Commit | Line | Data |
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760ac839 LW |
1 | =head1 NAME |
2 | ||
28757baa | 3 | perlapio - perl's IO abstraction interface. |
760ac839 LW |
4 | |
5 | =head1 SYNOPSIS | |
6 | ||
f185f654 KW |
7 | #define PERLIO_NOT_STDIO 0 /* For co-existence with stdio only */ |
8 | #include <perlio.h> /* Usually via #include <perl.h> */ | |
9 | ||
10 | PerlIO *PerlIO_stdin(void); | |
11 | PerlIO *PerlIO_stdout(void); | |
12 | PerlIO *PerlIO_stderr(void); | |
13 | ||
14 | PerlIO *PerlIO_open(const char *path,const char *mode); | |
15 | PerlIO *PerlIO_fdopen(int fd, const char *mode); | |
16 | PerlIO *PerlIO_reopen(const char *path, /* deprecated */ | |
17 | const char *mode, PerlIO *old); | |
18 | int PerlIO_close(PerlIO *f); | |
19 | ||
20 | int PerlIO_stdoutf(const char *fmt,...) | |
21 | int PerlIO_puts(PerlIO *f,const char *string); | |
22 | int PerlIO_putc(PerlIO *f,int ch); | |
23 | SSize_t PerlIO_write(PerlIO *f,const void *buf,size_t numbytes); | |
24 | int PerlIO_printf(PerlIO *f, const char *fmt,...); | |
25 | int PerlIO_vprintf(PerlIO *f, const char *fmt, va_list args); | |
26 | int PerlIO_flush(PerlIO *f); | |
27 | ||
28 | int PerlIO_eof(PerlIO *f); | |
29 | int PerlIO_error(PerlIO *f); | |
30 | void PerlIO_clearerr(PerlIO *f); | |
31 | ||
32 | int PerlIO_getc(PerlIO *d); | |
33 | int PerlIO_ungetc(PerlIO *f,int ch); | |
34 | SSize_t PerlIO_read(PerlIO *f, void *buf, size_t numbytes); | |
35 | ||
36 | int PerlIO_fileno(PerlIO *f); | |
37 | ||
38 | void PerlIO_setlinebuf(PerlIO *f); | |
39 | ||
40 | Off_t PerlIO_tell(PerlIO *f); | |
41 | int PerlIO_seek(PerlIO *f, Off_t offset, int whence); | |
42 | void PerlIO_rewind(PerlIO *f); | |
43 | ||
44 | int PerlIO_getpos(PerlIO *f, SV *save); /* prototype changed */ | |
45 | int PerlIO_setpos(PerlIO *f, SV *saved); /* prototype changed */ | |
46 | ||
47 | int PerlIO_fast_gets(PerlIO *f); | |
48 | int PerlIO_has_cntptr(PerlIO *f); | |
49 | SSize_t PerlIO_get_cnt(PerlIO *f); | |
50 | char *PerlIO_get_ptr(PerlIO *f); | |
51 | void PerlIO_set_ptrcnt(PerlIO *f, char *ptr, SSize_t count); | |
52 | ||
53 | int PerlIO_canset_cnt(PerlIO *f); /* deprecated */ | |
54 | void PerlIO_set_cnt(PerlIO *f, int count); /* deprecated */ | |
55 | ||
56 | int PerlIO_has_base(PerlIO *f); | |
57 | char *PerlIO_get_base(PerlIO *f); | |
58 | SSize_t PerlIO_get_bufsiz(PerlIO *f); | |
59 | ||
60 | PerlIO *PerlIO_importFILE(FILE *stdio, const char *mode); | |
463029d7 | 61 | FILE *PerlIO_exportFILE(PerlIO *f, const char *mode); |
f185f654 KW |
62 | FILE *PerlIO_findFILE(PerlIO *f); |
63 | void PerlIO_releaseFILE(PerlIO *f,FILE *stdio); | |
64 | ||
65 | int PerlIO_apply_layers(PerlIO *f, const char *mode, | |
66 | const char *layers); | |
67 | int PerlIO_binmode(PerlIO *f, int ptype, int imode, | |
68 | const char *layers); | |
678f21a2 KW |
69 | void PerlIO_debug(const char *fmt,...); |
70 | ||
71 | =for apidoc Amh|int |PerlIO_apply_layers|PerlIO *f|const char *mode|const char *layers | |
72 | =for apidoc Amh|int |PerlIO_binmode|PerlIO *f|int ptype|int imode|const char *layers | |
73 | =for apidoc ATmh|int |PerlIO_canset_cnt|PerlIO *f | |
74 | =for apidoc Amh|void |PerlIO_debug|const char *fmt|... | |
75 | =for apidoc ATmh|FILE *|PerlIO_exportFILE|PerlIO *f|const char *mode | |
76 | =for apidoc ATmh|int |PerlIO_fast_gets|PerlIO *f | |
77 | =for apidoc ATmh|PerlIO*|PerlIO_fdopen|int fd|const char *mode | |
78 | =for apidoc ATmh|FILE *|PerlIO_findFILE|PerlIO *f | |
79 | =for apidoc ATmh|int |PerlIO_getc|PerlIO *d | |
80 | =for apidoc ATmh|int |PerlIO_getpos|PerlIO *f|SV *save | |
81 | =for apidoc ATmh|int |PerlIO_has_base|PerlIO *f | |
82 | =for apidoc ATmh|int |PerlIO_has_cntptr|PerlIO *f | |
83 | =for apidoc ATmh|PerlIO*|PerlIO_importFILE|FILE *stdio|const char *mode | |
84 | =for apidoc ATmh|PerlIO*|PerlIO_open|const char *path|const char *mode | |
85 | =for apidoc Amh|int |PerlIO_printf|PerlIO *f|const char *fmt|... | |
86 | =for apidoc ATmh|int |PerlIO_putc|PerlIO *f|int ch | |
87 | =for apidoc ATmh|int |PerlIO_puts|PerlIO *f|const char *string | |
88 | =for apidoc ATmh|void |PerlIO_releaseFILE|PerlIO *f|FILE *stdio | |
89 | =for apidoc Amh|PerlIO *|PerlIO_reopen|const char *path|const char *mode|PerlIO *old | |
90 | =for apidoc ATmh|void |PerlIO_rewind|PerlIO *f | |
91 | =for apidoc ATmh|int |PerlIO_setpos|PerlIO *f|SV *saved | |
92 | =for apidoc Amh|int |PerlIO_stdoutf|const char *fmt|... | |
93 | =for apidoc ATmh|int |PerlIO_ungetc|PerlIO *f|int ch | |
94 | =for apidoc ATmh|int |PerlIO_vprintf|PerlIO *f|const char *fmt|va_list args | |
95 | ||
96 | =for apidoc PerlIO_stdin | |
97 | =for apidoc PerlIO_stdout | |
98 | =for apidoc PerlIO_stderr | |
99 | =for apidoc PerlIO_close | |
100 | =for apidoc PerlIO_write | |
101 | =for apidoc PerlIO_flush | |
102 | =for apidoc PerlIO_eof | |
103 | =for apidoc PerlIO_error | |
104 | =for apidoc PerlIO_clearerr | |
105 | =for apidoc PerlIO_read | |
106 | =for apidoc PerlIO_fileno | |
107 | =for apidoc PerlIO_setlinebuf | |
108 | =for apidoc PerlIO_tell | |
109 | =for apidoc PerlIO_seek | |
110 | =for apidoc PerlIO_get_cnt | |
111 | =for apidoc PerlIO_get_ptr | |
112 | =for apidoc PerlIO_set_ptrcnt | |
113 | =for apidoc PerlIO_set_cnt | |
114 | =for apidoc PerlIO_get_base | |
115 | =for apidoc PerlIO_get_bufsiz | |
760ac839 LW |
116 | |
117 | =head1 DESCRIPTION | |
118 | ||
06936a3c PN |
119 | Perl's source code, and extensions that want maximum portability, |
120 | should use the above functions instead of those defined in ANSI C's | |
121 | I<stdio.h>. The perl headers (in particular "perlio.h") will | |
122 | C<#define> them to the I/O mechanism selected at Configure time. | |
760ac839 LW |
123 | |
124 | The functions are modeled on those in I<stdio.h>, but parameter order | |
125 | has been "tidied up a little". | |
126 | ||
06936a3c PN |
127 | C<PerlIO *> takes the place of FILE *. Like FILE * it should be |
128 | treated as opaque (it is probably safe to assume it is a pointer to | |
129 | something). | |
50b80e25 | 130 | |
1549f383 | 131 | There are currently two implementations: |
50b80e25 | 132 | |
760ac839 LW |
133 | =over 4 |
134 | ||
50b80e25 | 135 | =item 1. USE_STDIO |
760ac839 | 136 | |
06936a3c PN |
137 | All above are #define'd to stdio functions or are trivial wrapper |
138 | functions which call stdio. In this case I<only> PerlIO * is a FILE *. | |
139 | This has been the default implementation since the abstraction was | |
140 | introduced in perl5.003_02. | |
50b80e25 | 141 | |
97cb92d6 | 142 | =item 2. USE_PERLIO |
50b80e25 | 143 | |
06936a3c PN |
144 | Introduced just after perl5.7.0, this is a re-implementation of the |
145 | above abstraction which allows perl more control over how IO is done | |
146 | as it decouples IO from the way the operating system and C library | |
147 | choose to do things. For USE_PERLIO PerlIO * has an extra layer of | |
148 | indirection - it is a pointer-to-a-pointer. This allows the PerlIO * | |
210b36aa | 149 | to remain with a known value while swapping the implementation around |
06936a3c PN |
150 | underneath I<at run time>. In this case all the above are true (but |
151 | very simple) functions which call the underlying implementation. | |
50b80e25 | 152 | |
06936a3c PN |
153 | This is the only implementation for which C<PerlIO_apply_layers()> |
154 | does anything "interesting". | |
50b80e25 NIS |
155 | |
156 | The USE_PERLIO implementation is described in L<perliol>. | |
157 | ||
158 | =back | |
159 | ||
06936a3c | 160 | Because "perlio.h" is a thin layer (for efficiency) the semantics of |
39ac7f1b LS |
161 | these functions are somewhat dependent on the underlying implementation. |
162 | Where these variations are understood they are noted below. | |
50b80e25 | 163 | |
39ac7f1b LS |
164 | Unless otherwise noted, functions return 0 on success, or a negative |
165 | value (usually C<EOF> which is usually -1) and set C<errno> on error. | |
50b80e25 NIS |
166 | |
167 | =over 4 | |
760ac839 LW |
168 | |
169 | =item B<PerlIO_stdin()>, B<PerlIO_stdout()>, B<PerlIO_stderr()> | |
170 | ||
171 | Use these rather than C<stdin>, C<stdout>, C<stderr>. They are written | |
172 | to look like "function calls" rather than variables because this makes | |
54310121 | 173 | it easier to I<make them> function calls if platform cannot export data |
174 | to loaded modules, or if (say) different "threads" might have different | |
760ac839 LW |
175 | values. |
176 | ||
177 | =item B<PerlIO_open(path, mode)>, B<PerlIO_fdopen(fd,mode)> | |
178 | ||
3039a93d | 179 | These correspond to fopen()/fdopen() and the arguments are the same. |
06936a3c PN |
180 | Return C<NULL> and set C<errno> if there is an error. There may be an |
181 | implementation limit on the number of open handles, which may be lower | |
182 | than the limit on the number of open files - C<errno> may not be set | |
210b36aa | 183 | when C<NULL> is returned if this limit is exceeded. |
50b80e25 | 184 | |
11e1c8f2 | 185 | =item B<PerlIO_reopen(path,mode,f)> |
50b80e25 | 186 | |
8cc92bd4 | 187 | While this currently exists in both implementations, perl itself |
50b80e25 NIS |
188 | does not use it. I<As perl does not use it, it is not well tested.> |
189 | ||
06936a3c PN |
190 | Perl prefers to C<dup> the new low-level descriptor to the descriptor |
191 | used by the existing PerlIO. This may become the behaviour of this | |
192 | function in the future. | |
760ac839 LW |
193 | |
194 | =item B<PerlIO_printf(f,fmt,...)>, B<PerlIO_vprintf(f,fmt,a)> | |
195 | ||
7b8d334a | 196 | These are fprintf()/vfprintf() equivalents. |
760ac839 LW |
197 | |
198 | =item B<PerlIO_stdoutf(fmt,...)> | |
199 | ||
200 | This is printf() equivalent. printf is #defined to this function, | |
84dc3c4d | 201 | so it is (currently) legal to use C<printf(fmt,...)> in perl sources. |
760ac839 LW |
202 | |
203 | =item B<PerlIO_read(f,buf,count)>, B<PerlIO_write(f,buf,count)> | |
204 | ||
2c2cb412 GA |
205 | These correspond functionally to fread() and fwrite() but the |
206 | arguments and return values are different. The PerlIO_read() and | |
207 | PerlIO_write() signatures have been modeled on the more sane low level | |
208 | read() and write() functions instead: The "file" argument is passed | |
209 | first, there is only one "count", and the return value can distinguish | |
210 | between error and C<EOF>. | |
211 | ||
212 | Returns a byte count if successful (which may be zero or | |
c0a503cc JH |
213 | positive), returns negative value and sets C<errno> on error. |
214 | Depending on implementation C<errno> may be C<EINTR> if operation was | |
215 | interrupted by a signal. | |
760ac839 LW |
216 | |
217 | =item B<PerlIO_close(f)> | |
218 | ||
06936a3c PN |
219 | Depending on implementation C<errno> may be C<EINTR> if operation was |
220 | interrupted by a signal. | |
50b80e25 | 221 | |
21917246 | 222 | =item B<PerlIO_puts(f,s)>, B<PerlIO_putc(f,c)> |
760ac839 | 223 | |
54310121 | 224 | These correspond to fputs() and fputc(). |
760ac839 LW |
225 | Note that arguments have been revised to have "file" first. |
226 | ||
21917246 | 227 | =item B<PerlIO_ungetc(f,c)> |
760ac839 | 228 | |
06936a3c PN |
229 | This corresponds to ungetc(). Note that arguments have been revised |
230 | to have "file" first. Arranges that next read operation will return | |
231 | the byte B<c>. Despite the implied "character" in the name only | |
232 | values in the range 0..0xFF are defined. Returns the byte B<c> on | |
233 | success or -1 (C<EOF>) on error. The number of bytes that can be | |
234 | "pushed back" may vary, only 1 character is certain, and then only if | |
235 | it is the last character that was read from the handle. | |
760ac839 LW |
236 | |
237 | =item B<PerlIO_getc(f)> | |
238 | ||
239 | This corresponds to getc(). | |
50b80e25 | 240 | Despite the c in the name only byte range 0..0xFF is supported. |
3039a93d | 241 | Returns the character read or -1 (C<EOF>) on error. |
760ac839 LW |
242 | |
243 | =item B<PerlIO_eof(f)> | |
244 | ||
06936a3c PN |
245 | This corresponds to feof(). Returns a true/false indication of |
246 | whether the handle is at end of file. For terminal devices this may | |
247 | or may not be "sticky" depending on the implementation. The flag is | |
248 | cleared by PerlIO_seek(), or PerlIO_rewind(). | |
760ac839 LW |
249 | |
250 | =item B<PerlIO_error(f)> | |
251 | ||
06936a3c PN |
252 | This corresponds to ferror(). Returns a true/false indication of |
253 | whether there has been an IO error on the handle. | |
760ac839 LW |
254 | |
255 | =item B<PerlIO_fileno(f)> | |
256 | ||
06936a3c PN |
257 | This corresponds to fileno(), note that on some platforms, the meaning |
258 | of "fileno" may not match Unix. Returns -1 if the handle has no open | |
259 | descriptor associated with it. | |
760ac839 LW |
260 | |
261 | =item B<PerlIO_clearerr(f)> | |
262 | ||
06936a3c PN |
263 | This corresponds to clearerr(), i.e., clears 'error' and (usually) |
264 | 'eof' flags for the "stream". Does not return a value. | |
760ac839 LW |
265 | |
266 | =item B<PerlIO_flush(f)> | |
267 | ||
06936a3c PN |
268 | This corresponds to fflush(). Sends any buffered write data to the |
269 | underlying file. If called with C<NULL> this may flush all open | |
fa11829f | 270 | streams (or core dump with some USE_STDIO implementations). Calling |
c0a503cc JH |
271 | on a handle open for read only, or on which last operation was a read |
272 | of some kind may lead to undefined behaviour on some USE_STDIO | |
273 | implementations. The USE_PERLIO (layers) implementation tries to | |
274 | behave better: it flushes all open streams when passed C<NULL>, and | |
275 | attempts to retain data on read streams either in the buffer or by | |
276 | seeking the handle to the current logical position. | |
760ac839 | 277 | |
50b80e25 | 278 | =item B<PerlIO_seek(f,offset,whence)> |
760ac839 | 279 | |
06936a3c PN |
280 | This corresponds to fseek(). Sends buffered write data to the |
281 | underlying file, or discards any buffered read data, then positions | |
d7f8936a | 282 | the file descriptor as specified by B<offset> and B<whence> (sic). |
06936a3c PN |
283 | This is the correct thing to do when switching between read and write |
284 | on the same handle (see issues with PerlIO_flush() above). Offset is | |
285 | of type C<Off_t> which is a perl Configure value which may not be same | |
50b80e25 | 286 | as stdio's C<off_t>. |
760ac839 | 287 | |
50b80e25 | 288 | =item B<PerlIO_tell(f)> |
760ac839 | 289 | |
06936a3c PN |
290 | This corresponds to ftell(). Returns the current file position, or |
291 | (Off_t) -1 on error. May just return value system "knows" without | |
292 | making a system call or checking the underlying file descriptor (so | |
293 | use on shared file descriptors is not safe without a | |
294 | PerlIO_seek()). Return value is of type C<Off_t> which is a perl | |
295 | Configure value which may not be same as stdio's C<off_t>. | |
760ac839 LW |
296 | |
297 | =item B<PerlIO_getpos(f,p)>, B<PerlIO_setpos(f,p)> | |
298 | ||
06936a3c PN |
299 | These correspond (loosely) to fgetpos() and fsetpos(). Rather than |
300 | stdio's Fpos_t they expect a "Perl Scalar Value" to be passed. What is | |
301 | stored there should be considered opaque. The layout of the data may | |
302 | vary from handle to handle. When not using stdio or if platform does | |
303 | not have the stdio calls then they are implemented in terms of | |
304 | PerlIO_tell() and PerlIO_seek(). | |
760ac839 LW |
305 | |
306 | =item B<PerlIO_rewind(f)> | |
307 | ||
50b80e25 NIS |
308 | This corresponds to rewind(). It is usually defined as being |
309 | ||
310 | PerlIO_seek(f,(Off_t)0L, SEEK_SET); | |
311 | PerlIO_clearerr(f); | |
312 | ||
760ac839 LW |
313 | =item B<PerlIO_tmpfile()> |
314 | ||
06936a3c PN |
315 | This corresponds to tmpfile(), i.e., returns an anonymous PerlIO or |
316 | NULL on error. The system will attempt to automatically delete the | |
317 | file when closed. On Unix the file is usually C<unlink>-ed just after | |
318 | it is created so it does not matter how it gets closed. On other | |
319 | systems the file may only be deleted if closed via PerlIO_close() | |
320 | and/or the program exits via C<exit>. Depending on the implementation | |
321 | there may be "race conditions" which allow other processes access to | |
322 | the file, though in general it will be safer in this regard than | |
323 | ad. hoc. schemes. | |
50b80e25 NIS |
324 | |
325 | =item B<PerlIO_setlinebuf(f)> | |
326 | ||
06936a3c PN |
327 | This corresponds to setlinebuf(). Does not return a value. What |
328 | constitutes a "line" is implementation dependent but usually means | |
329 | that writing "\n" flushes the buffer. What happens with things like | |
330 | "this\nthat" is uncertain. (Perl core uses it I<only> when "dumping"; | |
331 | it has nothing to do with $| auto-flush.) | |
760ac839 | 332 | |
54310121 | 333 | =back |
760ac839 | 334 | |
510d21e9 | 335 | =head2 Co-existence with stdio |
760ac839 | 336 | |
510d21e9 | 337 | There is outline support for co-existence of PerlIO with stdio. |
06936a3c PN |
338 | Obviously if PerlIO is implemented in terms of stdio there is no |
339 | problem. However in other cases then mechanisms must exist to create a | |
340 | FILE * which can be passed to library code which is going to use stdio | |
341 | calls. | |
50b80e25 | 342 | |
210b36aa | 343 | The first step is to add this line: |
50b80e25 NIS |
344 | |
345 | #define PERLIO_NOT_STDIO 0 | |
346 | ||
06936a3c PN |
347 | I<before> including any perl header files. (This will probably become |
348 | the default at some point). That prevents "perlio.h" from attempting | |
349 | to #define stdio functions onto PerlIO functions. | |
50b80e25 | 350 | |
06936a3c PN |
351 | XS code is probably better using "typemap" if it expects FILE * |
352 | arguments. The standard typemap will be adjusted to comprehend any | |
353 | changes in this area. | |
760ac839 LW |
354 | |
355 | =over 4 | |
356 | ||
4b069b44 | 357 | =item B<PerlIO_importFILE(f,mode)> |
760ac839 | 358 | |
22569500 | 359 | Used to get a PerlIO * from a FILE *. |
760ac839 | 360 | |
c0a503cc JH |
361 | The mode argument should be a string as would be passed to |
362 | fopen/PerlIO_open. If it is NULL then - for legacy support - the code | |
363 | will (depending upon the platform and the implementation) either | |
364 | attempt to empirically determine the mode in which I<f> is open, or | |
365 | use "r+" to indicate a read/write stream. | |
22569500 NIS |
366 | |
367 | Once called the FILE * should I<ONLY> be closed by calling | |
368 | C<PerlIO_close()> on the returned PerlIO *. | |
369 | ||
f504ae08 LC |
370 | The PerlIO is set to textmode. Use PerlIO_binmode if this is |
371 | not the desired mode. | |
372 | ||
b9d6bf13 JH |
373 | This is B<not> the reverse of PerlIO_exportFILE(). |
374 | ||
4b069b44 | 375 | =item B<PerlIO_exportFILE(f,mode)> |
760ac839 | 376 | |
8dcb5783 | 377 | Given a PerlIO * create a 'native' FILE * suitable for passing to code |
c0a503cc JH |
378 | expecting to be compiled and linked with ANSI C I<stdio.h>. The mode |
379 | argument should be a string as would be passed to fopen/PerlIO_open. | |
380 | If it is NULL then - for legacy support - the FILE * is opened in same | |
381 | mode as the PerlIO *. | |
382 | ||
383 | The fact that such a FILE * has been 'exported' is recorded, (normally | |
384 | by pushing a new :stdio "layer" onto the PerlIO *), which may affect | |
385 | future PerlIO operations on the original PerlIO *. You should not | |
386 | call C<fclose()> on the file unless you call C<PerlIO_releaseFILE()> | |
387 | to disassociate it from the PerlIO *. (Do not use PerlIO_importFILE() | |
388 | for doing the disassociation.) | |
760ac839 | 389 | |
22569500 NIS |
390 | Calling this function repeatedly will create a FILE * on each call |
391 | (and will push an :stdio layer each time as well). | |
760ac839 LW |
392 | |
393 | =item B<PerlIO_releaseFILE(p,f)> | |
394 | ||
06936a3c | 395 | Calling PerlIO_releaseFILE informs PerlIO that all use of FILE * is |
65dabbe3 LC |
396 | complete. It is removed from the list of 'exported' FILE *s, and the |
397 | associated PerlIO * should revert to its original behaviour. | |
760ac839 | 398 | |
b9d6bf13 JH |
399 | Use this to disassociate a file from a PerlIO * that was associated |
400 | using PerlIO_exportFILE(). | |
401 | ||
22569500 NIS |
402 | =item B<PerlIO_findFILE(f)> |
403 | ||
404 | Returns a native FILE * used by a stdio layer. If there is none, it | |
405 | will create one with PerlIO_exportFILE. In either case the FILE * | |
65dabbe3 | 406 | should be considered as belonging to PerlIO subsystem and should |
22569500 NIS |
407 | only be closed by calling C<PerlIO_close()>. |
408 | ||
8dcb5783 | 409 | |
760ac839 LW |
410 | =back |
411 | ||
50b80e25 NIS |
412 | =head2 "Fast gets" Functions |
413 | ||
06936a3c PN |
414 | In addition to standard-like API defined so far above there is an |
415 | "implementation" interface which allows perl to get at internals of | |
416 | PerlIO. The following calls correspond to the various FILE_xxx macros | |
417 | determined by Configure - or their equivalent in other | |
418 | implementations. This section is really of interest to only those | |
419 | concerned with detailed perl-core behaviour, implementing a PerlIO | |
420 | mapping or writing code which can make use of the "read ahead" that | |
421 | has been done by the IO system in the same way perl does. Note that | |
422 | any code that uses these interfaces must be prepared to do things the | |
423 | traditional way if a handle does not support them. | |
760ac839 LW |
424 | |
425 | =over 4 | |
426 | ||
50b80e25 | 427 | =item B<PerlIO_fast_gets(f)> |
760ac839 | 428 | |
50b80e25 | 429 | Returns true if implementation has all the interfaces required to |
c0a503cc JH |
430 | allow perl's C<sv_gets> to "bypass" normal IO mechanism. This can |
431 | vary from handle to handle. | |
760ac839 | 432 | |
50b80e25 NIS |
433 | PerlIO_fast_gets(f) = PerlIO_has_cntptr(f) && \ |
434 | PerlIO_canset_cnt(f) && \ | |
ccf3535a | 435 | 'Can set pointer into buffer' |
760ac839 | 436 | |
50b80e25 | 437 | =item B<PerlIO_has_cntptr(f)> |
760ac839 | 438 | |
06936a3c PN |
439 | Implementation can return pointer to current position in the "buffer" |
440 | and a count of bytes available in the buffer. Do not use this - use | |
441 | PerlIO_fast_gets. | |
760ac839 | 442 | |
50b80e25 | 443 | =item B<PerlIO_get_cnt(f)> |
760ac839 | 444 | |
06936a3c PN |
445 | Return count of readable bytes in the buffer. Zero or negative return |
446 | means no more bytes available. | |
760ac839 | 447 | |
50b80e25 | 448 | =item B<PerlIO_get_ptr(f)> |
760ac839 | 449 | |
06936a3c PN |
450 | Return pointer to next readable byte in buffer, accessing via the |
451 | pointer (dereferencing) is only safe if PerlIO_get_cnt() has returned | |
452 | a positive value. Only positive offsets up to value returned by | |
453 | PerlIO_get_cnt() are allowed. | |
760ac839 LW |
454 | |
455 | =item B<PerlIO_set_ptrcnt(f,p,c)> | |
456 | ||
54310121 | 457 | Set pointer into buffer, and a count of bytes still in the |
06936a3c PN |
458 | buffer. Should be used only to set pointer to within range implied by |
459 | previous calls to C<PerlIO_get_ptr> and C<PerlIO_get_cnt>. The two | |
460 | values I<must> be consistent with each other (implementation may only | |
461 | use one or the other or may require both). | |
50b80e25 NIS |
462 | |
463 | =item B<PerlIO_canset_cnt(f)> | |
464 | ||
465 | Implementation can adjust its idea of number of bytes in the buffer. | |
466 | Do not use this - use PerlIO_fast_gets. | |
760ac839 LW |
467 | |
468 | =item B<PerlIO_set_cnt(f,c)> | |
469 | ||
06936a3c PN |
470 | Obscure - set count of bytes in the buffer. Deprecated. Only usable |
471 | if PerlIO_canset_cnt() returns true. Currently used in only doio.c to | |
472 | force count less than -1 to -1. Perhaps should be PerlIO_set_empty or | |
473 | similar. This call may actually do nothing if "count" is deduced from | |
474 | pointer and a "limit". Do not use this - use PerlIO_set_ptrcnt(). | |
760ac839 LW |
475 | |
476 | =item B<PerlIO_has_base(f)> | |
477 | ||
50b80e25 | 478 | Returns true if implementation has a buffer, and can return pointer |
760ac839 LW |
479 | to whole buffer and its size. Used by perl for B<-T> / B<-B> tests. |
480 | Other uses would be very obscure... | |
481 | ||
482 | =item B<PerlIO_get_base(f)> | |
483 | ||
50b80e25 NIS |
484 | Return I<start> of buffer. Access only positive offsets in the buffer |
485 | up to the value returned by PerlIO_get_bufsiz(). | |
760ac839 LW |
486 | |
487 | =item B<PerlIO_get_bufsiz(f)> | |
488 | ||
06936a3c PN |
489 | Return the I<total number of bytes> in the buffer, this is neither the |
490 | number that can be read, nor the amount of memory allocated to the | |
491 | buffer. Rather it is what the operating system and/or implementation | |
492 | happened to C<read()> (or whatever) last time IO was requested. | |
50b80e25 NIS |
493 | |
494 | =back | |
495 | ||
496 | =head2 Other Functions | |
497 | ||
498 | =over 4 | |
499 | ||
500 | =item PerlIO_apply_layers(f,mode,layers) | |
501 | ||
502 | The new interface to the USE_PERLIO implementation. The layers ":crlf" | |
503 | and ":raw" are only ones allowed for other implementations and those | |
c0a503cc JH |
504 | are silently ignored. (As of perl5.8 ":raw" is deprecated.) Use |
505 | PerlIO_binmode() below for the portable case. | |
50b80e25 NIS |
506 | |
507 | =item PerlIO_binmode(f,ptype,imode,layers) | |
508 | ||
509 | The hook used by perl's C<binmode> operator. | |
210b36aa | 510 | B<ptype> is perl's character for the kind of IO: |
50b80e25 NIS |
511 | |
512 | =over 8 | |
513 | ||
11e1c8f2 | 514 | =item 'E<lt>' read |
50b80e25 | 515 | |
11e1c8f2 | 516 | =item 'E<gt>' write |
50b80e25 NIS |
517 | |
518 | =item '+' read/write | |
519 | ||
520 | =back | |
521 | ||
522 | B<imode> is C<O_BINARY> or C<O_TEXT>. | |
523 | ||
c0a503cc JH |
524 | B<layers> is a string of layers to apply, only ":crlf" makes sense in |
525 | the non USE_PERLIO case. (As of perl5.8 ":raw" is deprecated in favour | |
526 | of passing NULL.) | |
50b80e25 NIS |
527 | |
528 | Portable cases are: | |
529 | ||
9849c14c | 530 | PerlIO_binmode(f,ptype,O_BINARY,NULL); |
50b80e25 NIS |
531 | and |
532 | PerlIO_binmode(f,ptype,O_TEXT,":crlf"); | |
533 | ||
06936a3c PN |
534 | On Unix these calls probably have no effect whatsoever. Elsewhere |
535 | they alter "\n" to CR,LF translation and possibly cause a special text | |
536 | "end of file" indicator to be written or honoured on read. The effect | |
537 | of making the call after doing any IO to the handle depends on the | |
538 | implementation. (It may be ignored, affect any data which is already | |
539 | buffered as well, or only apply to subsequent data.) | |
50b80e25 NIS |
540 | |
541 | =item PerlIO_debug(fmt,...) | |
542 | ||
06936a3c PN |
543 | PerlIO_debug is a printf()-like function which can be used for |
544 | debugging. No return value. Its main use is inside PerlIO where using | |
545 | real printf, warn() etc. would recursively call PerlIO and be a | |
546 | problem. | |
50b80e25 | 547 | |
2104c695 CB |
548 | PerlIO_debug writes to the file named by $ENV{'PERLIO_DEBUG'} or defaults |
549 | to stderr if the environment variable is not defined. Typical | |
06936a3c | 550 | use might be |
50b80e25 | 551 | |
ada498b9 | 552 | Bourne shells (sh, ksh, bash, zsh, ash, ...): |
2104c695 | 553 | PERLIO_DEBUG=/tmp/perliodebug.log ./perl -Di somescript some args |
50b80e25 | 554 | |
ada498b9 | 555 | Csh/Tcsh: |
2104c695 CB |
556 | setenv PERLIO_DEBUG /tmp/perliodebug.log |
557 | ./perl -Di somescript some args | |
50b80e25 | 558 | |
ada498b9 | 559 | If you have the "env" utility: |
2104c695 | 560 | env PERLIO_DEBUG=/tmp/perliodebug.log ./perl -Di somescript args |
ada498b9 | 561 | |
50b80e25 | 562 | Win32: |
2104c695 CB |
563 | set PERLIO_DEBUG=perliodebug.log |
564 | perl -Di somescript some args | |
50b80e25 | 565 | |
2104c695 CB |
566 | On a Perl built without C<-DDEBUGGING>, or when the C<-Di> command-line switch |
567 | is not specified, or under taint, PerlIO_debug() is a no-op. | |
760ac839 | 568 | |
54310121 | 569 | =back |