ExtUtils::ConstanPerl)Programmers ReferenceExtUtils::Constant(3p)NAMEExtUtils::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
DESCRIPTIONExtUtils::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" func-
tion, 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 imple-
mented.
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", possibly "long
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
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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, 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 usu-
ally 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.
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 [, ...]
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A function to generate perl code for Makefile.PL that
will regenerate the constant subroutines. Parameters
are named as passed to "WriteConstants", with the addi-
tion 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.
WriteConstants ATTRIBUTE => VALUE [, ...]
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
Name of the module. This must be specified
DEFAULT_TYPE
The default type for the constants. If not speci-
fied "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 con-
taining names, or hashrefs as detailed in
"C_constant".
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_FILE
The name of the file to write containing the XS
code. The default is "const-xs.inc".
SUBNAME
The perl visible name of the XS subroutine generated
which will return the constants. The default is
"constant".
C_SUBNAME
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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.
AUTHOR
Nicholas Clark <nick@ccl4.org> based on the code in "h2xs"
by Larry Wall and others
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