDERSCORES` is set in *flags then the hex number may use '_' characters to separate digits.

              UV      grok_hex(char* start, STRLEN* len, I32* flags, NV *result)

grok_number
  Recognise (or not) a number. The type of the number is returned (0 if unrecognised), otherwise it is a bit-ORed combination of IS_NUMBER_IN_UV, IS_NUMBER_GREATER_THAN_UV_MAX, IS_NUMBER_NOT_INT, IS_NUMBER_NEG, IS_NUMBER_INFINITY, IS_NUMBER_NAN (defined in perl.h).

  If the value of the number can fit an in UV, it is returned in the *valuep IS_NUMBER_IN_UV will be set to indicate that *valuep is valid, IS_NUMBER_IN_UV will never be set unless *valuep is valid, but *valuep may have been assigned to during processing even though IS_NUMBER_IN_UV is not set on return. If valuep is NULL, IS_NUMBER_IN_UV will be set for the same cases as when valuep is non-NULL, but no actual assignment (or SEGV) will occur.

  IS_NUMBER_NOT_INT will be set with IS_NUMBER_IN_UV if trailing decimals were seen (in which case *valuep gives the true value truncated to an integer), and IS_NUMBER_NEG if the number is negative (in which case *valuep holds the absolute value). IS_NUMBER_IN_UV is not set if e notation was used or the number is larger than a UV.

              int     grok_number(const char *pv, STRLEN len, UV *valuep)

grok_numeric_radix
  Scan and skip for a numeric decimal separator (radix).

              bool    grok_numeric_radix(const char **sp, const char *send)

grok_oct
  converts a string representing an octal number to numeric form.

  On entry start and *len give the string to scan, *flags gives conversion flags, and result should be NULL or a pointer to an NV. The scan stops at the end of the string, or the first invalid character. Unless `PERL_SCAN_SILENT_ILLDIGIT` is set in *flags, encountering an invalid character will also trigger a warning. On return *len is set to the length of the scanned string, and *flags gives output flags.

  If the value is <= UV_MAX it is returned as a UV, the output flags are clear, and nothing is written to *result. If the value is > UV_MAX `grok_oct` returns UV_MAX, sets `PERL_SCAN_GREATER_THAN_UV_MAX` in the output flags, and writes the value to *result (or the value is discarded if result is NULL).

  If `PERL_SCAN_ALLOW_UNDERSCORES` is set in *flags then the octal number may use '_' characters to separate digits.

              UV      grok_oct(char* start, STRLEN* len, I32* flags, NV *result)

scan_bin
  For backwards compatibility. Use `grok_bin` instead.

              NV      scan_bin(char* start, STRLEN len, STRLEN* retlen)

scan_hex
  For backwards compatibility. Use `grok_hex` instead.

              NV      scan_hex(char* start, STRLEN len, STRLEN* retlen)

scan_oct
  For backwards compatibility. Use `grok_oct` instead.

              NV      scan_oct(char* start, STRLEN len, STRLEN* retlen)

# Optree Manipulation Functions

cv_const_sv
  If `cv` is a constant sub eligible for inlining. returns the constant value returned by the sub. Otherwise, returns NULL.

  Constant subs can be created with `newCONSTSUB` or as described in Constant Functions in the perlsub manpage.

              SV*     cv_const_sv(CV* cv)

newCONSTSUB
  Creates a constant sub equivalent to Perl `sub FOO () { 123 }` which is eligible for inlining at compile-time.

              CV*     newCONSTSUB(HV* stash, char* name, SV* sv)

newXS
  Used by `xsubpp` to hook up XSUBs as Perl subs.

# Pad Data Structures

pad_sv
  Get the value at offset po in the current pad. Use macro PAD_SV instead of calling this function directly.

              SV*     pad_sv(PADOFFSET po)

# Stack Manipulation Macros

dMARK
  Declare a stack marker variable, `mark`, for the XSUB. See `MARK` and `dORIGMARK`.

                      dMARK;

dORIGMARK
  Saves the original stack mark for the XSUB. See `ORIGMARK`.

                      dORIGMARK;

dSP
  Declares a local copy of perl's stack pointer for the XSUB, available via the `SP` macro. See `SP`.

                      dSP;

EXTEND
  Used to extend the argument stack for an XSUB's return values. Once used, guarantees that there is room for at least `nitems` to be pushed onto the stack.

              void    EXTEND(SP, int nitems)

MARK
  Stack marker variable for the XSUB. See `dMARK`.

mPUSHi
  Push an integer onto the stack. The stack must have room for this element. Handles 'set' magic. Does not use `TARG`. See also `PUSHi`, `mXPUSHi` and `XPUSHi`.

              void    mPUSHi(IV iv)

mPUSHn
  Push a double onto the stack. The stack must have room for this element. Handles 'set' magic. Does not use `TARG`. See also `PUSHn`, `mXPUSHn` and `XPUSHn`.

              void    mPUSHn(NV nv)

mPUSHp
  Push a string onto the stack. The stack must have room for this element. The `len` indicates the length of the string. Handles 'set' magic. Does not use `TARG`. See also `PUSHp`, `mXPUSHp` and `XPUSHp`.

              void    mPUSHp(char* str, STRLEN len)

mPUSHu
  Push an unsigned integer onto the stack. The stack must have room for this element. Handles 'set' magic. Does not use `TARG`. See also `PUSHu`, `mXPUSHu` and `XPUSHu`.

              void    mPUSHu(UV uv)

mXPUSHi
  Push an integer onto the stack, extending the stack if necessary. Handles 'set' magic. Does not use `TARG`. See also `XPUSHi`, `mPUSHi` and `PUSHi`.

              void    mXPUSHi(IV iv)

mXPUSHn
  Push a double onto the stack, extending the stack if necessary. Handles 'set' magic. Does not use `TARG`. See also `XPUSHn`, `mPUSHn` and `PUSHn`.

              void    mXPUSHn(NV nv)

mXPUSHp
  Push a string onto the stack, extending the stack if necessary. The `len` indicates the length of the string. Handles 'set' magic. Does not use `TARG`. See also `XPUSHp`, `mPUSHp` and `PUSHp`.

              void    mXPUSHp(char* str, STRLEN len)

mXPUSHu
  Push an unsigned integer onto the stack, extending the stack if necessary. Handles 'set' magic. Does not use `TARG`. See also `XPUSHu`, `mPUSHu` and `PUSHu`.

              void    mXPUSHu(UV uv)

ORIGMARK
  The original stack mark for the XSUB. See `dORIGMARK`.

POPi
  Pops an integer off the stack.

              IV      POPi

POPl
  Pops a long off the stack.

              long    POPl

POPn
  Pops a double off the stack.

              NV      POPn

POPp
  Pops a string off the stack. Deprecated. New code should provide a STRLEN n_a and use POPpx.

              char*   POPp

POPpbytex
  Pops a string off the stack which must consist of bytes i.e. characters < 256. Requires a variable STRLEN n_a in scope.

              char*   POPpbytex

POPpx
  Pops a string off the stack. Requires a variable STRLEN n_a in scope.

              char*   POPpx

POPs
  Pops an SV off the stack.

              SV*     POPs

PUSHi
  Push an integer onto the stack. The stack must have room for this element. Handles 'set' magic. Uses `TARG`, so `dTARGET` or `dXSTARG` should be called to declare it. Do not call multiple `TARG`-oriented macros to return lists from XSUB's - see `mPUSHi` instead. See also `XPUSHi` and `mXPUSHi`.

              void    PUSHi(IV iv)

PUSHMARK
  Opening bracket for arguments on a callback. See `PUTBACK` and the perlcall manpage.

              void    PUSHMARK(SP)

PUSHmortal
  Push a new mortal SV onto the stack. The stack must have room for this element. Does not handle 'set' magic. Does not use `TARG`. See also `PUSHs`, `XPUSHmortal` and `XPUSHs`.

              void    PUSHmortal()

PUSHn
  Push a double onto the stack. The stack must have room for this element. Handles 'set' magic. Uses `TARG`, so `dTARGET` or `dXSTARG` should be called to declare it. Do not call multiple `TARG`-oriented macros to return lists from XSUB's - see `mPUSHn` instead. See also `XPUSHn` and `mXPUSHn`.

              void    PUSHn(NV nv)

PUSHp
  Push a string onto the stack. The stack must have room for this element. The `len` indicates the length of the string. Handles 'set' magic. Uses `TARG`, so `dTARGET` or `dXSTARG` should be called to declare it. Do not call multiple `TARG`-oriented macros to return lists from XSUB's - see `mPUSHp` instead. See also `XPUSHp` and `mXPUSHp`.

              void    PUSHp(char* str, STRLEN len)

PUSHs
  Push an SV onto the stack. The stack must have room for this element. Does not handle 'set' magic. Does not use `TARG`. See also `PUSHmortal`, `XPUSHs` and `XPUSHmortal`.

              void    PUSHs(SV* sv)

PUSHu
  Push an unsigned integer onto the stack. The stack must have room for this element. Handles 'set' magic. Uses `TARG`, so `dTARGET` or `dXSTARG` should be called to declare it. Do not call multiple `TARG`-oriented macros to return lists from XSUB's - see `mPUSHu` instead. See also `XPUSHu` and `mXPUSHu`.

              void    PUSHu(UV uv)

PUTBACK
  Closing bracket for XSUB arguments. This is usually handled by `xsubpp`. See `PUSHMARK` and the perlcall manpage for other uses.

                      PUTBACK;

SP
  Stack pointer. This is usually handled by `xsubpp`. See `dSP` and `SPAGAIN`.

SPAGAIN
  Refetch the stack pointer. Used after a callback. See the perlcall manpage.

                      SPAGAIN;

XPUSHi
  Push an integer onto the stack, extending the stack if necessary. Handles 'set' magic. Uses `TARG`, so `dTARGET` or `dXSTARG` should be called to declare it. Do not call multiple `TARG`-oriented macros to return lists from XSUB's - see `mXPUSHi` instead. See also `PUSHi` and `mPUSHi`.

              void    XPUSHi(IV iv)

XPUSHmortal
  Push a new mortal SV onto the stack, extending the stack if necessary. Does not handle 'set' magic. Does not use `TARG`. See also `XPUSHs`, `PUSHmortal` and `PUSHs`.

              void    XPUSHmortal()

XPUSHn
  Push a double onto the stack, extending the stack if necessary. Handles 'set' magic. Uses `TARG`, so `dTARGET` or `dXSTARG` should be called to declare it. Do not call multiple `TARG`-oriented macros to return lists from XSUB's - see `mXPUSHn` instead. See also `PUSHn` and `mPUSHn`.

              void    XPUSHn(NV nv)

XPUSHp
  Push a string onto the stack, extending the stack if necessary. The `len` indicates the length of the string. Handles 'set' magic. Uses `TARG`, so `dTARGET` or `dXSTARG` should be called to declare it. Do not call multiple `TARG`-oriented macros to return lists from XSUB's - see `mXPUSHp` instead. See also `PUSHp` and `mPUSHp`.

              void    XPUSHp(char* str, STRLEN len)

XPUSHs
  Push an SV onto the stack, extending the stack if necessary. Does not handle 'set' magic. Does not use `TARG`. See also `XPUSHmortal`, `PUSHs` and `PUSHmortal`.

              void    XPUSHs(SV* sv)

XPUSHu
  Push an unsigned integer onto the stack, extending the stack if necessary. Handles 'set' magic. Uses `TARG`, so `dTARGET` or `dXSTARG` should be called to declare it. Do not call multiple `TARG`-oriented macros to return lists from XSUB's - see `mXPUSHu` instead. See also `PUSHu` and `mPUSHu`.

              void    XPUSHu(UV uv)

XSRETURN
  Return from XSUB, indicating number of items on the stack. This is usually handled by `xsubpp`.

              void    XSRETURN(int nitems)

XSRETURN_EMPTY
  Return an empty list from an XSUB immediately.

                      XSRETURN_EMPTY;

XSRETURN_IV
  Return an integer from an XSUB immediately. Uses `XST_mIV`.

              void    XSRETURN_IV(IV iv)

XSRETURN_NO
  Return `&PL_sv_no` from an XSUB immediately. Uses `XST_mNO`.

                      XSRETURN_NO;

XSRETURN_NV
  Return a double from an XSUB immediately. Uses `XST_mNV`.

              void    XSRETURN_NV(NV nv)

XSRETURN_PV
  Return a copy of a string from an XSUB immediately. Uses `XST_mPV`.

              void    XSRETURN_PV(char* str)

XSRETURN_UNDEF
  Return `&PL_sv_undef` from an XSUB immediately. Uses `XST_mUNDEF`.

                      XSRETURN_UNDEF;

XSRETURN_UV
  Return an integer from an XSUB immediately. Uses `XST_mUV`.

              void    XSRETURN_UV(IV uv)

XSRETURN_YES
  Return `&PL_sv_yes` from an XSUB immediately. Uses `XST_mYES`.

                      XSRETURN_YES;

XST_mIV
  Place an integer into the specified position `pos` on the stack. The value is stored in a new mortal SV.

              void    XST_mIV(int pos, IV iv)

XST_mNO
  Place `&PL_sv_no` into the specified position `pos` on the stack.

              void    XST_mNO(int pos)

XST_mNV
  Place a double into the specified position `pos` on the stack. The value is stored in a new mortal SV.

              void    XST_mNV(int pos, NV nv)

XST_mPV
  Place a copy of a string into the specified position `pos` on the stack. The value is stored in a new mortal SV.

              void    XST_mPV(int pos, char* str)

XST_mUNDEF
  Place `&PL_sv_undef` into the specified position `pos` on the stack.

              void    XST_mUNDEF(int pos)

XST_mYES
  Place `&PL_sv_yes` into the specified position `pos` on the stack.

              void    XST_mYES(int pos)

# SV Flags

svtype
  An enum of flags for Perl types. These are found in the file sv.h in the `svtype` enum. Test these flags with the `SvTYPE` macro.

SVt_IV
  Integer type flag for scalars. See `svtype`.

SVt_NV
  Double type flag for scalars. See `svtype`.

SVt_PV
  Pointer type flag for scalars. See `svtype`.

SVt_PVAV
  Type flag for arrays. See `svtype`.

SVt_PVCV
  Type flag for code refs. See `svtype`.

SVt_PVHV
  Type flag for hashes. See `svtype`.

SVt_PVMG
  Type flag for blessed scalars. See `svtype`.

# SV Manipulation Functions

get_sv
  Returns the SV of the specified Perl scalar. If `create` is set and the Perl variable does not exist then it will be created. If `create` is not set and the variable does not exist then NULL is returned.

  NOTE: the perl_ form of this function is deprecated.

              SV*     get_sv(const char* name, I32 create)

looks_like_number
  Test if the content of an SV looks like a number (or is a number). `Inf` and `Infinity` are treated as numbers (so will not issue a non-numeric warning), even if your `atof()` doesn't grok them.

              I32     looks_like_number(SV* sv)

newRV_inc
  Creates an RV wrapper for an SV. The reference count for the original SV is incremented.

              SV*     newRV_inc(SV* sv)

newRV_noinc
  Creates an RV wrapper for an SV. The reference count for the original SV is not incremented.

              SV*     newRV_noinc(SV *sv)

NEWSV
  Creates a new SV. A non-zero `len` parameter indicates the number of bytes of preallocated string space the SV should have. An extra byte for a tailing NUL is also reserved. (SvPOK is not set for the SV even if string space is allocated.) The reference count for the new SV is set to 1. `id` is an integer id between 0 and 1299 (used to identify leaks).

              SV*     NEWSV(int id, STRLEN len)

newSV
  Create a new null SV, or if len > 0, create a new empty SVt_PV type SV with an initial PV allocation of len+1. Normally accessed via the `NEWSV` macro.

              SV*     newSV(STRLEN len)

newSViv
  Creates a new SV and copies an integer into it. The reference count for the SV is set to 1.

              SV*     newSViv(IV i)

newSVnv
  Creates a new SV and copies a floating point value into it. The reference count for the SV is set to 1.

              SV*     newSVnv(NV n)

newSVpv
  Creates a new SV and copies a string into it. The reference count for the SV is set to 1. If `len` is zero, Perl will compute the length using strlen(). For efficiency, consider using `newSVpvn` instead.

              SV*     newSVpv(const char* s, STRLEN len)

newSVpvf
  Creates a new SV and initializes it with the string formatted like `sprintf`.

              SV*     newSVpvf(const char* pat, ...)

newSVpvn
  Creates a new SV and copies a string into it. The reference count for the SV is set to 1. Note that if `len` is zero, Perl will create a zero length string. You are responsible for ensuring that the source string is at least `len` bytes long. If the `s` argument is NULL the new SV will be undefined.

              SV*     newSVpvn(const char* s, STRLEN len)

newSVpvn_share
  Creates a new SV with its SvPVX pointing to a shared string in the string table. If the string does not already exist in the table, it is created first. Turns on READONLY and FAKE. The string's hash is stored in the UV slot of the SV; if the `hash` parameter is non-zero, that value is used; otherwise the hash is computed. The idea here is that as the string table is used for shared hash keys these strings will have SvPVX == HeKEY and hash lookup will avoid string compare.

              SV*     newSVpvn_share(const char* s, I32 len, U32 hash)

newSVrv
  Creates a new SV for the RV, `rv`, to point to. If `rv` is not an RV then it will be upgraded to one. If `classname` is non-null then the new SV will be blessed in the specified package. The new SV is returned and its reference count is 1.

              SV*     newSVrv(SV* rv, const char* classname)

newSVsv
  Creates a new SV which is an exact duplicate of the original SV. (Uses `sv_setsv`).

              SV*     newSVsv(SV* old)

newSVuv
  Creates a new SV and copies an unsigned integer into it. The reference count for the SV is set to 1.

              SV*     newSVuv(UV u)

SvCUR
  Returns the length of the string which is in the SV. See `SvLEN`.

              STRLEN  SvCUR(SV* sv)

SvCUR_set
  Set the length of the string which is in the SV. See `SvCUR`.

              void    SvCUR_set(SV* sv, STRLEN len)

SvEND
  Returns a pointer to the last character in the string which is in the SV. See `SvCUR`. Access the character as *(SvEND(sv)).

              char*   SvEND(SV* sv)

SvGROW
  Expands the character buffer in the SV so that it has room for the indicated number of bytes (remember to reserve space for an extra trailing NUL character). Calls `sv_grow` to perform the expansion if necessary. Returns a pointer to the character buffer.

              char *  SvGROW(SV* sv, STRLEN len)

SvIOK
  Returns a boolean indicating whether the SV contains an integer.

              bool    SvIOK(SV* sv)

SvIOKp
  Returns a boolean indicating whether the SV contains an integer. Checks the private setting. Use `SvIOK`.

              bool    SvIOKp(SV* sv)

SvIOK_notUV
  Returns a boolean indicating whether the SV contains a signed integer.

              bool    SvIOK_notUV(SV* sv)

SvIOK_off
  Unsets the IV status of an SV.

              void    SvIOK_off(SV* sv)

SvIOK_on
  Tells an SV that it is an integer.

              void    SvIOK_on(SV* sv)

SvIOK_only
  Tells an SV that it is an integer and disables all other OK bits.

              void    SvIOK_only(SV* sv)

SvIOK_only_UV
  Tells and SV that it is an unsigned integer and disables all other OK bits.

              void    SvIOK_only_UV(SV* sv)

SvIOK_UV
  Returns a boolean indicating whether the SV contains an unsigned integer.

              bool    SvIOK_UV(SV* sv)

SvIsCOW
  Returns a boolean indicating whether the SV is Copy-On-Write. (either shared hash key scalars, or full Copy On Write scalars if 5.9.0 is configured for COW)

              bool    SvIsCOW(SV* sv)

SvIsCOW_shared_hash
  Returns a boolean indicating whether the SV is Copy-On-Write shared hash key scalar.

              bool    SvIsCOW_shared_hash(SV* sv)

SvIV
  Coerces the given SV to an integer and returns it. See `SvIVx` for a version which guarantees to evaluate sv only once.

              IV      SvIV(SV* sv)

SvIVx
  Coerces the given SV to an integer and returns it. Guarantees to evaluate sv only once. Use the more efficient `SvIV` otherwise.

              IV      SvIVx(SV* sv)

SvIVX
  Returns the raw value in the SV's IV slot, without checks or conversions. Only use when you are sure SvIOK is true. See also `SvIV()`.

              IV      SvIVX(SV* sv)

SvLEN
  Returns the size of the string buffer in the SV, not including any part attributable to `SvOOK`. See `SvCUR`.

              STRLEN  SvLEN(SV* sv)

SvNIOK
  Returns a boolean indicating whether the SV contains a number, integer or double.

              bool    SvNIOK(SV* sv)

SvNIOKp
  Returns a boolean indicating whether the SV contains a number, integer or double. Checks the private setting. Use `SvNIOK`.

              bool    SvNIOKp(SV* sv)

SvNIOK_off
  Unsets the NV/IV status of an SV.

              void    SvNIOK_off(SV* sv)

SvNOK
  Returns a boolean indicating whether the SV contains a double.

              bool    SvNOK(SV* sv)

SvNOKp
  Returns a boolean indicating whether the SV contains a double. Checks the private setting. Use `SvNOK`.

              bool    SvNOKp(SV* sv)

SvNOK_off
  Unsets the NV status of an SV.

              void    SvNOK_off(SV* sv)

SvNOK_on
  Tells an SV that it is a double.

              void    SvNOK_on(SV* sv)

SvNOK_only
  Tells an SV that it is a double and disables all other OK bits.

              void    SvNOK_only(SV* sv)

SvNV
  Coerce the given SV to a double and return it. See `SvNVx` for a version which guarantees to evaluate sv only once.

              NV      SvNV(SV* sv)

SvNVx
  Coerces the given SV to a double and returns it. Guarantees to evaluate sv only once. Use the more efficient `SvNV` otherwise.

              NV      SvNVx(SV* sv)

SvNVX
  Returns the raw value in the SV's NV slot, without checks or conversions. Only use when you are sure SvNOK is true. See also `SvNV()`.

              NV      SvNVX(SV* sv)

SvOK
  Returns a boolean indicating whether the value is an SV. It also tells whether the value is defined or not.

              bool    SvOK(SV* sv)

SvOOK
  Returns a boolean indicating whether the SvIVX is a valid offset value for the SvPVX. This hack is used internally to speed up removal of characters from the beginning of a SvPV. When SvOOK is true, then the start of the allocated string buffer is really (SvPVX - SvIVX).

              bool    SvOOK(SV* sv)

SvPOK
  Returns a boolean indicating whether the SV contains a character string.

              bool    SvPOK(SV* sv)

SvPOKp
  Returns a boolean indicating whether the SV contains a character string. Checks the private setting. Use `SvPOK`.

              bool    SvPOKp(SV* sv)

SvPOK_off
  Unsets the PV status of an SV.

              void    SvPOK_off(SV* sv)

SvPOK_on
  Tells an SV that it is a string.

              void    SvPOK_on(SV* sv)

SvPOK_only
  Tells an SV that it is a string and disables all other OK bits. Will also turn off the UTF-8 status.

              void    SvPOK_only(SV* sv)

SvPOK_only_UTF8
  Tells an SV that it is a string and disables all other OK bits, and leaves the UTF-8 status as it was.

              void    SvPOK_only_UTF8(SV* sv)

SvPV
  Returns a pointer to the string in the SV, or a stringified form of the SV if the SV does not contain a string. The SV may cache the stringified version becoming `SvPOK`. Handles 'get' magic. See also `SvPVx` for a version which guarantees to evaluate sv only once.

              char*   SvPV(SV* sv, STRLEN len)

SvPVbyte
  Like `SvPV`, but converts sv to byte representation first if necessary.

              char*   SvPVbyte(SV* sv, STRLEN len)

SvPVbytex
  Like `SvPV`, but converts sv to byte representation first if necessary. Guarantees to evaluate sv only once; use the more efficient `SvPVbyte` otherwise.

              char*   SvPVbytex(SV* sv, STRLEN len)

SvPVbytex_force
  Like `SvPV_force`, but converts sv to byte representation first if necessary. Guarantees to evaluate sv only once; use the more efficient `SvPVbyte_force` otherwise.

              char*   SvPVbytex_force(SV* sv, STRLEN len)

SvPVbyte_force
  Like `SvPV_force`, but converts sv to byte representation first if necessary.

              char*   SvPVbyte_force(SV* sv, STRLEN len)

SvPVbyte_nolen
  Like `SvPV_nolen`, but converts sv to byte representation first if necessary.

              char*   SvPVbyte_nolen(SV* sv)

SvPVutf8
  Like `SvPV`, but converts sv to utf8 first if necessary.

              char*   SvPVutf8(SV* sv, STRLEN len)

SvPVutf8x
  Like `SvPV`, but converts sv to utf8 first if necessary. Guarantees to evaluate sv only once; use the more efficient `SvPVutf8` otherwise.

              char*   SvPVutf8x(SV* sv, STRLEN len)

SvPVutf8x_force
  Like `SvPV_force`, but converts sv to utf8 first if necessary. Guarantees to evaluate sv only once; use the more efficient `SvPVutf8_force` otherwise.

              char*   SvPVutf8x_force(SV* sv, STRLEN len)

SvPVutf8_force
  Like `SvPV_force`, but converts sv to utf8 first if necessary.

              char*   SvPVutf8_force(SV* sv, STRLEN len)

SvPVutf8_nolen
  Like `SvPV_nolen`, but converts sv to utf8 first if necessary.

              char*   SvPVutf8_nolen(SV* sv)

SvPVx
  A version of `SvPV` which guarantees to evaluate sv only once.

              char*   SvPVx(SV* sv, STRLEN len)

SvPVX
  Returns a pointer to the physical string in the SV. The SV must contain a string.

              char*   SvPVX(SV* sv)

SvPV_force
  Like `SvPV` but will force the SV into containing just a string (`SvPOK_only`). You want force if you are going to update the `SvPVX` directly.

              char*   SvPV_force(SV* sv, STRLEN len)

SvPV_force_nomg
  Like `SvPV` but will force the SV into containing just a string (`SvPOK_only`). You want force if you are going to update the `SvPVX` directly. Doesn't process magic.

              char*   SvPV_force_nomg(SV* sv, STRLEN len)

SvPV_nolen
  Returns a pointer to the string in the SV, or a stringified form of the SV if the SV does not contain a string. The SV may cache the stringified form becoming `SvPOK`. Handles 'get' magic.

              char*   SvPV_nolen(SV* sv)

SvREFCNT
  Returns the value of the object's reference count.

              U32     SvREFCNT(SV* sv)

SvREFCNT_dec
  Decrements the reference count of the given SV.

              void    SvREFCNT_dec(SV* sv)

SvREFCNT_inc
  Increments the reference count of the given SV.

              SV*     SvREFCNT_inc(SV* sv)

SvROK
  Tests if the SV is an RV.

              bool    SvROK(SV* sv)

SvROK_off
  Unsets the RV status of an SV.

              void    SvROK_off(SV* sv)

SvROK_on
  Tells an SV that it is an RV.

              void    SvROK_on(SV* sv)

SvRV
  Dereferences an RV to return the SV.

              SV*     SvRV(SV* sv)

SvSTASH
  Returns the stash of the SV.

              HV*     SvSTASH(SV* sv)

SvTAINT
  Taints an SV if tainting is enabled.

              void    SvTAINT(SV* sv)

SvTAINTED
  Checks to see if an SV is tainted. Returns TRUE if it is, FALSE if not.

              bool    SvTAINTED(SV* sv)

SvTAINTED_off
  Untaints an SV. Be very careful with this routine, as it short-circuits some of Perl's fundamental security features. XS module authors should not use this function unless they fully understand all the implications of unconditionally untainting the value. Untainting should be done in the standard perl fashion, via a carefully crafted regexp, rather than directly untainting variables.

              void    SvTAINTED_off(SV* sv)

SvTAINTED_on
  Marks an SV as tainted if tainting is enabled.

              void    SvTAINTED_on(SV* sv)

SvTRUE
  Returns a boolean indicating whether Perl would evaluate the SV as true or false, defined or undefined. Does not handle 'get' magic.

              bool    SvTRUE(SV* sv)

SvTYPE
  Returns the type of the SV. See `svtype`.

              svtype  SvTYPE(SV* sv)

SvUOK
  Returns a boolean indicating whether the SV contains an unsigned integer.

              void    SvUOK(SV* sv)

SvUPGRADE
  Used to upgrade an SV to a more complex form. Uses `sv_upgrade` to perform the upgrade if necessary. See `svtype`.

              void    SvUPGRADE(SV* sv, svtype type)

SvUTF8
  Returns a boolean indicating whether the SV contains UTF-8 encoded data.

              bool    SvUTF8(SV* sv)

SvUTF8_off
  Unsets the UTF-8 status of an SV.

              void    SvUTF8_off(SV *sv)

SvUTF8_on
  Turn on the UTF-8 status of an SV (the data is not changed, just the flag). Do not use frivolously.

              void    SvUTF8_on(SV *sv)

SvUV
  Coerces the given SV to an unsigned integer and returns it. See `SvUVx` for a version which guarantees to evaluate sv only once.

              UV      SvUV(SV* sv)

SvUVx
  Coerces the given SV to an unsigned integer and returns it. Guarantees to evaluate sv only once. Use the more efficient `SvUV` otherwise.

              UV      SvUVx(SV* sv)

SvUVX
  Returns the raw value in the SV's UV slot, without checks or conversions. Only use when you are sure SvIOK is true. See also `SvUV()`.

              UV      SvUVX(SV* sv)

sv_2bool
  This function is only called on magical items, and is only used by `sv_true()` or its macro equivalent.

              bool    sv_2bool(SV* sv)

sv_2cv
  Using various gambits, try to get a CV from an SV; in addition, try if possible to set `*st` and `*gvp` to the stash and GV associated with it.

              CV*     sv_2cv(SV* sv, HV** st, GV** gvp, I32 lref)

sv_2io
  Using various gambits, try to get an IO from an SV: the IO slot if its a GV; or the recursive result if we're an RV; or the IO slot of the symbol named after the PV if we're a string.

              IO*     sv_2io(SV* sv)

sv_2iv
  Return the integer value of an SV, doing any necessary string conversion, magic etc. Normally used via the `SvIV(sv)` and `SvIVx(sv)` macros.

              IV      sv_2iv(SV* sv)

sv_2mortal
  Marks an existing SV as mortal. The SV will be destroyed ``soon'', either by an explicit call to FREETMPS, or by an implicit call at places such as statement boundaries. `SvTEMP()` is turned on which means that the SV's string buffer can be ``stolen'' if this SV is copied. See also `sv_newmortal` and `sv_mortalcopy`.

              SV*     sv_2mortal(SV* sv)

sv_2nv
  Return the num value of an SV, doing any necessary string or integer conversion, magic etc. Normally used via the `SvNV(sv)` and `SvNVx(sv)` macros.

              NV      sv_2nv(SV* sv)

sv_2pvbyte
  Return a pointer to the byte-encoded representation of the SV, and set *lp to its length. May cause the SV to be downgraded from UTF-8 as a side-effect.

  Usually accessed via the `SvPVbyte` macro.

              char*   sv_2pvbyte(SV* sv, STRLEN* lp)

sv_2pvbyte_nolen
  Return a pointer to the byte-encoded representation of the SV. May cause the SV to be downgraded from UTF-8 as a side-effect.

  Usually accessed via the `SvPVbyte_nolen` macro.

              char*   sv_2pvbyte_nolen(SV* sv)

sv_2pvutf8
  Return a pointer to the UTF-8-encoded representation of the SV, and set *lp to its length. May cause the SV to be upgraded to UTF-8 as a side-effect.

  Usually accessed via the `SvPVutf8` macro.

              char*   sv_2pvutf8(SV* sv, STRLEN* lp)

sv_2pvutf8_nolen
  Return a pointer to the UTF-8-encoded representation of the SV. May cause the SV to be upgraded to UTF-8 as a side-effect.

  Usually accessed via the `SvPVutf8_nolen` macro.

              char*   sv_2pvutf8_nolen(SV* sv)

sv_2pv_flags
  Returns a pointer to the string value of an SV, and sets *lp to its length. If flags includes SV_GMAGIC, does an `mg_get()` first. Coerces sv to a string if necessary. Normally invoked via the `SvPV_flags` macro. `sv_2pv()` and `sv_2pv_nomg` usually end up here too.

              char*   sv_2pv_flags(SV* sv, STRLEN* lp, I32 flags)

sv_2pv_nolen
  Like `sv_2pv()`, but doesn't return the length too. You should usually use the macro wrapper `SvPV_nolen(sv)` instead. char* sv_2pv_nolen(SV* sv)

sv_2uv
  Return the unsigned integer value of an SV, doing any necessary string conversion, magic etc. Normally used via the `SvUV(sv)` and `SvUVx(sv)` macros.

              UV      sv_2uv(SV* sv)

sv_backoff
  Remove any string offset. You should normally use the `SvOOK_off` macro wrapper instead.

              int     sv_backoff(SV* sv)

sv_bless
  Blesses an SV into a specified package. The SV must be an RV. The package must be designated by its stash (see `gv_stashpv()`). The reference count of the SV is unaffected.

              SV*     sv_bless(SV* sv, HV* stash)

sv_catpv
  Concatenates the string onto the end of the string which is in the SV. If the SV has the UTF-8 status set, then the bytes appended should be valid UTF-8. Handles 'get' magic, but not 'set' magic. See `sv_catpv_mg`.

              void    sv_catpv(SV* sv, const char* ptr)

sv_catpvf
  Processes its arguments like `sprintf` and appends the formatted output to an SV. If the appended data contains ``wide'' characters (including, but not limited to, SVs with a UTF-8 PV formatted with %s, and characters >255 formatted with %c), the original SV might get upgraded to UTF-8. Handles 'get' magic, but not 'set' magic. See `sv_catpvf_mg`.

              void    sv_catpvf(SV* sv, const char* pat, ...)

sv_catpvf_mg
  Like `sv_catpvf`, but also handles 'set' magic.

              void    sv_catpvf_mg(SV *sv, const char* pat, ...)

sv_catpvn
  Concatenates the string onto the end of the string which is in the SV. The `len` indicates number of bytes to copy. If the SV has the UTF-8 status set, then the bytes appended should be valid UTF-8. Handles 'get' magic, but not 'set' magic. See `sv_catpvn_mg`.

              void    sv_catpvn(SV* sv, const char* ptr, STRLEN len)

sv_catpvn_flags
  Concatenates the string onto the end of the string which is in the SV. The `len` indicates number of bytes to copy. If the SV has the UTF-8 status set, then the bytes appended should be valid UTF-8. If `flags` has `SV_GMAGIC` bit set, will `mg_get` on `dsv` if appropriate, else not. `sv_catpvn` and `sv_catpvn_nomg` are implemented in terms of this function.

              void    sv_catpvn_flags(SV* sv, const char* ptr, STRLEN len, I32 flags)

sv_catpvn_mg
  Like `sv_catpvn`, but also handles 'set' magic.

              void    sv_catpvn_mg(SV *sv, const char *ptr, STRLEN len)

sv_catpvn_nomg
  Like `sv_catpvn` but doesn't process magic.

              void    sv_catpvn_nomg(SV* sv, const char* ptr, STRLEN len)

sv_catpv_mg
  Like `sv_catpv`, but also handles 'set' magic.

              void    sv_catpv_mg(SV *sv, const char *ptr)

sv_catsv
  Concatenates the string from SV `ssv` onto the end of the string in SV `dsv`. Modifies `dsv` but not `ssv`. Handles 'get' magic, but not 'set' magic. See `sv_catsv_mg`.

              void    sv_catsv(SV* dsv, SV* ssv)

sv_catsv_flags
  Concatenates the string from SV `ssv` onto the end of the string in SV `dsv`. Modifies `dsv` but not `ssv`. If `flags` has `SV_GMAGIC` bit set, will `mg_get` on the SVs if appropriate, else not. `sv_catsv` and `sv_catsv_nomg` are implemented in terms of this function.

              void    sv_catsv_flags(SV* dsv, SV* ssv, I32 flags)

sv_catsv_mg
  Like `sv_catsv`, but also handles 'set' magic.

              void    sv_catsv_mg(SV *dstr, SV *sstr)

sv_catsv_nomg
  Like `sv_catsv` but doesn't process magic.

              void    sv_catsv_nomg(SV* dsv, SV* ssv)

sv_chop
  Efficient removal of characters from the beginning of the string buffer. `SvPOK(sv)` must be true and the `ptr` must be a pointer to somewhere inside the string buffer. The `ptr` becomes the first character of the adjusted string. Uses the ``OOK hack''. Beware: after this function returns, `ptr` and `SvPVX(sv)` may no longer refer to the same chunk of data.

              void    sv_chop(SV* sv, char* ptr)

sv_clear
  Clear an SV: call any destructors, free up any memory used by the body, and free the body itself. The SV's head is not freed, although its type is set to all 1's so that it won't inadvertently be assumed to be live during global destruction etc. This function should only be called when REFCNT is zero. Most of the time you'll want to call `sv_free()` (or its macro wrapper `SvREFCNT_dec`) instead.

              void    sv_clear(SV* sv)

sv_cmp
  Compares the strings in two SVs. Returns -1, 0, or 1 indicating whether the string in `sv1` is less than, equal to, or greater than the string in `sv2`. Is UTF-8 and 'use bytes' aware, handles get magic, and will coerce its args to strings if necessary. See also `sv_cmp_locale`.

              I32     sv_cmp(SV* sv1, SV* sv2)

sv_cmp_locale
  Compares the strings in two SVs in a locale-aware manner. Is UTF-8 and 'use bytes' aware, handles get magic, and will coerce its args to strings if necessary. See also `sv_cmp_locale`. See also `sv_cmp`.

              I32     sv_cmp_locale(SV* sv1, SV* sv2)

sv_collxfrm
  Add Collate Transform magic to an SV if it doesn't already have it.

  Any scalar variable may carry PERL_MAGIC_collxfrm magic that contains the scalar data of the variable, but transformed to such a format that a normal memory comparison can be used to compare the data according to the locale settings.

              char*   sv_collxfrm(SV* sv, STRLEN* nxp)

sv_copypv
  Copies a stringified representation of the source SV into the destination SV. Automatically performs any necessary mg_get and coercion of numeric values into strings. Guaranteed to preserve UTF-8 flag even from overloaded objects. Similar in nature to sv_2pv[_flags] but operates directly on an SV instead of just the string. Mostly uses sv_2pv_flags to do its work, except when that would lose the UTF-8'ness of the PV.

              void    sv_copypv(SV* dsv, SV* ssv)

sv_dec
  Auto-decrement of the value in the SV, doing string to numeric conversion if necessary. Handles 'get' magic.

              void    sv_dec(SV* sv)

sv_derived_from
  Returns a boolean indicating whether the SV is derived from the specified class. This is the function that implements `UNIVERSAL::isa`. It works for class names as well as for objects.

              bool    sv_derived_from(SV* sv, const char* name)

sv_eq
  Returns a boolean indicating whether the strings in the two SVs are identical. Is UTF-8 and 'use bytes' aware, handles get magic, and will coerce its args to strings if necessary.

              I32     sv_eq(SV* sv1, SV* sv2)

sv_force_normal
  Undo various types of fakery on an SV: if the PV is a shared string, make a private copy; if we're a ref, stop refing; if we're a glob, downgrade to an xpvmg. See also `sv_force_normal_flags`.

              void    sv_force_normal(SV *sv)

sv_force_normal_flags
  Undo various types of fakery on an SV: if the PV is a shared string, make a private copy; if we're a ref, stop refing; if we're a glob, downgrade to an xpvmg. The `flags` parameter gets passed to `sv_unref_flags()` when unrefing. `sv_force_normal` calls this function with flags set to 0.

              void    sv_force_normal_flags(SV *sv, U32 flags)

sv_free
  Decrement an SV's reference count, and if it drops to zero, call `sv_clear` to invoke destructors and free up any memory used by the body; finally, deallocate the SV's head itself. Normally called via a wrapper macro `SvREFCNT_dec`.

              void    sv_free(SV* sv)

sv_gets
  Get a line from the filehandle and store it into the SV, optionally appending to the currently-stored string.

              char*   sv_gets(SV* sv, PerlIO* fp, I32 append)

sv_grow
  Expands the character buffer in the SV. If necessary, uses `sv_unref` and upgrades the SV to `SVt_PV`. Returns a pointer to the character buffer. Use the `SvGROW` wrapper instead.

              char*   sv_grow(SV* sv, STRLEN newlen)

sv_inc
  Auto-increment of the value in the SV, doing string to numeric conversion if necessary. Handles 'get' magic.

              void    sv_inc(SV* sv)

sv_insert
  Inserts a string at the specified offset/length within the SV. Similar to the Perl `substr()` function.

              void    sv_insert(SV* bigsv, STRLEN offset, STRLEN len, char* little, STRLEN littlelen)

sv_isa
  Returns a boolean indicating whether the SV is blessed into the specified class. This does not check for subtypes; use `sv_derived_from` to verify an inheritance relationship.

              int     sv_isa(SV* sv, const char* name)

sv_isobject
  Returns a boolean indicating whether the SV is an RV pointing to a blessed object. If the SV is not an RV, or if the object is not blessed, then this will return false.

              int     sv_isobject(SV* sv)

sv_iv
  A private implementation of the `SvIVx` macro for compilers which can't cope with complex macro expressions. Always use the macro instead.

              IV      sv_iv(SV* sv)

sv_len
  Returns the length of the string in the SV. Handles magic and type coercion. See also `SvCUR`, which gives raw access to the xpv_cur slot.

              STRLEN  sv_len(SV* sv)

sv_len_utf8
  Returns the number of characters in the string in an SV, counting wide UTF-8 bytes as a single character. Handles magic and type coercion.

              STRLEN  sv_len_utf8(SV* sv)

sv_magic
  Adds magic to an SV. First upgrades `sv` to type `SVt_PVMG` if necessary, then adds a new magic item of type `how` to the head of the magic list.

  See `sv_magicext` (which `sv_magic` now calls) for a description of the handling of the `name` and `namlen` arguments.

              void    sv_magic(SV* sv, SV* obj, int how, const char* name, I32 namlen)

sv_magicext
  Adds magic to an SV, upgrading it if necessary. Applies the supplied vtable and returns a pointer to the magic added.

  Note that `sv_magicext` will allow things that `sv_magic` will not. In particular, you can add magic to SvREADONLY SVs, and add more than one instance of the same 'how'.

  If `namlen` is greater than zero then a `savepvn` copy of `name` is stored, if `namlen` is zero then `name` is stored as-is and - as another special case - if `(name && namlen == HEf_SVKEY)` then `name` is assumed to contain an `SV*` and is stored as-is with its REFCNT incremented.

  (This is now used as a subroutine by `sv_magic`.)

              MAGIC * sv_magicext(SV* sv, SV* obj, int how, MGVTBL *vtbl, const char* name, I32 namlen        )

sv_mortalcopy
  Creates a new SV which is a copy of the original SV (using `sv_setsv`). The new SV is marked as mortal. It will be destroyed ``soon'', either by an explicit call to FREETMPS, or by an implicit call at places such as statement boundaries. See also `sv_newmortal` and `sv_2mortal`.

              SV*     sv_mortalcopy(SV* oldsv)

sv_newmortal
  Creates a new null SV which is mortal. The reference count of the SV is set to 1. It will be destroyed ``soon'', either by an explicit call to FREETMPS, or by an implicit call at places such as statement boundaries. See also `sv_mortalcopy` and `sv_2mortal`.

              SV*     sv_newmortal()

sv_newref
  Increment an SV's reference count. Use the `SvREFCNT_inc()` wrapper instead.

              SV*     sv_newref(SV* sv)

sv_nv
  A private implementation of the `SvNVx` macro for compilers which can't cope with complex macro expressions. Always use the macro instead.

              NV      sv_nv(SV* sv)

sv_pos_b2u
  Converts the value pointed to by offsetp from a count of bytes from the start of the string, to a count of the equivalent number of UTF-8 chars. Handles magic and type coercion.

              void    sv_pos_b2u(SV* sv, I32* offsetp)

sv_pos_u2b
  Converts the value pointed to by offsetp from a count of UTF-8 chars from the start of the string, to a count of the equivalent number of bytes; if lenp is non-zero, it does the same to lenp, but this time starting from the offset, rather than from the start of the string. Handles magic and type coercion.

              void    sv_pos_u2b(SV* sv, I32* offsetp, I32* lenp)

sv_pv
  Use the `SvPV_nolen` macro instead

              char*   sv_pv(SV *sv)

sv_pvbyte
  Use `SvPVbyte_nolen` instead.

              char*   sv_pvbyte(SV *sv)

sv_pvbyten
  A private implementation of the `SvPVbyte` macro for compilers which can't cope with complex macro expressions. Always use the macro instead.

              char*   sv_pvbyten(SV *sv, STRLEN *len)

sv_pvbyten_force
  A private implementation of the `SvPVbytex_force` macro for compilers which can't cope with complex macro expressions. Always use the macro instead.

              char*   sv_pvbyten_force(SV* sv, STRLEN* lp)

sv_pvn
  A private implementation of the `SvPV` macro for compilers which can't cope with complex macro expressions. Always use the macro instead.

              char*   sv_pvn(SV *sv, STRLEN *len)

sv_pvn_force
  Get a sensible string out of the SV somehow. A private implementation of the `SvPV_force` macro for compilers which can't cope with complex macro expressions. Always use the macro instead.

              char*   sv_pvn_force(SV* sv, STRLEN* lp)

sv_pvn_force_flags
  Get a sensible string out of the SV somehow. If `flags` has `SV_GMAGIC` bit set, will `mg_get` on `sv` if appropriate, else not. `sv_pvn_force` and `sv_pvn_force_nomg` are implemented in terms of this function. You normally want to use the various wrapper macros instead: see `SvPV_force` and `SvPV_force_nomg`

              char*   sv_pvn_force_flags(SV* sv, STRLEN* lp, I32 flags)

sv_pvutf8
  Use the `SvPVutf8_nolen` macro instead

              char*   sv_pvutf8(SV *sv)

sv_pvutf8n
  A private implementation of the `SvPVutf8` macro for compilers which can't cope with complex macro expressions. Always use the macro instead.

              char*   sv_pvutf8n(SV *sv, STRLEN *len)

sv_pvutf8n_force
  A private implementation of the `SvPVutf8_force` macro for compilers which can't cope with complex macro expressions. Always use the macro instead.

              char*   sv_pvutf8n_force(SV* sv, STRLEN* lp)

sv_reftype
  Returns a string describing what the SV is a reference to.

              char*   sv_reftype(SV* sv, int ob)

sv_replace
  Make the first argument a copy of the second, then delete the original. The target SV physically takes over ownership of the body of the source SV and inherits its flags; however, the target keeps any magic it owns, and any magic in the source is discarded. Note that this is a rather specialist SV copying operation; most of the time you'll want to use `sv_setsv` or one of its many macro front-ends.

              void    sv_replace(SV* sv, SV* nsv)

sv_report_used
  Dump the contents of all SVs not yet freed. (Debugging aid).

              void    sv_report_used()

sv_reset
  Underlying implementation for the `reset` Perl function. Note that the perl-level function is vaguely deprecated.

              void    sv_reset(char* s, HV* stash)

sv_rvweaken
  Weaken a reference: set the `SvWEAKREF` flag on this RV; give the referred-to SV `PERL_MAGIC_backref` magic if it hasn't already; and push a back-reference to this RV onto the array of backreferences associated with that magic.

              SV*     sv_rvweaken(SV *sv)

sv_setiv
  Copies an integer into the given SV, upgrading first if necessary. Does not handle 'set' magic. See also `sv_setiv_mg`.

              void    sv_setiv(SV* sv, IV num)

sv_setiv_mg
  Like `sv_setiv`, but also handles 'set' magic.

              void    sv_setiv_mg(SV *sv, IV i)

sv_setnv
  Copies a double into the given SV, upgrading first if necessary. Does not handle 'set' magic. See also `sv_setnv_mg`.

              void    sv_setnv(SV* sv, NV num)

sv_setnv_mg
  Like `sv_setnv`, but also handles 'set' magic.

              void    sv_setnv_mg(SV *sv, NV num)

sv_setpv
  Copies a string into an SV. The string must be null-terminated. Does not handle 'set' magic. See `sv_setpv_mg`.

              void    sv_setpv(SV* sv, const char* ptr)

sv_setpvf
  Works like `sv_catpvf` but copies the text into the SV instead of appending it. Does not handle 'set' magic. See `sv_setpvf_mg`.

              void    sv_setpvf(SV* sv, const char* pat, ...)

sv_setpvf_mg
  Like `sv_setpvf`, but also handles 'set' magic.

              void    sv_setpvf_mg(SV *sv, const char* pat, ...)

sv_setpviv
  Copies an integer into the given SV, also updating its string value. Does not handle 'set' magic. See `sv_setpviv_mg`.

              void    sv_setpviv(SV* sv, IV num)

sv_setpviv_mg
  Like `sv_setpviv`, but also handles 'set' magic.

              void    sv_setpviv_mg(SV *sv, IV iv)

sv_setpvn
  Copies a string into an SV. The `len` parameter indicates the number of bytes to be copied. If the `ptr` argument is NULL the SV will become undefined. Does not handle 'set' magic. See `sv_setpvn_mg`.

              void    sv_setpvn(SV* sv, const char* ptr, STRLEN len)

sv_setpvn_mg
  Like `sv_setpvn`, but also handles 'set' magic.

              void    sv_setpvn_mg(SV *sv, const char *ptr, STRLEN len)

sv_setpv_mg
  Like `sv_setpv`, but also handles 'set' magic.

              void    sv_setpv_mg(SV *sv, const char *ptr)

sv_setref_iv
  Copies an integer into a new SV, optionally blessing the SV. The `rv` argument will be upgraded to an RV. That RV will be modified to point to the new SV. The `classname` argument indicates the package for the blessing. Set `classname` to `Nullch` to avoid the blessing. The new SV will have a reference count of 1, and the RV will be returned.

              SV*     sv_setref_iv(SV* rv, const char* classname, IV iv)

sv_setref_nv
  Copies a double into a new SV, optionally blessing the SV. The `rv` argument will be upgraded to an RV. That RV will be modified to point to the new SV. The `classname` argument indicates the package for the blessing. Set `classname` to `Nullch` to avoid the blessing. The new SV will have a reference count of 1, and the RV will be returned.

              SV*     sv_setref_nv(SV* rv, const char* classname, NV nv)

sv_setref_pv
  Copies a pointer into a new SV, optionally blessing the SV. The `rv` argument will be upgraded to an RV. That RV will be modified to point to the new SV. If the `pv` argument is NULL then `PL_sv_undef` will be placed into the SV. The `classname` argument indicates the package for the blessing. Set `classname` to `Nullch` to avoid the blessing. The new SV will have a reference count of 1, and the RV will be returned.

  Do not use with other Perl types such as HV, AV, SV, CV, because those objects will become corrupted by the pointer copy process.

  Note that `sv_setref_pvn` copies the string while this copies the pointer.

              SV*     sv_setref_pv(SV* rv, const char* classname, void* pv)

sv_setref_pvn
  Copies a string into a new SV, optionally blessing the SV. The length of the string must be specified with `n`. The `rv` argument will be upgraded to an RV. That RV will be modified to point to the new SV. The `classname` argument indicates the package for the blessing. Set `classname` to `Nullch` to avoid the blessing. The new SV will have a reference count of 1, and the RV will be returned.

  Note that `sv_setref_pv` copies the pointer while this copies the string.

              SV*     sv_setref_pvn(SV* rv, const char* classname, char* pv, STRLEN n)

sv_setref_uv
  Copies an unsigned integer into a new SV, optionally blessing the SV. The `rv` argument will be upgraded to an RV. That RV will be modified to point to the new SV. The `classname` argument indicates the package for the blessing. Set `classname` to `Nullch` to avoid the blessing. The new SV will have a reference count of 1, and the RV will be returned.

              SV*     sv_setref_uv(SV* rv, const char* classname, UV uv)

sv_setsv
  Copies the contents of the source SV `ssv` into the destination SV `dsv`. The source SV may be destroyed if it is mortal, so don't use this function if the source SV needs to be reused. Does not handle 'set' magic. Loosely speaking, it performs a copy-by-value, obliterating any previous content of the destination.

  You probably want to use one of the assortment of wrappers, such as `SvSetSV`, `SvSetSV_nosteal`, `SvSetMagicSV` and `SvSetMagicSV_nosteal`.

              void    sv_setsv(SV* dsv, SV* ssv)

sv_setsv_flags
  Copies the contents of the source SV `ssv` into the destination SV `dsv`. The source SV may be destroyed if it is mortal, so don't use this function if the source SV needs to be reused. Does not handle 'set' magic. Loosely speaking, it performs a copy-by-value, obliterating any previous content of the destination. If the `flags` parameter has the `SV_GMAGIC` bit set, will `mg_get` on `ssv` if appropriate, else not. If the `flags` parameter has the `NOSTEAL` bit set then the buffers of temps will not be stolen. <sv_setsv> and `sv_setsv_nomg` are implemented in terms of this function.

  You probably want to use one of the assortment of wrappers, such as `SvSetSV`, `SvSetSV_nosteal`, `SvSetMagicSV` and `SvSetMagicSV_nosteal`.

  This is the primary function for copying scalars, and most other copy-ish functions and macros use this underneath.

              void    sv_setsv_flags(SV* dsv, SV* ssv, I32 flags)

sv_setsv_mg
  Like `sv_setsv`, but also handles 'set' magic.

              void    sv_setsv_mg(SV *dstr, SV *sstr)

sv_setsv_nomg
  Like `sv_setsv` but doesn't process magic.

              void    sv_setsv_nomg(SV* dsv, SV* ssv)

sv_setuv
  Copies an unsigned integer into the given SV, upgrading first if necessary. Does not handle 'set' magic. See also `sv_setuv_mg`.

              void    sv_setuv(SV* sv, UV num)

sv_setuv_mg
  Like `sv_setuv`, but also handles 'set' magic.

              void    sv_setuv_mg(SV *sv, UV u)

sv_taint

  Taint an SV. Use `SvTAINTED_on` instead.
  | void | sv_taint(SV* sv)

sv_tainted

  Test an SV for taintedness. Use `SvTAINTED` instead.
  | bool | sv_tainted(SV* sv)

sv_true
  Returns true if the SV has a true value by Perl's rules. Use the `SvTRUE` macro instead, which may call `sv_true()` or may instead use an in-line version.

              I32     sv_true(SV *sv)

sv_unmagic
  Removes all magic of type `type` from an SV.

              int     sv_unmagic(SV* sv, int type)

sv_unref
  Unsets the RV status of the SV, and decrements the reference count of whatever was being referenced by the RV. This can almost be thought of as a reversal of `newSVrv`. This is `sv_unref_flags` with the `flag` being zero. See `SvROK_off`.

              void    sv_unref(SV* sv)

sv_unref_flags
  Unsets the RV status of the SV, and decrements the reference count of whatever was being referenced by the RV. This can almost be thought of as a reversal of `newSVrv`. The `cflags` argument can contain `SV_IMMEDIATE_UNREF` to force the reference count to be decremented (otherwise the decrementing is conditional on the reference count being different from one or the reference being a readonly SV). See `SvROK_off`.

              void    sv_unref_flags(SV* sv, U32 flags)

sv_untaint

  Untaint an SV. Use `SvTAINTED_off` instead.
  | void | sv_untaint(SV* sv)

sv_upgrade
  Upgrade an SV to a more complex form. Generally adds a new body type to the SV, then copies across as much information as possible from the old body. You generally want to use the `SvUPGRADE` macro wrapper. See also `svtype`.

              bool    sv_upgrade(SV* sv, U32 mt)

sv_usepvn
  Tells an SV to use `ptr` to find its string value. Normally the string is stored inside the SV but sv_usepvn allows the SV to use an outside string. The `ptr` should point to memory that was allocated by `malloc`. The string length, `len`, must be supplied. This function will realloc the memory pointed to by `ptr`, so that pointer should not be freed or used by the programmer after giving it to sv_usepvn. Does not handle 'set' magic. See `sv_usepvn_mg`.

              void    sv_usepvn(SV* sv, char* ptr, STRLEN len)

sv_usepvn_mg
  Like `sv_usepvn`, but also handles 'set' magic.

              void    sv_usepvn_mg(SV *sv, char *ptr, STRLEN len)

sv_utf8_decode
  If the PV of the SV is an octet sequence in UTF-8 and contains a multiple-byte character, the `SvUTF8` flag is turned on so that it looks like a character. If the PV contains only single-byte characters, the `SvUTF8` flag stays being off. Scans PV for validity and returns false if the PV is invalid UTF-8.

  NOTE: this function is experimental and may change or be removed without notice.

              bool    sv_utf8_decode(SV *sv)

sv_utf8_downgrade
  Attempts to convert the PV of an SV from characters to bytes. If the PV contains a character beyond byte, this conversion will fail; in this case, either returns false or, if `fail_ok` is not true, croaks.

  This is not as a general purpose Unicode to byte encoding interface: use the Encode extension for that.

  NOTE: this function is experimental and may change or be removed without notice.

              bool    sv_utf8_downgrade(SV *sv, bool fail_ok)

sv_utf8_encode
  Converts the PV of an SV to UTF-8, but then turns the `SvUTF8` flag off so that it looks like octets again.

              void    sv_utf8_encode(SV *sv)

sv_utf8_upgrade
  Converts the PV of an SV to its UTF-8-encoded form. Forces the SV to string form if it is not already. Always sets the SvUTF8 flag to avoid future validity checks even if all the bytes have hibit clear.

  This is not as a general purpose byte encoding to Unicode interface: use the Encode extension for that.

              STRLEN  sv_utf8_upgrade(SV *sv)

sv_utf8_upgrade_flags
  Converts the PV of an SV to its UTF-8-encoded form. Forces the SV to string form if it is not already. Always sets the SvUTF8 flag to avoid future validity checks even if all the bytes have hibit clear. If `flags` has `SV_GMAGIC` bit set, will `mg_get` on `sv` if appropriate, else not. `sv_utf8_upgrade` and `sv_utf8_upgrade_nomg` are implemented in terms of this function.

  This is not as a general purpose byte encoding to Unicode interface: use the Encode extension for that.

              STRLEN  sv_utf8_upgrade_flags(SV *sv, I32 flags)

sv_uv
  A private implementation of the `SvUVx` macro for compilers which can't cope with complex macro expressions. Always use the macro instead.

              UV      sv_uv(SV* sv)

sv_vcatpvf
  Processes its arguments like `vsprintf` and appends the formatted output to an SV. Does not handle 'set' magic. See `sv_vcatpvf_mg`.

  Usually used via its frontend `sv_catpvf`.

              void    sv_vcatpvf(SV* sv, const char* pat, va_list* args)

sv_vcatpvfn
  Processes its arguments like `vsprintf` and appends the formatted output to an SV. Uses an array of SVs if the C style variable argument list is missing (NULL). When running with taint checks enabled, indicates via `maybe_tainted` if results are untrustworthy (often due to the use of locales).

  Usually used via one of its frontends `sv_vcatpvf` and `sv_vcatpvf_mg`.

              void    sv_vcatpvfn(SV* sv, const char* pat, STRLEN patlen, va_list* args, SV** svargs, I32 svmax, bool *maybe_tainted)

sv_vcatpvf_mg
  Like `sv_vcatpvf`, but also handles 'set' magic.

  Usually used via its frontend `sv_catpvf_mg`.

              void    sv_vcatpvf_mg(SV* sv, const char* pat, va_list* args)

sv_vsetpvf
  Works like `sv_vcatpvf` but copies the text into the SV instead of appending it. Does not handle 'set' magic. See `sv_vsetpvf_mg`.

  Usually used via its frontend `sv_setpvf`.

              void    sv_vsetpvf(SV* sv, const char* pat, va_list* args)

sv_vsetpvfn
  Works like `sv_vcatpvfn` but copies the text into the SV instead of appending it.

  Usually used via one of its frontends `sv_vsetpvf` and `sv_vsetpvf_mg`.

              void    sv_vsetpvfn(SV* sv, const char* pat, STRLEN patlen, va_list* args, SV** svargs, I32 svmax, bool *maybe_tainted)

sv_vsetpvf_mg
  Like `sv_vsetpvf`, but also handles 'set' magic.

  Usually used via its frontend `sv_setpvf_mg`.

              void    sv_vsetpvf_mg(SV* sv, const char* pat, va_list* args)

# Unicode Support

bytes_from_utf8
  Converts a string `s` of length `len` from UTF-8 into byte encoding. Unlike <utf8_to_bytes> but like `bytes_to_utf8`, returns a pointer to the newly-created string, and updates `len` to contain the new length. Returns the original string if no conversion occurs, `len` is unchanged. Do nothing if `is_utf8` points to 0. Sets `is_utf8` to 0 if `s` is converted or contains all 7bit characters.

  NOTE: this function is experimental and may change or be removed without notice.

              U8*     bytes_from_utf8(U8 *s, STRLEN *len, bool *is_utf8)

bytes_to_utf8
  Converts a string `s` of length `len` from ASCII into UTF-8 encoding. Returns a pointer to the newly-created string, and sets `len` to reflect the new length.

  If you want to convert to UTF-8 from other encodings than ASCII, see sv_recode_to_utf8().

  NOTE: this function is experimental and may change or be removed without notice.

              U8*     bytes_to_utf8(U8 *s, STRLEN *len)

ibcmp_utf8
  Return true if the strings s1 and s2 differ case-insensitively, false if not (if they are equal case-insensitively). If u1 is true, the string s1 is assumed to be in UTF-8-encoded Unicode. If u2 is true, the string s2 is assumed to be in UTF-8-encoded Unicode. If u1 or u2 are false, the respective string is assumed to be in native 8-bit encoding.

  If the pe1 and pe2 are non-NULL, the scanning pointers will be copied in there (they will point at the beginning of the next character). If the pointers behind pe1 or pe2 are non-NULL, they are the end pointers beyond which scanning will not continue under any circumstances. If the byte lengths l1 and l2 are non-zero, s1+l1 and s2+l2 will be used as goal end pointers that will also stop the scan, and which qualify towards defining a successful match: all the scans that define an explicit length must reach their goal pointers for a match to succeed).

  For case-insensitiveness, the ``casefolding'' of Unicode is used instead of upper/lowercasing both the characters, see http://www.unicode.org/unicode/reports/tr21/ (Case Mappings).

              I32     ibcmp_utf8(const char* a, char **pe1, UV l1, bool u1, const char* b, char **pe2, UV l2, bool u2)

is_utf8_char
  Tests if some arbitrary number of bytes begins in a valid UTF-8 character. Note that an INVARIANT (i.e. ASCII) character is a valid UTF-8 character. The actual number of bytes in the UTF-8 character will be returned if it is valid, otherwise 0.

              STRLEN  is_utf8_char(U8 *p)

is_utf8_string
  Returns true if first `len` bytes of the given string form a valid UTF-8 string, false otherwise. Note that 'a valid UTF-8 string' does not mean 'a string that contains code points above 0x7F encoded in UTF-8' because a valid ASCII string is a valid UTF-8 string.

              bool    is_utf8_string(U8 *s, STRLEN len)

is_utf8_string_loc
  Like is_ut8_string but store the location of the failure in the last argument.

              bool    is_utf8_string_loc(U8 *s, STRLEN len, U8 **p)

pv_uni_display
  Build to the scalar dsv a displayable version of the string spv, length len, the displayable version being at most pvlim bytes long (if longer, the rest is truncated and ``...'' will be appended).

  The flags argument can have UNI_DISPLAY_ISPRINT set to display isPRINT()able characters as themselves, UNI_DISPLAY_BACKSLASH to display the \\[nrfta\\] as the backslashed versions (like '\n') (UNI_DISPLAY_BACKSLASH is preferred over UNI_DISPLAY_ISPRINT for \\). UNI_DISPLAY_QQ (and its alias UNI_DISPLAY_REGEX) have both UNI_DISPLAY_BACKSLASH and UNI_DISPLAY_ISPRINT turned on.

  The pointer to the PV of the dsv is returned.

              char*   pv_uni_display(SV *dsv, U8 *spv, STRLEN len, STRLEN pvlim, UV flags)

sv_cat_decode
  The encoding is assumed to be an Encode object, the PV of the ssv is assumed to be octets in that encoding and decoding the input starts from the position which (PV + *offset) pointed to. The dsv will be concatenated the decoded UTF-8 string from ssv. Decoding will terminate when the string tstr appears in decoding output or the input ends on the PV of the ssv. The value which the offset points will be modified to the last input position on the ssv.

  Returns TRUE if the terminator was found, else returns FALSE.

              bool    sv_cat_decode(SV* dsv, SV *encoding, SV *ssv, int *offset, char* tstr, int tlen)

sv_recode_to_utf8
  The encoding is assumed to be an Encode object, on entry the PV of the sv is assumed to be octets in that encoding, and the sv will be converted into Unicode (and UTF-8).

  If the sv already is UTF-8 (or if it is not POK), or if the encoding is not a reference, nothing is done to the sv. If the encoding is not an `Encode::XS` Encoding object, bad things will happen. (See lib/encoding.pm and the Encode manpage).

  The PV of the sv is returned.

              char*   sv_recode_to_utf8(SV* sv, SV *encoding)

sv_uni_display
  Build to the scalar dsv a displayable version of the scalar sv, the displayable version being at most pvlim bytes long (if longer, the rest is truncated and ``...'' will be appended).

  The flags argument is as in pv_uni_display().

  The pointer to the PV of the dsv is returned.

              char*   sv_uni_display(SV *dsv, SV *ssv, STRLEN pvlim, UV flags)

to_utf8_case
  The ``p'' contains the pointer to the UTF-8 string encoding the character that is being converted.

  The ``ustrp'' is a pointer to the character buffer to put the conversion result to. The ``lenp'' is a pointer to the length of the result.

  The ``swashp'' is a pointer to the swash to use.

  Both the special and normal mappings are stored lib/unicore/To/Foo.pl, and loaded by SWASHGET, using lib/utf8_heavy.pl. The special (usually, but not always, a multicharacter mapping), is tried first.

  The ``special'' is a string like ``utf8::ToSpecLower'', which means the hash %utf8::ToSpecLower. The access to the hash is through Perl_to_utf8_case().

  The ``normal'' is a string like ``ToLower'' which means the swash %utf8::ToLower.

              UV      to_utf8_case(U8 *p, U8* ustrp, STRLEN *lenp, SV **swash, char *normal, char *special)

to_utf8_fold
  Convert the UTF-8 encoded character at p to its foldcase version and store that in UTF-8 in ustrp and its length in bytes in lenp. Note that the ustrp needs to be at least UTF8_MAXLEN_FOLD+1 bytes since the foldcase version may be longer than the original character (up to three characters).

  The first character of the foldcased version is returned (but note, as explained above, that there may be more.)

              UV      to_utf8_fold(U8 *p, U8* ustrp, STRLEN *lenp)

to_utf8_lower
  Convert the UTF-8 encoded character at p to its lowercase version and store that in UTF-8 in ustrp and its length in bytes in lenp. Note that the ustrp needs to be at least UTF8_MAXLEN_UCLC+1 bytes since the lowercase version may be longer than the original character (up to two characters).

  The first character of the lowercased version is returned (but note, as explained above, that there may be more.)

              UV      to_utf8_lower(U8 *p, U8* ustrp, STRLEN *lenp)

to_utf8_title
  Convert the UTF-8 encoded character at p to its titlecase version and store that in UTF-8 in ustrp and its length in bytes in lenp. Note that the ustrp needs to be at least UTF8_MAXLEN_UCLC+1 bytes since the titlecase version may be longer than the original character (up to two characters).

  The first character of the titlecased version is returned (but note, as explained above, that there may be more.)

              UV      to_utf8_title(U8 *p, U8* ustrp, STRLEN *lenp)

to_utf8_upper
  Convert the UTF-8 encoded character at p to its uppercase version and store that in UTF-8 in ustrp and its length in bytes in lenp. Note that the ustrp needs to be at least UTF8_MAXLEN_UCLC+1 bytes since the uppercase version may be longer than the original character (up to two characters).

  The first character of the uppercased version is returned (but note, as explained above, that there may be more.)

              UV      to_utf8_upper(U8 *p, U8* ustrp, STRLEN *lenp)

utf8n_to_uvchr
  Returns the native character value of the first character in the string `s` which is assumed to be in UTF-8 encoding; `retlen` will be set to the length, in bytes, of that character.

  Allows length and flags to be passed to low level routine.

              UV      utf8n_to_uvchr(U8 *s, STRLEN curlen, STRLEN* retlen, U32 flags)

utf8n_to_uvuni
  Bottom level UTF-8 decode routine. Returns the unicode code point value of the first character in the string `s` which is assumed to be in UTF-8 encoding and no longer than `curlen`; `retlen` will be set to the length, in bytes, of that character.

  If `s` does not point to a well-formed UTF-8 character, the behaviour is dependent on the value of `flags`: if it contains UTF8_CHECK_ONLY, it is assumed that the caller will raise a warning, and this function will silently just set `retlen` to `-1` and return zero. If the `flags` does not contain UTF8_CHECK_ONLY, warnings about malformations will be given, `retlen` will be set to the expected length of the UTF-8 character in bytes, and zero will be returned.

  The `flags` can also contain various flags to allow deviations from the strict UTF-8 encoding (see utf8.h).

  Most code should use `utf8_to_uvchr()` rather than call this directly.

              UV      utf8n_to_uvuni(U8 *s, STRLEN curlen, STRLEN* retlen, U32 flags)

utf8_distance
  Returns the number of UTF-8 characters between the UTF-8 pointers `a` and `b`.

  WARNING: use only if you *know* that the pointers point inside the same UTF-8 buffer.

              IV      utf8_distance(U8 *a, U8 *b)

utf8_hop
  Return the UTF-8 pointer `s` displaced by `off` characters, either forward or backward.

  WARNING: do not use the following unless you *know* `off` is within the UTF-8 data pointed to by `s` *and* that on entry `s` is aligned on the first byte of character or just after the last byte of a character.

              U8*     utf8_hop(U8 *s, I32 off)

utf8_length
  Return the length of the UTF-8 char encoded string `s` in characters. Stops at `e` (inclusive). If `e < s` or if the scan would end up past `e`, croaks.

              STRLEN  utf8_length(U8* s, U8 *e)

utf8_to_bytes
  Converts a string `s` of length `len` from UTF-8 into byte encoding. Unlike `bytes_to_utf8`, this over-writes the original string, and updates len to contain the new length. Returns zero on failure, setting `len` to -1.

  NOTE: this function is experimental and may change or be removed without notice.

              U8*     utf8_to_bytes(U8 *s, STRLEN *len)

utf8_to_uvchr
  Returns the native character value of the first character in the string `s` which is assumed to be in UTF-8 encoding; `retlen` will be set to the length, in bytes, of that character.

  If `s` does not point to a well-formed UTF-8 character, zero is returned and retlen is set, if possible, to -1.

              UV      utf8_to_uvchr(U8 *s, STRLEN* retlen)

utf8_to_uvuni
  Returns the Unicode code point of the first character in the string `s` which is assumed to be in UTF-8 encoding; `retlen` will be set to the length, in bytes, of that character.

  This function should only be used when returned UV is considered an index into the Unicode semantic tables (e.g. swashes).

  If `s` does not point to a well-formed UTF-8 character, zero is returned and retlen is set, if possible, to -1.

              UV      utf8_to_uvuni(U8 *s, STRLEN* retlen)

uvchr_to_utf8
  Adds the UTF-8 representation of the Native codepoint `uv` to the end of the string `d`; `d` should be have at least `UTF8_MAXLEN+1` free bytes available. The return value is the pointer to the byte after the end of the new character. In other words,

          d = uvchr_to_utf8(d, uv);

  is the recommended wide native character-aware way of saying

          *(d++) = uv;

              U8*     uvchr_to_utf8(U8 *d, UV uv)

uvuni_to_utf8_flags
  Adds the UTF-8 representation of the Unicode codepoint `uv` to the end of the string `d`; `d` should be have at least `UTF8_MAXLEN+1` free bytes available. The return value is the pointer to the byte after the end of the new character. In other words,

          d = uvuni_to_utf8_flags(d, uv, flags);

  or, in most cases,

          d = uvuni_to_utf8(d, uv);

  (which is equivalent to)

          d = uvuni_to_utf8_flags(d, uv, 0);

  is the recommended Unicode-aware way of saying

          *(d++) = uv;

              U8*     uvuni_to_utf8_flags(U8 *d, UV uv, UV flags)

# Variables created by `xsubpp` and `xsubpp` internal functions

ax
  Variable which is setup by `xsubpp` to indicate the stack base offset, used by the `ST`, `XSprePUSH` and `XSRETURN` macros. The `dMARK` macro must be called prior to setup the `MARK` variable.

              I32     ax

CLASS
  Variable which is setup by `xsubpp` to indicate the class name for a C++ XS constructor. This is always a `char*`. See `THIS`.

              char*   CLASS

dAX
  Sets up the `ax` variable. This is usually handled automatically by `xsubpp` by calling `dXSARGS`.

                      dAX;

dITEMS
  Sets up the `items` variable. This is usually handled automatically by `xsubpp` by calling `dXSARGS`.

                      dITEMS;

dXSARGS
  Sets up stack and mark pointers for an XSUB, calling dSP and dMARK. Sets up the `ax` and `items` variables by calling `dAX` and `dITEMS`. This is usually handled automatically by `xsubpp`.

                      dXSARGS;

dXSI32
  Sets up the `ix` variable for an XSUB which has aliases. This is usually handled automatically by `xsubpp`.

                      dXSI32;

items
  Variable which is setup by `xsubpp` to indicate the number of items on the stack. See Variable-length Parameter Lists in the perlxs manpage.

              I32     items

ix
  Variable which is setup by `xsubpp` to indicate which of an XSUB's aliases was used to invoke it. See The ALIAS: Keyword in the perlxs manpage.

              I32     ix

newXSproto
  Used by `xsubpp` to hook up XSUBs as Perl subs. Adds Perl prototypes to the subs.

RETVAL
  Variable which is setup by `xsubpp` to hold the return value for an XSUB. This is always the proper type for the XSUB. See The RETVAL Variable in the perlxs manpage.

              (whatever)      RETVAL

ST
  Used to access elements on the XSUB's stack.

              SV*     ST(int ix)

THIS
  Variable which is setup by `xsubpp` to designate the object in a C++ XSUB. This is always the proper type for the C++ object. See `CLASS` and Using XS With C++ in the perlxs manpage.

              (whatever)      THIS

XS
  Macro to declare an XSUB and its C parameter list. This is handled by `xsubpp`.

XS_VERSION
  The version identifier for an XS module. This is usually handled automatically by `ExtUtils::MakeMaker`. See `XS_VERSION_BOOTCHECK`.

XS_VERSION_BOOTCHECK
  Macro to verify that a PM module's $VERSION variable matches the XS module's `XS_VERSION` variable. This is usually handled automatically by `xsubpp`. See The VERSIONCHECK: Keyword in the perlxs manpage.

                      XS_VERSION_BOOTCHECK;

# Warning and Dieing

croak
  This is the XSUB-writer's interface to Perl's `die` function. Normally call this function the same way you call the C `printf` function. Calling `croak` returns control directly to Perl, sidestepping the normal C order of execution. See `warn`.

  If you want to throw an exception object, assign the object to `$@` and then pass `Nullch` to croak():

         errsv = get_sv("@", TRUE);
         sv_setsv(errsv, exception_object);
         croak(Nullch);

              void    croak(const char* pat, ...)

warn
  This is the XSUB-writer's interface to Perl's `warn` function. Call this function the same way you call the C `printf` function. See `croak`.

              void    warn(const char* pat, ...)

# AUTHORS

Until May 1997, this document was maintained by Jeff Okamoto <okamoto@corp.hp.com>. It is now maintained as part of Perl itself.

With lots of help and suggestions from Dean Roehrich, Malcolm Beattie, Andreas Koenig, Paul Hudson, Ilya Zakharevich, Paul Marquess, Neil Bowers, Matthew Green, Tim Bunce, Spider Boardman, Ulrich Pfeifer, Stephen McCamant, and Gurusamy Sarathy.

API Listing originally by Dean Roehrich <roehrich@cray.com>.

Updated to be autogenerated from comments in the source by Benjamin Stuhl.

# SEE ALSO

perlguts(1), perlxs(1), perlxstut(1), `perlintern(1)`

perlapi - autogenerated documentation for the perl public API