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Diffstat (limited to 'pod/perlxs.pod')
| -rw-r--r-- | pod/perlxs.pod | 333 |
1 files changed, 305 insertions, 28 deletions
diff --git a/pod/perlxs.pod b/pod/perlxs.pod index b663dcfa2d..0c376047ba 100644 --- a/pod/perlxs.pod +++ b/pod/perlxs.pod @@ -129,6 +129,16 @@ 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 @@ -278,10 +288,20 @@ The XSUB follows. 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 @@ -362,6 +382,86 @@ the parameters in the correct order for that function. 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 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 @@ -385,14 +485,12 @@ The XS code, with ellipsis, follows. 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 ); - } + CODE: + if( items > 1 ) + host = (char *)SvPV(ST(1), na); + RETVAL = rpcb_gettime( host, &timep ); OUTPUT: timep RETVAL @@ -414,15 +512,14 @@ Perl as a single list. 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(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 @@ -466,14 +563,13 @@ the default return value. void 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. @@ -481,10 +577,10 @@ return value, should the need arise. void 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); @@ -492,7 +588,6 @@ return value, should the need arise. 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. @@ -500,16 +595,15 @@ then not push return values on the stack. void rpcb_gettime(host) char *host - PPCODE: - { + PREINIT: time_t timep; + PPCODE: if( rpcb_gettime( host, &timep ) ) PUSHs(sv_2mortal(newSViv(timep))); else{ /* Nothing pushed on stack, so an empty */ /* list is implicitly returned. */ } - } =head2 The REQUIRE: Keyword @@ -545,6 +639,186 @@ terminate the code block. # 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 commandline +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 commandline 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"; + CODE: + if( items > 1 ) + host = (char *)SvPV(ST(1), na); + RETVAL = rpcb_gettime( host, &timep ); + OUTPUT: + timep + RETVAL + +=head2 The ALIAS: Keyword + +The ALIAS: keyword allows an XSUB to have two more 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 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()> it's parameters are the usual C<(char *host, time_t +*timep)>, but when the function is called as C<x_gettime()> is 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 @@ -635,7 +909,7 @@ example. # 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) ) @@ -787,13 +1061,12 @@ File C<RPC.xs>: Interface to some ONC+ RPC bind library functions. void 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") @@ -840,7 +1113,11 @@ File C<rpctest.pl>: Perl test program for the RPC extension. print "netconf = $netconf\n"; +=head1 XS VERSION + +This document covers features supported by C<xsubpp> 1.931. + =head1 AUTHOR Dean Roehrich F<E<lt>roehrich@cray.comE<gt>> -Dec 10, 1995 +Jan 25, 1996 |