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
in the C section of
in the XS section of
For greater flexibility use
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
NUL terminated string, length will be determined with
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.
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
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
C_constant may have different ideas about the number of parameters passed to the C function
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).
XS_FILE are recognised.
Writes a file of C code and a file of XS code which you should
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".
A filehandle to write the C code to. If not given, then C_FILE is opened for writing.
The name of the file to write containing the C code. The default is
- 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
A filehandle to write the XS code to. If not given, then XS_FILE is opened for writing.
The name of the file to write containing the XS code. The default is
The perl visible name of the XS subroutine generated which will return the constants. The default is
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 <firstname.lastname@example.org> based on the code in
h2xs by Larry Wall and others