to handle special structures and types for the library being
linked.
-=head2 Getting Started
-
-A new extension should begin with the B<h2xs> tool. This will generate
-templates for the new Perl module (PM), the XS source file (XS), the MANIFEST
-file, and the Makefile.PL (PL) files. The Makefile.PL file is a Perl script
-which will generate a Makefile. This makefile knows how to find and run
-xsubpp for your extension. When you type "make" your XS file will be run
-through xsubpp and a C file will be produced. Then the C file will be
-compiled. A simple example looks like this for an example module named
-B<Foo>:
-
- $ h2xs -Afn Foo
- $ cd ext/Foo
- $ ls
- Foo.pm Foo.xs MANIFEST Makefile.PL
- $ perl5 Makefile.PL
- $ ls
- Foo.pm Foo.xs MANIFEST Makefile.PL Makefile
- $ <edit Foo.pm and Foo.xs to add your stuff>
- $ make
- <you will see xsubpp run on Foo.xs and you'll see the C compiler
- <run on Foo.c, and a bunch of other less-interesting things
- <will happen.
-
-If your Perl was built with dynamic loading then the makefile will build a
-dynamically loadable extension. If you don't have dynamic loading then the
-makefile will build a static extension and should create a new Perl binary.
-The default behavior depends on what is available.
-
-For more information about h2xs consult its manpage, embedded in the
-source. For information about the Makefile.PL and Makefile consult the
-MakeMaker manpage.
+See L<perlxstut> for a tutorial on the whole extension creation process.
+
+Note: For many extensions, Dave Beazley's SWIG system provides a
+significantly more convenient mechanism for creating the XS glue
+code. See L<http://www.cs.utah.edu/~beazley/SWIG> for more
+information.
=head2 On The Road
-Many of the examples which follow will concentrate on creating an
-interface between Perl and the ONC+ RPC bind library functions.
-Specifically, the rpcb_gettime() function will be used to demonstrate many
-features of the XS language. This function has two parameters; the first
-is an input parameter and the second is an output parameter. The function
-also returns a status value.
+Many of the examples which follow will concentrate on creating an interface
+between Perl and the ONC+ RPC bind library functions. The rpcb_gettime()
+function is used to demonstrate many features of the XS language. This
+function has two parameters; the first is an input parameter and the second
+is an output parameter. The function also returns a status value.
bool_t rpcb_gettime(const char *host, time_t *timep);
the section on typemaps for more about handling qualifiers and unary
operators in C types.
-The parameter list of a function must not have whitespace after the
-open-parenthesis or before the close-parenthesis. (This restriction will be
-relaxed in later versions of B<xsubpp>.)
-
- INCORRECT CORRECT
-
- double double
- sin( x ) sin(x)
- double x double x
-
The function name and the return type must be placed on
separate lines.
double x sin(x)
double x
+The function body may be indented or left-adjusted. The following example
+shows a function with its body left-adjusted. Most examples in this
+document will indent the body.
+
+ CORRECT
+
+ double
+ sin(x)
+ double x
+
=head2 The Argument Stack
The argument stack is used to store the values which are
If the XSUB has a return type of C<void> then the compiler will
not supply a RETVAL variable for that function. When using
-the PPCODE: directive the RETVAL variable may not be needed.
+the PPCODE: directive the RETVAL variable is not needed, unless used
+explicitly.
+
+If PPCODE: directive is not used, C<void> return value should be used
+only for subroutines which do not return a value, I<even if> CODE:
+directive is used which sets ST(0) explicitly.
+
+Older versions of this document recommended to use C<void> return
+value in such cases. It was discovered that this could lead to
+segfaults in cases when XSUB was I<truly> C<void>. This practice is
+now deprecated, and may be not supported at some future version. Use
+the return value C<SV *> in such cases. (Currently C<xsubpp> contains
+some heuristic code which tries to disambiguate between "truly-void"
+and "old-practice-declared-as-void" functions. Hence your code is at
+mercy of this heuristics unless you use C<SV *> as return value.)
=head2 The MODULE Keyword
OUTPUT:
timep sv_setnv(ST(1), (double)timep);
+B<xsubpp> emits an automatic C<SvSETMAGIC()> for all parameters in the
+OUTPUT section of the XSUB, except RETVAL. This is the usually desired
+behavior, as it takes care of properly invoking 'set' magic on output
+parameters (needed for hash or array element parameters that must be
+created if they didn't exist). If for some reason, this behavior is
+not desired, the OUTPUT section may contain a C<SETMAGIC: DISABLE> line
+to disable it for the remainder of the parameters in the OUTPUT section.
+Likewise, C<SETMAGIC: ENABLE> can be used to reenable it for the
+remainder of the OUTPUT section. See L<perlguts> for more details
+about 'set' magic.
+
=head2 The CODE: Keyword
This keyword is used in more complicated XSUBs which require
$status = rpcb_gettime( "localhost", $timep );
-The XSUB follows.
+The XSUB follows.
bool_t
rpcb_gettime(host,timep)
timep
RETVAL
-In many of the examples shown here the CODE: block (and
-other blocks) will often be contained within braces ( C<{> and
-C<}> ). This protects the CODE: block from complex INPUT
-typemaps and ensures the resulting C code is legal.
+=head2 The INIT: Keyword
+
+The INIT: keyword allows initialization to be inserted into the XSUB before
+the compiler generates the call to the C function. Unlike the CODE: keyword
+above, this keyword does not affect the way the compiler handles RETVAL.
+
+ bool_t
+ rpcb_gettime(host,timep)
+ char *host
+ time_t &timep
+ INIT:
+ printf("# Host is %s\n", host );
+ OUTPUT:
+ timep
=head2 The NO_INIT Keyword
The NO_INIT keyword is used to indicate that a function
-parameter is being used as only an output value. The B<xsubpp>
+parameter is being used only as an output value. The B<xsubpp>
compiler will normally generate code to read the values of
all function parameters from the argument stack and assign
them to C variables upon entry to the function. NO_INIT
before the function terminates.
The following example shows a variation of the rpcb_gettime() function.
-This function uses the timep variable as only an output variable and does
+This function uses the timep variable only as an output variable and does
not care about its initial contents.
bool_t
values from the argument stack. The typemaps contain the
code segments which are used to transfer the Perl values to
the C parameters. The programmer, however, is allowed to
-override the typemaps and supply alternate initialization
-code.
+override the typemaps and supply alternate (or additional)
+initialization code.
The following code demonstrates how to supply initialization code for
-function parameters. The initialization code is eval'd by the compiler
-before it is added to the output so anything which should be interpreted
-literally, such as double quotes, must be protected with backslashes.
+function parameters. The initialization code is eval'd within double
+quotes by the compiler before it is added to the output so anything
+which should be interpreted literally [mainly C<$>, C<@>, or C<\\>]
+must be protected with backslashes. The variables $var, $arg,
+and $type can be used as in typemaps.
bool_t
rpcb_gettime(host,timep)
- char *host = (char *)SvPV(ST(0),na);
+ char *host = (char *)SvPV($arg,PL_na);
time_t &timep = 0;
OUTPUT:
timep
another library function before it can be used. Default parameters are
covered in the next section.
+If the initialization begins with C<=>, then it is output on
+the same line where the input variable is declared. If the
+initialization begins with C<;> or C<+>, then it is output after
+all of the input variables have been declared. The C<=> and C<;>
+cases replace the initialization normally supplied from the typemap.
+For the C<+> case, the initialization from the typemap will precede
+the initialization code included after the C<+>. A global
+variable, C<%v>, is available for the truly rare case where
+information from one initialization is needed in another
+initialization.
+
+ bool_t
+ rpcb_gettime(host,timep)
+ time_t &timep ; /*\$v{time}=@{[$v{time}=$arg]}*/
+ char *host + SvOK($v{time}) ? SvPV($arg,PL_na) : NULL;
+ OUTPUT:
+ timep
+
=head2 Default Parameter Values
Default values can be specified for function parameters by
timep
RETVAL
+=head2 The PREINIT: Keyword
+
+The PREINIT: keyword allows extra variables to be declared before the
+typemaps are expanded. If a variable is declared in a CODE: block then that
+variable will follow any typemap code. This may result in a C syntax
+error. To force the variable to be declared before the typemap code, place
+it into a PREINIT: block. The PREINIT: keyword may be used one or more
+times within an XSUB.
+
+The following examples are equivalent, but if the code is using complex
+typemaps then the first example is safer.
+
+ bool_t
+ rpcb_gettime(timep)
+ time_t timep = NO_INIT
+ PREINIT:
+ char *host = "localhost";
+ CODE:
+ RETVAL = rpcb_gettime( host, &timep );
+ OUTPUT:
+ timep
+ RETVAL
+
+A correct, but error-prone example.
+
+ bool_t
+ rpcb_gettime(timep)
+ time_t timep = NO_INIT
+ CODE:
+ char *host = "localhost";
+ RETVAL = rpcb_gettime( host, &timep );
+ OUTPUT:
+ timep
+ RETVAL
+
+=head2 The SCOPE: Keyword
+
+The SCOPE: keyword allows scoping to be enabled for a particular XSUB. If
+enabled, the XSUB will invoke ENTER and LEAVE automatically.
+
+To support potentially complex type mappings, if a typemap entry used
+by this XSUB contains a comment like C</*scope*/> then scoping will
+automatically be enabled for that XSUB.
+
+To enable scoping:
+
+ SCOPE: ENABLE
+
+To disable scoping:
+
+ SCOPE: DISABLE
+
+=head2 The INPUT: Keyword
+
+The XSUB's parameters are usually evaluated immediately after entering the
+XSUB. The INPUT: keyword can be used to force those parameters to be
+evaluated a little later. The INPUT: keyword can be used multiple times
+within an XSUB and can be used to list one or more input variables. This
+keyword is used with the PREINIT: keyword.
+
+The following example shows how the input parameter C<timep> can be
+evaluated late, after a PREINIT.
+
+ bool_t
+ rpcb_gettime(host,timep)
+ char *host
+ PREINIT:
+ time_t tt;
+ INPUT:
+ time_t timep
+ CODE:
+ RETVAL = rpcb_gettime( host, &tt );
+ timep = tt;
+ OUTPUT:
+ timep
+ RETVAL
+
+The next example shows each input parameter evaluated late.
+
+ bool_t
+ rpcb_gettime(host,timep)
+ PREINIT:
+ time_t tt;
+ INPUT:
+ char *host
+ PREINIT:
+ char *h;
+ INPUT:
+ time_t timep
+ CODE:
+ h = host;
+ RETVAL = rpcb_gettime( h, &tt );
+ timep = tt;
+ OUTPUT:
+ timep
+ RETVAL
+
=head2 Variable-length Parameter Lists
XSUBs can have variable-length parameter lists by specifying an ellipsis
bool_t
rpcb_gettime(timep, ...)
time_t timep = NO_INIT
- CODE:
- {
+ PREINIT:
char *host = "localhost";
-
- if( items > 1 )
- host = (char *)SvPV(ST(1), na);
- RETVAL = rpcb_gettime( host, &timep );
- }
+ STRLEN n_a;
+ CODE:
+ if( items > 1 )
+ host = (char *)SvPV(ST(1), n_a);
+ RETVAL = rpcb_gettime( host, &timep );
OUTPUT:
timep
RETVAL
+=head2 The C_ARGS: Keyword
+
+The C_ARGS: keyword allows creating of XSUBS which have different
+calling sequence from Perl than from C, without a need to write
+CODE: or CPPCODE: section. The contents of the C_ARGS: paragraph is
+put as the argument to the called C function without any change.
+
+For example, suppose that C function is declared as
+
+ symbolic nth_derivative(int n, symbolic function, int flags);
+
+and that the default flags are kept in a global C variable
+C<default_flags>. Suppose that you want to create an interface which
+is called as
+
+ $second_deriv = $function->nth_derivative(2);
+
+To do this, declare the XSUB as
+
+ symbolic
+ nth_derivative(function, n)
+ symbolic function
+ int n
+ C_ARGS:
+ n, function, default_flags
+
=head2 The PPCODE: Keyword
The PPCODE: keyword is an alternate form of the CODE: keyword and is used
void
rpcb_gettime(host)
char *host
- PPCODE:
- {
+ PREINIT:
time_t timep;
bool_t status;
+ PPCODE:
status = rpcb_gettime( host, &timep );
- EXTEND(sp, 2);
- PUSHs(sv_2mortal(newSVnv(status)));
- PUSHs(sv_2mortal(newSVnv(timep)));
- }
+ EXTEND(SP, 2);
+ PUSHs(sv_2mortal(newSViv(status)));
+ PUSHs(sv_2mortal(newSViv(timep)));
Notice that the programmer must supply the C code necessary
to have the real rpcb_gettime() function called and to have
The EXTEND() macro is used to make room on the argument
stack for 2 return values. The PPCODE: directive causes the
-B<xsubpp> compiler to create a stack pointer called C<sp>, and it
+B<xsubpp> compiler to create a stack pointer available as C<SP>, and it
is this pointer which is being used in the EXTEND() macro.
The values are then pushed onto the stack with the PUSHs()
macro.
($status, $timep) = rpcb_gettime("localhost");
+When handling output parameters with a PPCODE section, be sure to handle
+'set' magic properly. See L<perlguts> for details about 'set' magic.
+
=head2 Returning Undef And Empty Lists
-Occasionally the programmer will want to simply return
+Occasionally the programmer will want to return simply
C<undef> or an empty list if a function fails rather than a
separate status value. The rpcb_gettime() function offers
just this situation. If the function succeeds we would like
$timep = rpcb_gettime( "localhost" );
-The following XSUB uses the C<void> return type to disable the generation of
-the RETVAL variable and uses a CODE: block to indicate to the compiler
+The following XSUB uses the C<SV *> return type as a mnemonic only,
+and uses a CODE: block to indicate to the compiler
that the programmer has supplied all the necessary code. The
sv_newmortal() call will initialize the return value to undef, making that
the default return value.
- void
+ SV *
rpcb_gettime(host)
char * host
- CODE:
- {
+ PREINIT:
time_t timep;
bool_t x;
+ CODE:
ST(0) = sv_newmortal();
if( rpcb_gettime( host, &timep ) )
sv_setnv( ST(0), (double)timep);
- }
The next example demonstrates how one would place an explicit undef in the
return value, should the need arise.
- void
+ SV *
rpcb_gettime(host)
char * host
- CODE:
- {
+ PREINIT:
time_t timep;
bool_t x;
+ CODE:
ST(0) = sv_newmortal();
if( rpcb_gettime( host, &timep ) ){
sv_setnv( ST(0), (double)timep);
}
else{
- ST(0) = &sv_undef;
- }
+ ST(0) = &PL_sv_undef;
}
To return an empty list one must use a PPCODE: block and
void
rpcb_gettime(host)
char *host
- PPCODE:
- {
+ PREINIT:
time_t timep;
+ PPCODE:
if( rpcb_gettime( host, &timep ) )
- PUSHs(sv_2mortal(newSVnv(timep)));
+ PUSHs(sv_2mortal(newSViv(timep)));
else{
/* Nothing pushed on stack, so an empty */
/* list is implicitly returned. */
}
- }
+
+Some people may be inclined to include an explicit C<return> in the above
+XSUB, rather than letting control fall through to the end. In those
+situations C<XSRETURN_EMPTY> should be used, instead. This will ensure that
+the XSUB stack is properly adjusted. Consult L<perlguts/"API LISTING"> for
+other C<XSRETURN> macros.
+
+=head2 The REQUIRE: Keyword
+
+The REQUIRE: keyword is used to indicate the minimum version of the
+B<xsubpp> compiler needed to compile the XS module. An XS module which
+contains the following statement will compile with only B<xsubpp> version
+1.922 or greater:
+
+ REQUIRE: 1.922
=head2 The CLEANUP: Keyword
# bootstrap function executes.
printf("Hello from the bootstrap!\n");
+=head2 The VERSIONCHECK: Keyword
+
+The VERSIONCHECK: keyword corresponds to B<xsubpp>'s C<-versioncheck> and
+C<-noversioncheck> options. This keyword overrides the command line
+options. Version checking is enabled by default. When version checking is
+enabled the XS module will attempt to verify that its version matches the
+version of the PM module.
+
+To enable version checking:
+
+ VERSIONCHECK: ENABLE
+
+To disable version checking:
+
+ VERSIONCHECK: DISABLE
+
+=head2 The PROTOTYPES: Keyword
+
+The PROTOTYPES: keyword corresponds to B<xsubpp>'s C<-prototypes> and
+C<-noprototypes> options. This keyword overrides the command line options.
+Prototypes are enabled by default. When prototypes are enabled XSUBs will
+be given Perl prototypes. This keyword may be used multiple times in an XS
+module to enable and disable prototypes for different parts of the module.
+
+To enable prototypes:
+
+ PROTOTYPES: ENABLE
+
+To disable prototypes:
+
+ PROTOTYPES: DISABLE
+
+=head2 The PROTOTYPE: Keyword
+
+This keyword is similar to the PROTOTYPES: keyword above but can be used to
+force B<xsubpp> to use a specific prototype for the XSUB. This keyword
+overrides all other prototype options and keywords but affects only the
+current XSUB. Consult L<perlsub/Prototypes> for information about Perl
+prototypes.
+
+ bool_t
+ rpcb_gettime(timep, ...)
+ time_t timep = NO_INIT
+ PROTOTYPE: $;$
+ PREINIT:
+ char *host = "localhost";
+ STRLEN n_a;
+ CODE:
+ if( items > 1 )
+ host = (char *)SvPV(ST(1), n_a);
+ RETVAL = rpcb_gettime( host, &timep );
+ OUTPUT:
+ timep
+ RETVAL
+
+=head2 The ALIAS: Keyword
+
+The ALIAS: keyword allows an XSUB to have two or more unique Perl names
+and to know which of those names was used when it was invoked. The Perl
+names may be fully-qualified with package names. Each alias is given an
+index. The compiler will setup a variable called C<ix> which contain the
+index of the alias which was used. When the XSUB is called with its
+declared name C<ix> will be 0.
+
+The following example will create aliases C<FOO::gettime()> and
+C<BAR::getit()> for this function.
+
+ bool_t
+ rpcb_gettime(host,timep)
+ char *host
+ time_t &timep
+ ALIAS:
+ FOO::gettime = 1
+ BAR::getit = 2
+ INIT:
+ printf("# ix = %d\n", ix );
+ OUTPUT:
+ timep
+
+=head2 The INTERFACE: Keyword
+
+This keyword declares the current XSUB as a keeper of the given
+calling signature. If some text follows this keyword, it is
+considered as a list of functions which have this signature, and
+should be attached to XSUBs.
+
+Say, if you have 4 functions multiply(), divide(), add(), subtract() all
+having the signature
+
+ symbolic f(symbolic, symbolic);
+
+you code them all by using XSUB
+
+ symbolic
+ interface_s_ss(arg1, arg2)
+ symbolic arg1
+ symbolic arg2
+ INTERFACE:
+ multiply divide
+ add subtract
+
+The advantage of this approach comparing to ALIAS: keyword is that one
+can attach an extra function remainder() at runtime by using
+
+ CV *mycv = newXSproto("Symbolic::remainder",
+ XS_Symbolic_interface_s_ss, __FILE__, "$$");
+ XSINTERFACE_FUNC_SET(mycv, remainder);
+
+(This example supposes that there was no INTERFACE_MACRO: section,
+otherwise one needs to use something else instead of
+C<XSINTERFACE_FUNC_SET>.)
+
+=head2 The INTERFACE_MACRO: Keyword
+
+This keyword allows one to define an INTERFACE using a different way
+to extract a function pointer from an XSUB. The text which follows
+this keyword should give the name of macros which would extract/set a
+function pointer. The extractor macro is given return type, C<CV*>,
+and C<XSANY.any_dptr> for this C<CV*>. The setter macro is given cv,
+and the function pointer.
+
+The default value is C<XSINTERFACE_FUNC> and C<XSINTERFACE_FUNC_SET>.
+An INTERFACE keyword with an empty list of functions can be omitted if
+INTERFACE_MACRO keyword is used.
+
+Suppose that in the previous example functions pointers for
+multiply(), divide(), add(), subtract() are kept in a global C array
+C<fp[]> with offsets being C<multiply_off>, C<divide_off>, C<add_off>,
+C<subtract_off>. Then one can use
+
+ #define XSINTERFACE_FUNC_BYOFFSET(ret,cv,f) \
+ ((XSINTERFACE_CVT(ret,))fp[CvXSUBANY(cv).any_i32])
+ #define XSINTERFACE_FUNC_BYOFFSET_set(cv,f) \
+ CvXSUBANY(cv).any_i32 = CAT2( f, _off )
+
+in C section,
+
+ symbolic
+ interface_s_ss(arg1, arg2)
+ symbolic arg1
+ symbolic arg2
+ INTERFACE_MACRO:
+ XSINTERFACE_FUNC_BYOFFSET
+ XSINTERFACE_FUNC_BYOFFSET_set
+ INTERFACE:
+ multiply divide
+ add subtract
+
+in XSUB section.
+
+=head2 The INCLUDE: Keyword
+
+This keyword can be used to pull other files into the XS module. The other
+files may have XS code. INCLUDE: can also be used to run a command to
+generate the XS code to be pulled into the module.
+
+The file F<Rpcb1.xsh> contains our C<rpcb_gettime()> function:
+
+ bool_t
+ rpcb_gettime(host,timep)
+ char *host
+ time_t &timep
+ OUTPUT:
+ timep
+
+The XS module can use INCLUDE: to pull that file into it.
+
+ INCLUDE: Rpcb1.xsh
+
+If the parameters to the INCLUDE: keyword are followed by a pipe (C<|>) then
+the compiler will interpret the parameters as a command.
+
+ INCLUDE: cat Rpcb1.xsh |
+
+=head2 The CASE: Keyword
+
+The CASE: keyword allows an XSUB to have multiple distinct parts with each
+part acting as a virtual XSUB. CASE: is greedy and if it is used then all
+other XS keywords must be contained within a CASE:. This means nothing may
+precede the first CASE: in the XSUB and anything following the last CASE: is
+included in that case.
+
+A CASE: might switch via a parameter of the XSUB, via the C<ix> ALIAS:
+variable (see L<"The ALIAS: Keyword">), or maybe via the C<items> variable
+(see L<"Variable-length Parameter Lists">). The last CASE: becomes the
+B<default> case if it is not associated with a conditional. The following
+example shows CASE switched via C<ix> with a function C<rpcb_gettime()>
+having an alias C<x_gettime()>. When the function is called as
+C<rpcb_gettime()> its parameters are the usual C<(char *host, time_t *timep)>,
+but when the function is called as C<x_gettime()> its parameters are
+reversed, C<(time_t *timep, char *host)>.
+
+ long
+ rpcb_gettime(a,b)
+ CASE: ix == 1
+ ALIAS:
+ x_gettime = 1
+ INPUT:
+ # 'a' is timep, 'b' is host
+ char *b
+ time_t a = NO_INIT
+ CODE:
+ RETVAL = rpcb_gettime( b, &a );
+ OUTPUT:
+ a
+ RETVAL
+ CASE:
+ # 'a' is host, 'b' is timep
+ char *a
+ time_t &b = NO_INIT
+ OUTPUT:
+ b
+ RETVAL
+
+That function can be called with either of the following statements. Note
+the different argument lists.
+
+ $status = rpcb_gettime( $host, $timep );
+
+ $status = x_gettime( $timep, $host );
+
+=head2 The & Unary Operator
+
+The & unary operator is used to tell the compiler that it should dereference
+the object when it calls the C function. This is used when a CODE: block is
+not used and the object is a not a pointer type (the object is an C<int> or
+C<long> but not a C<int*> or C<long*>).
+
+The following XSUB will generate incorrect C code. The xsubpp compiler will
+turn this into code which calls C<rpcb_gettime()> with parameters C<(char
+*host, time_t timep)>, but the real C<rpcb_gettime()> wants the C<timep>
+parameter to be of type C<time_t*> rather than C<time_t>.
+
+ bool_t
+ rpcb_gettime(host,timep)
+ char *host
+ time_t timep
+ OUTPUT:
+ timep
+
+That problem is corrected by using the C<&> operator. The xsubpp compiler
+will now turn this into code which calls C<rpcb_gettime()> correctly with
+parameters C<(char *host, time_t *timep)>. It does this by carrying the
+C<&> through, so the function call looks like C<rpcb_gettime(host, &timep)>.
+
+ bool_t
+ rpcb_gettime(host,timep)
+ char *host
+ time_t &timep
+ OUTPUT:
+ timep
+
=head2 Inserting Comments and C Preprocessor Directives
-Comments and C preprocessor directives are allowed within
-CODE:, PPCODE:, BOOT:, and CLEANUP: blocks. The compiler
-will pass the preprocessor directives through untouched and
-will remove the commented lines. Comments can be added to
-XSUBs by placing a C<#> at the beginning of the line. Care
-should be taken to avoid making the comment look like a C
-preprocessor directive, lest it be interpreted as such.
+C preprocessor directives are allowed within BOOT:, PREINIT: INIT:,
+CODE:, PPCODE:, and CLEANUP: blocks, as well as outside the functions.
+Comments are allowed anywhere after the MODULE keyword. The compiler
+will pass the preprocessor directives through untouched and will remove
+the commented lines.
+
+Comments can be added to XSUBs by placing a C<#> as the first
+non-whitespace of a line. Care should be taken to avoid making the
+comment look like a C preprocessor directive, lest it be interpreted as
+such. The simplest way to prevent this is to put whitespace in front of
+the C<#>.
+
+If you use preprocessor directives to choose one of two
+versions of a function, use
+
+ #if ... version1
+ #else /* ... version2 */
+ #endif
+
+and not
+
+ #if ... version1
+ #endif
+ #if ... version2
+ #endif
+
+because otherwise xsubpp will believe that you made a duplicate
+definition of the function. Also, put a blank line before the
+#else/#endif so it will not be seen as part of the function body.
=head2 Using XS With C++
its first argument is an object pointer. The object pointer
will be stored in a variable called THIS. The object should
have been created by C++ with the new() function and should
-be blessed by Perl with the sv_setptrobj() macro. The
-blessing of the object by Perl can be handled by the
-T_PTROBJ typemap.
+be blessed by Perl with the sv_setref_pv() macro. The
+blessing of the object by Perl can be handled by a typemap. An example
+typemap is shown at the end of this section.
If the method is defined as static it will call the C++
function using the class::method() syntax. If the method is not static
-the function will be called using the THIS->method() syntax.
+the function will be called using the THIS-E<gt>method() syntax.
+
+The next examples will use the following C++ class.
+
+ class color {
+ public:
+ color();
+ ~color();
+ int blue();
+ void set_blue( int );
-=head2 Perl Variables
+ private:
+ int c_blue;
+ };
-The following demonstrates how the Perl variable $host can
-be accessed from an XSUB. The function B<perl_get_sv()> is
-used to obtain a pointer to the variable, known as an B<SV>
-(Scalar Variable) internally. The package name C<RPC> will be
-added to the name of the variable so perl_get_sv() will know
-in which package $host can be found. If the package name is
-not supplied then perl_get_sv() will search package C<main> for
-the variable. The macro B<SvPVX()> is then used to dereference
-the SV to obtain a C<char*> pointer to its contents.
+The XSUBs for the blue() and set_blue() methods are defined with the class
+name but the parameter for the object (THIS, or "self") is implicit and is
+not listed.
+
+ int
+ color::blue()
void
- rpcb_gettime()
- PPCODE:
- {
- char *host;
- SV *hostsv;
- time_t timep;
-
- hostsv = perl_get_sv( "RPC::host", FALSE );
- if( hostsv != NULL ){
- host = SvPVX( hostsv );
- if( rpcb_gettime( host, &timep ) )
- PUSHs(sv_2mortal(newSVnv(timep)));
- }
- }
+ color::set_blue( val )
+ int val
-This Perl code can be used to call that XSUB.
+Both functions will expect an object as the first parameter. The xsubpp
+compiler will call that object C<THIS> and will use it to call the specified
+method. So in the C++ code the blue() and set_blue() methods will be called
+in the following manner.
- $RPC::host = "localhost";
- $timep = rpcb_gettime();
+ RETVAL = THIS->blue();
-In the above example the SV contained a C C<char*> but a Perl
-scalar variable may also contain numbers and references. If
-the SV is expected to have a C C<int> then the macro B<SvIVX()>
-should be used to dereference the SV. When the SV contains
-a C double then B<SvNVX()> should be used.
+ THIS->set_blue( val );
-The macro B<SvRV()> can be used to dereference an SV when it is a Perl
-reference. The result will be another SV which points to the actual Perl
-variable. This can then be dereferenced with SvPVX(), SvNVX(), or
-SvIVX(). The following XSUB will use SvRV().
+If the function's name is B<DESTROY> then the C++ C<delete> function will be
+called and C<THIS> will be given as its parameter.
void
- rpcb_gettime()
- PPCODE:
- {
- char *host;
- SV *rv;
- SV *hostsv;
- time_t timep;
-
- rv = perl_get_sv( "RPC::host", FALSE );
- if( rv != NULL ){
- hostsv = SvRV( rv );
- host = SvPVX( hostsv );
- if( rpcb_gettime( host, &timep ) )
- PUSHs(sv_2mortal(newSVnv(timep)));
- }
- }
+ color::DESTROY()
+
+The C++ code will call C<delete>.
-This Perl code will create a variable $RPC::host which is a
-reference to $MY::host. The variable $MY::host contains the
-hostname which will be used.
+ delete THIS;
- $MY::host = "localhost";
- $RPC::host = \$MY::host;
- $timep = rpcb_gettime();
+If the function's name is B<new> then the C++ C<new> function will be called
+to create a dynamic C++ object. The XSUB will expect the class name, which
+will be kept in a variable called C<CLASS>, to be given as the first
+argument.
-The second argument to perl_get_sv() will normally be B<FALSE>
-as shown in the above examples. An argument of B<TRUE> will
-cause variables to be created if they do not already exist.
-One should not use TRUE unless steps are taken to deal with
-a possibly empty SV.
+ color *
+ color::new()
-XSUBs may use B<perl_get_av()>, B<perl_get_hv()>, and B<perl_get_cv()> to
-access Perl arrays, hashes, and code values.
+The C++ code will call C<new>.
+
+ RETVAL = new color();
+
+The following is an example of a typemap that could be used for this C++
+example.
+
+ TYPEMAP
+ color * O_OBJECT
+
+ OUTPUT
+ # The Perl object is blessed into 'CLASS', which should be a
+ # char* having the name of the package for the blessing.
+ O_OBJECT
+ sv_setref_pv( $arg, CLASS, (void*)$var );
+
+ INPUT
+ O_OBJECT
+ if( sv_isobject($arg) && (SvTYPE(SvRV($arg)) == SVt_PVMG) )
+ $var = ($type)SvIV((SV*)SvRV( $arg ));
+ else{
+ warn( \"${Package}::$func_name() -- $var is not a blessed SV reference\" );
+ XSRETURN_UNDEF;
+ }
=head2 Interface Strategy
these structures so they can be manipulated by Perl as
blessed objects.
-=head2 The Perl Module
-
-The Perl module is the link between the extension library,
-which was generated from XS code, and the Perl interpreter.
-The module is used to tell Perl what the extension library
-contains. The name and package of the module should match
-the name of the library.
-
-The following is a Perl module for an extension containing
-some ONC+ RPC bind library functions.
-
- package RPC;
-
- require Exporter;
- require DynaLoader;
- @ISA = qw(Exporter DynaLoader);
- @EXPORT = qw( rpcb_gettime rpcb_getmaps rpcb_getaddr
- rpcb_rmtcall rpcb_set rpcb_unset );
-
- bootstrap RPC;
- 1;
-
-The RPC extension contains the functions found in the
-@EXPORT list. By using the C<Exporter> module the RPC module
-can make these function names visible to the rest of the
-Perl program. The C<DynaLoader> module will allow the RPC
-module to bootstrap the extension library. To load this
-extension and make the functions available, the following
-Perl statement should be used.
-
- use RPC;
-
-For more information about the DynaLoader consult its documentation in the
-ext/DynaLoader directory in the Perl source.
-
=head2 Perl Objects And C Structures
When dealing with C structures one should select either
this sense, there is no difference between the object created by the
getnetconfigent() XSUB and an object created by a normal Perl subroutine.
-=head2 C Headers and Perl
-
-The B<h2xs> compiler is designed to convert C header files in
-/usr/include into Perl extensions. This compiler will
-create a directory under the C<ext> directory of the Perl
-source and will populate it with a Makefile, a Perl Module,
-an XS source file, and a MANIFEST file.
-
-The following command will create an extension called C<Rusers>
-from the <rpcsvc/rusers.h> header.
-
- h2xs rpcsvc/rusers
-
-When the Rusers extension has been compiled and installed
-Perl can use it to retrieve any C<#define> statements which
-were in the C header.
-
- use Rusers;
- print "RPC program number for rusers service: ";
- print &RUSERSPROG, "\n";
-
-=head2 Creating A New Extension
-
-The B<h2xs> compiler can generate template source files and
-Makefiles. These templates offer a suitable starting point
-for most extensions. The following example demonstrates how
-one might use B<h2xs> to create an extension containing the RPC
-functions in this document.
-
-The extension will not use autoloaded functions and will not define
-constants, so the B<-A> option will be given to B<h2xs>. When run from the
-Perl source directory, the B<h2xs> compiler will create the directory
-ext/RPC and will populate it with files called RPC.xs, RPC.pm, Makefile.PL,
-and MANIFEST. The XS code for the RPC functions should be added to the
-RPC.xs file. The @EXPORT list in RPC.pm should be updated to include the
-functions from RPC.xs.
-
- h2xs -An RPC
-
-To compile the extension for dynamic loading the following
-command should be executed from the ext/RPC directory.
-
- make dynamic
-
-If the extension will be statically linked into the Perl
-binary then the makefile (use C<makefile>, not C<Makefile>) in the
-Perl source directory should be edited to add C<ext/RPC/RPC.a>
-to the C<static_ext> variable. Before making this change Perl
-should have already been built. After the makefile has been
-updated the following command should be executed from the
-Perl source directory.
-
- make
-
-Perl's B<Configure> script can also be used to add extensions. The extension
-should be placed in the C<ext> directory under the Perl source before Perl
-has been built and prior to running Configure. When Configure is run it
-will find the extension along with the other extensions in the C<ext>
-directory and will add it to the list of extensions to be built. When make
-is run the extension will be built along with the other extensions.
-
-Configure recognizes extensions if they have an XS source
-file which matches the name of the extension directory. If
-the extension directory includes a MANIFEST file Configure
-will search that file for any B<.SH> files and extract them
-after it extracts all the other .SH files listed in the main
-MANIFEST. The main Perl Makefile will then run B<make> in the
-extension's directory if it finds an XS file matching the
-name of the extension's directory.
-
=head2 The Typemap
The typemap is a collection of code fragments which are used by the B<xsubpp>
compiler to map C function parameters and values to Perl values. The
typemap file may consist of three sections labeled C<TYPEMAP>, C<INPUT>, and
-C<OUTPUT>. The INPUT section tells the compiler how to translate Perl values
+C<OUTPUT>. Any unlabelled initial section is assumed to be a C<TYPEMAP>
+section if a name is not explicitly specified. The INPUT section tells
+the compiler how to translate Perl values
into variables of certain C types. The OUTPUT section tells the compiler
how to translate the values from certain C types into values Perl can
understand. The TYPEMAP section tells the compiler which of the INPUT and
OUTPUT code fragments should be used to map a given C type to a Perl value.
-Each of the sections of the typemap must be preceded by one of the TYPEMAP,
-INPUT, or OUTPUT keywords.
+The section labels C<TYPEMAP>, C<INPUT>, or C<OUTPUT> must begin
+in the first column on a line by themselves, and must be in uppercase.
The default typemap in the C<ext> directory of the Perl source contains many
useful types which can be used by Perl extensions. Some extensions define
TYPEMAP
Netconfig *<tab>T_PTROBJ
+Here's a more complicated example: suppose that you wanted C<struct
+netconfig> to be blessed into the class C<Net::Config>. One way to do
+this is to use underscores (_) to separate package names, as follows:
+
+ typedef struct netconfig * Net_Config;
+
+And then provide a typemap entry C<T_PTROBJ_SPECIAL> that maps underscores to
+double-colons (::), and declare C<Net_Config> to be of that type:
+
+
+ TYPEMAP
+ Net_Config T_PTROBJ_SPECIAL
+
+ INPUT
+ T_PTROBJ_SPECIAL
+ if (sv_derived_from($arg, \"${(my $ntt=$ntype)=~s/_/::/g;\$ntt}\")) {
+ IV tmp = SvIV((SV*)SvRV($arg));
+ $var = ($type) tmp;
+ }
+ else
+ croak(\"$var is not of type ${(my $ntt=$ntype)=~s/_/::/g;\$ntt}\")
+
+ OUTPUT
+ T_PTROBJ_SPECIAL
+ sv_setref_pv($arg, \"${(my $ntt=$ntype)=~s/_/::/g;\$ntt}\",
+ (void*)$var);
+
+The INPUT and OUTPUT sections substitute underscores for double-colons
+on the fly, giving the desired effect. This example demonstrates some
+of the power and versatility of the typemap facility.
+
=head1 EXAMPLES
File C<RPC.xs>: Interface to some ONC+ RPC bind library functions.
MODULE = RPC PACKAGE = RPC
- void
+ SV *
rpcb_gettime(host="localhost")
char *host
- CODE:
- {
+ PREINIT:
time_t timep;
+ CODE:
ST(0) = sv_newmortal();
if( rpcb_gettime( host, &timep ) )
sv_setnv( ST(0), (double)timep );
- }
Netconfig *
getnetconfigent(netid="udp")
print "netconf = $netconf\n";
+=head1 XS VERSION
+
+This document covers features supported by C<xsubpp> 1.935.
+
=head1 AUTHOR
-Dean Roehrich F<E<lt>roehrich@cray.comE<gt>>
-Oct 12, 1995
+Dean Roehrich <F<roehrich@cray.com>>
+Jul 8, 1996
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