ExtUtils::Constant(3pm) Perl Programmers Reference Guide ExtUtils::Constant(3pm)
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" and "XS_constant", with which "WriteCon-stants" "WriteConstants"
stants" 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", 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 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 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 parame-ter parameter
ter 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 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 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".
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
The name of the C subroutine generated which will return the constants. The default is SUB-NAME. SUBNAME.
NAME. Child subroutines have "_" and the name length appended, so constants with 10 charac-ter character
ter 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
perl v5.8.8 2001-09-21 ExtUtils::Constant(3pm)
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