Skip to content

HTTPS clone URL

Subversion checkout URL

You can clone with HTTPS or Subversion.

Download ZIP
Newer
Older
100644 1041 lines (718 sloc) 33.82 kb
50b80e2 PerlIO documentation. Proofing and sub-editing requested.
Nick Ing-Simmons authored
1 =head1 NAME
2
3 perliol - C API for Perl's implementation of IO in Layers.
4
5 =head1 SYNOPSIS
6
7 /* Defining a layer ... */
8 #include <perliol.h>
9
10 =head1 DESCRIPTION
11
9d79914 GNU 'merge' Simon's copy of perliol.pod with version
Nick Ing-Simmons authored
12 This document describes the behavior and implementation of the PerlIO
13 abstraction described in L<perlapio> when C<USE_PERLIO> is defined (and
14 C<USE_SFIO> is not).
50b80e2 PerlIO documentation. Proofing and sub-editing requested.
Nick Ing-Simmons authored
15
16 =head2 History and Background
17
9d79914 GNU 'merge' Simon's copy of perliol.pod with version
Nick Ing-Simmons authored
18 The PerlIO abstraction was introduced in perl5.003_02 but languished as
19 just an abstraction until perl5.7.0. However during that time a number
d1be940 a few typo fixes
Jeffrey Friedl authored
20 of perl extensions switched to using it, so the API is mostly fixed to
9d79914 GNU 'merge' Simon's copy of perliol.pod with version
Nick Ing-Simmons authored
21 maintain (source) compatibility.
50b80e2 PerlIO documentation. Proofing and sub-editing requested.
Nick Ing-Simmons authored
22
9d79914 GNU 'merge' Simon's copy of perliol.pod with version
Nick Ing-Simmons authored
23 The aim of the implementation is to provide the PerlIO API in a flexible
24 and platform neutral manner. It is also a trial of an "Object Oriented
241e738 @chromatic Change "Perl6" to "Perl 6" in pod/*
chromatic authored
25 C, with vtables" approach which may be applied to Perl 6.
50b80e2 PerlIO documentation. Proofing and sub-editing requested.
Nick Ing-Simmons authored
26
cc83745 @jhi More PerlIO documentation.
jhi authored
27 =head2 Basic Structure
28
cc7ef05 @jhi Some more perlio doc tweaks based on NI-S.
jhi authored
29 PerlIO is a stack of layers.
cc83745 @jhi More PerlIO documentation.
jhi authored
30
31 The low levels of the stack work with the low-level operating system
32 calls (file descriptors in C) getting bytes in and out, the higher
cc7ef05 @jhi Some more perlio doc tweaks based on NI-S.
jhi authored
33 layers of the stack buffer, filter, and otherwise manipulate the I/O,
34 and return characters (or bytes) to Perl. Terms I<above> and I<below>
35 are used to refer to the relative positioning of the stack layers.
cc83745 @jhi More PerlIO documentation.
jhi authored
36
37 A layer contains a "vtable", the table of I/O operations (at C level
38 a table of function pointers), and status flags. The functions in the
39 vtable implement operations like "open", "read", and "write".
40
41 When I/O, for example "read", is requested, the request goes from Perl
42 first down the stack using "read" functions of each layer, then at the
43 bottom the input is requested from the operating system services, then
44 the result is returned up the stack, finally being interpreted as Perl
45 data.
46
cc7ef05 @jhi Some more perlio doc tweaks based on NI-S.
jhi authored
47 The requests do not necessarily go always all the way down to the
48 operating system: that's where PerlIO buffering comes into play.
49
cc83745 @jhi More PerlIO documentation.
jhi authored
50 When you do an open() and specify extra PerlIO layers to be deployed,
51 the layers you specify are "pushed" on top of the already existing
cc7ef05 @jhi Some more perlio doc tweaks based on NI-S.
jhi authored
52 default stack. One way to see it is that "operating system is
53 on the left" and "Perl is on the right".
54
55 What exact layers are in this default stack depends on a lot of
56 things: your operating system, Perl version, Perl compile time
57 configuration, and Perl runtime configuration. See L<PerlIO>,
cc83745 @jhi More PerlIO documentation.
jhi authored
58 L<perlrun/PERLIO>, and L<open> for more information.
59
60 binmode() operates similarly to open(): by default the specified
61 layers are pushed on top of the existing stack.
62
63 However, note that even as the specified layers are "pushed on top"
64 for open() and binmode(), this doesn't mean that the effects are
65 limited to the "top": PerlIO layers can be very 'active' and inspect
66 and affect layers also deeper in the stack. As an example there
67 is a layer called "raw" which repeatedly "pops" layers until
68 it reaches the first layer that has declared itself capable of
69 handling binary data. The "pushed" layers are processed in left-to-right
70 order.
71
72 sysopen() operates (unsurprisingly) at a lower level in the stack than
e102041 PATCH: minor typo cleanup of pod/ directory
Tom Christiansen authored
73 open(). For example in Unix or Unix-like systems sysopen() operates
cc83745 @jhi More PerlIO documentation.
jhi authored
74 directly at the level of file descriptors: in the terms of PerlIO
75 layers, it uses only the "unix" layer, which is a rather thin wrapper
e102041 PATCH: minor typo cleanup of pod/ directory
Tom Christiansen authored
76 on top of the Unix file descriptors.
cc83745 @jhi More PerlIO documentation.
jhi authored
77
50b80e2 PerlIO documentation. Proofing and sub-editing requested.
Nick Ing-Simmons authored
78 =head2 Layers vs Disciplines
79
9d79914 GNU 'merge' Simon's copy of perliol.pod with version
Nick Ing-Simmons authored
80 Initial discussion of the ability to modify IO streams behaviour used
81 the term "discipline" for the entities which were added. This came (I
82 believe) from the use of the term in "sfio", which in turn borrowed it
83 from "line disciplines" on Unix terminals. However, this document (and
84 the C code) uses the term "layer".
85
1d11c88 @jhi Paragraph rewrapping.
jhi authored
86 This is, I hope, a natural term given the implementation, and should
87 avoid connotations that are inherent in earlier uses of "discipline"
88 for things which are rather different.
50b80e2 PerlIO documentation. Proofing and sub-editing requested.
Nick Ing-Simmons authored
89
90 =head2 Data Structures
91
92 The basic data structure is a PerlIOl:
93
94 typedef struct _PerlIO PerlIOl;
95 typedef struct _PerlIO_funcs PerlIO_funcs;
96 typedef PerlIOl *PerlIO;
97
98 struct _PerlIO
99 {
100 PerlIOl * next; /* Lower layer */
101 PerlIO_funcs * tab; /* Functions for this layer */
102 IV flags; /* Various flags for state */
103 };
104
1d11c88 @jhi Paragraph rewrapping.
jhi authored
105 A C<PerlIOl *> is a pointer to the struct, and the I<application>
106 level C<PerlIO *> is a pointer to a C<PerlIOl *> - i.e. a pointer
107 to a pointer to the struct. This allows the application level C<PerlIO *>
108 to remain constant while the actual C<PerlIOl *> underneath
109 changes. (Compare perl's C<SV *> which remains constant while its
110 C<sv_any> field changes as the scalar's type changes.) An IO stream is
111 then in general represented as a pointer to this linked-list of
112 "layers".
50b80e2 PerlIO documentation. Proofing and sub-editing requested.
Nick Ing-Simmons authored
113
9d79914 GNU 'merge' Simon's copy of perliol.pod with version
Nick Ing-Simmons authored
114 It should be noted that because of the double indirection in a C<PerlIO *>,
d4165bd @stas00 Re: [PATCH pod/perliol.pod] resend
stas00 authored
115 a C<< &(perlio->next) >> "is" a C<PerlIO *>, and so to some degree
11e1c8f pod problems in io
Peter Prymmer authored
116 at least one layer can use the "standard" API on the next layer down.
50b80e2 PerlIO documentation. Proofing and sub-editing requested.
Nick Ing-Simmons authored
117
118 A "layer" is composed of two parts:
119
120 =over 4
121
210b36a [PATCH] Doc spellcheck + podcheck
Abhijit Menon-Sen authored
122 =item 1.
50b80e2 PerlIO documentation. Proofing and sub-editing requested.
Nick Ing-Simmons authored
123
210b36a [PATCH] Doc spellcheck + podcheck
Abhijit Menon-Sen authored
124 The functions and attributes of the "layer class".
125
126 =item 2.
127
128 The per-instance data for a particular handle.
50b80e2 PerlIO documentation. Proofing and sub-editing requested.
Nick Ing-Simmons authored
129
130 =back
131
132 =head2 Functions and Attributes
133
9d79914 GNU 'merge' Simon's copy of perliol.pod with version
Nick Ing-Simmons authored
134 The functions and attributes are accessed via the "tab" (for table)
135 member of C<PerlIOl>. The functions (methods of the layer "class") are
136 fixed, and are defined by the C<PerlIO_funcs> type. They are broadly the
137 same as the public C<PerlIO_xxxxx> functions:
50b80e2 PerlIO documentation. Proofing and sub-editing requested.
Nick Ing-Simmons authored
138
b76cc8b Tweak docs for C<open> (boy does that need wholesale revision...)
Nick Ing-Simmons authored
139 struct _PerlIO_funcs
140 {
2dc2558 PerlIO Layer implementation future proofing.
Nick Ing-Simmons authored
141 Size_t fsize;
b76cc8b Tweak docs for C<open> (boy does that need wholesale revision...)
Nick Ing-Simmons authored
142 char * name;
143 Size_t size;
144 IV kind;
2dc2558 PerlIO Layer implementation future proofing.
Nick Ing-Simmons authored
145 IV (*Pushed)(pTHX_ PerlIO *f,const char *mode,SV *arg, PerlIO_funcs *tab);
d4165bd @stas00 Re: [PATCH pod/perliol.pod] resend
stas00 authored
146 IV (*Popped)(pTHX_ PerlIO *f);
b76cc8b Tweak docs for C<open> (boy does that need wholesale revision...)
Nick Ing-Simmons authored
147 PerlIO * (*Open)(pTHX_ PerlIO_funcs *tab,
2556f95 @gfx Re: [perl #56644] PerlIO resource leaks on open() and then :pop in :unix...
gfx authored
148 PerlIO_list_t *layers, IV n,
b76cc8b Tweak docs for C<open> (boy does that need wholesale revision...)
Nick Ing-Simmons authored
149 const char *mode,
150 int fd, int imode, int perm,
151 PerlIO *old,
152 int narg, SV **args);
86e05cf "Clean" implementation of binmode(FH)/":raw" identity.
Nick Ing-Simmons authored
153 IV (*Binmode)(pTHX_ PerlIO *f);
d4165bd @stas00 Re: [PATCH pod/perliol.pod] resend
stas00 authored
154 SV * (*Getarg)(pTHX_ PerlIO *f, CLONE_PARAMS *param, int flags)
155 IV (*Fileno)(pTHX_ PerlIO *f);
156 PerlIO * (*Dup)(pTHX_ PerlIO *f, PerlIO *o, CLONE_PARAMS *param, int flags)
b76cc8b Tweak docs for C<open> (boy does that need wholesale revision...)
Nick Ing-Simmons authored
157 /* Unix-like functions - cf sfio line disciplines */
d4165bd @stas00 Re: [PATCH pod/perliol.pod] resend
stas00 authored
158 SSize_t (*Read)(pTHX_ PerlIO *f, void *vbuf, Size_t count);
159 SSize_t (*Unread)(pTHX_ PerlIO *f, const void *vbuf, Size_t count);
160 SSize_t (*Write)(pTHX_ PerlIO *f, const void *vbuf, Size_t count);
161 IV (*Seek)(pTHX_ PerlIO *f, Off_t offset, int whence);
162 Off_t (*Tell)(pTHX_ PerlIO *f);
163 IV (*Close)(pTHX_ PerlIO *f);
b76cc8b Tweak docs for C<open> (boy does that need wholesale revision...)
Nick Ing-Simmons authored
164 /* Stdio-like buffered IO functions */
d4165bd @stas00 Re: [PATCH pod/perliol.pod] resend
stas00 authored
165 IV (*Flush)(pTHX_ PerlIO *f);
166 IV (*Fill)(pTHX_ PerlIO *f);
167 IV (*Eof)(pTHX_ PerlIO *f);
168 IV (*Error)(pTHX_ PerlIO *f);
169 void (*Clearerr)(pTHX_ PerlIO *f);
170 void (*Setlinebuf)(pTHX_ PerlIO *f);
b76cc8b Tweak docs for C<open> (boy does that need wholesale revision...)
Nick Ing-Simmons authored
171 /* Perl's snooping functions */
d4165bd @stas00 Re: [PATCH pod/perliol.pod] resend
stas00 authored
172 STDCHAR * (*Get_base)(pTHX_ PerlIO *f);
173 Size_t (*Get_bufsiz)(pTHX_ PerlIO *f);
174 STDCHAR * (*Get_ptr)(pTHX_ PerlIO *f);
175 SSize_t (*Get_cnt)(pTHX_ PerlIO *f);
176 void (*Set_ptrcnt)(pTHX_ PerlIO *f,STDCHAR *ptr,SSize_t cnt);
b76cc8b Tweak docs for C<open> (boy does that need wholesale revision...)
Nick Ing-Simmons authored
177 };
178
2dc2558 PerlIO Layer implementation future proofing.
Nick Ing-Simmons authored
179 The first few members of the struct give a function table size for
180 compatibility check "name" for the layer, the size to C<malloc> for the per-instance data,
181 and some flags which are attributes of the class as whole (such as whether it is a buffering
9d79914 GNU 'merge' Simon's copy of perliol.pod with version
Nick Ing-Simmons authored
182 layer), then follow the functions which fall into four basic groups:
50b80e2 PerlIO documentation. Proofing and sub-editing requested.
Nick Ing-Simmons authored
183
184 =over 4
185
aa500c9 minor pod nits
Robin Barker authored
186 =item 1.
50b80e2 PerlIO documentation. Proofing and sub-editing requested.
Nick Ing-Simmons authored
187
aa500c9 minor pod nits
Robin Barker authored
188 Opening and setup functions
50b80e2 PerlIO documentation. Proofing and sub-editing requested.
Nick Ing-Simmons authored
189
aa500c9 minor pod nits
Robin Barker authored
190 =item 2.
50b80e2 PerlIO documentation. Proofing and sub-editing requested.
Nick Ing-Simmons authored
191
aa500c9 minor pod nits
Robin Barker authored
192 Basic IO operations
193
194 =item 3.
195
196 Stdio class buffering options.
197
198 =item 4.
199
200 Functions to support Perl's traditional "fast" access to the buffer.
50b80e2 PerlIO documentation. Proofing and sub-editing requested.
Nick Ing-Simmons authored
201
202 =back
203
1d11c88 @jhi Paragraph rewrapping.
jhi authored
204 A layer does not have to implement all the functions, but the whole
205 table has to be present. Unimplemented slots can be NULL (which will
206 result in an error when called) or can be filled in with stubs to
207 "inherit" behaviour from a "base class". This "inheritance" is fixed
208 for all instances of the layer, but as the layer chooses which stubs
209 to populate the table, limited "multiple inheritance" is possible.
50b80e2 PerlIO documentation. Proofing and sub-editing requested.
Nick Ing-Simmons authored
210
211 =head2 Per-instance Data
212
1d11c88 @jhi Paragraph rewrapping.
jhi authored
213 The per-instance data are held in memory beyond the basic PerlIOl
214 struct, by making a PerlIOl the first member of the layer's struct
215 thus:
50b80e2 PerlIO documentation. Proofing and sub-editing requested.
Nick Ing-Simmons authored
216
217 typedef struct
218 {
219 struct _PerlIO base; /* Base "class" info */
220 STDCHAR * buf; /* Start of buffer */
221 STDCHAR * end; /* End of valid part of buffer */
222 STDCHAR * ptr; /* Current position in buffer */
223 Off_t posn; /* Offset of buf into the file */
224 Size_t bufsiz; /* Real size of buffer */
225 IV oneword; /* Emergency buffer */
226 } PerlIOBuf;
227
1d11c88 @jhi Paragraph rewrapping.
jhi authored
228 In this way (as for perl's scalars) a pointer to a PerlIOBuf can be
229 treated as a pointer to a PerlIOl.
50b80e2 PerlIO documentation. Proofing and sub-editing requested.
Nick Ing-Simmons authored
230
231 =head2 Layers in action.
232
233 table perlio unix
234 | |
235 +-----------+ +----------+ +--------+
236 PerlIO ->| |--->| next |--->| NULL |
237 +-----------+ +----------+ +--------+
238 | | | buffer | | fd |
239 +-----------+ | | +--------+
240 | | +----------+
241
242
243 The above attempts to show how the layer scheme works in a simple case.
9d79914 GNU 'merge' Simon's copy of perliol.pod with version
Nick Ing-Simmons authored
244 The application's C<PerlIO *> points to an entry in the table(s)
245 representing open (allocated) handles. For example the first three slots
246 in the table correspond to C<stdin>,C<stdout> and C<stderr>. The table
247 in turn points to the current "top" layer for the handle - in this case
248 an instance of the generic buffering layer "perlio". That layer in turn
353c650 @dland POD cleanups
dland authored
249 points to the next layer down - in this case the low-level "unix" layer.
50b80e2 PerlIO documentation. Proofing and sub-editing requested.
Nick Ing-Simmons authored
250
9d79914 GNU 'merge' Simon's copy of perliol.pod with version
Nick Ing-Simmons authored
251 The above is roughly equivalent to a "stdio" buffered stream, but with
252 much more flexibility:
50b80e2 PerlIO documentation. Proofing and sub-editing requested.
Nick Ing-Simmons authored
253
254 =over 4
255
256 =item *
257
9d79914 GNU 'merge' Simon's copy of perliol.pod with version
Nick Ing-Simmons authored
258 If Unix level C<read>/C<write>/C<lseek> is not appropriate for (say)
259 sockets then the "unix" layer can be replaced (at open time or even
260 dynamically) with a "socket" layer.
50b80e2 PerlIO documentation. Proofing and sub-editing requested.
Nick Ing-Simmons authored
261
262 =item *
263
1d11c88 @jhi Paragraph rewrapping.
jhi authored
264 Different handles can have different buffering schemes. The "top"
265 layer could be the "mmap" layer if reading disk files was quicker
266 using C<mmap> than C<read>. An "unbuffered" stream can be implemented
267 simply by not having a buffer layer.
50b80e2 PerlIO documentation. Proofing and sub-editing requested.
Nick Ing-Simmons authored
268
269 =item *
270
271 Extra layers can be inserted to process the data as it flows through.
9d79914 GNU 'merge' Simon's copy of perliol.pod with version
Nick Ing-Simmons authored
272 This was the driving need for including the scheme in perl 5.7.0+ - we
d1be940 a few typo fixes
Jeffrey Friedl authored
273 needed a mechanism to allow data to be translated between perl's
9d79914 GNU 'merge' Simon's copy of perliol.pod with version
Nick Ing-Simmons authored
274 internal encoding (conceptually at least Unicode as UTF-8), and the
275 "native" format used by the system. This is provided by the
276 ":encoding(xxxx)" layer which typically sits above the buffering layer.
50b80e2 PerlIO documentation. Proofing and sub-editing requested.
Nick Ing-Simmons authored
277
278 =item *
279
1d11c88 @jhi Paragraph rewrapping.
jhi authored
280 A layer can be added that does "\n" to CRLF translation. This layer
281 can be used on any platform, not just those that normally do such
282 things.
50b80e2 PerlIO documentation. Proofing and sub-editing requested.
Nick Ing-Simmons authored
283
284 =back
285
286 =head2 Per-instance flag bits
287
1d11c88 @jhi Paragraph rewrapping.
jhi authored
288 The generic flag bits are a hybrid of C<O_XXXXX> style flags deduced
289 from the mode string passed to C<PerlIO_open()>, and state bits for
290 typical buffer layers.
50b80e2 PerlIO documentation. Proofing and sub-editing requested.
Nick Ing-Simmons authored
291
9d79914 GNU 'merge' Simon's copy of perliol.pod with version
Nick Ing-Simmons authored
292 =over 4
50b80e2 PerlIO documentation. Proofing and sub-editing requested.
Nick Ing-Simmons authored
293
294 =item PERLIO_F_EOF
295
296 End of file.
297
298 =item PERLIO_F_CANWRITE
299
3039a93 PerlIO doc tweaks from Craig A. Berry <craig.berry@psinetcs.com>
Nick Ing-Simmons authored
300 Writes are permitted, i.e. opened as "w" or "r+" or "a", etc.
50b80e2 PerlIO documentation. Proofing and sub-editing requested.
Nick Ing-Simmons authored
301
302 =item PERLIO_F_CANREAD
303
3039a93 PerlIO doc tweaks from Craig A. Berry <craig.berry@psinetcs.com>
Nick Ing-Simmons authored
304 Reads are permitted i.e. opened "r" or "w+" (or even "a+" - ick).
50b80e2 PerlIO documentation. Proofing and sub-editing requested.
Nick Ing-Simmons authored
305
306 =item PERLIO_F_ERROR
307
d4165bd @stas00 Re: [PATCH pod/perliol.pod] resend
stas00 authored
308 An error has occurred (for C<PerlIO_error()>).
50b80e2 PerlIO documentation. Proofing and sub-editing requested.
Nick Ing-Simmons authored
309
310 =item PERLIO_F_TRUNCATE
311
312 Truncate file suggested by open mode.
313
314 =item PERLIO_F_APPEND
315
316 All writes should be appends.
317
318 =item PERLIO_F_CRLF
319
11e1c8f pod problems in io
Peter Prymmer authored
320 Layer is performing Win32-like "\n" mapped to CR,LF for output and CR,LF
321 mapped to "\n" for input. Normally the provided "crlf" layer is the only
322 layer that need bother about this. C<PerlIO_binmode()> will mess with this
9d79914 GNU 'merge' Simon's copy of perliol.pod with version
Nick Ing-Simmons authored
323 flag rather than add/remove layers if the C<PERLIO_K_CANCRLF> bit is set
324 for the layers class.
50b80e2 PerlIO documentation. Proofing and sub-editing requested.
Nick Ing-Simmons authored
325
326 =item PERLIO_F_UTF8
327
3039a93 PerlIO doc tweaks from Craig A. Berry <craig.berry@psinetcs.com>
Nick Ing-Simmons authored
328 Data written to this layer should be UTF-8 encoded; data provided
50b80e2 PerlIO documentation. Proofing and sub-editing requested.
Nick Ing-Simmons authored
329 by this layer should be considered UTF-8 encoded. Can be set on any layer
330 by ":utf8" dummy layer. Also set on ":encoding" layer.
331
332 =item PERLIO_F_UNBUF
333
334 Layer is unbuffered - i.e. write to next layer down should occur for
335 each write to this layer.
336
337 =item PERLIO_F_WRBUF
338
339 The buffer for this layer currently holds data written to it but not sent
340 to next layer.
341
342 =item PERLIO_F_RDBUF
343
344 The buffer for this layer currently holds unconsumed data read from
345 layer below.
346
347 =item PERLIO_F_LINEBUF
348
9d79914 GNU 'merge' Simon's copy of perliol.pod with version
Nick Ing-Simmons authored
349 Layer is line buffered. Write data should be passed to next layer down
350 whenever a "\n" is seen. Any data beyond the "\n" should then be
351 processed.
50b80e2 PerlIO documentation. Proofing and sub-editing requested.
Nick Ing-Simmons authored
352
353 =item PERLIO_F_TEMP
354
9d79914 GNU 'merge' Simon's copy of perliol.pod with version
Nick Ing-Simmons authored
355 File has been C<unlink()>ed, or should be deleted on C<close()>.
50b80e2 PerlIO documentation. Proofing and sub-editing requested.
Nick Ing-Simmons authored
356
357 =item PERLIO_F_OPEN
358
359 Handle is open.
360
361 =item PERLIO_F_FASTGETS
362
9d79914 GNU 'merge' Simon's copy of perliol.pod with version
Nick Ing-Simmons authored
363 This instance of this layer supports the "fast C<gets>" interface.
364 Normally set based on C<PERLIO_K_FASTGETS> for the class and by the
d1be940 a few typo fixes
Jeffrey Friedl authored
365 existence of the function(s) in the table. However a class that
50b80e2 PerlIO documentation. Proofing and sub-editing requested.
Nick Ing-Simmons authored
366 normally provides that interface may need to avoid it on a
367 particular instance. The "pending" layer needs to do this when
d1be940 a few typo fixes
Jeffrey Friedl authored
368 it is pushed above a layer which does not support the interface.
9d79914 GNU 'merge' Simon's copy of perliol.pod with version
Nick Ing-Simmons authored
369 (Perl's C<sv_gets()> does not expect the streams fast C<gets> behaviour
50b80e2 PerlIO documentation. Proofing and sub-editing requested.
Nick Ing-Simmons authored
370 to change during one "get".)
371
372 =back
373
374 =head2 Methods in Detail
375
376 =over 4
377
e2d9456 @lizmat [DOC PATCH] perliol.pod nit
lizmat authored
378 =item fsize
2dc2558 PerlIO Layer implementation future proofing.
Nick Ing-Simmons authored
379
380 Size_t fsize;
381
a489db4 @jhi Slight rewording from Stas, paragraph rewrappings.
jhi authored
382 Size of the function table. This is compared against the value PerlIO
383 code "knows" as a compatibility check. Future versions I<may> be able
384 to tolerate layers compiled against an old version of the headers.
2dc2558 PerlIO Layer implementation future proofing.
Nick Ing-Simmons authored
385
5cb3728 Re: [PATCH @14870] long C<=item>s and other pod->man->troff problems
Robin Barker authored
386 =item name
387
388 char * name;
d4165bd @stas00 Re: [PATCH pod/perliol.pod] resend
stas00 authored
389
390 The name of the layer whose open() method Perl should invoke on
391 open(). For example if the layer is called APR, you will call:
392
393 open $fh, ">:APR", ...
394
395 and Perl knows that it has to invoke the PerlIOAPR_open() method
396 implemented by the APR layer.
397
5cb3728 Re: [PATCH @14870] long C<=item>s and other pod->man->troff problems
Robin Barker authored
398 =item size
399
400 Size_t size;
d4165bd @stas00 Re: [PATCH pod/perliol.pod] resend
stas00 authored
401
402 The size of the per-instance data structure, e.g.:
403
404 sizeof(PerlIOAPR)
405
a489db4 @jhi Slight rewording from Stas, paragraph rewrappings.
jhi authored
406 If this field is zero then C<PerlIO_pushed> does not malloc anything
407 and assumes layer's Pushed function will do any required layer stack
408 manipulation - used to avoid malloc/free overhead for dummy layers.
2dc2558 PerlIO Layer implementation future proofing.
Nick Ing-Simmons authored
409 If the field is non-zero it must be at least the size of C<PerlIOl>,
410 C<PerlIO_pushed> will allocate memory for the layer's data structures
411 and link new layer onto the stream's stack. (If the layer's Pushed
412 method returns an error indication the layer is popped again.)
413
5cb3728 Re: [PATCH @14870] long C<=item>s and other pod->man->troff problems
Robin Barker authored
414 =item kind
415
416 IV kind;
d4165bd @stas00 Re: [PATCH pod/perliol.pod] resend
stas00 authored
417
418 =over 4
419
420 =item * PERLIO_K_BUFFERED
421
86e05cf "Clean" implementation of binmode(FH)/":raw" identity.
Nick Ing-Simmons authored
422 The layer is buffered.
423
424 =item * PERLIO_K_RAW
425
426 The layer is acceptable to have in a binmode(FH) stack - i.e. it does not
427 (or will configure itself not to) transform bytes passing through it.
428
d4165bd @stas00 Re: [PATCH pod/perliol.pod] resend
stas00 authored
429 =item * PERLIO_K_CANCRLF
430
86e05cf "Clean" implementation of binmode(FH)/":raw" identity.
Nick Ing-Simmons authored
431 Layer can translate between "\n" and CRLF line ends.
432
d4165bd @stas00 Re: [PATCH pod/perliol.pod] resend
stas00 authored
433 =item * PERLIO_K_FASTGETS
434
86e05cf "Clean" implementation of binmode(FH)/":raw" identity.
Nick Ing-Simmons authored
435 Layer allows buffer snooping.
436
d4165bd @stas00 Re: [PATCH pod/perliol.pod] resend
stas00 authored
437 =item * PERLIO_K_MULTIARG
438
439 Used when the layer's open() accepts more arguments than usual. The
440 extra arguments should come not before the C<MODE> argument. When this
441 flag is used it's up to the layer to validate the args.
442
443 =back
444
5cb3728 Re: [PATCH @14870] long C<=item>s and other pod->man->troff problems
Robin Barker authored
445 =item Pushed
446
447 IV (*Pushed)(pTHX_ PerlIO *f,const char *mode, SV *arg);
50b80e2 PerlIO documentation. Proofing and sub-editing requested.
Nick Ing-Simmons authored
448
1d11c88 @jhi Paragraph rewrapping.
jhi authored
449 The only absolutely mandatory method. Called when the layer is pushed
450 onto the stack. The C<mode> argument may be NULL if this occurs
451 post-open. The C<arg> will be non-C<NULL> if an argument string was
452 passed. In most cases this should call C<PerlIOBase_pushed()> to
453 convert C<mode> into the appropriate C<PERLIO_F_XXXXX> flags in
454 addition to any actions the layer itself takes. If a layer is not
455 expecting an argument it need neither save the one passed to it, nor
456 provide C<Getarg()> (it could perhaps C<Perl_warn> that the argument
457 was un-expected).
50b80e2 PerlIO documentation. Proofing and sub-editing requested.
Nick Ing-Simmons authored
458
d4165bd @stas00 Re: [PATCH pod/perliol.pod] resend
stas00 authored
459 Returns 0 on success. On failure returns -1 and should set errno.
460
5cb3728 Re: [PATCH @14870] long C<=item>s and other pod->man->troff problems
Robin Barker authored
461 =item Popped
462
463 IV (*Popped)(pTHX_ PerlIO *f);
50b80e2 PerlIO documentation. Proofing and sub-editing requested.
Nick Ing-Simmons authored
464
1d11c88 @jhi Paragraph rewrapping.
jhi authored
465 Called when the layer is popped from the stack. A layer will normally
466 be popped after C<Close()> is called. But a layer can be popped
467 without being closed if the program is dynamically managing layers on
468 the stream. In such cases C<Popped()> should free any resources
469 (buffers, translation tables, ...) not held directly in the layer's
470 struct. It should also C<Unread()> any unconsumed data that has been
471 read and buffered from the layer below back to that layer, so that it
472 can be re-provided to what ever is now above.
b76cc8b Tweak docs for C<open> (boy does that need wholesale revision...)
Nick Ing-Simmons authored
473
3077d0b @jhi More perlio docs from Stas.
jhi authored
474 Returns 0 on success and failure. If C<Popped()> returns I<true> then
475 I<perlio.c> assumes that either the layer has popped itself, or the
476 layer is super special and needs to be retained for other reasons.
477 In most cases it should return I<false>.
d4165bd @stas00 Re: [PATCH pod/perliol.pod] resend
stas00 authored
478
5cb3728 Re: [PATCH @14870] long C<=item>s and other pod->man->troff problems
Robin Barker authored
479 =item Open
480
481 PerlIO * (*Open)(...);
b76cc8b Tweak docs for C<open> (boy does that need wholesale revision...)
Nick Ing-Simmons authored
482
1d11c88 @jhi Paragraph rewrapping.
jhi authored
483 The C<Open()> method has lots of arguments because it combines the
484 functions of perl's C<open>, C<PerlIO_open>, perl's C<sysopen>,
485 C<PerlIO_fdopen> and C<PerlIO_reopen>. The full prototype is as
486 follows:
b76cc8b Tweak docs for C<open> (boy does that need wholesale revision...)
Nick Ing-Simmons authored
487
488 PerlIO * (*Open)(pTHX_ PerlIO_funcs *tab,
2556f95 @gfx Re: [perl #56644] PerlIO resource leaks on open() and then :pop in :unix...
gfx authored
489 PerlIO_list_t *layers, IV n,
b76cc8b Tweak docs for C<open> (boy does that need wholesale revision...)
Nick Ing-Simmons authored
490 const char *mode,
491 int fd, int imode, int perm,
492 PerlIO *old,
493 int narg, SV **args);
494
1d11c88 @jhi Paragraph rewrapping.
jhi authored
495 Open should (perhaps indirectly) call C<PerlIO_allocate()> to allocate
496 a slot in the table and associate it with the layers information for
2556f95 @gfx Re: [perl #56644] PerlIO resource leaks on open() and then :pop in :unix...
gfx authored
497 the opened file, by calling C<PerlIO_push>. The I<layers> is an
1d11c88 @jhi Paragraph rewrapping.
jhi authored
498 array of all the layers destined for the C<PerlIO *>, and any
499 arguments passed to them, I<n> is the index into that array of the
500 layer being called. The macro C<PerlIOArg> will return a (possibly
501 C<NULL>) SV * for the argument passed to the layer.
502
503 The I<mode> string is an "C<fopen()>-like" string which would match
504 the regular expression C</^[I#]?[rwa]\+?[bt]?$/>.
505
506 The C<'I'> prefix is used during creation of C<stdin>..C<stderr> via
507 special C<PerlIO_fdopen> calls; the C<'#'> prefix means that this is
508 C<sysopen> and that I<imode> and I<perm> should be passed to
509 C<PerlLIO_open3>; C<'r'> means B<r>ead, C<'w'> means B<w>rite and
510 C<'a'> means B<a>ppend. The C<'+'> suffix means that both reading and
a489db4 @jhi Slight rewording from Stas, paragraph rewrappings.
jhi authored
511 writing/appending are permitted. The C<'b'> suffix means file should
512 be binary, and C<'t'> means it is text. (Almost all layers should do
513 the IO in binary mode, and ignore the b/t bits. The C<:crlf> layer
514 should be pushed to handle the distinction.)
1d11c88 @jhi Paragraph rewrapping.
jhi authored
515
516 If I<old> is not C<NULL> then this is a C<PerlIO_reopen>. Perl itself
517 does not use this (yet?) and semantics are a little vague.
518
519 If I<fd> not negative then it is the numeric file descriptor I<fd>,
520 which will be open in a manner compatible with the supplied mode
521 string, the call is thus equivalent to C<PerlIO_fdopen>. In this case
522 I<nargs> will be zero.
523
524 If I<nargs> is greater than zero then it gives the number of arguments
525 passed to C<open>, otherwise it will be 1 if for example
526 C<PerlIO_open> was called. In simple cases SvPV_nolen(*args) is the
527 pathname to open.
528
81fe74f @Leont Define PerlIOBase_open
Leont authored
529 If a layer provides C<Open()> it should normally call the C<Open()>
530 method of next layer down (if any) and then push itself on top if that
531 succeeds. C<PerlIOBase_open> is provided to do exactly that, so in
532 most cases you don't have to write your own C<Open()> method. If this
533 method is not defined, other layers may have difficulty pushing
534 themselves on top of it during open.
b76cc8b Tweak docs for C<open> (boy does that need wholesale revision...)
Nick Ing-Simmons authored
535
3077d0b @jhi More perlio docs from Stas.
jhi authored
536 If C<PerlIO_push> was performed and open has failed, it must
537 C<PerlIO_pop> itself, since if it's not, the layer won't be removed
538 and may cause bad problems.
539
d4165bd @stas00 Re: [PATCH pod/perliol.pod] resend
stas00 authored
540 Returns C<NULL> on failure.
541
86e05cf "Clean" implementation of binmode(FH)/":raw" identity.
Nick Ing-Simmons authored
542 =item Binmode
543
544 IV (*Binmode)(pTHX_ PerlIO *f);
545
546 Optional. Used when C<:raw> layer is pushed (explicitly or as a result
547 of binmode(FH)). If not present layer will be popped. If present
548 should configure layer as binary (or pop itself) and return 0.
549 If it returns -1 for error C<binmode> will fail with layer
550 still on the stack.
551
5cb3728 Re: [PATCH @14870] long C<=item>s and other pod->man->troff problems
Robin Barker authored
552 =item Getarg
553
554 SV * (*Getarg)(pTHX_ PerlIO *f,
555 CLONE_PARAMS *param, int flags);
b76cc8b Tweak docs for C<open> (boy does that need wholesale revision...)
Nick Ing-Simmons authored
556
d4165bd @stas00 Re: [PATCH pod/perliol.pod] resend
stas00 authored
557 Optional. If present should return an SV * representing the string
558 argument passed to the layer when it was
559 pushed. e.g. ":encoding(ascii)" would return an SvPV with value
560 "ascii". (I<param> and I<flags> arguments can be ignored in most
561 cases)
b76cc8b Tweak docs for C<open> (boy does that need wholesale revision...)
Nick Ing-Simmons authored
562
15355bd Rewrite #21447.
Abhijit Menon-Sen authored
563 C<Dup> uses C<Getarg> to retrieve the argument originally passed to
564 C<Pushed>, so you must implement this function if your layer has an
565 extra argument to C<Pushed> and will ever be C<Dup>ed.
8741baa @stas00 [patch pod/perliol.pod]
stas00 authored
566
5cb3728 Re: [PATCH @14870] long C<=item>s and other pod->man->troff problems
Robin Barker authored
567 =item Fileno
568
569 IV (*Fileno)(pTHX_ PerlIO *f);
b76cc8b Tweak docs for C<open> (boy does that need wholesale revision...)
Nick Ing-Simmons authored
570
d1be940 a few typo fixes
Jeffrey Friedl authored
571 Returns the Unix/Posix numeric file descriptor for the handle. Normally
b76cc8b Tweak docs for C<open> (boy does that need wholesale revision...)
Nick Ing-Simmons authored
572 C<PerlIOBase_fileno()> (which just asks next layer down) will suffice
573 for this.
50b80e2 PerlIO documentation. Proofing and sub-editing requested.
Nick Ing-Simmons authored
574
a489db4 @jhi Slight rewording from Stas, paragraph rewrappings.
jhi authored
575 Returns -1 on error, which is considered to include the case where the
576 layer cannot provide such a file descriptor.
d4165bd @stas00 Re: [PATCH pod/perliol.pod] resend
stas00 authored
577
5cb3728 Re: [PATCH @14870] long C<=item>s and other pod->man->troff problems
Robin Barker authored
578 =item Dup
579
580 PerlIO * (*Dup)(pTHX_ PerlIO *f, PerlIO *o,
581 CLONE_PARAMS *param, int flags);
d4165bd @stas00 Re: [PATCH pod/perliol.pod] resend
stas00 authored
582
2dc2558 PerlIO Layer implementation future proofing.
Nick Ing-Simmons authored
583 XXX: Needs more docs.
584
a489db4 @jhi Slight rewording from Stas, paragraph rewrappings.
jhi authored
585 Used as part of the "clone" process when a thread is spawned (in which
586 case param will be non-NULL) and when a stream is being duplicated via
587 '&' in the C<open>.
d4165bd @stas00 Re: [PATCH pod/perliol.pod] resend
stas00 authored
588
589 Similar to C<Open>, returns PerlIO* on success, C<NULL> on failure.
590
5cb3728 Re: [PATCH @14870] long C<=item>s and other pod->man->troff problems
Robin Barker authored
591 =item Read
592
593 SSize_t (*Read)(pTHX_ PerlIO *f, void *vbuf, Size_t count);
d4165bd @stas00 Re: [PATCH pod/perliol.pod] resend
stas00 authored
594
595 Basic read operation.
50b80e2 PerlIO documentation. Proofing and sub-editing requested.
Nick Ing-Simmons authored
596
d4165bd @stas00 Re: [PATCH pod/perliol.pod] resend
stas00 authored
597 Typically will call C<Fill> and manipulate pointers (possibly via the
598 API). C<PerlIOBuf_read()> may be suitable for derived classes which
599 provide "fast gets" methods.
50b80e2 PerlIO documentation. Proofing and sub-editing requested.
Nick Ing-Simmons authored
600
d4165bd @stas00 Re: [PATCH pod/perliol.pod] resend
stas00 authored
601 Returns actual bytes read, or -1 on an error.
602
5cb3728 Re: [PATCH @14870] long C<=item>s and other pod->man->troff problems
Robin Barker authored
603 =item Unread
604
605 SSize_t (*Unread)(pTHX_ PerlIO *f,
606 const void *vbuf, Size_t count);
50b80e2 PerlIO documentation. Proofing and sub-editing requested.
Nick Ing-Simmons authored
607
9d79914 GNU 'merge' Simon's copy of perliol.pod with version
Nick Ing-Simmons authored
608 A superset of stdio's C<ungetc()>. Should arrange for future reads to
609 see the bytes in C<vbuf>. If there is no obviously better implementation
610 then C<PerlIOBase_unread()> provides the function by pushing a "fake"
611 "pending" layer above the calling layer.
50b80e2 PerlIO documentation. Proofing and sub-editing requested.
Nick Ing-Simmons authored
612
d4165bd @stas00 Re: [PATCH pod/perliol.pod] resend
stas00 authored
613 Returns the number of unread chars.
614
5cb3728 Re: [PATCH @14870] long C<=item>s and other pod->man->troff problems
Robin Barker authored
615 =item Write
616
617 SSize_t (*Write)(PerlIO *f, const void *vbuf, Size_t count);
50b80e2 PerlIO documentation. Proofing and sub-editing requested.
Nick Ing-Simmons authored
618
d4165bd @stas00 Re: [PATCH pod/perliol.pod] resend
stas00 authored
619 Basic write operation.
50b80e2 PerlIO documentation. Proofing and sub-editing requested.
Nick Ing-Simmons authored
620
d4165bd @stas00 Re: [PATCH pod/perliol.pod] resend
stas00 authored
621 Returns bytes written or -1 on an error.
622
5cb3728 Re: [PATCH @14870] long C<=item>s and other pod->man->troff problems
Robin Barker authored
623 =item Seek
624
625 IV (*Seek)(pTHX_ PerlIO *f, Off_t offset, int whence);
50b80e2 PerlIO documentation. Proofing and sub-editing requested.
Nick Ing-Simmons authored
626
1d11c88 @jhi Paragraph rewrapping.
jhi authored
627 Position the file pointer. Should normally call its own C<Flush>
628 method and then the C<Seek> method of next layer down.
50b80e2 PerlIO documentation. Proofing and sub-editing requested.
Nick Ing-Simmons authored
629
d4165bd @stas00 Re: [PATCH pod/perliol.pod] resend
stas00 authored
630 Returns 0 on success, -1 on failure.
631
5cb3728 Re: [PATCH @14870] long C<=item>s and other pod->man->troff problems
Robin Barker authored
632 =item Tell
633
634 Off_t (*Tell)(pTHX_ PerlIO *f);
50b80e2 PerlIO documentation. Proofing and sub-editing requested.
Nick Ing-Simmons authored
635
9d79914 GNU 'merge' Simon's copy of perliol.pod with version
Nick Ing-Simmons authored
636 Return the file pointer. May be based on layers cached concept of
637 position to avoid overhead.
50b80e2 PerlIO documentation. Proofing and sub-editing requested.
Nick Ing-Simmons authored
638
d4165bd @stas00 Re: [PATCH pod/perliol.pod] resend
stas00 authored
639 Returns -1 on failure to get the file pointer.
640
5cb3728 Re: [PATCH @14870] long C<=item>s and other pod->man->troff problems
Robin Barker authored
641 =item Close
642
643 IV (*Close)(pTHX_ PerlIO *f);
50b80e2 PerlIO documentation. Proofing and sub-editing requested.
Nick Ing-Simmons authored
644
9d79914 GNU 'merge' Simon's copy of perliol.pod with version
Nick Ing-Simmons authored
645 Close the stream. Should normally call C<PerlIOBase_close()> to flush
646 itself and close layers below, and then deallocate any data structures
647 (buffers, translation tables, ...) not held directly in the data
648 structure.
50b80e2 PerlIO documentation. Proofing and sub-editing requested.
Nick Ing-Simmons authored
649
d4165bd @stas00 Re: [PATCH pod/perliol.pod] resend
stas00 authored
650 Returns 0 on success, -1 on failure.
651
5cb3728 Re: [PATCH @14870] long C<=item>s and other pod->man->troff problems
Robin Barker authored
652 =item Flush
653
654 IV (*Flush)(pTHX_ PerlIO *f);
50b80e2 PerlIO documentation. Proofing and sub-editing requested.
Nick Ing-Simmons authored
655
9d79914 GNU 'merge' Simon's copy of perliol.pod with version
Nick Ing-Simmons authored
656 Should make stream's state consistent with layers below. That is, any
657 buffered write data should be written, and file position of lower layers
d1be940 a few typo fixes
Jeffrey Friedl authored
658 adjusted for data read from below but not actually consumed.
b76cc8b Tweak docs for C<open> (boy does that need wholesale revision...)
Nick Ing-Simmons authored
659 (Should perhaps C<Unread()> such data to the lower layer.)
50b80e2 PerlIO documentation. Proofing and sub-editing requested.
Nick Ing-Simmons authored
660
d4165bd @stas00 Re: [PATCH pod/perliol.pod] resend
stas00 authored
661 Returns 0 on success, -1 on failure.
662
5cb3728 Re: [PATCH @14870] long C<=item>s and other pod->man->troff problems
Robin Barker authored
663 =item Fill
664
665 IV (*Fill)(pTHX_ PerlIO *f);
d4165bd @stas00 Re: [PATCH pod/perliol.pod] resend
stas00 authored
666
667 The buffer for this layer should be filled (for read) from layer
668 below. When you "subclass" PerlIOBuf layer, you want to use its
669 I<_read> method and to supply your own fill method, which fills the
670 PerlIOBuf's buffer.
50b80e2 PerlIO documentation. Proofing and sub-editing requested.
Nick Ing-Simmons authored
671
d4165bd @stas00 Re: [PATCH pod/perliol.pod] resend
stas00 authored
672 Returns 0 on success, -1 on failure.
50b80e2 PerlIO documentation. Proofing and sub-editing requested.
Nick Ing-Simmons authored
673
5cb3728 Re: [PATCH @14870] long C<=item>s and other pod->man->troff problems
Robin Barker authored
674 =item Eof
675
676 IV (*Eof)(pTHX_ PerlIO *f);
50b80e2 PerlIO documentation. Proofing and sub-editing requested.
Nick Ing-Simmons authored
677
9d79914 GNU 'merge' Simon's copy of perliol.pod with version
Nick Ing-Simmons authored
678 Return end-of-file indicator. C<PerlIOBase_eof()> is normally sufficient.
50b80e2 PerlIO documentation. Proofing and sub-editing requested.
Nick Ing-Simmons authored
679
d4165bd @stas00 Re: [PATCH pod/perliol.pod] resend
stas00 authored
680 Returns 0 on end-of-file, 1 if not end-of-file, -1 on error.
681
5cb3728 Re: [PATCH @14870] long C<=item>s and other pod->man->troff problems
Robin Barker authored
682 =item Error
683
684 IV (*Error)(pTHX_ PerlIO *f);
50b80e2 PerlIO documentation. Proofing and sub-editing requested.
Nick Ing-Simmons authored
685
9d79914 GNU 'merge' Simon's copy of perliol.pod with version
Nick Ing-Simmons authored
686 Return error indicator. C<PerlIOBase_error()> is normally sufficient.
50b80e2 PerlIO documentation. Proofing and sub-editing requested.
Nick Ing-Simmons authored
687
d4165bd @stas00 Re: [PATCH pod/perliol.pod] resend
stas00 authored
688 Returns 1 if there is an error (usually when C<PERLIO_F_ERROR> is set,
689 0 otherwise.
690
5cb3728 Re: [PATCH @14870] long C<=item>s and other pod->man->troff problems
Robin Barker authored
691 =item Clearerr
692
693 void (*Clearerr)(pTHX_ PerlIO *f);
50b80e2 PerlIO documentation. Proofing and sub-editing requested.
Nick Ing-Simmons authored
694
9d79914 GNU 'merge' Simon's copy of perliol.pod with version
Nick Ing-Simmons authored
695 Clear end-of-file and error indicators. Should call C<PerlIOBase_clearerr()>
696 to set the C<PERLIO_F_XXXXX> flags, which may suffice.
50b80e2 PerlIO documentation. Proofing and sub-editing requested.
Nick Ing-Simmons authored
697
5cb3728 Re: [PATCH @14870] long C<=item>s and other pod->man->troff problems
Robin Barker authored
698 =item Setlinebuf
699
700 void (*Setlinebuf)(pTHX_ PerlIO *f);
50b80e2 PerlIO documentation. Proofing and sub-editing requested.
Nick Ing-Simmons authored
701
b76cc8b Tweak docs for C<open> (boy does that need wholesale revision...)
Nick Ing-Simmons authored
702 Mark the stream as line buffered. C<PerlIOBase_setlinebuf()> sets the
703 PERLIO_F_LINEBUF flag and is normally sufficient.
50b80e2 PerlIO documentation. Proofing and sub-editing requested.
Nick Ing-Simmons authored
704
5cb3728 Re: [PATCH @14870] long C<=item>s and other pod->man->troff problems
Robin Barker authored
705 =item Get_base
706
707 STDCHAR * (*Get_base)(pTHX_ PerlIO *f);
50b80e2 PerlIO documentation. Proofing and sub-editing requested.
Nick Ing-Simmons authored
708
709 Allocate (if not already done so) the read buffer for this layer and
d4165bd @stas00 Re: [PATCH pod/perliol.pod] resend
stas00 authored
710 return pointer to it. Return NULL on failure.
50b80e2 PerlIO documentation. Proofing and sub-editing requested.
Nick Ing-Simmons authored
711
5cb3728 Re: [PATCH @14870] long C<=item>s and other pod->man->troff problems
Robin Barker authored
712 =item Get_bufsiz
713
714 Size_t (*Get_bufsiz)(pTHX_ PerlIO *f);
50b80e2 PerlIO documentation. Proofing and sub-editing requested.
Nick Ing-Simmons authored
715
9d79914 GNU 'merge' Simon's copy of perliol.pod with version
Nick Ing-Simmons authored
716 Return the number of bytes that last C<Fill()> put in the buffer.
50b80e2 PerlIO documentation. Proofing and sub-editing requested.
Nick Ing-Simmons authored
717
5cb3728 Re: [PATCH @14870] long C<=item>s and other pod->man->troff problems
Robin Barker authored
718 =item Get_ptr
719
720 STDCHAR * (*Get_ptr)(pTHX_ PerlIO *f);
50b80e2 PerlIO documentation. Proofing and sub-editing requested.
Nick Ing-Simmons authored
721
3039a93 PerlIO doc tweaks from Craig A. Berry <craig.berry@psinetcs.com>
Nick Ing-Simmons authored
722 Return the current read pointer relative to this layer's buffer.
50b80e2 PerlIO documentation. Proofing and sub-editing requested.
Nick Ing-Simmons authored
723
5cb3728 Re: [PATCH @14870] long C<=item>s and other pod->man->troff problems
Robin Barker authored
724 =item Get_cnt
725
726 SSize_t (*Get_cnt)(pTHX_ PerlIO *f);
50b80e2 PerlIO documentation. Proofing and sub-editing requested.
Nick Ing-Simmons authored
727
728 Return the number of bytes left to be read in the current buffer.
729
5cb3728 Re: [PATCH @14870] long C<=item>s and other pod->man->troff problems
Robin Barker authored
730 =item Set_ptrcnt
731
732 void (*Set_ptrcnt)(pTHX_ PerlIO *f,
733 STDCHAR *ptr, SSize_t cnt);
50b80e2 PerlIO documentation. Proofing and sub-editing requested.
Nick Ing-Simmons authored
734
735 Adjust the read pointer and count of bytes to match C<ptr> and/or C<cnt>.
736 The application (or layer above) must ensure they are consistent.
737 (Checking is allowed by the paranoid.)
738
739 =back
740
b0a2be7 @jhi perliol tweaks.
jhi authored
741 =head2 Utilities
742
743 To ask for the next layer down use PerlIONext(PerlIO *f).
744
745 To check that a PerlIO* is valid use PerlIOValid(PerlIO *f). (All
746 this does is really just to check that the pointer is non-NULL and
747 that the pointer behind that is non-NULL.)
748
749 PerlIOBase(PerlIO *f) returns the "Base" pointer, or in other words,
750 the C<PerlIOl*> pointer.
751
752 PerlIOSelf(PerlIO* f, type) return the PerlIOBase cast to a type.
753
754 Perl_PerlIO_or_Base(PerlIO* f, callback, base, failure, args) either
755 calls the I<callback> from the functions of the layer I<f> (just by
756 the name of the IO function, like "Read") with the I<args>, or if
757 there is no such callback, calls the I<base> version of the callback
758 with the same args, or if the f is invalid, set errno to EBADF and
759 return I<failure>.
760
761 Perl_PerlIO_or_fail(PerlIO* f, callback, failure, args) either calls
762 the I<callback> of the functions of the layer I<f> with the I<args>,
763 or if there is no such callback, set errno to EINVAL. Or if the f is
764 invalid, set errno to EBADF and return I<failure>.
765
766 Perl_PerlIO_or_Base_void(PerlIO* f, callback, base, args) either calls
767 the I<callback> of the functions of the layer I<f> with the I<args>,
768 or if there is no such callback, calls the I<base> version of the
769 callback with the same args, or if the f is invalid, set errno to
770 EBADF.
771
772 Perl_PerlIO_or_fail_void(PerlIO* f, callback, args) either calls the
773 I<callback> of the functions of the layer I<f> with the I<args>, or if
774 there is no such callback, set errno to EINVAL. Or if the f is
775 invalid, set errno to EBADF.
776
210e727 @jhi Try to plug more potential PerlIO NULL method
jhi authored
777 =head2 Implementing PerlIO Layers
778
2535a4f @jhi A suggested perlio doc addition from Stas.
jhi authored
779 If you find the implementation document unclear or not sufficient,
b0a2be7 @jhi perliol tweaks.
jhi authored
780 look at the existing PerlIO layer implementations, which include:
2535a4f @jhi A suggested perlio doc addition from Stas.
jhi authored
781
782 =over
783
784 =item * C implementations
785
eae154c @jhi One obvious place to look for PerlIO implementations.
jhi authored
786 The F<perlio.c> and F<perliol.h> in the Perl core implement the
787 "unix", "perlio", "stdio", "crlf", "utf8", "byte", "raw", "pending"
788 layers, and also the "mmap" and "win32" layers if applicable.
789 (The "win32" is currently unfinished and unused, to see what is used
790 instead in Win32, see L<PerlIO/"Querying the layers of filehandles"> .)
791
2535a4f @jhi A suggested perlio doc addition from Stas.
jhi authored
792 PerlIO::encoding, PerlIO::scalar, PerlIO::via in the Perl core.
793
794 PerlIO::gzip and APR::PerlIO (mod_perl 2.0) on CPAN.
795
796 =item * Perl implementations
797
798 PerlIO::via::QuotedPrint in the Perl core and PerlIO::via::* on CPAN.
799
800 =back
801
210e727 @jhi Try to plug more potential PerlIO NULL method
jhi authored
802 If you are creating a PerlIO layer, you may want to be lazy, in other
803 words, implement only the methods that interest you. The other methods
804 you can either replace with the "blank" methods
805
806 PerlIOBase_noop_ok
807 PerlIOBase_noop_fail
808
809 (which do nothing, and return zero and -1, respectively) or for
810 certain methods you may assume a default behaviour by using a NULL
61bdada @jhi Fixup the method behaviour table.
jhi authored
811 method. The Open method looks for help in the 'parent' layer.
812 The following table summarizes the behaviour:
210e727 @jhi Try to plug more potential PerlIO NULL method
jhi authored
813
814 method behaviour with NULL
815
816 Clearerr PerlIOBase_clearerr
817 Close PerlIOBase_close
61bdada @jhi Fixup the method behaviour table.
jhi authored
818 Dup PerlIOBase_dup
210e727 @jhi Try to plug more potential PerlIO NULL method
jhi authored
819 Eof PerlIOBase_eof
820 Error PerlIOBase_error
821 Fileno PerlIOBase_fileno
822 Fill FAILURE
823 Flush SUCCESS
61bdada @jhi Fixup the method behaviour table.
jhi authored
824 Getarg SUCCESS
210e727 @jhi Try to plug more potential PerlIO NULL method
jhi authored
825 Get_base FAILURE
826 Get_bufsiz FAILURE
827 Get_cnt FAILURE
828 Get_ptr FAILURE
61bdada @jhi Fixup the method behaviour table.
jhi authored
829 Open INHERITED
830 Popped SUCCESS
831 Pushed SUCCESS
210e727 @jhi Try to plug more potential PerlIO NULL method
jhi authored
832 Read PerlIOBase_read
833 Seek FAILURE
834 Set_cnt FAILURE
835 Set_ptrcnt FAILURE
836 Setlinebuf PerlIOBase_setlinebuf
837 Tell FAILURE
838 Unread PerlIOBase_unread
839 Write FAILURE
50b80e2 PerlIO documentation. Proofing and sub-editing requested.
Nick Ing-Simmons authored
840
e102041 PATCH: minor typo cleanup of pod/ directory
Tom Christiansen authored
841 FAILURE Set errno (to EINVAL in Unixish, to LIB$_INVARG in VMS) and
61bdada @jhi Fixup the method behaviour table.
jhi authored
842 return -1 (for numeric return values) or NULL (for pointers)
843 INHERITED Inherited from the layer below
844 SUCCESS Return 0 (for numeric return values) or a pointer
845
50b80e2 PerlIO documentation. Proofing and sub-editing requested.
Nick Ing-Simmons authored
846 =head2 Core Layers
847
848 The file C<perlio.c> provides the following layers:
849
850 =over 4
851
852 =item "unix"
853
9d79914 GNU 'merge' Simon's copy of perliol.pod with version
Nick Ing-Simmons authored
854 A basic non-buffered layer which calls Unix/POSIX C<read()>, C<write()>,
855 C<lseek()>, C<close()>. No buffering. Even on platforms that distinguish
856 between O_TEXT and O_BINARY this layer is always O_BINARY.
50b80e2 PerlIO documentation. Proofing and sub-editing requested.
Nick Ing-Simmons authored
857
858 =item "perlio"
859
9d79914 GNU 'merge' Simon's copy of perliol.pod with version
Nick Ing-Simmons authored
860 A very complete generic buffering layer which provides the whole of
861 PerlIO API. It is also intended to be used as a "base class" for other
1d11c88 @jhi Paragraph rewrapping.
jhi authored
862 layers. (For example its C<Read()> method is implemented in terms of
863 the C<Get_cnt()>/C<Get_ptr()>/C<Set_ptrcnt()> methods).
50b80e2 PerlIO documentation. Proofing and sub-editing requested.
Nick Ing-Simmons authored
864
9d79914 GNU 'merge' Simon's copy of perliol.pod with version
Nick Ing-Simmons authored
865 "perlio" over "unix" provides a complete replacement for stdio as seen
866 via PerlIO API. This is the default for USE_PERLIO when system's stdio
1d11c88 @jhi Paragraph rewrapping.
jhi authored
867 does not permit perl's "fast gets" access, and which do not
868 distinguish between C<O_TEXT> and C<O_BINARY>.
50b80e2 PerlIO documentation. Proofing and sub-editing requested.
Nick Ing-Simmons authored
869
870 =item "stdio"
871
9d79914 GNU 'merge' Simon's copy of perliol.pod with version
Nick Ing-Simmons authored
872 A layer which provides the PerlIO API via the layer scheme, but
873 implements it by calling system's stdio. This is (currently) the default
874 if system's stdio provides sufficient access to allow perl's "fast gets"
875 access and which do not distinguish between C<O_TEXT> and C<O_BINARY>.
50b80e2 PerlIO documentation. Proofing and sub-editing requested.
Nick Ing-Simmons authored
876
877 =item "crlf"
878
9d79914 GNU 'merge' Simon's copy of perliol.pod with version
Nick Ing-Simmons authored
879 A layer derived using "perlio" as a base class. It provides Win32-like
880 "\n" to CR,LF translation. Can either be applied above "perlio" or serve
881 as the buffer layer itself. "crlf" over "unix" is the default if system
882 distinguishes between C<O_TEXT> and C<O_BINARY> opens. (At some point
883 "unix" will be replaced by a "native" Win32 IO layer on that platform,
884 as Win32's read/write layer has various drawbacks.) The "crlf" layer is
885 a reasonable model for a layer which transforms data in some way.
50b80e2 PerlIO documentation. Proofing and sub-editing requested.
Nick Ing-Simmons authored
886
887 =item "mmap"
888
9d79914 GNU 'merge' Simon's copy of perliol.pod with version
Nick Ing-Simmons authored
889 If Configure detects C<mmap()> functions this layer is provided (with
890 "perlio" as a "base") which does "read" operations by mmap()ing the
891 file. Performance improvement is marginal on modern systems, so it is
892 mainly there as a proof of concept. It is likely to be unbundled from
893 the core at some point. The "mmap" layer is a reasonable model for a
894 minimalist "derived" layer.
50b80e2 PerlIO documentation. Proofing and sub-editing requested.
Nick Ing-Simmons authored
895
896 =item "pending"
897
9d79914 GNU 'merge' Simon's copy of perliol.pod with version
Nick Ing-Simmons authored
898 An "internal" derivative of "perlio" which can be used to provide
1d11c88 @jhi Paragraph rewrapping.
jhi authored
899 Unread() function for layers which have no buffer or cannot be
900 bothered. (Basically this layer's C<Fill()> pops itself off the stack
901 and so resumes reading from layer below.)
50b80e2 PerlIO documentation. Proofing and sub-editing requested.
Nick Ing-Simmons authored
902
903 =item "raw"
904
9d79914 GNU 'merge' Simon's copy of perliol.pod with version
Nick Ing-Simmons authored
905 A dummy layer which never exists on the layer stack. Instead when
86e05cf "Clean" implementation of binmode(FH)/":raw" identity.
Nick Ing-Simmons authored
906 "pushed" it actually pops the stack removing itself, it then calls
907 Binmode function table entry on all the layers in the stack - normally
908 this (via PerlIOBase_binmode) removes any layers which do not have
909 C<PERLIO_K_RAW> bit set. Layers can modify that behaviour by defining
910 their own Binmode entry.
50b80e2 PerlIO documentation. Proofing and sub-editing requested.
Nick Ing-Simmons authored
911
912 =item "utf8"
913
9d79914 GNU 'merge' Simon's copy of perliol.pod with version
Nick Ing-Simmons authored
914 Another dummy layer. When pushed it pops itself and sets the
1d11c88 @jhi Paragraph rewrapping.
jhi authored
915 C<PERLIO_F_UTF8> flag on the layer which was (and now is once more)
916 the top of the stack.
50b80e2 PerlIO documentation. Proofing and sub-editing requested.
Nick Ing-Simmons authored
917
918 =back
919
9d79914 GNU 'merge' Simon's copy of perliol.pod with version
Nick Ing-Simmons authored
920 In addition F<perlio.c> also provides a number of C<PerlIOBase_xxxx()>
921 functions which are intended to be used in the table slots of classes
922 which do not need to do anything special for a particular method.
50b80e2 PerlIO documentation. Proofing and sub-editing requested.
Nick Ing-Simmons authored
923
924 =head2 Extension Layers
925
37b6382 @alanhaggai Corrected: 'can made' => 'can be made'
alanhaggai authored
926 Layers can be made available by extension modules. When an unknown layer
1d11c88 @jhi Paragraph rewrapping.
jhi authored
927 is encountered the PerlIO code will perform the equivalent of :
b76cc8b Tweak docs for C<open> (boy does that need wholesale revision...)
Nick Ing-Simmons authored
928
929 use PerlIO 'layer';
930
1d11c88 @jhi Paragraph rewrapping.
jhi authored
931 Where I<layer> is the unknown layer. F<PerlIO.pm> will then attempt to:
b76cc8b Tweak docs for C<open> (boy does that need wholesale revision...)
Nick Ing-Simmons authored
932
933 require PerlIO::layer;
934
1d11c88 @jhi Paragraph rewrapping.
jhi authored
935 If after that process the layer is still not defined then the C<open>
936 will fail.
b76cc8b Tweak docs for C<open> (boy does that need wholesale revision...)
Nick Ing-Simmons authored
937
938 The following extension layers are bundled with perl:
50b80e2 PerlIO documentation. Proofing and sub-editing requested.
Nick Ing-Simmons authored
939
940 =over 4
941
b76cc8b Tweak docs for C<open> (boy does that need wholesale revision...)
Nick Ing-Simmons authored
942 =item ":encoding"
50b80e2 PerlIO documentation. Proofing and sub-editing requested.
Nick Ing-Simmons authored
943
944 use Encoding;
945
1d11c88 @jhi Paragraph rewrapping.
jhi authored
946 makes this layer available, although F<PerlIO.pm> "knows" where to
947 find it. It is an example of a layer which takes an argument as it is
948 called thus:
50b80e2 PerlIO documentation. Proofing and sub-editing requested.
Nick Ing-Simmons authored
949
b31b80f @lizmat [PATCH] Removing example layers from MIME::QuotedPrint
lizmat authored
950 open( $fh, "<:encoding(iso-8859-7)", $pathname );
50b80e2 PerlIO documentation. Proofing and sub-editing requested.
Nick Ing-Simmons authored
951
385e1f9 @lizmat [DOC PATCH] some doc nits after 17463
lizmat authored
952 =item ":scalar"
b76cc8b Tweak docs for C<open> (boy does that need wholesale revision...)
Nick Ing-Simmons authored
953
b31b80f @lizmat [PATCH] Removing example layers from MIME::QuotedPrint
lizmat authored
954 Provides support for reading data from and writing data to a scalar.
b76cc8b Tweak docs for C<open> (boy does that need wholesale revision...)
Nick Ing-Simmons authored
955
385e1f9 @lizmat [DOC PATCH] some doc nits after 17463
lizmat authored
956 open( $fh, "+<:scalar", \$scalar );
50b80e2 PerlIO documentation. Proofing and sub-editing requested.
Nick Ing-Simmons authored
957
1d11c88 @jhi Paragraph rewrapping.
jhi authored
958 When a handle is so opened, then reads get bytes from the string value
959 of I<$scalar>, and writes change the value. In both cases the position
960 in I<$scalar> starts as zero but can be altered via C<seek>, and
961 determined via C<tell>.
b76cc8b Tweak docs for C<open> (boy does that need wholesale revision...)
Nick Ing-Simmons authored
962
385e1f9 @lizmat [DOC PATCH] some doc nits after 17463
lizmat authored
963 Please note that this layer is implied when calling open() thus:
964
965 open( $fh, "+<", \$scalar );
966
967 =item ":via"
b76cc8b Tweak docs for C<open> (boy does that need wholesale revision...)
Nick Ing-Simmons authored
968
4f7853f @gisle PerlIO::Via reference
gisle authored
969 Provided to allow layers to be implemented as Perl code. For instance:
970
e934609 @jhi Change PerlIO::Scalar and Via to scalar and via.
jhi authored
971 use PerlIO::via::StripHTML;
385e1f9 @lizmat [DOC PATCH] some doc nits after 17463
lizmat authored
972 open( my $fh, "<:via(StripHTML)", "index.html" );
4f7853f @gisle PerlIO::Via reference
gisle authored
973
e934609 @jhi Change PerlIO::Scalar and Via to scalar and via.
jhi authored
974 See L<PerlIO::via> for details.
b76cc8b Tweak docs for C<open> (boy does that need wholesale revision...)
Nick Ing-Simmons authored
975
976 =back
50b80e2 PerlIO documentation. Proofing and sub-editing requested.
Nick Ing-Simmons authored
977
d4165bd @stas00 Re: [PATCH pod/perliol.pod] resend
stas00 authored
978 =head1 TODO
979
980 Things that need to be done to improve this document.
981
982 =over
983
984 =item *
985
986 Explain how to make a valid fh without going through open()(i.e. apply
987 a layer). For example if the file is not opened through perl, but we
988 want to get back a fh, like it was opened by Perl.
989
990 How PerlIO_apply_layera fits in, where its docs, was it made public?
991
992 Currently the example could be something like this:
993
994 PerlIO *foo_to_PerlIO(pTHX_ char *mode, ...)
995 {
996 char *mode; /* "w", "r", etc */
997 const char *layers = ":APR"; /* the layer name */
998 PerlIO *f = PerlIO_allocate(aTHX);
999 if (!f) {
1000 return NULL;
1001 }
1002
1003 PerlIO_apply_layers(aTHX_ f, mode, layers);
1004
1005 if (f) {
1006 PerlIOAPR *st = PerlIOSelf(f, PerlIOAPR);
1007 /* fill in the st struct, as in _open() */
1008 st->file = file;
1009 PerlIOBase(f)->flags |= PERLIO_F_OPEN;
1010
1011 return f;
1012 }
1013 return NULL;
1014 }
1015
1016 =item *
1017
1018 fix/add the documentation in places marked as XXX.
1019
1020 =item *
1021
1022 The handling of errors by the layer is not specified. e.g. when $!
1023 should be set explicitly, when the error handling should be just
1024 delegated to the top layer.
1025
1026 Probably give some hints on using SETERRNO() or pointers to where they
1027 can be found.
1028
1029 =item *
1030
1031 I think it would help to give some concrete examples to make it easier
1032 to understand the API. Of course I agree that the API has to be
1033 concise, but since there is no second document that is more of a
1034 guide, I think that it'd make it easier to start with the doc which is
1035 an API, but has examples in it in places where things are unclear, to
1036 a person who is not a PerlIO guru (yet).
1037
1038 =back
1039
50b80e2 PerlIO documentation. Proofing and sub-editing requested.
Nick Ing-Simmons authored
1040 =cut
Something went wrong with that request. Please try again.