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