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18 Apr 2018 06:11:57 UTC
- Distribution: ExtUtils-Constant
- Module version: 0.25
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NAME
ExtUtils::Constant - generate XS code to import C header constants
SYNOPSIS
use ExtUtils::Constant qw (WriteConstants); WriteConstants( NAME => 'Foo', NAMES => [qw(FOO BAR BAZ)], ); # Generates wrapper code to make the values of the constants FOO BAR BAZ # available to perl
DESCRIPTION
ExtUtils::Constant facilitates generating C and XS wrapper code to allow perl modules to AUTOLOAD constants defined in C library header files. It is principally used by the
h2xs
utility, on which this code is based. It doesn't contain the routines to scan header files to extract these constants.USAGE
Generally one only needs to call the
WriteConstants
function, and then#include "const-c.inc"
in the C section of
Foo.xs
INCLUDE: const-xs.inc
in the XS section of
Foo.xs
.For greater flexibility use
constant_types()
,C_constant
andXS_constant
, with whichWriteConstants
is implemented.Currently this module understands the following types. h2xs may only know a subset. The sizes of the numeric types are chosen by the
Configure
script at compile time.- IV
-
signed integer, at least 32 bits.
- UV
-
unsigned integer, the same size as IV
- NV
-
floating point type, probably
double
, possiblylong double
- PV
-
NUL terminated string, length will be determined with
strlen
- PVN
-
A fixed length thing, given as a [pointer, length] pair. If you know the length of a string at compile time you may use this instead of PV
- SV
-
A mortal SV.
- YES
-
Truth. (
PL_sv_yes
) The value is not needed (and ignored). - NO
-
Defined Falsehood. (
PL_sv_no
) The value is not needed (and ignored). - UNDEF
-
undef
. The value of the macro is not needed.
FUNCTIONS
- constant_types
-
A function returning a single scalar with
#define
definitions for the constants used internally between the generated C and XS functions. - XS_constant PACKAGE, TYPES, XS_SUBNAME, C_SUBNAME
-
A function to generate the XS code to implement the perl subroutine PACKAGE::constant used by PACKAGE::AUTOLOAD to load constants. This XS code is a wrapper around a C subroutine usually generated by
C_constant
, and usually namedconstant
.TYPES should be given either as a comma separated list of types that the C subroutine
constant
will generate or as a reference to a hash. It should be the same list of types asC_constant
was given. [OtherwiseXS_constant
andC_constant
may have different ideas about the number of parameters passed to the C functionconstant
]You can call the perl visible subroutine something other than
constant
if you give the parameter XS_SUBNAME. The C subroutine it calls defaults to the name of the perl visible subroutine, unless you give the parameter C_SUBNAME. - autoload PACKAGE, VERSION, AUTOLOADER
-
A function to generate the AUTOLOAD subroutine for the module PACKAGE VERSION is the perl version the code should be backwards compatible with. It defaults to the version of perl running the subroutine. If AUTOLOADER is true, the AUTOLOAD subroutine falls back on AutoLoader::AUTOLOAD for all names that the constant() routine doesn't recognise.
- WriteMakefileSnippet
-
WriteMakefileSnippet ATTRIBUTE => VALUE [, ...]
A function to generate perl code for Makefile.PL that will regenerate the constant subroutines. Parameters are named as passed to
WriteConstants
, with the addition ofINDENT
to specify the number of leading spaces (default 2).Currently only
INDENT
,NAME
,DEFAULT_TYPE
,NAMES
,C_FILE
andXS_FILE
are recognised. - WriteConstants ATTRIBUTE => VALUE [, ...]
-
Writes a file of C code and a file of XS code which you should
#include
andINCLUDE
in the C and XS sections respectively of your module's XS code. You probably want to do this in yourMakefile.PL
, so that you can easily edit the list of constants without touching the rest of your module. The attributes supported are- NAME
-
Name of the module. This must be specified
- DEFAULT_TYPE
-
The default type for the constants. If not specified
IV
is assumed. - BREAKOUT_AT
-
The names of the constants are grouped by length. Generate child subroutines for each group with this number or more names in.
- NAMES
-
An array of constants' names, either scalars containing names, or hashrefs as detailed in "C_constant".
- PROXYSUBS
-
If true, uses proxy subs. See ExtUtils::Constant::ProxySubs.
- C_FH
-
A filehandle to write the C code to. If not given, then C_FILE is opened for writing.
- C_FILE
-
The name of the file to write containing the C code. The default is
const-c.inc
. The-
in the name ensures that the file can't be mistaken for anything related to a legitimate perl package name, and not naming the file.c
avoids having to override Makefile.PL's.xs
to.c
rules. - XS_FH
-
A filehandle to write the XS code to. If not given, then XS_FILE is opened for writing.
- XS_FILE
-
The name of the file to write containing the XS code. The default is
const-xs.inc
. - XS_SUBNAME
-
The perl visible name of the XS subroutine generated which will return the constants. The default is
constant
. - C_SUBNAME
-
The name of the C subroutine generated which will return the constants. The default is XS_SUBNAME. Child subroutines have
_
and the name length appended, so constants with 10 character names would be inconstant_10
with the default XS_SUBNAME.
AUTHOR
Nicholas Clark <nick@ccl4.org> based on the code in
h2xs
by Larry Wall and othersModule Install Instructions
To install ExtUtils::Constant, copy and paste the appropriate command in to your terminal.
cpanm ExtUtils::Constant
perl -MCPAN -e shell install ExtUtils::Constant
For more information on module installation, please visit the detailed CPAN module installation guide.