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.
- 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.
- 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
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
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 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".
- 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 in
"constant_10" with the default
XS_SUBNAME.
Nicholas Clark <nick@ccl4.org> based on the code in
"h2xs" by Larry Wall and others