NAME
    Inline::C - Write Perl Subroutines in C

DESCRIPTION
    "Inline::C" is a module that allows you to write Perl subroutines in C.
    Since version 0.30 the Inline module supports multiple programming
    languages and each language has its own support module. This document
    describes how to use Inline with the C programming language. It also
    goes a bit into Perl C internals.

    If you want to start working with programming examples right away, check
    out Inline::C::Cookbook. For more information on Inline in general, see
    Inline.

USAGE
    You never actually use "Inline::C" directly. It is just a support module
    for using "Inline.pm" with C. So the usage is always:

        use Inline C => ...;

    or

        bind Inline C => ...;

FUNCTION DEFINITIONS
    The Inline grammar for C recognizes certain function definitions (or
    signatures) in your C code. If a signature is recognized by Inline, then
    it will be available in Perl-space. That is, Inline will generate the
    "glue" necessary to call that function as if it were a Perl subroutine.
    If the signature is not recognized, Inline will simply ignore it, with
    no complaints. It will not be available from Perl-space, although it
    *will* be available from C-space.

    Inline looks for ANSI/prototype style function definitions. They must be
    of the form:

        return-type function-name ( type-name-pairs ) { ... }

    The most common types are: "int", "long", "double", "char*", and "SV*".
    But you can use any type for which Inline can find a typemap. Inline
    uses the "typemap" file distributed with Perl as the default. You can
    specify more typemaps with the TYPEMAPS configuration option.

    A return type of "void" may also be used. The following are examples of
    valid function definitions.

        int Foo(double num, char* str) {
        void Foo(double num, char* str) {
        void Foo(SV*, ...) {
        long Foo(int i, int j, ...) {
        SV* Foo(void) { # 'void' arg invalid with the ParseRecDescent parser.
                        # Works only with the ParseRegExp parser.
                        # See the section on USING (below).
        SV* Foo() {  # Alternative to specifying 'void' arg. Is valid with
                     # both the ParseRecDescent and ParseRegExp parsers.

    The following definitions would not be recognized:

        Foo(int i) {               # no return type
        int Foo(float f) {         # no (default) typemap for float
        int Foo(num, str) double num; char* str; {

    Notice that Inline only looks for function *definitions*, not function
    *prototypes*. Definitions are the syntax directly preceding a function
    body. Also Inline does not scan external files, like headers. Only the
    code passed to Inline is used to create bindings; although other
    libraries can linked in, and called from C-space.

C CONFIGURATION OPTIONS
    For information on how to specify Inline configuration options, see
    Inline. This section describes each of the configuration options
    available for C. Most of the options correspond either to MakeMaker or
    XS options of the same name. See ExtUtils::MakeMaker and perlxs.

  AUTO_INCLUDE
    Specifies extra statements to automatically included. They will be added
    onto the defaults. A newline char will be automatically added.

        use Inline C => Config => AUTO_INCLUDE => '#include "yourheader.h"';

  AUTOWRAP
    If you 'ENABLE => AUTOWRAP', Inline::C will parse function declarations
    (prototype statements) in your C code. For each declaration it can bind
    to, it will create a dummy wrapper that will call the real function
    which may be in an external library. This is a nice convenience for
    functions that would otherwise just require an empty wrapper function.

    This is similar to the base functionality you get from "h2xs". It can be
    very useful for binding to external libraries.

  BOOT
    Specifies C code to be executed in the XS BOOT section. Corresponds to
    the XS parameter.

  CC
    Specify which compiler to use.

  CCFLAGS
    Specify compiler flags - same as ExtUtils::MakeMaker's CCFLAGS option.
    Whatever gets specified here replaces the default $Config{ccflags}.
    Often, you'll want to add an extra flag or two without clobbering the
    default flags in which case you could instead use CCFLAGSEX (see below)
    or, iff Config.pm has already been loaded:

        use Inline C => Config => CCFLAGS => $Config{ccflags} . " -DXTRA -DTOO";

  CCFLAGSEX
    Extend compiler flags. Sets CCFLAGS to $Config{ccflags} followed by a
    space, followed by the specified value:

        use Inline C => Config => CCFLAGSEX => "-DXTRA -DTOO";

  FILTERS
    Allows you to specify a list of source code filters. If more than one is
    requested, be sure to group them with an array ref. The filters can
    either be subroutine references or names of filters provided by the
    supplementary Inline::Filters module.

    Your source code will be filtered just before it is parsed by Inline.
    The MD5 fingerprint is generated before filtering. Source code filters
    can be used to do things like stripping out POD documentation,
    pre-expanding "#include" statements or whatever else you please. For
    example:

        use Inline C => DATA =>
                   FILTERS => [Strip_POD => \&MyFilter => Preprocess ];

    Filters are invoked in the order specified. See Inline::Filters for more
    information.

  INC
    Specifies an include path to use. Corresponds to the MakeMaker
    parameter. Expects a fully qualified path.

        use Inline C => Config => INC => '-I/inc/path';

  LD
    Specify which linker to use.

  LDDLFLAGS
    Specify which linker flags to use.

    NOTE: These flags will completely override the existing flags, instead
    of just adding to them. So if you need to use those too, you must
    respecify them here.

  LIBS
    Specifies external libraries that should be linked into your code.
    Corresponds to the MakeMaker parameter. Provide a fully qualified path
    with the -L switch if the library is in a location where it won't be
    found automatically.

        use Inline C => Config => LIBS => '-lyourlib';

    or

        use Inline C => Config => LIBS => '-L/your/path -lyourlib';

  MAKE
    Specify the name of the 'make' utility to use.

  MYEXTLIB
    Specifies a user compiled object that should be linked in. Corresponds
    to the MakeMaker parameter. Expects a fully qualified path.

        use Inline C => Config => MYEXTLIB => '/your/path/yourmodule.so';

  OPTIMIZE
    This controls the MakeMaker OPTIMIZE setting. By setting this value to
    "'- g'", you can turn on debugging support for your Inline extensions.
    This will allow you to be able to set breakpoints in your C code using a
    debugger like gdb.

  PREFIX
    Specifies a prefix that will be automatically stripped from C functions
    when they are bound to Perl. Useful for creating wrappers for shared
    library API-s, and binding to the original names in Perl. Also useful
    when names conflict with Perl internals. Corresponds to the XS
    parameter.

        use Inline C => Config => PREFIX => 'ZLIB_';

  PRE_HEAD
    Specifies code that will precede the inclusion of all files specified in
    AUTO_INCLUDE (ie EXTERN.h, perl.h, XSUB.h, INLINE.h and anything else
    that might have been added to AUTO_INCLUDE by the user). If the
    specified value identifies a file, the contents of that file will be
    inserted, otherwise the specified value is inserted.

        use Inline C => Config => PRE_HEAD => $code_or_filename;

  PROTOTYPE
    Corresponds to the XS keyword 'PROTOTYPE'. See the perlxs documentation
    for both 'PROTOTYPES' and 'PROTOTYPE'. As an example, the following will
    set the PROTOTYPE of the 'foo' function to '$', and disable prototyping
    for the 'bar' function.

        use Inline C => Config => PROTOTYPE => {foo => '$', bar => 'DISABLE'}

  PROTOTYPES
    Corresponds to the XS keyword 'PROTOTYPES'. Can take only values of
    'ENABLE' or 'DISABLE'. (Contrary to XS, default value is 'DISABLE'). See
    the perlxs documentation for both 'PROTOTYPES' and 'PROTOTYPE'.

        use Inline C => Config => PROTOTYPES => 'ENABLE';

  TYPEMAPS
    Specifies extra typemap files to use. These types will modify the
    behaviour of the C parsing. Corresponds to the MakeMaker parameter.
    Specify either a fully qualified path or a path relative to the cwd (ie
    relative to what the cwd is at the time the script is loaded).

        use Inline C => Config => TYPEMAPS => '/your/path/typemap';

  USING
    Specifies which parser to use. Default is 'ParseRecDescent', which uses
    the Parse::RecDescent module. The only other option is 'ParseRegExp',
    which uses the Inline::C::ParseRegExp module that ships with Inline.

          use Inline C => Config => USING => 'ParseRegExp';

C-PERL BINDINGS
    This section describes how the "Perl" variables get mapped to "C"
    variables and back again.

    First, you need to know how "Perl" passes arguments back and forth to
    subroutines. Basically it uses a stack (also known as the Stack). When a
    sub is called, all of the parenthesized arguments get expanded into a
    list of scalars and pushed onto the Stack. The subroutine then pops all
    of its parameters off of the Stack. When the sub is done, it pushes all
    of its return values back onto the Stack.

    The Stack is an array of scalars known internally as "SV"'s. The Stack
    is actually an array of pointers to SV or "SV*"; therefore every element
    of the Stack is natively a "SV*". For *FMTYEWTK* about this, read
    "perldoc perlguts".

    So back to variable mapping. XS uses a thing known as "typemaps" to turn
    each "SV*" into a "C" type and back again. This is done through various
    XS macro calls, casts and the Perl API. See "perldoc perlapi". XS allows
    you to define your own typemaps as well for fancier non-standard types
    such as "typedef"- ed structs.

    Inline uses the default Perl typemap file for its default types. This
    file is called "/usr/local/lib/perl5/5.6.1/ExtUtils/typemap", or
    something similar, depending on your Perl installation. It has
    definitions for over 40 types, which are automatically used by Inline.
    (You should probably browse this file at least once, just to get an idea
    of the possibilities.)

    Inline parses your code for these types and generates the XS code to map
    them. The most commonly used types are:

    *   int

    *   long

    *   double

    *   char*

    *   void

    *   SV*

    If you need to deal with a type that is not in the defaults, just use
    the generic "SV*" type in the function definition. Then inside your
    code, do the mapping yourself. Alternatively, you can create your own
    typemap files and specify them using the "TYPEMAPS" configuration
    option.

    A return type of "void" has a special meaning to Inline. It means that
    you plan to push the values back onto the Stack yourself. This is what
    you need to do to return a list of values. If you really don't want to
    return anything (the traditional meaning of "void") then simply don't
    push anything back.

    If ellipsis or "..." is used at the end of an argument list, it means
    that any number of "SV*"s may follow. Again you will need to pop the
    values off of the "Stack" yourself.

    See "Examples" below.

THE INLINE STACK MACROS
    When you write Inline C, the following lines are automatically prepended
    to your code (by default):

        #include "EXTERN.h"
        #include "perl.h"
        #include "XSUB.h"
        #include "INLINE.h"

    The file "INLINE.h" defines a set of macros that are useful for handling
    the Perl Stack from your C functions.

    Inline_Stack_Vars
        You'll need to use this one, if you want to use the others. It sets
        up a few local variables: "sp", "items", "ax" and "mark", for use by
        the other macros. It's not important to know what they do, but I
        mention them to avoid possible name conflicts.

        NOTE: Since this macro declares variables, you'll need to put it
        with your other variable declarations at the top of your function.
        It must come before any executable statements and before any other
        "Inline_Stack" macros.

    Inline_Stack_Items
        Returns the number of arguments passed in on the Stack.

    Inline_Stack_Item(i)
        Refers to a particular "SV*" in the Stack, where "i" is an index
        number starting from zero. Can be used to get or set the value.

    Inline_Stack_Reset
        Use this before pushing anything back onto the Stack. It resets the
        internal Stack pointer to the beginning of the Stack.

    Inline_Stack_Push(sv)
        Push a return value back onto the Stack. The value must be of type
        "SV*".

    Inline_Stack_Done
        After you have pushed all of your return values, you must call this
        macro.

    Inline_Stack_Return(n)
        Return "n" items on the Stack.

    Inline_Stack_Void
        A special macro to indicate that you really don't want to return
        anything. Same as:

            Inline_Stack_Return(0);

        Please note that this macro actually returns from your function.

    Each of these macros is available in 3 different styles to suit your
    coding tastes. The following macros are equivalent.

        Inline_Stack_Vars
        inline_stack_vars
        INLINE_STACK_VARS

    All of this functionality is available through XS macro calls as well.
    So why duplicate the functionality? There are a few reasons why I
    decided to offer this set of macros. First, as a convenient way to
    access the Stack. Second, for consistent, self documenting, non-cryptic
    coding. Third, for future compatibility. It occurred to me that if a lot
    of people started using XS macros for their C code, the interface might
    break under Perl6. By using this set, hopefully I will be able to insure
    future compatibility of argument handling.

    Of course, if you use the rest of the Perl API, your code will most
    likely break under Perl6. So this is not a 100% guarantee. But since
    argument handling is the most common interface you're likely to use, it
    seemed like a wise thing to do.

WRITING C SUBROUTINES
    The definitions of your C functions will fall into one of the following
    four categories. For each category there are special considerations.

    "int Foo(int arg1, char* arg2, SV* arg3) {"
        This is the simplest case. You have a non "void" return type and a
        fixed length argument list. You don't need to worry about much. All
        the conversions will happen automatically.

    "void Foo(int arg1, char* arg2, SV* arg3) {"
        In this category you have a "void" return type. This means that
        either you want to return nothing, or that you want to return a
        list. In the latter case you'll need to push values onto the Stack
        yourself. There are a few Inline macros that make this easy. Code
        something like this:

            int i, max; SV* my_sv[10];
            Inline_Stack_Vars;
            Inline_Stack_Reset;
            for (i = 0; i < max; i++)
              Inline_Stack_Push(my_sv[i]);
            Inline_Stack_Done;

        After resetting the Stack pointer, this code pushes a series of
        return values. At the end it uses "Inline_Stack_Done" to mark the
        end of the return stack.

        If you really want to return nothing, then don't use the
        "Inline_Stack_" macros. If you must use them, then set use
        "Inline_Stack_Void" at the end of your function.

    "char* Foo(SV* arg1, ...) {"
        In this category you have an unfixed number of arguments. This means
        that you'll have to pop values off the Stack yourself. Do it like
        this:

            int i;
            Inline_Stack_Vars;
            for (i = 0; i < Inline_Stack_Items; i++)
              handle_sv(Inline_Stack_Item(i));

        The return type of Inline_Stack_Item(i) is "SV*".

    "void* Foo(SV* arg1, ...) {"
        In this category you have both a "void" return type and an unfixed
        number of arguments. Just combine the techniques from Categories 3
        and 4.

EXAMPLES
    Here are a few examples. Each one is a complete program that you can try
    running yourself. For many more examples see Inline::C-Cookbook.

  Example #1 - Greetings
    This example will take one string argument (a name) and print a
    greeting. The function is called with a string and with a number. In the
    second case the number is forced to a string.

    Notice that you do not need to "#include <stdio.h">. The "perl.h" header
    file which gets included by default, automatically loads the standard C
    header files for you.

        use Inline C;
        greet('Ingy');
        greet(42);
        __END__
        __C__
        void greet(char* name) {
          printf("Hello %s!\n", name);
        }

  Example #2 - and Salutations
    This is similar to the last example except that the name is passed in as
    a "SV*" (pointer to Scalar Value) rather than a string ("char*"). That
    means we need to convert the "SV" to a string ourselves. This is
    accomplished using the "SvPVX" function which is part of the "Perl"
    internal API. See "perldoc perlapi" for more info.

    One problem is that "SvPVX" doesn't automatically convert strings to
    numbers, so we get a little surprise when we try to greet 42. The
    program segfaults, a common occurrence when delving into the guts of
    Perl.

        use Inline C;
        greet('Ingy');
        greet(42);
        __END__
        __C__
        void greet(SV* sv_name) {
          printf("Hello %s!\n", SvPVX(sv_name));
        }

  Example #3 - Fixing the problem
    We can fix the problem in Example #2 by using the "SvPV" function
    instead. This function will stringify the "SV" if it does not contain a
    string. "SvPV" returns the length of the string as it's second
    parameter. Since we don't care about the length, we can just put "PL_na"
    there, which is a special variable designed for that purpose.

        use Inline C;
        greet('Ingy');
        greet(42);
        __END__
        __C__
        void greet(SV* sv_name) {
          printf("Hello %s!\n", SvPV(sv_name, PL_na));
        }

SEE ALSO
    For general information about Inline see Inline.

    For sample programs using Inline with C see Inline::C-Cookbook.

    For information on supported languages and platforms see Inline-Support.

    For information on writing your own Inline Language Support Module, see
    Inline-API.

    Inline's mailing list is inline@perl.org

    To subscribe, send email to inline-subscribe@perl.org

BUGS AND DEFICIENCIES
    If you use C function names that happen to be used internally by Perl,
    you will get a load error at run time. There is currently no
    functionality to prevent this or to warn you. For now, a list of Perl's
    internal symbols is packaged in the Inline module distribution under the
    filename 'symbols.perl'. Avoid using these in your code.

AUTHOR
    Brian Ingerson <INGY@cpan.org>

    Sisyphus <sisyphus@cpan.org> fixed some bugs and is current
    co-maintainer.

COPYRIGHT
    Copyright 2000-2002. Brian Ingerson.

    Copyright 2008, 2010-2014. Sisyphus.

    Copyright 2014, Ingy döt Net.

    This program is free software; you can redistribute it and/or modify it
    under the same terms as Perl itself.

    See <http://www.perl.com/perl/misc/Artistic.html>

