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ExtUtils::Constant - generate XS code to import C header constants
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
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.
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 and
XS_constant, with which WriteConstants 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.
signed integer, at least 32 bits.
unsigned integer, the same size as IV
floating point type, probably double, possibly long double
NUL terminated string, length will be determined with strlen
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
A mortal SV.
Truth. (PL_sv_yes) The value is not needed (and ignored).
Defined Falsehood. (PL_sv_no) The value is not needed (and ignored).
undef. The value of the macro is not needed.
A function returning a single scalar with #define definitions for the
constants used internally between the generated C and XS functions.
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 named constant.
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 as C_constant was given.
[Otherwise XS_constant and C_constant may have different ideas about
the number of parameters passed to the C function constant]
You can call the perl visible subroutine something other than constant if
you give the parameter SUBNAME. The C subroutine it calls defaults to
the name of the perl visible subroutine, unless you give the parameter
C_SUBNAME.
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 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 of INDENT to specify the number of leading spaces
(default 2).
Currently only INDENT, NAME, DEFAULT_TYPE, NAMES, C_FILE and
XS_FILE are recognised.
Writes a file of C code and a file of XS code which you should #include
and INCLUDE in the C and XS sections respectively of your module's XS
code. You probably want to do this in your Makefile.PL, so that you can
easily edit the list of constants without touching the rest of your module.
The attributes supported are
Name of the module. This must be specified
The default type for the constants. If not specified IV is assumed.
The names of the constants are grouped by length. Generate child subroutines for each group with this number or more names in.
An array of constants' names, either scalars containing names, or hashrefs as detailed in C_constant.
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.
The name of the file to write containing the XS code. The default is
const-xs.inc.
The perl visible name of the XS subroutine generated which will return the
constants. The default is constant.
The name of the C subroutine generated which will return the constants.
The default is SUBNAME. Child subroutines have _ and the name
length appended, so constants with 10 character names would be in
constant_10 with the default XS_SUBNAME.
Nicholas Clark <nick@ccl4.org> based on the code in h2xs by Larry Wall and
others