ExtUtils::Constant - phpMan

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 "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.

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, 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*.

AUTHOR
    Nicholas Clark <nick AT ccl4.org> based on the code in "h2xs" by Larry Wall
    and others