perlapi man page on NeXTSTEP

Man page or keyword search:  
man Server   1419 pages
apropos Keyword Search (all sections)
Output format
NeXTSTEP logo
[printable version]


PERLAPI(1)							    PERLAPI(1)

NAME
       perlapi - Perl 5 application programming interface for C extensions

DESCRIPTION
       Introduction

       XS is a language used to create an extension interface between Perl and
       some C library which one wishes to use with Perl.  The XS interface is
       combined with the library to create a new library which can be linked
       to Perl.	 An XSUB is a function in the XS language and is the core
       component of the Perl application interface.

       The XS compiler is called xsubpp.  This compiler will embed the
       constructs necessary to let an XSUB, which is really a C function in
       disguise, manipulate Perl values and creates the glue necessary to let
       Perl access the XSUB.  The compiler uses typemaps to determine how to
       map C function parameters and variables to Perl values.	The default
       typemap handles many common C types.  A supplement typemap must be
       created to handle special structures and types for the library being
       linked.

       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.

	       bool_t rpcb_gettime(const char *host, time_t *timep);

       From C this function will be called with the following statements.

	    #include <rpc/rpc.h>
	    bool_t status;
	    time_t timep;
	    status = rpcb_gettime( "localhost", &timep );

       If an XSUB is created to offer a direct translation between this
       function and Perl, then this XSUB will be used from Perl with the
       following code.	The $status and $timep variables will contain the
       output of the function.

	    use RPC;
	    $status = rpcb_gettime( "localhost", $timep );

       The following XS file shows an XS subroutine, or XSUB, which
       demonstrates one possible interface to the rpcb_gettime() function.
       This XSUB represents a direct translation between C and Perl and so
       preserves the interface even from Perl.	This XSUB will be invoked from
       Perl with the usage shown above.	 Note that the first three #include
       statements, for EXTERN.h, perl.h, and XSUB.h, will always be present at
       the beginning of an XS file.  This approach and others will be expanded
       later in this document.

	    #include "EXTERN.h"
	    #include "perl.h"
	    #include "XSUB.h"
	    #include <rpc/rpc.h>

	    MODULE = RPC  PACKAGE = RPC

	    bool_t
	    rpcb_gettime(host,timep)
		 char *	 host
		 time_t	 &timep
		 OUTPUT:
		 timep

       Any extension to Perl, including those containing XSUBs, should have a
       Perl module to serve as the bootstrap which pulls the extension into
       Perl.  This module will export the extension's functions and variables
       to the Perl program and will cause the extension's XSUBs to be linked
       into Perl.  The following module will be used for most of the examples
       in this document and should be used from Perl with the use command as
       shown earlier.  Perl modules are explained in more detail later in this
       document.

	    package RPC;

	    require Exporter;
	    require DynaLoader;
	    @ISA = qw(Exporter DynaLoader);
	    @EXPORT = qw( rpcb_gettime );

	    bootstrap RPC;
	    1;

       Throughout this document a variety of interfaces to the rpcb_gettime()
       XSUB will be explored.  The XSUBs will take their parameters in
       different orders or will take different numbers of parameters.  In each
       case the XSUB is an abstraction between Perl and the real C
       rpcb_gettime() function, and the XSUB must always ensure that the real
       rpcb_gettime() function is called with the correct parameters.  This
       abstraction will allow the programmer to create a more Perl-like
       interface to the C function.

       It is recommended that the h2xs tool be used when creating new
       extensions.  This tool will generate template source files and
       Makefiles.  This is discussed in more detail in the section titled
       "Creating A New Extension" and in the h2xs manpage.

       The Anatomy of an XSUB

       The following XSUB allows a Perl program to access a  C	library
       function	 called	 sin().	 The XSUB will imitate the C function which
       takes a single argument and returns a  single value.

	    double
	    sin(x)
	      double<tab>x

       The compiler expects a tab between the parameter name and its type, and
       any or no whitespace before the type.  When using C pointers the
       indirection operator * should be considered part of the type and the
       address operator & should be considered part of the variable, as is
       demonstrated in the rpcb_gettime() function above.  See 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.

	  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.

	 INCORRECT			  CORRECT

	 double sin(x)			  double
	   double  x			  sin(x)
					    double  x

       The Argument Stack

       The argument stack is used to store the values which are sent as
       parameters to the XSUB and to store the XSUB's return value.  In
       reality all Perl functions keep their values on this stack at the same
       time, each limited to its own range of positions on the stack.  In this
       document the first position on that stack which belongs to the active
       function will be referred to as position 0 for that function.

       XSUBs refer to their stack arguments with the macro ST(x), where x
       refers to a position in this XSUB's part of the stack.  Position 0 for
       that function would be known to the XSUB as ST(0).  The XSUB's incoming
       parameters and outgoing return values always begin at ST(0).  For many
       simple cases the xsubpp compiler will generate the code necessary to
       handle the argument stack by embedding code fragments found in the
       typemaps.  In more complex cases the programmer must supply the code.

       The RETVAL Variable

       The RETVAL variable is a magic variable which always matches the return
       type of the C library function.	The xsubpp compiler will supply this
       variable in each XSUB and by default will use it to hold the return
       value of the C library function being called.  In simple cases the
       value of RETVAL will be placed in ST(0) of the argument stack where it
       can be received by Perl as the return value of the XSUB.

       If the XSUB has a return type of 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 MODULE Keyword

       The MODULE keyword is used to start the XS code and to specify the
       package of the functions which are being defined.  All text preceding
       the first MODULE keyword is considered C code and is passed through to
       the output untouched.  Every XS module will have a bootstrap function
       which is used to hook the XSUBs into Perl.  The package name of this
       bootstrap function will match the value of the last MODULE statement in
       the XS source files.  The value of MODULE should always remain constant
       within the same XS file, though this is not required.

       The following example will start the XS code and will place all
       functions in a package named RPC.

	    MODULE = RPC

       The PACKAGE Keyword

       When functions within an XS source file must be separated into packages
       the PACKAGE keyword should be used.  This keyword is used with the
       MODULE keyword and must follow immediately after it when used.

	    MODULE = RPC  PACKAGE = RPC

	    [ XS code in package RPC ]

	    MODULE = RPC  PACKAGE = RPCB

	    [ XS code in package RPCB ]

	    MODULE = RPC  PACKAGE = RPC

	    [ XS code in package RPC ]

       Although this keyword is optional and in some cases provides redundant
       information it should always be used.  This keyword will ensure that
       the XSUBs appear in the desired package.

       The PREFIX Keyword

       The PREFIX keyword designates prefixes which should be removed from the
       Perl function names.  If the C function is rpcb_gettime() and the
       PREFIX value is rpcb_ then Perl will see this function as gettime().

       This keyword should follow the PACKAGE keyword when used.  If PACKAGE
       is not used then PREFIX should follow the MODULE keyword.

	    MODULE = RPC  PREFIX = rpc_

	    MODULE = RPC  PACKAGE = RPCB  PREFIX = rpcb_

       The OUTPUT: Keyword

       The OUTPUT: keyword indicates that certain function parameters should
       be updated (new values made visible to Perl) when the XSUB terminates
       or that certain values should be returned to the calling Perl function.
       For simple functions, such as the sin() function above, the RETVAL
       variable is automatically designated as an output value.	 In more
       complex functions the xsubpp compiler will need help to determine which
       variables are output variables.

       This keyword will normally be used to complement the CODE:  keyword.
       The RETVAL variable is not recognized as an output variable when the
       CODE: keyword is present.  The OUTPUT:  keyword is used in this
       situation to tell the compiler that RETVAL really is an output
       variable.

       The OUTPUT: keyword can also be used to indicate that function
       parameters are output variables.	 This may be necessary when a
       parameter has been modified within the function and the programmer
       would like the update to be seen by Perl.  If function parameters are
       listed under OUTPUT: along with the RETVAL variable then the RETVAL
       variable must be the last one listed.

	    bool_t
	    rpcb_gettime(host,timep)
		 char *	 host
		 time_t	 &timep
		 OUTPUT:
		 timep

       The OUTPUT: keyword will also allow an output parameter to be mapped to
       a matching piece of code rather than to a typemap.

	    bool_t
	    rpcb_gettime(host,timep)
		 char *	 host
		 time_t	 &timep
		 OUTPUT:
		 timep<tab>sv_setnv(ST(1), (double)timep);

       The CODE: Keyword

       This keyword is used in more complicated XSUBs which require special
       handling for the C function.  The RETVAL variable is available but will
       not be returned unless it is specified under the OUTPUT: keyword.

       The following XSUB is for a C function which requires special handling
       of its parameters.  The Perl usage is given first.

	    $status = rpcb_gettime( "localhost", $timep );

       The XSUB follows.

	    bool_t
	    rpcb_gettime(host,timep)
		 char *	 host
		 time_t	 timep
		 CODE:
		      RETVAL = rpcb_gettime( host, &timep );
		 OUTPUT:
		 timep
		 RETVAL

       In many of the examples shown here the CODE: block (and other blocks)
       will often be contained within braces ( { and } ).  This protects the
       CODE: block from complex INPUT typemaps and ensures the resulting C
       code is legal.

       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 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 will tell the compiler that some parameters will be
       used for output rather than for input and that they will be handled
       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 not care about its initial contents.

	    bool_t
	    rpcb_gettime(host,timep)
		 char *	 host
		 time_t	 &timep = NO_INIT
		 OUTPUT:
		 timep

       Initializing Function Parameters

       Function parameters are normally initialized with their 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.

       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.

	    bool_t
	    rpcb_gettime(host,timep)
		 char *	 host = (char *)SvPV(ST(0),na);
		 time_t	 &timep = 0;
		 OUTPUT:
		 timep

       This should not be used to supply default values for parameters.	 One
       would normally use this when a function parameter must be processed by
       another library function before it can be used.	Default parameters are
       covered in the next section.

       Default Parameter Values

       Default values can be specified for function parameters by placing an
       assignment statement in the parameter list.  The default value may be a
       number or a string.  Defaults should always be used on the right-most
       parameters only.

       To allow the XSUB for rpcb_gettime() to have a default host value the
       parameters to the XSUB could be rearranged.  The XSUB will then call
       the real rpcb_gettime() function with the parameters in the correct
       order.  Perl will call this XSUB with either of the following
       statements.

	    $status = rpcb_gettime( $timep, $host );

	    $status = rpcb_gettime( $timep );

       The XSUB will look like the code	 which	follows.   A  CODE: block  is
       used to call the real rpcb_gettime() function with the parameters in
       the correct order for that function.

	    bool_t
	    rpcb_gettime(timep,host="localhost")
		 char *	 host
		 time_t	 timep = NO_INIT
		 CODE:
		      RETVAL = rpcb_gettime( host, &timep );
		 OUTPUT:
		 timep
		 RETVAL

       Variable-length Parameter Lists

       XSUBs can have variable-length parameter lists by specifying an
       ellipsis (...) in the parameter list.  This use of the ellipsis is
       similar to that found in ANSI C.	 The programmer is able to determine
       the number of arguments passed to the XSUB by examining the items
       variable which the xsubpp compiler supplies for all XSUBs.  By using
       this mechanism one can create an XSUB which accepts a list of
       parameters of unknown length.

       The host parameter for the rpcb_gettime() XSUB can be optional so the
       ellipsis can be used to indicate that the XSUB will take a variable
       number of parameters.  Perl should be able to call this XSUB with
       either of the following statements.

	    $status = rpcb_gettime( $timep, $host );

	    $status = rpcb_gettime( $timep );

       The XS code, with ellipsis, follows.

	    bool_t
	    rpcb_gettime(timep, ...)
		 time_t	 timep = NO_INIT
		 CODE:
		 {
		 char *host = "localhost";

		 if( items > 1 )
		      host = (char *)SvPV(ST(1), na);
		 RETVAL = rpcb_gettime( host, &timep );
		 }
		 OUTPUT:
		 timep
		 RETVAL

       The PPCODE: Keyword

       The PPCODE: keyword is an alternate form of the CODE: keyword and is
       used to tell the xsubpp compiler that the programmer is supplying the
       code to control the argument stack for the XSUBs return values.
       Occasionally one will want an XSUB to return a list of values rather
       than a single value.  In these cases one must use PPCODE: and then
       explicitly push the list of values on the stack.	 The PPCODE: and CODE:
       keywords are not used together within the same XSUB.

       The following XSUB will call the C rpcb_gettime() function and will
       return its two output values, timep and status, to Perl as a single
       list.

	    void
	    rpcb_gettime(host)
		 char *	 host
		 PPCODE:
		 {
		 time_t	 timep;
		 bool_t	 status;
		 status = rpcb_gettime( host, &timep );
		 EXTEND(sp, 2);
		 PUSHs(sv_2mortal(newSVnv(status)));
		 PUSHs(sv_2mortal(newSVnv(timep)));
		 }

       Notice that the programmer must supply the C code necessary to have the
       real rpcb_gettime() function called and to have the return values
       properly placed on the argument stack.

       The void return type for this function tells the xsubpp compiler that
       the RETVAL variable is not needed or used and that it should not be
       created.	 In most scenarios the void return type should be used with
       the PPCODE: directive.

       The EXTEND() macro is used to make room on the argument stack for 2
       return values.  The PPCODE: directive causes the xsubpp compiler to
       create a stack pointer called 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.

       Now the rpcb_gettime() function can be used from Perl with the
       following statement.

	    ($status, $timep) = rpcb_gettime("localhost");

       Returning Undef And Empty Lists

       Occasionally the programmer will want to simply return 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 to have it return the time and if it
       fails we would like to have undef returned.  In the following Perl code
       the value of $timep will either be undef or it will be a valid time.

	    $timep = rpcb_gettime( "localhost" );

       The following XSUB uses the void return type to disable the generation
       of the RETVAL variable 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
	    rpcb_gettime(host)
		 char *	 host
		 CODE:
		 {
		 time_t	 timep;
		 bool_t x;
		 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
	    rpcb_gettime(host)
		 char *	 host
		 CODE:
		 {
		 time_t	 timep;
		 bool_t x;
		 ST(0) = sv_newmortal();
		 if( rpcb_gettime( host, &timep ) ){
		      sv_setnv( ST(0), (double)timep);
		 }
		 else{
		      ST(0) = &sv_undef;
		 }
		 }

       To return an empty list one must use a PPCODE: block and then not push
       return values on the stack.

	    void
	    rpcb_gettime(host)
		 char *	 host
		 PPCODE:
		 {
		 time_t	 timep;
		 if( rpcb_gettime( host, &timep ) )
		      PUSHs(sv_2mortal(newSVnv(timep)));
		 else{
		 /* Nothing pushed on stack, so an empty */
		 /* list is implicitly returned. */
		 }
		 }

       The CLEANUP: Keyword

       This keyword can be used when an XSUB requires special cleanup
       procedures before it terminates.	 When the CLEANUP:  keyword is used it
       must follow any CODE:, PPCODE:, or OUTPUT: blocks which are present in
       the XSUB.  The code specified for the cleanup block will be added as
       the last statements in the XSUB.

       The BOOT: Keyword

       The BOOT: keyword is used to add code to the extension's bootstrap
       function.  The bootstrap function is generated by the xsubpp compiler
       and normally holds the statements necessary to register any XSUBs with
       Perl.  With the BOOT: keyword the programmer can tell the compiler to
       add extra statements to the bootstrap function.

       This keyword may be used any time after the first MODULE keyword and
       should appear on a line by itself.  The first blank line after the
       keyword will terminate the code block.

	    BOOT:
	    # The following message will be printed when the
	    # bootstrap function executes.
	    printf("Hello from the bootstrap!\n");

       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 # 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.

       Using XS With C++

       If a function is defined as a C++ method then it will assume 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.

       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.

       Perl Variables

       The following demonstrates how the Perl variable $host can be accessed
       from an XSUB.  The function perl_get_sv() is used to obtain a pointer
       to the variable, known as an SV (Scalar Variable) internally.  The
       package name 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
       main for the variable.  The macro SvPVX() is then used to dereference
       the SV to obtain a char* pointer to its contents.

	    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)));
		 }
		 }

       This Perl code can be used to call that XSUB.

	    $RPC::host = "localhost";
	    $timep = rpcb_gettime();

       In the above example the SV contained a C char* but a Perl scalar
       variable may also contain numbers and references.  If the SV is
       expected to have a C int then the macro SvIVX() should be used to
       dereference the SV.  When the SV contains a C double then SvNVX()
       should be used.

       The macro 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().

	    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)));
		 }
		 }

       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.

	    $MY::host = "localhost";
	    $RPC::host = \$MY::host;
	    $timep = rpcb_gettime();

       The second argument to perl_get_sv() will normally be FALSE as shown in
       the above examples.  An argument of 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.

       XSUBs may use perl_get_av(), perl_get_hv(), and perl_get_cv() to access
       Perl arrays, hashes, and code values.

       Interface Strategy

       When designing an interface between Perl and a C library a straight
       translation from C to XS is often sufficient.  The interface will often
       be very C-like and occasionally nonintuitive, especially when the C
       function modifies one of its parameters.	 In cases where the programmer
       wishes to create a more Perl-like interface the following strategy may
       help to identify the more critical parts of the interface.

       Identify the C functions which modify their parameters.	The XSUBs for
       these functions may be able to return lists to Perl, or may be
       candidates to return undef or an empty list in case of failure.

       Identify which values are used by only the C and XSUB functions
       themselves.  If Perl does not need to access the contents of the value
       then it may not be necessary to provide a translation for that value
       from C to Perl.

       Identify the pointers in the C function parameter lists and return
       values.	Some pointers can be handled in XS with the & unary operator
       on the variable name while others will require the use of the *
       operator on the type name.  In general it is easier to work with the &
       operator.

       Identify the structures used by the C functions.	 In many cases it may
       be helpful to use the T_PTROBJ typemap for these structures so they can
       be manipulated by Perl as blessed objects.

       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 Exporter module the RPC module can make these function names
       visible to the rest of the Perl program.	 The 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.

       Perl Objects And C Structures

       When dealing with C structures one should select either T_PTROBJ or
       T_PTRREF for the XS type.  Both types are designed to handle pointers
       to complex objects.  The T_PTRREF type will allow the Perl object to be
       unblessed while the T_PTROBJ type requires that the object be blessed.
       By using T_PTROBJ one can achieve a form of type-checking because the
       XSUB will attempt to verify that the Perl object is of the expected
       type.

       The following XS code shows the getnetconfigent() function which is
       used with ONC TIRPC.  The getnetconfigent() function will return a
       pointer to a C structure and has the C prototype shown below.  The
       example will demonstrate how the C pointer will become a Perl
       reference.  Perl will consider this reference to be a pointer to a
       blessed object and will attempt to call a destructor for the object.  A
       destructor will be provided in the XS source to free the memory used by
       getnetconfigent().  Destructors in XS can be created by specifying an
       XSUB function whose name ends with the word DESTROY.  XS destructors
       can be used to free memory which may have been malloc'd by another
       XSUB.

	    struct netconfig *getnetconfigent(const char *netid);

       A typedef will be created for struct netconfig.	The Perl object will
       be blessed in a class matching the name of the C type, with the tag Ptr
       appended, and the name should not have embedded spaces if it will be a
       Perl package name.  The destructor will be placed in a class
       corresponding to the class of the object and the PREFIX keyword will be
       used to trim the name to the word DESTROY as Perl will expect.

	    typedef struct netconfig Netconfig;

	    MODULE = RPC  PACKAGE = RPC

	    Netconfig *
	    getnetconfigent(netid)
		 char *	 netid

	    MODULE = RPC  PACKAGE = NetconfigPtr  PREFIX = rpcb_

	    void
	    rpcb_DESTROY(netconf)
		 Netconfig *  netconf
		 CODE:
		 printf("Now in NetconfigPtr::DESTROY\n");
		 free( netconf );

       This example requires the following typemap entry.  Consult the typemap
       section for more information about adding new typemaps for an
       extension.

	    TYPEMAP
	    Netconfig *	 T_PTROBJ

       This example will be used with the following Perl statements.

	    use RPC;
	    $netconf = getnetconfigent("udp");

       When Perl destroys the object referenced by $netconf it will send the
       object to the supplied XSUB DESTROY function.  Perl cannot determine,
       and does not care, that this object is a C struct and not a Perl
       object.	In this sense, there is no difference between the object
       created by the getnetconfigent() XSUB and an object created by a normal
       Perl subroutine.

       C Headers and Perl

       The h2xs compiler is designed to convert C header files in /usr/include
       into Perl extensions.  This compiler will create a directory under the
       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 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 #define statements which were in the C header.

	    use Rusers;
	    print "RPC program number for rusers service: ";
	    print &RUSERSPROG, "\n";

       Creating A New Extension

       The 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 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 -A option will be given to h2xs.  When run from the
       Perl source directory, the 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 makefile, not Makefile) in the Perl source directory
       should be edited to add ext/RPC/RPC.a to the 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 Configure script can also be used to add extensions.  The
       extension should be placed in the 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 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 .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 make in the extension's directory if it finds an XS file matching
       the name of the extension's directory.

       The Typemap

       The typemap is a collection of code fragments which are used by the
       xsubpp compiler to map C function parameters and values to Perl values.
       The typemap file may consist of three sections labeled TYPEMAP, INPUT,
       and OUTPUT.  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 default typemap in the ext directory of the Perl source contains
       many useful types which can be used by Perl extensions.	Some
       extensions define additional typemaps which they keep in their own
       directory.  These additional typemaps may reference INPUT and OUTPUT
       maps in the main typemap.  The xsubpp compiler will allow the
       extension's own typemap to override any mappings which are in the
       default typemap.

       Most extensions which require a custom typemap will need only the
       TYPEMAP section of the typemap file.  The custom typemap used in the
       getnetconfigent() example shown earlier demonstrates what may be the
       typical use of extension typemaps.  That typemap is used to equate a C
       structure with the T_PTROBJ typemap.  The typemap used by
       getnetconfigent() is shown here.	 Note that the C type is separated
       from the XS type with a tab and that the C unary operator * is
       considered to be a part of the C type name.

	    TYPEMAP
	    Netconfig *<tab>T_PTROBJ

EXAMPLES
       File RPC.xs: Interface to some ONC+ RPC bind library functions.

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

	    #include <rpc/rpc.h>

	    typedef struct netconfig Netconfig;

	    MODULE = RPC  PACKAGE = RPC

	    void
	    rpcb_gettime(host="localhost")
		 char *	 host
		 CODE:
		 {
		 time_t	 timep;
		 ST(0) = sv_newmortal();
		 if( rpcb_gettime( host, &timep ) )
		      sv_setnv( ST(0), (double)timep );
		 }

	    Netconfig *
	    getnetconfigent(netid="udp")
		 char *	 netid

	    MODULE = RPC  PACKAGE = NetconfigPtr  PREFIX = rpcb_

	    void
	    rpcb_DESTROY(netconf)
		 Netconfig *  netconf
		 CODE:
		 printf("NetconfigPtr::DESTROY\n");
		 free( netconf );

       File typemap: Custom typemap for RPC.xs.

	    TYPEMAP
	    Netconfig *	 T_PTROBJ

       File RPC.pm: Perl module for the RPC extension.

	    package RPC;

	    require Exporter;
	    require DynaLoader;
	    @ISA = qw(Exporter DynaLoader);
	    @EXPORT = qw(rpcb_gettime getnetconfigent);

	    bootstrap RPC;
	    1;

       File rpctest.pl: Perl test program for the RPC extension.

	    use RPC;

	    $netconf = getnetconfigent();
	    $a = rpcb_gettime();
	    print "time = $a\n";
	    print "netconf = $netconf\n";

	    $netconf = getnetconfigent("tcp");
	    $a = rpcb_gettime("poplar");
	    print "time = $a\n";
	    print "netconf = $netconf\n";

AUTHOR
       Dean Roehrich <roehrich@cray.com> May 3, 1995

3rd Berkeley Distribution					    PERLAPI(1)
[top]

List of man pages available for NeXTSTEP

Copyright (c) for man pages and the logo by the respective OS vendor.

For those who want to learn more, the polarhome community provides shell access and support.

[legal] [privacy] [GNU] [policy] [cookies] [netiquette] [sponsors] [FAQ]
Tweet
Polarhome, production since 1999.
Member of Polarhome portal.
Based on Fawad Halim's script.
....................................................................
Vote for polarhome
Free Shell Accounts :: the biggest list on the net