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1 | =head1 NAME |
2 | |
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3 | perlxs - XS language reference manual |
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4 | |
5 | =head1 DESCRIPTION |
6 | |
7 | =head2 Introduction |
8 | |
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9 | XS is an interface description file format used to create an extension |
10 | interface between Perl and C code (or a C library) which one wishes |
11 | to use with Perl. The XS interface is combined with the library to |
12 | create a new library which can then be either dynamically loaded |
13 | or statically linked into perl. The XS interface description is |
14 | written in the XS language and is the core component of the Perl |
15 | extension interface. |
16 | |
17 | An B<XSUB> forms the basic unit of the XS interface. After compilation |
18 | by the B<xsubpp> compiler, each XSUB amounts to a C function definition |
19 | which will provide the glue between Perl calling conventions and C |
20 | calling conventions. |
21 | |
22 | The glue code pulls the arguments from the Perl stack, converts these |
23 | Perl values to the formats expected by a C function, call this C function, |
24 | transfers the return values of the C function back to Perl. |
25 | Return values here may be a conventional C return value or any C |
26 | function arguments that may serve as output parameters. These return |
27 | values may be passed back to Perl either by putting them on the |
28 | Perl stack, or by modifying the arguments supplied from the Perl side. |
29 | |
30 | The above is a somewhat simplified view of what really happens. Since |
31 | Perl allows more flexible calling conventions than C, XSUBs may do much |
32 | more in practice, such as checking input parameters for validity, |
33 | throwing exceptions (or returning undef/empty list) if the return value |
34 | from the C function indicates failure, calling different C functions |
35 | based on numbers and types of the arguments, providing an object-oriented |
36 | interface, etc. |
37 | |
38 | Of course, one could write such glue code directly in C. However, this |
39 | would be a tedious task, especially if one needs to write glue for |
40 | multiple C functions, and/or one is not familiar enough with the Perl |
41 | stack discipline and other such arcana. XS comes to the rescue here: |
42 | instead of writing this glue C code in long-hand, one can write |
43 | a more concise short-hand I<description> of what should be done by |
44 | the glue, and let the XS compiler B<xsubpp> handle the rest. |
45 | |
46 | The XS language allows one to describe the mapping between how the C |
47 | routine is used, and how the corresponding Perl routine is used. It |
48 | also allows creation of Perl routines which are directly translated to |
49 | C code and which are not related to a pre-existing C function. In cases |
50 | when the C interface coincides with the Perl interface, the XSUB |
51 | declaration is almost identical to a declaration of a C function (in K&R |
52 | style). In such circumstances, there is another tool called C<h2xs> |
53 | that is able to translate an entire C header file into a corresponding |
54 | XS file that will provide glue to the functions/macros described in |
55 | the header file. |
56 | |
57 | The XS compiler is called B<xsubpp>. This compiler creates |
58 | the constructs necessary to let an XSUB manipulate Perl values, and |
59 | creates the glue necessary to let Perl call the XSUB. The compiler |
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60 | uses B<typemaps> to determine how to map C function parameters |
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61 | and output values to Perl values and back. The default typemap |
62 | (which comes with Perl) handles many common C types. A supplementary |
63 | typemap may also be needed to handle any special structures and types |
64 | for the library being linked. |
65 | |
66 | A file in XS format starts with a C language section which goes until the |
67 | first C<MODULE =Z<>> directive. Other XS directives and XSUB definitions |
68 | may follow this line. The "language" used in this part of the file |
69 | is usually referred to as the XS language. |
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70 | |
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71 | See L<perlxstut> for a tutorial on the whole extension creation process. |
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72 | |
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73 | Note: For some extensions, Dave Beazley's SWIG system may provide a |
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74 | significantly more convenient mechanism for creating the extension |
75 | glue code. See http://www.swig.org/ for more information. |
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76 | |
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77 | =head2 On The Road |
78 | |
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79 | Many of the examples which follow will concentrate on creating an interface |
80 | between Perl and the ONC+ RPC bind library functions. The rpcb_gettime() |
81 | function is used to demonstrate many features of the XS language. This |
82 | function has two parameters; the first is an input parameter and the second |
83 | is an output parameter. The function also returns a status value. |
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84 | |
85 | bool_t rpcb_gettime(const char *host, time_t *timep); |
86 | |
87 | From C this function will be called with the following |
88 | statements. |
89 | |
90 | #include <rpc/rpc.h> |
91 | bool_t status; |
92 | time_t timep; |
93 | status = rpcb_gettime( "localhost", &timep ); |
94 | |
95 | If an XSUB is created to offer a direct translation between this function |
96 | and Perl, then this XSUB will be used from Perl with the following code. |
97 | The $status and $timep variables will contain the output of the function. |
98 | |
99 | use RPC; |
100 | $status = rpcb_gettime( "localhost", $timep ); |
101 | |
102 | The following XS file shows an XS subroutine, or XSUB, which |
103 | demonstrates one possible interface to the rpcb_gettime() |
104 | function. This XSUB represents a direct translation between |
105 | C and Perl and so preserves the interface even from Perl. |
106 | This XSUB will be invoked from Perl with the usage shown |
107 | above. Note that the first three #include statements, for |
108 | C<EXTERN.h>, C<perl.h>, and C<XSUB.h>, will always be present at the |
109 | beginning of an XS file. This approach and others will be |
110 | expanded later in this document. |
111 | |
112 | #include "EXTERN.h" |
113 | #include "perl.h" |
114 | #include "XSUB.h" |
115 | #include <rpc/rpc.h> |
116 | |
117 | MODULE = RPC PACKAGE = RPC |
118 | |
119 | bool_t |
120 | rpcb_gettime(host,timep) |
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121 | char *host |
122 | time_t &timep |
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123 | OUTPUT: |
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124 | timep |
125 | |
126 | Any extension to Perl, including those containing XSUBs, |
127 | should have a Perl module to serve as the bootstrap which |
128 | pulls the extension into Perl. This module will export the |
129 | extension's functions and variables to the Perl program and |
130 | will cause the extension's XSUBs to be linked into Perl. |
131 | The following module will be used for most of the examples |
132 | in this document and should be used from Perl with the C<use> |
133 | command as shown earlier. Perl modules are explained in |
134 | more detail later in this document. |
135 | |
136 | package RPC; |
137 | |
138 | require Exporter; |
139 | require DynaLoader; |
140 | @ISA = qw(Exporter DynaLoader); |
141 | @EXPORT = qw( rpcb_gettime ); |
142 | |
143 | bootstrap RPC; |
144 | 1; |
145 | |
146 | Throughout this document a variety of interfaces to the rpcb_gettime() |
147 | XSUB will be explored. The XSUBs will take their parameters in different |
148 | orders or will take different numbers of parameters. In each case the |
149 | XSUB is an abstraction between Perl and the real C rpcb_gettime() |
150 | function, and the XSUB must always ensure that the real rpcb_gettime() |
151 | function is called with the correct parameters. This abstraction will |
152 | allow the programmer to create a more Perl-like interface to the C |
153 | function. |
154 | |
155 | =head2 The Anatomy of an XSUB |
156 | |
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157 | The simplest XSUBs consist of 3 parts: a description of the return |
158 | value, the name of the XSUB routine and the names of its arguments, |
159 | and a description of types or formats of the arguments. |
160 | |
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161 | The following XSUB allows a Perl program to access a C library function |
162 | called sin(). The XSUB will imitate the C function which takes a single |
163 | argument and returns a single value. |
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164 | |
165 | double |
166 | sin(x) |
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167 | double x |
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168 | |
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169 | When using parameters with C pointer types, as in |
170 | |
171 | double string_to_double(char *s); |
172 | |
173 | there may be two ways to describe this argument to B<xsubpp>: |
174 | |
175 | char * s |
176 | char &s |
177 | |
178 | Both these XS declarations correspond to the C<char*> C type, but they have |
179 | different semantics. It is convenient to think that the indirection operator |
180 | C<*> should be considered as a part of the type and the address operator C<&> |
181 | should be considered part of the variable. See L<"The Typemap"> and |
182 | L<"The & Unary Operator"> for more info about handling qualifiers and unary |
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183 | operators in C types. |
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184 | |
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185 | The function name and the return type must be placed on |
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186 | separate lines and should be flush left-adjusted. |
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187 | |
188 | INCORRECT CORRECT |
189 | |
190 | double sin(x) double |
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191 | double x sin(x) |
192 | double x |
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193 | |
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194 | The function body may be indented or left-adjusted. The following example |
195 | shows a function with its body left-adjusted. Most examples in this |
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196 | document will indent the body for better readability. |
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197 | |
198 | CORRECT |
199 | |
200 | double |
201 | sin(x) |
202 | double x |
203 | |
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204 | More complicated XSUBs may contain many other sections. Each section of |
205 | an XSUB starts with the corresponding keyword, such as INIT: or CLEANUP:. |
206 | However, the first two lines of an XSUB always contain the same data: |
207 | descriptions of the return type and the names of the function and its |
208 | parameters. Whatever immediately follows these is considered to be |
209 | an INPUT: section unless explicitly marked with another keyword. |
210 | (See L<The INPUT: Keyword>.) |
211 | |
212 | An XSUB section continues until another section-start keyword is found. |
213 | |
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214 | =head2 The Argument Stack |
215 | |
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216 | The Perl argument stack is used to store the values which are |
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217 | sent as parameters to the XSUB and to store the XSUB's |
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218 | return value(s). In reality all Perl functions (including non-XSUB |
219 | ones) keep their values on this stack all the same time, each limited |
220 | to its own range of positions on the stack. In this document the |
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221 | first position on that stack which belongs to the active |
222 | function will be referred to as position 0 for that function. |
223 | |
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224 | XSUBs refer to their stack arguments with the macro B<ST(x)>, where I<x> |
225 | refers to a position in this XSUB's part of the stack. Position 0 for that |
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226 | function would be known to the XSUB as ST(0). The XSUB's incoming |
227 | parameters and outgoing return values always begin at ST(0). For many |
228 | simple cases the B<xsubpp> compiler will generate the code necessary to |
229 | handle the argument stack by embedding code fragments found in the |
230 | typemaps. In more complex cases the programmer must supply the code. |
231 | |
232 | =head2 The RETVAL Variable |
233 | |
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234 | The RETVAL variable is a special C variable that is declared automatically |
235 | for you. The C type of RETVAL matches the return type of the C library |
236 | function. The B<xsubpp> compiler will declare this variable in each XSUB |
237 | with non-C<void> return type. By default the generated C function |
238 | will use RETVAL to hold the return value of the C library function being |
239 | called. In simple cases the value of RETVAL will be placed in ST(0) of |
240 | the argument stack where it can be received by Perl as the return value |
241 | of the XSUB. |
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242 | |
243 | If the XSUB has a return type of C<void> then the compiler will |
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244 | not declare a RETVAL variable for that function. When using |
245 | a PPCODE: section no manipulation of the RETVAL variable is required, the |
246 | section may use direct stack manipulation to place output values on the stack. |
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247 | |
248 | If PPCODE: directive is not used, C<void> return value should be used |
249 | only for subroutines which do not return a value, I<even if> CODE: |
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250 | directive is used which sets ST(0) explicitly. |
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251 | |
252 | Older versions of this document recommended to use C<void> return |
253 | value in such cases. It was discovered that this could lead to |
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254 | segfaults in cases when XSUB was I<truly> C<void>. This practice is |
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255 | now deprecated, and may be not supported at some future version. Use |
256 | the return value C<SV *> in such cases. (Currently C<xsubpp> contains |
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257 | some heuristic code which tries to disambiguate between "truly-void" |
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258 | and "old-practice-declared-as-void" functions. Hence your code is at |
259 | mercy of this heuristics unless you use C<SV *> as return value.) |
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260 | |
261 | =head2 The MODULE Keyword |
262 | |
263 | The MODULE keyword is used to start the XS code and to |
264 | specify the package of the functions which are being |
265 | defined. All text preceding the first MODULE keyword is |
266 | considered C code and is passed through to the output |
267 | untouched. Every XS module will have a bootstrap function |
268 | which is used to hook the XSUBs into Perl. The package name |
269 | of this bootstrap function will match the value of the last |
270 | MODULE statement in the XS source files. The value of |
271 | MODULE should always remain constant within the same XS |
272 | file, though this is not required. |
273 | |
274 | The following example will start the XS code and will place |
275 | all functions in a package named RPC. |
276 | |
277 | MODULE = RPC |
278 | |
279 | =head2 The PACKAGE Keyword |
280 | |
281 | When functions within an XS source file must be separated into packages |
282 | the PACKAGE keyword should be used. This keyword is used with the MODULE |
283 | keyword and must follow immediately after it when used. |
284 | |
285 | MODULE = RPC PACKAGE = RPC |
286 | |
287 | [ XS code in package RPC ] |
288 | |
289 | MODULE = RPC PACKAGE = RPCB |
290 | |
291 | [ XS code in package RPCB ] |
292 | |
293 | MODULE = RPC PACKAGE = RPC |
294 | |
295 | [ XS code in package RPC ] |
296 | |
297 | Although this keyword is optional and in some cases provides redundant |
298 | information it should always be used. This keyword will ensure that the |
299 | XSUBs appear in the desired package. |
300 | |
301 | =head2 The PREFIX Keyword |
302 | |
303 | The PREFIX keyword designates prefixes which should be |
304 | removed from the Perl function names. If the C function is |
305 | C<rpcb_gettime()> and the PREFIX value is C<rpcb_> then Perl will |
306 | see this function as C<gettime()>. |
307 | |
308 | This keyword should follow the PACKAGE keyword when used. |
309 | If PACKAGE is not used then PREFIX should follow the MODULE |
310 | keyword. |
311 | |
312 | MODULE = RPC PREFIX = rpc_ |
313 | |
314 | MODULE = RPC PACKAGE = RPCB PREFIX = rpcb_ |
315 | |
316 | =head2 The OUTPUT: Keyword |
317 | |
318 | The OUTPUT: keyword indicates that certain function parameters should be |
319 | updated (new values made visible to Perl) when the XSUB terminates or that |
320 | certain values should be returned to the calling Perl function. For |
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321 | simple functions which have no CODE: or PPCODE: section, |
322 | such as the sin() function above, the RETVAL variable is |
323 | automatically designated as an output value. For more complex functions |
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324 | the B<xsubpp> compiler will need help to determine which variables are output |
325 | variables. |
326 | |
327 | This keyword will normally be used to complement the CODE: keyword. |
328 | The RETVAL variable is not recognized as an output variable when the |
329 | CODE: keyword is present. The OUTPUT: keyword is used in this |
330 | situation to tell the compiler that RETVAL really is an output |
331 | variable. |
332 | |
333 | The OUTPUT: keyword can also be used to indicate that function parameters |
334 | are output variables. This may be necessary when a parameter has been |
335 | modified within the function and the programmer would like the update to |
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336 | be seen by Perl. |
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337 | |
338 | bool_t |
339 | rpcb_gettime(host,timep) |
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340 | char *host |
341 | time_t &timep |
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342 | OUTPUT: |
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343 | timep |
344 | |
345 | The OUTPUT: keyword will also allow an output parameter to |
346 | be mapped to a matching piece of code rather than to a |
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347 | typemap. |
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348 | |
349 | bool_t |
350 | rpcb_gettime(host,timep) |
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351 | char *host |
352 | time_t &timep |
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353 | OUTPUT: |
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354 | timep sv_setnv(ST(1), (double)timep); |
355 | |
356 | B<xsubpp> emits an automatic C<SvSETMAGIC()> for all parameters in the |
357 | OUTPUT section of the XSUB, except RETVAL. This is the usually desired |
358 | behavior, as it takes care of properly invoking 'set' magic on output |
359 | parameters (needed for hash or array element parameters that must be |
360 | created if they didn't exist). If for some reason, this behavior is |
361 | not desired, the OUTPUT section may contain a C<SETMAGIC: DISABLE> line |
362 | to disable it for the remainder of the parameters in the OUTPUT section. |
363 | Likewise, C<SETMAGIC: ENABLE> can be used to reenable it for the |
364 | remainder of the OUTPUT section. See L<perlguts> for more details |
365 | about 'set' magic. |
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366 | |
367 | =head2 The CODE: Keyword |
368 | |
369 | This keyword is used in more complicated XSUBs which require |
370 | special handling for the C function. The RETVAL variable is |
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371 | still declared, but it will not be returned unless it is specified |
372 | in the OUTPUT: section. |
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373 | |
374 | The following XSUB is for a C function which requires special handling of |
375 | its parameters. The Perl usage is given first. |
376 | |
377 | $status = rpcb_gettime( "localhost", $timep ); |
378 | |
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379 | The XSUB follows. |
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380 | |
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381 | bool_t |
382 | rpcb_gettime(host,timep) |
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383 | char *host |
384 | time_t timep |
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385 | CODE: |
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386 | RETVAL = rpcb_gettime( host, &timep ); |
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387 | OUTPUT: |
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388 | timep |
389 | RETVAL |
390 | |
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391 | =head2 The INIT: Keyword |
392 | |
393 | The INIT: keyword allows initialization to be inserted into the XSUB before |
394 | the compiler generates the call to the C function. Unlike the CODE: keyword |
395 | above, this keyword does not affect the way the compiler handles RETVAL. |
396 | |
397 | bool_t |
398 | rpcb_gettime(host,timep) |
399 | char *host |
400 | time_t &timep |
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401 | INIT: |
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402 | printf("# Host is %s\n", host ); |
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403 | OUTPUT: |
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404 | timep |
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405 | |
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406 | Another use for the INIT: section is to check for preconditions before |
407 | making a call to the C function: |
408 | |
409 | long long |
410 | lldiv(a,b) |
411 | long long a |
412 | long long b |
413 | INIT: |
414 | if (a == 0 && b == 0) |
415 | XSRETURN_UNDEF; |
416 | if (b == 0) |
417 | croak("lldiv: cannot divide by 0"); |
418 | |
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419 | =head2 The NO_INIT Keyword |
420 | |
421 | The NO_INIT keyword is used to indicate that a function |
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422 | parameter is being used only as an output value. The B<xsubpp> |
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423 | compiler will normally generate code to read the values of |
424 | all function parameters from the argument stack and assign |
425 | them to C variables upon entry to the function. NO_INIT |
426 | will tell the compiler that some parameters will be used for |
427 | output rather than for input and that they will be handled |
428 | before the function terminates. |
429 | |
430 | The following example shows a variation of the rpcb_gettime() function. |
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431 | This function uses the timep variable only as an output variable and does |
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432 | not care about its initial contents. |
433 | |
434 | bool_t |
435 | rpcb_gettime(host,timep) |
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436 | char *host |
437 | time_t &timep = NO_INIT |
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438 | OUTPUT: |
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439 | timep |
440 | |
441 | =head2 Initializing Function Parameters |
442 | |
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443 | C function parameters are normally initialized with their values from |
444 | the argument stack (which in turn contains the parameters that were |
445 | passed to the XSUB from Perl). The typemaps contain the |
446 | code segments which are used to translate the Perl values to |
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447 | the C parameters. The programmer, however, is allowed to |
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448 | override the typemaps and supply alternate (or additional) |
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449 | initialization code. Initialization code starts with the first |
450 | C<=>, C<;> or C<+> on a line in the INPUT: section. The only |
451 | exception happens if this C<;> terminates the line, then this C<;> |
452 | is quietly ignored. |
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453 | |
454 | The following code demonstrates how to supply initialization code for |
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455 | function parameters. The initialization code is eval'd within double |
456 | quotes by the compiler before it is added to the output so anything |
457 | which should be interpreted literally [mainly C<$>, C<@>, or C<\\>] |
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458 | must be protected with backslashes. The variables $var, $arg, |
459 | and $type can be used as in typemaps. |
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460 | |
461 | bool_t |
462 | rpcb_gettime(host,timep) |
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463 | char *host = (char *)SvPV($arg,PL_na); |
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464 | time_t &timep = 0; |
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465 | OUTPUT: |
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466 | timep |
467 | |
468 | This should not be used to supply default values for parameters. One |
469 | would normally use this when a function parameter must be processed by |
470 | another library function before it can be used. Default parameters are |
471 | covered in the next section. |
472 | |
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473 | If the initialization begins with C<=>, then it is output in |
474 | the declaration for the input variable, replacing the initialization |
475 | supplied by the typemap. If the initialization |
476 | begins with C<;> or C<+>, then it is performed after |
477 | all of the input variables have been declared. In the C<;> |
478 | case the initialization normally supplied by the typemap is not performed. |
479 | For the C<+> case, the declaration for the variable will include the |
480 | initialization from the typemap. A global |
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481 | variable, C<%v>, is available for the truly rare case where |
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482 | information from one initialization is needed in another |
483 | initialization. |
484 | |
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485 | Here's a truly obscure example: |
486 | |
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487 | bool_t |
488 | rpcb_gettime(host,timep) |
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489 | time_t &timep ; /* \$v{timep}=@{[$v{timep}=$arg]} */ |
490 | char *host + SvOK($v{timep}) ? SvPV($arg,PL_na) : NULL; |
491 | OUTPUT: |
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492 | timep |
493 | |
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494 | The construct C<\$v{timep}=@{[$v{timep}=$arg]}> used in the above |
495 | example has a two-fold purpose: first, when this line is processed by |
496 | B<xsubpp>, the Perl snippet C<$v{timep}=$arg> is evaluated. Second, |
497 | the text of the evaluated snippet is output into the generated C file |
498 | (inside a C comment)! During the processing of C<char *host> line, |
499 | $arg will evaluate to C<ST(0)>, and C<$v{timep}> will evaluate to |
500 | C<ST(1)>. |
501 | |
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502 | =head2 Default Parameter Values |
503 | |
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504 | Default values for XSUB arguments can be specified by placing an |
505 | assignment statement in the parameter list. The default value may |
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506 | be a number, a string or the special string C<NO_INIT>. Defaults should |
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507 | always be used on the right-most parameters only. |
508 | |
509 | To allow the XSUB for rpcb_gettime() to have a default host |
510 | value the parameters to the XSUB could be rearranged. The |
511 | XSUB will then call the real rpcb_gettime() function with |
beb31b0b |
512 | the parameters in the correct order. This XSUB can be called |
513 | from Perl with either of the following statements: |
a0d0e21e |
514 | |
515 | $status = rpcb_gettime( $timep, $host ); |
516 | |
517 | $status = rpcb_gettime( $timep ); |
518 | |
519 | The XSUB will look like the code which follows. A CODE: |
520 | block is used to call the real rpcb_gettime() function with |
521 | the parameters in the correct order for that function. |
522 | |
523 | bool_t |
524 | rpcb_gettime(timep,host="localhost") |
8e07c86e |
525 | char *host |
526 | time_t timep = NO_INIT |
beb31b0b |
527 | CODE: |
a0d0e21e |
528 | RETVAL = rpcb_gettime( host, &timep ); |
beb31b0b |
529 | OUTPUT: |
a0d0e21e |
530 | timep |
531 | RETVAL |
532 | |
c07a80fd |
533 | =head2 The PREINIT: Keyword |
534 | |
beb31b0b |
535 | The PREINIT: keyword allows extra variables to be declared immediately |
a2293a43 |
536 | before or after the declarations of the parameters from the INPUT: section |
beb31b0b |
537 | are emitted. |
538 | |
539 | If a variable is declared inside a CODE: section it will follow any typemap |
540 | code that is emitted for the input parameters. This may result in the |
541 | declaration ending up after C code, which is C syntax error. Similar |
542 | errors may happen with an explicit C<;>-type or C<+>-type initialization of |
543 | parameters is used (see L<"Initializing Function Parameters">). Declaring |
544 | these variables in an INIT: section will not help. |
545 | |
546 | In such cases, to force an additional variable to be declared together |
547 | with declarations of other variables, place the declaration into a |
548 | PREINIT: section. The PREINIT: keyword may be used one or more times |
549 | within an XSUB. |
c07a80fd |
550 | |
551 | The following examples are equivalent, but if the code is using complex |
552 | typemaps then the first example is safer. |
553 | |
554 | bool_t |
555 | rpcb_gettime(timep) |
556 | time_t timep = NO_INIT |
beb31b0b |
557 | PREINIT: |
c07a80fd |
558 | char *host = "localhost"; |
beb31b0b |
559 | CODE: |
c07a80fd |
560 | RETVAL = rpcb_gettime( host, &timep ); |
beb31b0b |
561 | OUTPUT: |
c07a80fd |
562 | timep |
563 | RETVAL |
564 | |
beb31b0b |
565 | For this particular case an INIT: keyword would generate the |
566 | same C code as the PREINIT: keyword. Another correct, but error-prone example: |
c07a80fd |
567 | |
568 | bool_t |
569 | rpcb_gettime(timep) |
570 | time_t timep = NO_INIT |
beb31b0b |
571 | CODE: |
c07a80fd |
572 | char *host = "localhost"; |
573 | RETVAL = rpcb_gettime( host, &timep ); |
beb31b0b |
574 | OUTPUT: |
575 | timep |
576 | RETVAL |
577 | |
578 | Another way to declare C<host> is to use a C block in the CODE: section: |
579 | |
580 | bool_t |
581 | rpcb_gettime(timep) |
582 | time_t timep = NO_INIT |
583 | CODE: |
584 | { |
585 | char *host = "localhost"; |
586 | RETVAL = rpcb_gettime( host, &timep ); |
587 | } |
588 | OUTPUT: |
589 | timep |
590 | RETVAL |
591 | |
592 | The ability to put additional declarations before the typemap entries are |
593 | processed is very handy in the cases when typemap conversions manipulate |
594 | some global state: |
595 | |
596 | MyObject |
597 | mutate(o) |
598 | PREINIT: |
599 | MyState st = global_state; |
600 | INPUT: |
601 | MyObject o; |
602 | CLEANUP: |
603 | reset_to(global_state, st); |
604 | |
605 | Here we suppose that conversion to C<MyObject> in the INPUT: section and from |
606 | MyObject when processing RETVAL will modify a global variable C<global_state>. |
607 | After these conversions are performed, we restore the old value of |
608 | C<global_state> (to avoid memory leaks, for example). |
609 | |
610 | There is another way to trade clarity for compactness: INPUT sections allow |
611 | declaration of C variables which do not appear in the parameter list of |
612 | a subroutine. Thus the above code for mutate() can be rewritten as |
613 | |
614 | MyObject |
615 | mutate(o) |
616 | MyState st = global_state; |
617 | MyObject o; |
618 | CLEANUP: |
619 | reset_to(global_state, st); |
620 | |
621 | and the code for rpcb_gettime() can be rewritten as |
622 | |
623 | bool_t |
624 | rpcb_gettime(timep) |
625 | time_t timep = NO_INIT |
626 | char *host = "localhost"; |
627 | C_ARGS: |
628 | host, &timep |
629 | OUTPUT: |
c07a80fd |
630 | timep |
631 | RETVAL |
632 | |
84287afe |
633 | =head2 The SCOPE: Keyword |
634 | |
635 | The SCOPE: keyword allows scoping to be enabled for a particular XSUB. If |
636 | enabled, the XSUB will invoke ENTER and LEAVE automatically. |
637 | |
638 | To support potentially complex type mappings, if a typemap entry used |
beb31b0b |
639 | by an XSUB contains a comment like C</*scope*/> then scoping will |
640 | be automatically enabled for that XSUB. |
84287afe |
641 | |
642 | To enable scoping: |
643 | |
644 | SCOPE: ENABLE |
645 | |
646 | To disable scoping: |
647 | |
648 | SCOPE: DISABLE |
649 | |
c07a80fd |
650 | =head2 The INPUT: Keyword |
651 | |
652 | The XSUB's parameters are usually evaluated immediately after entering the |
653 | XSUB. The INPUT: keyword can be used to force those parameters to be |
654 | evaluated a little later. The INPUT: keyword can be used multiple times |
655 | within an XSUB and can be used to list one or more input variables. This |
656 | keyword is used with the PREINIT: keyword. |
657 | |
658 | The following example shows how the input parameter C<timep> can be |
659 | evaluated late, after a PREINIT. |
660 | |
661 | bool_t |
662 | rpcb_gettime(host,timep) |
663 | char *host |
beb31b0b |
664 | PREINIT: |
c07a80fd |
665 | time_t tt; |
beb31b0b |
666 | INPUT: |
c07a80fd |
667 | time_t timep |
beb31b0b |
668 | CODE: |
c07a80fd |
669 | RETVAL = rpcb_gettime( host, &tt ); |
670 | timep = tt; |
beb31b0b |
671 | OUTPUT: |
c07a80fd |
672 | timep |
673 | RETVAL |
674 | |
675 | The next example shows each input parameter evaluated late. |
676 | |
677 | bool_t |
678 | rpcb_gettime(host,timep) |
beb31b0b |
679 | PREINIT: |
c07a80fd |
680 | time_t tt; |
beb31b0b |
681 | INPUT: |
c07a80fd |
682 | char *host |
beb31b0b |
683 | PREINIT: |
c07a80fd |
684 | char *h; |
beb31b0b |
685 | INPUT: |
c07a80fd |
686 | time_t timep |
beb31b0b |
687 | CODE: |
c07a80fd |
688 | h = host; |
689 | RETVAL = rpcb_gettime( h, &tt ); |
690 | timep = tt; |
beb31b0b |
691 | OUTPUT: |
692 | timep |
693 | RETVAL |
694 | |
695 | Since INPUT sections allow declaration of C variables which do not appear |
696 | in the parameter list of a subroutine, this may be shortened to: |
697 | |
698 | bool_t |
699 | rpcb_gettime(host,timep) |
700 | time_t tt; |
701 | char *host; |
702 | char *h = host; |
703 | time_t timep; |
704 | CODE: |
705 | RETVAL = rpcb_gettime( h, &tt ); |
706 | timep = tt; |
707 | OUTPUT: |
c07a80fd |
708 | timep |
709 | RETVAL |
710 | |
beb31b0b |
711 | (We used our knowledge that input conversion for C<char *> is a "simple" one, |
712 | thus C<host> is initialized on the declaration line, and our assignment |
713 | C<h = host> is not performed too early. Otherwise one would need to have the |
714 | assignment C<h = host> in a CODE: or INIT: section.) |
715 | |
a0d0e21e |
716 | =head2 Variable-length Parameter Lists |
717 | |
718 | XSUBs can have variable-length parameter lists by specifying an ellipsis |
719 | C<(...)> in the parameter list. This use of the ellipsis is similar to that |
720 | found in ANSI C. The programmer is able to determine the number of |
721 | arguments passed to the XSUB by examining the C<items> variable which the |
722 | B<xsubpp> compiler supplies for all XSUBs. By using this mechanism one can |
723 | create an XSUB which accepts a list of parameters of unknown length. |
724 | |
725 | The I<host> parameter for the rpcb_gettime() XSUB can be |
726 | optional so the ellipsis can be used to indicate that the |
727 | XSUB will take a variable number of parameters. Perl should |
d1b91892 |
728 | be able to call this XSUB with either of the following statements. |
a0d0e21e |
729 | |
730 | $status = rpcb_gettime( $timep, $host ); |
731 | |
732 | $status = rpcb_gettime( $timep ); |
733 | |
734 | The XS code, with ellipsis, follows. |
735 | |
736 | bool_t |
737 | rpcb_gettime(timep, ...) |
8e07c86e |
738 | time_t timep = NO_INIT |
beb31b0b |
739 | PREINIT: |
a0d0e21e |
740 | char *host = "localhost"; |
2d8e6c8d |
741 | STRLEN n_a; |
beb31b0b |
742 | CODE: |
743 | if( items > 1 ) |
744 | host = (char *)SvPV(ST(1), n_a); |
745 | RETVAL = rpcb_gettime( host, &timep ); |
746 | OUTPUT: |
a0d0e21e |
747 | timep |
748 | RETVAL |
749 | |
cfc02341 |
750 | =head2 The C_ARGS: Keyword |
751 | |
752 | The C_ARGS: keyword allows creating of XSUBS which have different |
753 | calling sequence from Perl than from C, without a need to write |
beb31b0b |
754 | CODE: or PPCODE: section. The contents of the C_ARGS: paragraph is |
cfc02341 |
755 | put as the argument to the called C function without any change. |
756 | |
beb31b0b |
757 | For example, suppose that a C function is declared as |
cfc02341 |
758 | |
759 | symbolic nth_derivative(int n, symbolic function, int flags); |
760 | |
761 | and that the default flags are kept in a global C variable |
762 | C<default_flags>. Suppose that you want to create an interface which |
763 | is called as |
764 | |
765 | $second_deriv = $function->nth_derivative(2); |
766 | |
767 | To do this, declare the XSUB as |
768 | |
769 | symbolic |
770 | nth_derivative(function, n) |
771 | symbolic function |
772 | int n |
beb31b0b |
773 | C_ARGS: |
cfc02341 |
774 | n, function, default_flags |
775 | |
a0d0e21e |
776 | =head2 The PPCODE: Keyword |
777 | |
778 | The PPCODE: keyword is an alternate form of the CODE: keyword and is used |
779 | to tell the B<xsubpp> compiler that the programmer is supplying the code to |
d1b91892 |
780 | control the argument stack for the XSUBs return values. Occasionally one |
a0d0e21e |
781 | will want an XSUB to return a list of values rather than a single value. |
782 | In these cases one must use PPCODE: and then explicitly push the list of |
beb31b0b |
783 | values on the stack. The PPCODE: and CODE: keywords should not be used |
a0d0e21e |
784 | together within the same XSUB. |
785 | |
beb31b0b |
786 | The actual difference between PPCODE: and CODE: sections is in the |
787 | initialization of C<SP> macro (which stands for the I<current> Perl |
788 | stack pointer), and in the handling of data on the stack when returning |
789 | from an XSUB. In CODE: sections SP preserves the value which was on |
790 | entry to the XSUB: SP is on the function pointer (which follows the |
791 | last parameter). In PPCODE: sections SP is moved backward to the |
792 | beginning of the parameter list, which allows C<PUSH*()> macros |
793 | to place output values in the place Perl expects them to be when |
794 | the XSUB returns back to Perl. |
795 | |
796 | The generated trailer for a CODE: section ensures that the number of return |
797 | values Perl will see is either 0 or 1 (depending on the C<void>ness of the |
798 | return value of the C function, and heuristics mentioned in |
799 | L<"The RETVAL Variable">). The trailer generated for a PPCODE: section |
800 | is based on the number of return values and on the number of times |
801 | C<SP> was updated by C<[X]PUSH*()> macros. |
802 | |
803 | Note that macros C<ST(i)>, C<XST_m*()> and C<XSRETURN*()> work equally |
804 | well in CODE: sections and PPCODE: sections. |
805 | |
a0d0e21e |
806 | The following XSUB will call the C rpcb_gettime() function |
807 | and will return its two output values, timep and status, to |
808 | Perl as a single list. |
809 | |
d1b91892 |
810 | void |
811 | rpcb_gettime(host) |
8e07c86e |
812 | char *host |
beb31b0b |
813 | PREINIT: |
a0d0e21e |
814 | time_t timep; |
815 | bool_t status; |
beb31b0b |
816 | PPCODE: |
a0d0e21e |
817 | status = rpcb_gettime( host, &timep ); |
924508f0 |
818 | EXTEND(SP, 2); |
cb1a09d0 |
819 | PUSHs(sv_2mortal(newSViv(status))); |
820 | PUSHs(sv_2mortal(newSViv(timep))); |
a0d0e21e |
821 | |
822 | Notice that the programmer must supply the C code necessary |
823 | to have the real rpcb_gettime() function called and to have |
824 | the return values properly placed on the argument stack. |
825 | |
826 | The C<void> return type for this function tells the B<xsubpp> compiler that |
827 | the RETVAL variable is not needed or used and that it should not be created. |
828 | In most scenarios the void return type should be used with the PPCODE: |
829 | directive. |
830 | |
831 | The EXTEND() macro is used to make room on the argument |
832 | stack for 2 return values. The PPCODE: directive causes the |
924508f0 |
833 | B<xsubpp> compiler to create a stack pointer available as C<SP>, and it |
a0d0e21e |
834 | is this pointer which is being used in the EXTEND() macro. |
835 | The values are then pushed onto the stack with the PUSHs() |
836 | macro. |
837 | |
838 | Now the rpcb_gettime() function can be used from Perl with |
839 | the following statement. |
840 | |
841 | ($status, $timep) = rpcb_gettime("localhost"); |
842 | |
ef50df4b |
843 | When handling output parameters with a PPCODE section, be sure to handle |
844 | 'set' magic properly. See L<perlguts> for details about 'set' magic. |
845 | |
a0d0e21e |
846 | =head2 Returning Undef And Empty Lists |
847 | |
5f05dabc |
848 | Occasionally the programmer will want to return simply |
a0d0e21e |
849 | C<undef> or an empty list if a function fails rather than a |
850 | separate status value. The rpcb_gettime() function offers |
851 | just this situation. If the function succeeds we would like |
852 | to have it return the time and if it fails we would like to |
853 | have undef returned. In the following Perl code the value |
854 | of $timep will either be undef or it will be a valid time. |
855 | |
856 | $timep = rpcb_gettime( "localhost" ); |
857 | |
7b8d334a |
858 | The following XSUB uses the C<SV *> return type as a mnemonic only, |
e7ea3e70 |
859 | and uses a CODE: block to indicate to the compiler |
a0d0e21e |
860 | that the programmer has supplied all the necessary code. The |
861 | sv_newmortal() call will initialize the return value to undef, making that |
862 | the default return value. |
863 | |
e7ea3e70 |
864 | SV * |
a0d0e21e |
865 | rpcb_gettime(host) |
866 | char * host |
beb31b0b |
867 | PREINIT: |
a0d0e21e |
868 | time_t timep; |
869 | bool_t x; |
beb31b0b |
870 | CODE: |
a0d0e21e |
871 | ST(0) = sv_newmortal(); |
872 | if( rpcb_gettime( host, &timep ) ) |
873 | sv_setnv( ST(0), (double)timep); |
a0d0e21e |
874 | |
875 | The next example demonstrates how one would place an explicit undef in the |
876 | return value, should the need arise. |
877 | |
e7ea3e70 |
878 | SV * |
a0d0e21e |
879 | rpcb_gettime(host) |
880 | char * host |
beb31b0b |
881 | PREINIT: |
a0d0e21e |
882 | time_t timep; |
883 | bool_t x; |
beb31b0b |
884 | CODE: |
a0d0e21e |
885 | ST(0) = sv_newmortal(); |
886 | if( rpcb_gettime( host, &timep ) ){ |
887 | sv_setnv( ST(0), (double)timep); |
888 | } |
889 | else{ |
9cde0e7f |
890 | ST(0) = &PL_sv_undef; |
a0d0e21e |
891 | } |
a0d0e21e |
892 | |
893 | To return an empty list one must use a PPCODE: block and |
894 | then not push return values on the stack. |
895 | |
896 | void |
897 | rpcb_gettime(host) |
8e07c86e |
898 | char *host |
beb31b0b |
899 | PREINIT: |
a0d0e21e |
900 | time_t timep; |
beb31b0b |
901 | PPCODE: |
a0d0e21e |
902 | if( rpcb_gettime( host, &timep ) ) |
cb1a09d0 |
903 | PUSHs(sv_2mortal(newSViv(timep))); |
a0d0e21e |
904 | else{ |
beb31b0b |
905 | /* Nothing pushed on stack, so an empty |
906 | * list is implicitly returned. */ |
a0d0e21e |
907 | } |
a0d0e21e |
908 | |
f27cfbbe |
909 | Some people may be inclined to include an explicit C<return> in the above |
910 | XSUB, rather than letting control fall through to the end. In those |
911 | situations C<XSRETURN_EMPTY> should be used, instead. This will ensure that |
912 | the XSUB stack is properly adjusted. Consult L<perlguts/"API LISTING"> for |
913 | other C<XSRETURN> macros. |
914 | |
beb31b0b |
915 | Since C<XSRETURN_*> macros can be used with CODE blocks as well, one can |
916 | rewrite this example as: |
917 | |
918 | int |
919 | rpcb_gettime(host) |
920 | char *host |
921 | PREINIT: |
922 | time_t timep; |
923 | CODE: |
924 | RETVAL = rpcb_gettime( host, &timep ); |
925 | if (RETVAL == 0) |
926 | XSRETURN_UNDEF; |
927 | OUTPUT: |
928 | RETVAL |
929 | |
930 | In fact, one can put this check into a CLEANUP: section as well. Together |
931 | with PREINIT: simplifications, this leads to: |
932 | |
933 | int |
934 | rpcb_gettime(host) |
935 | char *host |
936 | time_t timep; |
937 | CLEANUP: |
938 | if (RETVAL == 0) |
939 | XSRETURN_UNDEF; |
940 | |
4633a7c4 |
941 | =head2 The REQUIRE: Keyword |
942 | |
943 | The REQUIRE: keyword is used to indicate the minimum version of the |
944 | B<xsubpp> compiler needed to compile the XS module. An XS module which |
5f05dabc |
945 | contains the following statement will compile with only B<xsubpp> version |
4633a7c4 |
946 | 1.922 or greater: |
947 | |
948 | REQUIRE: 1.922 |
949 | |
a0d0e21e |
950 | =head2 The CLEANUP: Keyword |
951 | |
952 | This keyword can be used when an XSUB requires special cleanup procedures |
953 | before it terminates. When the CLEANUP: keyword is used it must follow |
954 | any CODE:, PPCODE:, or OUTPUT: blocks which are present in the XSUB. The |
955 | code specified for the cleanup block will be added as the last statements |
956 | in the XSUB. |
957 | |
958 | =head2 The BOOT: Keyword |
959 | |
960 | The BOOT: keyword is used to add code to the extension's bootstrap |
961 | function. The bootstrap function is generated by the B<xsubpp> compiler and |
962 | normally holds the statements necessary to register any XSUBs with Perl. |
963 | With the BOOT: keyword the programmer can tell the compiler to add extra |
964 | statements to the bootstrap function. |
965 | |
966 | This keyword may be used any time after the first MODULE keyword and should |
967 | appear on a line by itself. The first blank line after the keyword will |
968 | terminate the code block. |
969 | |
970 | BOOT: |
971 | # The following message will be printed when the |
972 | # bootstrap function executes. |
973 | printf("Hello from the bootstrap!\n"); |
974 | |
c07a80fd |
975 | =head2 The VERSIONCHECK: Keyword |
976 | |
977 | The VERSIONCHECK: keyword corresponds to B<xsubpp>'s C<-versioncheck> and |
5f05dabc |
978 | C<-noversioncheck> options. This keyword overrides the command line |
c07a80fd |
979 | options. Version checking is enabled by default. When version checking is |
980 | enabled the XS module will attempt to verify that its version matches the |
981 | version of the PM module. |
982 | |
983 | To enable version checking: |
984 | |
985 | VERSIONCHECK: ENABLE |
986 | |
987 | To disable version checking: |
988 | |
989 | VERSIONCHECK: DISABLE |
990 | |
991 | =head2 The PROTOTYPES: Keyword |
992 | |
993 | The PROTOTYPES: keyword corresponds to B<xsubpp>'s C<-prototypes> and |
54310121 |
994 | C<-noprototypes> options. This keyword overrides the command line options. |
c07a80fd |
995 | Prototypes are enabled by default. When prototypes are enabled XSUBs will |
996 | be given Perl prototypes. This keyword may be used multiple times in an XS |
997 | module to enable and disable prototypes for different parts of the module. |
998 | |
999 | To enable prototypes: |
1000 | |
1001 | PROTOTYPES: ENABLE |
1002 | |
1003 | To disable prototypes: |
1004 | |
1005 | PROTOTYPES: DISABLE |
1006 | |
1007 | =head2 The PROTOTYPE: Keyword |
1008 | |
1009 | This keyword is similar to the PROTOTYPES: keyword above but can be used to |
1010 | force B<xsubpp> to use a specific prototype for the XSUB. This keyword |
1011 | overrides all other prototype options and keywords but affects only the |
1012 | current XSUB. Consult L<perlsub/Prototypes> for information about Perl |
1013 | prototypes. |
1014 | |
1015 | bool_t |
1016 | rpcb_gettime(timep, ...) |
1017 | time_t timep = NO_INIT |
beb31b0b |
1018 | PROTOTYPE: $;$ |
1019 | PREINIT: |
c07a80fd |
1020 | char *host = "localhost"; |
2d8e6c8d |
1021 | STRLEN n_a; |
beb31b0b |
1022 | CODE: |
c07a80fd |
1023 | if( items > 1 ) |
2d8e6c8d |
1024 | host = (char *)SvPV(ST(1), n_a); |
c07a80fd |
1025 | RETVAL = rpcb_gettime( host, &timep ); |
beb31b0b |
1026 | OUTPUT: |
c07a80fd |
1027 | timep |
1028 | RETVAL |
1029 | |
1030 | =head2 The ALIAS: Keyword |
1031 | |
cfc02341 |
1032 | The ALIAS: keyword allows an XSUB to have two or more unique Perl names |
c07a80fd |
1033 | and to know which of those names was used when it was invoked. The Perl |
1034 | names may be fully-qualified with package names. Each alias is given an |
1035 | index. The compiler will setup a variable called C<ix> which contain the |
1036 | index of the alias which was used. When the XSUB is called with its |
1037 | declared name C<ix> will be 0. |
1038 | |
1039 | The following example will create aliases C<FOO::gettime()> and |
1040 | C<BAR::getit()> for this function. |
1041 | |
1042 | bool_t |
1043 | rpcb_gettime(host,timep) |
1044 | char *host |
1045 | time_t &timep |
beb31b0b |
1046 | ALIAS: |
c07a80fd |
1047 | FOO::gettime = 1 |
1048 | BAR::getit = 2 |
beb31b0b |
1049 | INIT: |
c07a80fd |
1050 | printf("# ix = %d\n", ix ); |
beb31b0b |
1051 | OUTPUT: |
c07a80fd |
1052 | timep |
1053 | |
cfc02341 |
1054 | =head2 The INTERFACE: Keyword |
1055 | |
1056 | This keyword declares the current XSUB as a keeper of the given |
1057 | calling signature. If some text follows this keyword, it is |
1058 | considered as a list of functions which have this signature, and |
beb31b0b |
1059 | should be attached to the current XSUB. |
cfc02341 |
1060 | |
beb31b0b |
1061 | For example, if you have 4 C functions multiply(), divide(), add(), |
1062 | subtract() all having the signature: |
cfc02341 |
1063 | |
1064 | symbolic f(symbolic, symbolic); |
1065 | |
beb31b0b |
1066 | you can make them all to use the same XSUB using this: |
cfc02341 |
1067 | |
1068 | symbolic |
1069 | interface_s_ss(arg1, arg2) |
1070 | symbolic arg1 |
1071 | symbolic arg2 |
1072 | INTERFACE: |
1073 | multiply divide |
1074 | add subtract |
1075 | |
beb31b0b |
1076 | (This is the complete XSUB code for 4 Perl functions!) Four generated |
1077 | Perl function share names with corresponding C functions. |
1078 | |
1079 | The advantage of this approach comparing to ALIAS: keyword is that there |
1080 | is no need to code a switch statement, each Perl function (which shares |
1081 | the same XSUB) knows which C function it should call. Additionally, one |
cfc02341 |
1082 | can attach an extra function remainder() at runtime by using |
beb31b0b |
1083 | |
cfc02341 |
1084 | CV *mycv = newXSproto("Symbolic::remainder", |
1085 | XS_Symbolic_interface_s_ss, __FILE__, "$$"); |
1086 | XSINTERFACE_FUNC_SET(mycv, remainder); |
1087 | |
beb31b0b |
1088 | say, from another XSUB. (This example supposes that there was no |
1089 | INTERFACE_MACRO: section, otherwise one needs to use something else instead of |
1090 | C<XSINTERFACE_FUNC_SET>, see the next section.) |
cfc02341 |
1091 | |
1092 | =head2 The INTERFACE_MACRO: Keyword |
1093 | |
1094 | This keyword allows one to define an INTERFACE using a different way |
1095 | to extract a function pointer from an XSUB. The text which follows |
1096 | this keyword should give the name of macros which would extract/set a |
1097 | function pointer. The extractor macro is given return type, C<CV*>, |
1098 | and C<XSANY.any_dptr> for this C<CV*>. The setter macro is given cv, |
1099 | and the function pointer. |
1100 | |
1101 | The default value is C<XSINTERFACE_FUNC> and C<XSINTERFACE_FUNC_SET>. |
1102 | An INTERFACE keyword with an empty list of functions can be omitted if |
1103 | INTERFACE_MACRO keyword is used. |
1104 | |
1105 | Suppose that in the previous example functions pointers for |
1106 | multiply(), divide(), add(), subtract() are kept in a global C array |
1107 | C<fp[]> with offsets being C<multiply_off>, C<divide_off>, C<add_off>, |
1108 | C<subtract_off>. Then one can use |
1109 | |
1110 | #define XSINTERFACE_FUNC_BYOFFSET(ret,cv,f) \ |
1111 | ((XSINTERFACE_CVT(ret,))fp[CvXSUBANY(cv).any_i32]) |
1112 | #define XSINTERFACE_FUNC_BYOFFSET_set(cv,f) \ |
1113 | CvXSUBANY(cv).any_i32 = CAT2( f, _off ) |
1114 | |
1115 | in C section, |
1116 | |
1117 | symbolic |
1118 | interface_s_ss(arg1, arg2) |
1119 | symbolic arg1 |
1120 | symbolic arg2 |
beb31b0b |
1121 | INTERFACE_MACRO: |
cfc02341 |
1122 | XSINTERFACE_FUNC_BYOFFSET |
1123 | XSINTERFACE_FUNC_BYOFFSET_set |
beb31b0b |
1124 | INTERFACE: |
cfc02341 |
1125 | multiply divide |
1126 | add subtract |
1127 | |
1128 | in XSUB section. |
1129 | |
c07a80fd |
1130 | =head2 The INCLUDE: Keyword |
1131 | |
1132 | This keyword can be used to pull other files into the XS module. The other |
1133 | files may have XS code. INCLUDE: can also be used to run a command to |
1134 | generate the XS code to be pulled into the module. |
1135 | |
1136 | The file F<Rpcb1.xsh> contains our C<rpcb_gettime()> function: |
1137 | |
1138 | bool_t |
1139 | rpcb_gettime(host,timep) |
1140 | char *host |
1141 | time_t &timep |
beb31b0b |
1142 | OUTPUT: |
c07a80fd |
1143 | timep |
1144 | |
1145 | The XS module can use INCLUDE: to pull that file into it. |
1146 | |
1147 | INCLUDE: Rpcb1.xsh |
1148 | |
1149 | If the parameters to the INCLUDE: keyword are followed by a pipe (C<|>) then |
1150 | the compiler will interpret the parameters as a command. |
1151 | |
1152 | INCLUDE: cat Rpcb1.xsh | |
1153 | |
1154 | =head2 The CASE: Keyword |
1155 | |
1156 | The CASE: keyword allows an XSUB to have multiple distinct parts with each |
1157 | part acting as a virtual XSUB. CASE: is greedy and if it is used then all |
1158 | other XS keywords must be contained within a CASE:. This means nothing may |
1159 | precede the first CASE: in the XSUB and anything following the last CASE: is |
1160 | included in that case. |
1161 | |
1162 | A CASE: might switch via a parameter of the XSUB, via the C<ix> ALIAS: |
1163 | variable (see L<"The ALIAS: Keyword">), or maybe via the C<items> variable |
1164 | (see L<"Variable-length Parameter Lists">). The last CASE: becomes the |
1165 | B<default> case if it is not associated with a conditional. The following |
1166 | example shows CASE switched via C<ix> with a function C<rpcb_gettime()> |
1167 | having an alias C<x_gettime()>. When the function is called as |
b772cb6e |
1168 | C<rpcb_gettime()> its parameters are the usual C<(char *host, time_t *timep)>, |
1169 | but when the function is called as C<x_gettime()> its parameters are |
c07a80fd |
1170 | reversed, C<(time_t *timep, char *host)>. |
1171 | |
1172 | long |
1173 | rpcb_gettime(a,b) |
1174 | CASE: ix == 1 |
beb31b0b |
1175 | ALIAS: |
c07a80fd |
1176 | x_gettime = 1 |
beb31b0b |
1177 | INPUT: |
c07a80fd |
1178 | # 'a' is timep, 'b' is host |
1179 | char *b |
1180 | time_t a = NO_INIT |
beb31b0b |
1181 | CODE: |
c07a80fd |
1182 | RETVAL = rpcb_gettime( b, &a ); |
beb31b0b |
1183 | OUTPUT: |
c07a80fd |
1184 | a |
1185 | RETVAL |
1186 | CASE: |
1187 | # 'a' is host, 'b' is timep |
1188 | char *a |
1189 | time_t &b = NO_INIT |
beb31b0b |
1190 | OUTPUT: |
c07a80fd |
1191 | b |
1192 | RETVAL |
1193 | |
1194 | That function can be called with either of the following statements. Note |
1195 | the different argument lists. |
1196 | |
1197 | $status = rpcb_gettime( $host, $timep ); |
1198 | |
1199 | $status = x_gettime( $timep, $host ); |
1200 | |
1201 | =head2 The & Unary Operator |
1202 | |
beb31b0b |
1203 | The C<&> unary operator in the INPUT: section is used to tell B<xsubpp> |
1204 | that it should convert a Perl value to/from C using the C type to the left |
1205 | of C<&>, but provide a pointer to this value when the C function is called. |
1206 | |
1207 | This is useful to avoid a CODE: block for a C function which takes a parameter |
1208 | by reference. Typically, the parameter should be not a pointer type (an |
1209 | C<int> or C<long> but not a C<int*> or C<long*>). |
c07a80fd |
1210 | |
beb31b0b |
1211 | The following XSUB will generate incorrect C code. The B<xsubpp> compiler will |
c07a80fd |
1212 | turn this into code which calls C<rpcb_gettime()> with parameters C<(char |
1213 | *host, time_t timep)>, but the real C<rpcb_gettime()> wants the C<timep> |
1214 | parameter to be of type C<time_t*> rather than C<time_t>. |
1215 | |
1216 | bool_t |
1217 | rpcb_gettime(host,timep) |
1218 | char *host |
1219 | time_t timep |
beb31b0b |
1220 | OUTPUT: |
c07a80fd |
1221 | timep |
1222 | |
beb31b0b |
1223 | That problem is corrected by using the C<&> operator. The B<xsubpp> compiler |
c07a80fd |
1224 | will now turn this into code which calls C<rpcb_gettime()> correctly with |
1225 | parameters C<(char *host, time_t *timep)>. It does this by carrying the |
1226 | C<&> through, so the function call looks like C<rpcb_gettime(host, &timep)>. |
1227 | |
1228 | bool_t |
1229 | rpcb_gettime(host,timep) |
1230 | char *host |
1231 | time_t &timep |
beb31b0b |
1232 | OUTPUT: |
c07a80fd |
1233 | timep |
1234 | |
a0d0e21e |
1235 | =head2 Inserting Comments and C Preprocessor Directives |
1236 | |
f27cfbbe |
1237 | C preprocessor directives are allowed within BOOT:, PREINIT: INIT:, |
5f05dabc |
1238 | CODE:, PPCODE:, and CLEANUP: blocks, as well as outside the functions. |
f27cfbbe |
1239 | Comments are allowed anywhere after the MODULE keyword. The compiler |
1240 | will pass the preprocessor directives through untouched and will remove |
1241 | the commented lines. |
b772cb6e |
1242 | |
f27cfbbe |
1243 | Comments can be added to XSUBs by placing a C<#> as the first |
1244 | non-whitespace of a line. Care should be taken to avoid making the |
1245 | comment look like a C preprocessor directive, lest it be interpreted as |
1246 | such. The simplest way to prevent this is to put whitespace in front of |
1247 | the C<#>. |
1248 | |
f27cfbbe |
1249 | If you use preprocessor directives to choose one of two |
1250 | versions of a function, use |
1251 | |
1252 | #if ... version1 |
1253 | #else /* ... version2 */ |
1254 | #endif |
1255 | |
1256 | and not |
1257 | |
1258 | #if ... version1 |
1259 | #endif |
1260 | #if ... version2 |
1261 | #endif |
1262 | |
beb31b0b |
1263 | because otherwise B<xsubpp> will believe that you made a duplicate |
f27cfbbe |
1264 | definition of the function. Also, put a blank line before the |
1265 | #else/#endif so it will not be seen as part of the function body. |
a0d0e21e |
1266 | |
1267 | =head2 Using XS With C++ |
1268 | |
beb31b0b |
1269 | If an XSUB name contains C<::>, it is considered to be a C++ method. |
1270 | The generated Perl function will assume that |
a0d0e21e |
1271 | its first argument is an object pointer. The object pointer |
1272 | will be stored in a variable called THIS. The object should |
1273 | have been created by C++ with the new() function and should |
cb1a09d0 |
1274 | be blessed by Perl with the sv_setref_pv() macro. The |
1275 | blessing of the object by Perl can be handled by a typemap. An example |
1276 | typemap is shown at the end of this section. |
a0d0e21e |
1277 | |
beb31b0b |
1278 | If the return type of the XSUB includes C<static>, the method is considered |
1279 | to be a static method. It will call the C++ |
a0d0e21e |
1280 | function using the class::method() syntax. If the method is not static |
f27cfbbe |
1281 | the function will be called using the THIS-E<gt>method() syntax. |
a0d0e21e |
1282 | |
cb1a09d0 |
1283 | The next examples will use the following C++ class. |
a0d0e21e |
1284 | |
a5f75d66 |
1285 | class color { |
cb1a09d0 |
1286 | public: |
a5f75d66 |
1287 | color(); |
1288 | ~color(); |
cb1a09d0 |
1289 | int blue(); |
1290 | void set_blue( int ); |
1291 | |
1292 | private: |
1293 | int c_blue; |
1294 | }; |
1295 | |
1296 | The XSUBs for the blue() and set_blue() methods are defined with the class |
1297 | name but the parameter for the object (THIS, or "self") is implicit and is |
1298 | not listed. |
1299 | |
1300 | int |
1301 | color::blue() |
a0d0e21e |
1302 | |
1303 | void |
cb1a09d0 |
1304 | color::set_blue( val ) |
1305 | int val |
a0d0e21e |
1306 | |
beb31b0b |
1307 | Both Perl functions will expect an object as the first parameter. In the |
1308 | generated C++ code the object is called C<THIS>, and the method call will |
1309 | be performed on this object. So in the C++ code the blue() and set_blue() |
1310 | methods will be called as this: |
a0d0e21e |
1311 | |
cb1a09d0 |
1312 | RETVAL = THIS->blue(); |
a0d0e21e |
1313 | |
cb1a09d0 |
1314 | THIS->set_blue( val ); |
a0d0e21e |
1315 | |
4628e4f8 |
1316 | You could also write a single get/set method using an optional argument: |
1317 | |
1318 | int |
a104f515 |
1319 | color::blue( val = NO_INIT ) |
4628e4f8 |
1320 | int val |
1321 | PROTOTYPE $;$ |
1322 | CODE: |
1323 | if (items > 1) |
1324 | THIS->set_blue( val ); |
1325 | RETVAL = THIS->blue(); |
1326 | OUTPUT: |
1327 | RETVAL |
1328 | |
cb1a09d0 |
1329 | If the function's name is B<DESTROY> then the C++ C<delete> function will be |
beb31b0b |
1330 | called and C<THIS> will be given as its parameter. The generated C++ code for |
a0d0e21e |
1331 | |
d1b91892 |
1332 | void |
cb1a09d0 |
1333 | color::DESTROY() |
1334 | |
beb31b0b |
1335 | will look like this: |
1336 | |
1337 | color *THIS = ...; // Initialized as in typemap |
cb1a09d0 |
1338 | |
1339 | delete THIS; |
a0d0e21e |
1340 | |
cb1a09d0 |
1341 | If the function's name is B<new> then the C++ C<new> function will be called |
1342 | to create a dynamic C++ object. The XSUB will expect the class name, which |
1343 | will be kept in a variable called C<CLASS>, to be given as the first |
1344 | argument. |
a0d0e21e |
1345 | |
cb1a09d0 |
1346 | color * |
1347 | color::new() |
a0d0e21e |
1348 | |
beb31b0b |
1349 | The generated C++ code will call C<new>. |
a0d0e21e |
1350 | |
beb31b0b |
1351 | RETVAL = new color(); |
cb1a09d0 |
1352 | |
1353 | The following is an example of a typemap that could be used for this C++ |
1354 | example. |
1355 | |
1356 | TYPEMAP |
1357 | color * O_OBJECT |
1358 | |
1359 | OUTPUT |
1360 | # The Perl object is blessed into 'CLASS', which should be a |
1361 | # char* having the name of the package for the blessing. |
1362 | O_OBJECT |
1363 | sv_setref_pv( $arg, CLASS, (void*)$var ); |
a6006777 |
1364 | |
cb1a09d0 |
1365 | INPUT |
1366 | O_OBJECT |
1367 | if( sv_isobject($arg) && (SvTYPE(SvRV($arg)) == SVt_PVMG) ) |
1368 | $var = ($type)SvIV((SV*)SvRV( $arg )); |
1369 | else{ |
1370 | warn( \"${Package}::$func_name() -- $var is not a blessed SV reference\" ); |
1371 | XSRETURN_UNDEF; |
1372 | } |
a0d0e21e |
1373 | |
d1b91892 |
1374 | =head2 Interface Strategy |
a0d0e21e |
1375 | |
1376 | When designing an interface between Perl and a C library a straight |
beb31b0b |
1377 | translation from C to XS (such as created by C<h2xs -x>) is often sufficient. |
1378 | However, sometimes the interface will look |
a0d0e21e |
1379 | very C-like and occasionally nonintuitive, especially when the C function |
beb31b0b |
1380 | modifies one of its parameters, or returns failure inband (as in "negative |
1381 | return values mean failure"). In cases where the programmer wishes to |
a0d0e21e |
1382 | create a more Perl-like interface the following strategy may help to |
1383 | identify the more critical parts of the interface. |
1384 | |
beb31b0b |
1385 | Identify the C functions with input/output or output parameters. The XSUBs for |
1386 | these functions may be able to return lists to Perl. |
1387 | |
1388 | Identify the C functions which use some inband info as an indication |
1389 | of failure. They may be |
1390 | candidates to return undef or an empty list in case of failure. If the |
1391 | failure may be detected without a call to the C function, you may want to use |
1392 | an INIT: section to report the failure. For failures detectable after the C |
1393 | function returns one may want to use a CLEANUP: section to process the |
1394 | failure. In more complicated cases use CODE: or PPCODE: sections. |
1395 | |
1396 | If many functions use the same failure indication based on the return value, |
1397 | you may want to create a special typedef to handle this situation. Put |
1398 | |
1399 | typedef int negative_is_failure; |
1400 | |
1401 | near the beginning of XS file, and create an OUTPUT typemap entry |
1402 | for C<negative_is_failure> which converts negative values to C<undef>, or |
1403 | maybe croak()s. After this the return value of type C<negative_is_failure> |
1404 | will create more Perl-like interface. |
a0d0e21e |
1405 | |
d1b91892 |
1406 | Identify which values are used by only the C and XSUB functions |
beb31b0b |
1407 | themselves, say, when a parameter to a function should be a contents of a |
1408 | global variable. If Perl does not need to access the contents of the value |
a0d0e21e |
1409 | then it may not be necessary to provide a translation for that value |
1410 | from C to Perl. |
1411 | |
1412 | Identify the pointers in the C function parameter lists and return |
beb31b0b |
1413 | values. Some pointers may be used to implement input/output or |
1414 | output parameters, they can be handled in XS with the C<&> unary operator, |
1415 | and, possibly, using the NO_INIT keyword. |
1416 | Some others will require handling of types like C<int *>, and one needs |
1417 | to decide what a useful Perl translation will do in such a case. When |
1418 | the semantic is clear, it is advisable to put the translation into a typemap |
1419 | file. |
a0d0e21e |
1420 | |
1421 | Identify the structures used by the C functions. In many |
1422 | cases it may be helpful to use the T_PTROBJ typemap for |
1423 | these structures so they can be manipulated by Perl as |
beb31b0b |
1424 | blessed objects. (This is handled automatically by C<h2xs -x>.) |
1425 | |
1426 | If the same C type is used in several different contexts which require |
1427 | different translations, C<typedef> several new types mapped to this C type, |
1428 | and create separate F<typemap> entries for these new types. Use these |
1429 | types in declarations of return type and parameters to XSUBs. |
a0d0e21e |
1430 | |
a0d0e21e |
1431 | =head2 Perl Objects And C Structures |
1432 | |
1433 | When dealing with C structures one should select either |
1434 | B<T_PTROBJ> or B<T_PTRREF> for the XS type. Both types are |
1435 | designed to handle pointers to complex objects. The |
1436 | T_PTRREF type will allow the Perl object to be unblessed |
1437 | while the T_PTROBJ type requires that the object be blessed. |
1438 | By using T_PTROBJ one can achieve a form of type-checking |
d1b91892 |
1439 | because the XSUB will attempt to verify that the Perl object |
a0d0e21e |
1440 | is of the expected type. |
1441 | |
1442 | The following XS code shows the getnetconfigent() function which is used |
8e07c86e |
1443 | with ONC+ TIRPC. The getnetconfigent() function will return a pointer to a |
a0d0e21e |
1444 | C structure and has the C prototype shown below. The example will |
1445 | demonstrate how the C pointer will become a Perl reference. Perl will |
1446 | consider this reference to be a pointer to a blessed object and will |
1447 | attempt to call a destructor for the object. A destructor will be |
1448 | provided in the XS source to free the memory used by getnetconfigent(). |
1449 | Destructors in XS can be created by specifying an XSUB function whose name |
1450 | ends with the word B<DESTROY>. XS destructors can be used to free memory |
1451 | which may have been malloc'd by another XSUB. |
1452 | |
1453 | struct netconfig *getnetconfigent(const char *netid); |
1454 | |
1455 | A C<typedef> will be created for C<struct netconfig>. The Perl |
1456 | object will be blessed in a class matching the name of the C |
1457 | type, with the tag C<Ptr> appended, and the name should not |
1458 | have embedded spaces if it will be a Perl package name. The |
1459 | destructor will be placed in a class corresponding to the |
1460 | class of the object and the PREFIX keyword will be used to |
1461 | trim the name to the word DESTROY as Perl will expect. |
1462 | |
1463 | typedef struct netconfig Netconfig; |
1464 | |
1465 | MODULE = RPC PACKAGE = RPC |
1466 | |
1467 | Netconfig * |
1468 | getnetconfigent(netid) |
8e07c86e |
1469 | char *netid |
a0d0e21e |
1470 | |
1471 | MODULE = RPC PACKAGE = NetconfigPtr PREFIX = rpcb_ |
1472 | |
1473 | void |
1474 | rpcb_DESTROY(netconf) |
8e07c86e |
1475 | Netconfig *netconf |
beb31b0b |
1476 | CODE: |
a0d0e21e |
1477 | printf("Now in NetconfigPtr::DESTROY\n"); |
1478 | free( netconf ); |
1479 | |
1480 | This example requires the following typemap entry. Consult the typemap |
1481 | section for more information about adding new typemaps for an extension. |
1482 | |
1483 | TYPEMAP |
1484 | Netconfig * T_PTROBJ |
1485 | |
1486 | This example will be used with the following Perl statements. |
1487 | |
1488 | use RPC; |
1489 | $netconf = getnetconfigent("udp"); |
1490 | |
1491 | When Perl destroys the object referenced by $netconf it will send the |
1492 | object to the supplied XSUB DESTROY function. Perl cannot determine, and |
1493 | does not care, that this object is a C struct and not a Perl object. In |
1494 | this sense, there is no difference between the object created by the |
1495 | getnetconfigent() XSUB and an object created by a normal Perl subroutine. |
1496 | |
a0d0e21e |
1497 | =head2 The Typemap |
1498 | |
1499 | The typemap is a collection of code fragments which are used by the B<xsubpp> |
1500 | compiler to map C function parameters and values to Perl values. The |
1501 | typemap file may consist of three sections labeled C<TYPEMAP>, C<INPUT>, and |
beb31b0b |
1502 | C<OUTPUT>. An unlabelled initial section is assumed to be a C<TYPEMAP> |
1503 | section. The INPUT section tells |
7e9d670d |
1504 | the compiler how to translate Perl values |
a0d0e21e |
1505 | into variables of certain C types. The OUTPUT section tells the compiler |
1506 | how to translate the values from certain C types into values Perl can |
1507 | understand. The TYPEMAP section tells the compiler which of the INPUT and |
1508 | OUTPUT code fragments should be used to map a given C type to a Perl value. |
7e9d670d |
1509 | The section labels C<TYPEMAP>, C<INPUT>, or C<OUTPUT> must begin |
1510 | in the first column on a line by themselves, and must be in uppercase. |
a0d0e21e |
1511 | |
1512 | The default typemap in the C<ext> directory of the Perl source contains many |
1513 | useful types which can be used by Perl extensions. Some extensions define |
1514 | additional typemaps which they keep in their own directory. These |
1515 | additional typemaps may reference INPUT and OUTPUT maps in the main |
1516 | typemap. The B<xsubpp> compiler will allow the extension's own typemap to |
1517 | override any mappings which are in the default typemap. |
1518 | |
1519 | Most extensions which require a custom typemap will need only the TYPEMAP |
1520 | section of the typemap file. The custom typemap used in the |
1521 | getnetconfigent() example shown earlier demonstrates what may be the typical |
1522 | use of extension typemaps. That typemap is used to equate a C structure |
1523 | with the T_PTROBJ typemap. The typemap used by getnetconfigent() is shown |
1524 | here. Note that the C type is separated from the XS type with a tab and |
1525 | that the C unary operator C<*> is considered to be a part of the C type name. |
1526 | |
beb31b0b |
1527 | TYPEMAP |
1528 | Netconfig *<tab>T_PTROBJ |
a0d0e21e |
1529 | |
1748e8dd |
1530 | Here's a more complicated example: suppose that you wanted C<struct |
1531 | netconfig> to be blessed into the class C<Net::Config>. One way to do |
1532 | this is to use underscores (_) to separate package names, as follows: |
1533 | |
1534 | typedef struct netconfig * Net_Config; |
1535 | |
1536 | And then provide a typemap entry C<T_PTROBJ_SPECIAL> that maps underscores to |
1537 | double-colons (::), and declare C<Net_Config> to be of that type: |
1538 | |
1539 | |
1540 | TYPEMAP |
1541 | Net_Config T_PTROBJ_SPECIAL |
1542 | |
1543 | INPUT |
1544 | T_PTROBJ_SPECIAL |
1545 | if (sv_derived_from($arg, \"${(my $ntt=$ntype)=~s/_/::/g;\$ntt}\")) { |
1546 | IV tmp = SvIV((SV*)SvRV($arg)); |
1547 | $var = ($type) tmp; |
1548 | } |
1549 | else |
1550 | croak(\"$var is not of type ${(my $ntt=$ntype)=~s/_/::/g;\$ntt}\") |
1551 | |
1552 | OUTPUT |
1553 | T_PTROBJ_SPECIAL |
1554 | sv_setref_pv($arg, \"${(my $ntt=$ntype)=~s/_/::/g;\$ntt}\", |
1555 | (void*)$var); |
1556 | |
1557 | The INPUT and OUTPUT sections substitute underscores for double-colons |
1558 | on the fly, giving the desired effect. This example demonstrates some |
1559 | of the power and versatility of the typemap facility. |
1560 | |
a0d0e21e |
1561 | =head1 EXAMPLES |
1562 | |
1563 | File C<RPC.xs>: Interface to some ONC+ RPC bind library functions. |
1564 | |
1565 | #include "EXTERN.h" |
1566 | #include "perl.h" |
1567 | #include "XSUB.h" |
1568 | |
1569 | #include <rpc/rpc.h> |
1570 | |
1571 | typedef struct netconfig Netconfig; |
1572 | |
1573 | MODULE = RPC PACKAGE = RPC |
1574 | |
e7ea3e70 |
1575 | SV * |
a0d0e21e |
1576 | rpcb_gettime(host="localhost") |
8e07c86e |
1577 | char *host |
beb31b0b |
1578 | PREINIT: |
a0d0e21e |
1579 | time_t timep; |
beb31b0b |
1580 | CODE: |
a0d0e21e |
1581 | ST(0) = sv_newmortal(); |
1582 | if( rpcb_gettime( host, &timep ) ) |
1583 | sv_setnv( ST(0), (double)timep ); |
a0d0e21e |
1584 | |
1585 | Netconfig * |
1586 | getnetconfigent(netid="udp") |
8e07c86e |
1587 | char *netid |
a0d0e21e |
1588 | |
1589 | MODULE = RPC PACKAGE = NetconfigPtr PREFIX = rpcb_ |
1590 | |
1591 | void |
1592 | rpcb_DESTROY(netconf) |
8e07c86e |
1593 | Netconfig *netconf |
beb31b0b |
1594 | CODE: |
a0d0e21e |
1595 | printf("NetconfigPtr::DESTROY\n"); |
1596 | free( netconf ); |
1597 | |
1598 | File C<typemap>: Custom typemap for RPC.xs. |
1599 | |
1600 | TYPEMAP |
1601 | Netconfig * T_PTROBJ |
1602 | |
1603 | File C<RPC.pm>: Perl module for the RPC extension. |
1604 | |
1605 | package RPC; |
1606 | |
1607 | require Exporter; |
1608 | require DynaLoader; |
1609 | @ISA = qw(Exporter DynaLoader); |
1610 | @EXPORT = qw(rpcb_gettime getnetconfigent); |
1611 | |
1612 | bootstrap RPC; |
1613 | 1; |
1614 | |
1615 | File C<rpctest.pl>: Perl test program for the RPC extension. |
1616 | |
1617 | use RPC; |
1618 | |
1619 | $netconf = getnetconfigent(); |
1620 | $a = rpcb_gettime(); |
1621 | print "time = $a\n"; |
1622 | print "netconf = $netconf\n"; |
1623 | |
1624 | $netconf = getnetconfigent("tcp"); |
1625 | $a = rpcb_gettime("poplar"); |
1626 | print "time = $a\n"; |
1627 | print "netconf = $netconf\n"; |
1628 | |
1629 | |
c07a80fd |
1630 | =head1 XS VERSION |
1631 | |
f27cfbbe |
1632 | This document covers features supported by C<xsubpp> 1.935. |
c07a80fd |
1633 | |
a0d0e21e |
1634 | =head1 AUTHOR |
1635 | |
beb31b0b |
1636 | Originally written by Dean Roehrich <F<roehrich@cray.com>>. |
1637 | |
7f2de2d2 |
1638 | Maintained since 1996 by The Perl Porters <F<perlbug@perl.org>>. |