summary refs log tree commit diff
path: root/stdio/internals.c
blob: c238bf39f9cf18e5a79bcb4f0f0679a57f8329bc (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
/* Copyright (C) 1991, 1992, 1993, 1994, 1995 Free Software Foundation, Inc.
This file is part of the GNU C Library.

The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Library General Public License as
published by the Free Software Foundation; either version 2 of the
License, or (at your option) any later version.

The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
Library General Public License for more details.

You should have received a copy of the GNU Library General Public
License along with the GNU C Library; see the file COPYING.LIB.  If
not, write to the Free Software Foundation, Inc., 675 Mass Ave,
Cambridge, MA 02139, USA.  */

#include <ansidecl.h>
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>


/* Make sure that FP has its functions set.  */
void
DEFUN(__stdio_check_funcs, (fp), register FILE *fp)
{
  if (!fp->__seen)
    {
      /* Initialize the stream's info, including buffering info.
	 This may give a buffer, change I/O functions, etc.
	 If no buffer is set (and the stream is not made explicitly
	 unbuffered), we allocate a buffer below, using the bufsize
	 set by this function.  */
      extern void EXFUN(__stdio_init_stream, (FILE *));
      fp->__room_funcs = __default_room_functions;
      fp->__io_funcs = __default_io_functions;
      __stdio_init_stream (fp);
      fp->__seen = 1;
    }
}


/* Minimum size of a buffer we will allocate by default.
   If this much memory is not available,
   the stream in question will be made unbuffered instead.  */
#define	MIN_BUFSIZE	128

/* Figure out what kind of buffering (none, line, or full)
   and what buffer size to give FP.  */
static void
DEFUN(init_stream, (fp), register FILE *fp)
{
  __stdio_check_funcs (fp);

  if (fp->__buffer == NULL && !fp->__userbuf)
    {
      int save;

      if (fp->__bufsize == 0)
	fp->__bufsize = BUFSIZ;

      /* Try to get however many bytes of buffering __stdio_pickbuf
	 specified, but if that much memory isn't available,
	 try half as much each time until it succeeds or the buffer
	 size becomes too small to be useful.  */
      save = errno;
      while (fp->__bufsize >= MIN_BUFSIZE)
	{
	  fp->__buffer = (char *) malloc(fp->__bufsize);
	  if (fp->__buffer == NULL)
	    fp->__bufsize /= 2;
	  else
	    break;
	}
      errno = save;

      if (fp->__buffer == NULL)
	{
	  /* We can't get space for the buffer, so make it unbuffered.  */
	  fp->__userbuf = 1;
	  fp->__bufsize = 0;
	}
    }

  if (fp->__bufp == NULL)
    {
      /* Set the buffer pointer to the beginning of the buffer.  */
      fp->__bufp = fp->__buffer;
      fp->__put_limit = fp->__get_limit = fp->__buffer;
    }
}


/* Determine the current file position of STREAM if it is unknown.  */
int
DEFUN(__stdio_check_offset, (stream), FILE *stream)
{
  init_stream (stream);

  if (stream->__offset == (fpos_t) -1)
    {
      /* This stream's offset is unknown or unknowable.  */
      if (stream->__io_funcs.__seek == NULL)
	{
	  /* Unknowable.  */
	  errno = ESPIPE;
	  return EOF;
	}
      else
	{
	  /* Unknown.  Find it out.  */
	  fpos_t pos = (fpos_t) 0;
	  if ((*stream->__io_funcs.__seek)(stream->__cookie,
					   &pos, SEEK_CUR) < 0)
	    {
	      if (errno == ESPIPE)
		/* Object is incapable of seeking.  */
		stream->__io_funcs.__seek = NULL;
	      return EOF;
	    }
	  stream->__offset = pos;
	}
    }

  if (stream->__target == (fpos_t) -1)
    /* This stream was opened on an existing object with
       an unknown file position.  The position is now known.
       Make this the target position.  */
    stream->__target = stream->__offset;

  return 0;
}


/* Move FP's file position to its target file position,
   seeking as necessary and updating its `offset' field.
   Sets ferror(FP) (and possibly errno) for errors.  */
static void
DEFUN(seek_to_target, (fp), FILE *fp)
{
  int save = errno;
  if (__stdio_check_offset (fp) == EOF)
    {
      if (errno == ESPIPE)
	errno = save;
      else
	fp->__error = 1;
    }
  else if (fp->__target != fp->__offset)
    {
      /* We are not at the target file position.
	 Seek to that position.  */
      if (fp->__io_funcs.__seek == NULL)
	{
	  /* We can't seek!  */
	  errno = ESPIPE;
	  fp->__error = 1;
	}
      else
	{
	  fpos_t pos = fp->__target;
	  if ((*fp->__io_funcs.__seek)(fp->__cookie, &pos, SEEK_SET) < 0)
	    /* Seek failed!  */
	    fp->__error = 1;
	  else
	    {
	      fp->__offset = pos;
	      if (pos != fp->__target)
		/* Seek didn't go to the right place!  */
		fp->__error = 1;
	    }
	}
    }
}

/* Flush the buffer for FP.
   If C is not EOF, it is also to be written.
   If the stream is line buffered and C is a newline, it is written
   to the output, otherwise it is put in the buffer after it has been
   flushed to avoid a system call for a single character.
   This is the default `output room' function.  */
static void
DEFUN(flushbuf, (fp, c),
      register FILE *fp AND int c)
{
  int flush_only = c == EOF;
  size_t buffer_written;
  size_t to_write;

  /* Set if target and get_limit have already been twiddled appropriately.  */
  int twiddled = 0;

  if (fp->__put_limit == fp->__buffer)
    {
      /* The stream needs to be primed for writing.  */

      size_t buffer_offset = 0;

      /* If the user has read some of the buffer, the target position
	 is incremented for each character he has read.  */
      fp->__target += fp->__bufp - fp->__buffer;

      if (fp->__mode.__read && fp->__room_funcs.__input != NULL &&
	  !fp->__mode.__append)
	{
	  int save = errno;
	  CONST int aligned = (fp->__buffer == NULL ||
			       __stdio_check_offset(fp) == EOF ||
			       fp->__target % fp->__bufsize == 0);
	  errno = save;

	  if (!aligned)
	    {
	      /* Move to a block (buffer size) boundary and read in a block.
		 Then the output will be written as a whole block, too.  */
	      CONST size_t o = fp->__target % fp->__bufsize;
	      fp->__target -= o;
	      if ((*fp->__room_funcs.__input)(fp) == EOF && ferror(fp))
		return;
	      else
		__clearerr(fp);

	      if (fp->__get_limit - fp->__buffer < o)
		/* Oops.  We didn't read enough (probably because we got EOF).
		   Forget we even mentioned it.  */
		fp->__target += o;
	      else
		/* Start bufp as far into the buffer as we were into
		   this block before we read it.  */
		buffer_offset = o;
	    }

	  /* The target position is now set to where the beginning of the
	     buffer maps to; and the get_limit was set by the input-room
	     function.  */
	  twiddled = 1;
	}

      if (fp->__buffer != NULL)
	{
	  /* Set up to write output into the buffer.  */
	  fp->__put_limit = fp->__buffer + fp->__bufsize;
	  fp->__bufp = fp->__buffer + buffer_offset;

	  if (!flush_only)
	    {
	      /* Put C in the buffer to be written out.
		 We only need to actually write it out now if
		 it is a newline on a line-buffered stream.  */
	      *fp->__bufp++ = (unsigned char) c;
	      if (!fp->__linebuf || (unsigned char) c != '\n')
		{
		  /* There is no need to flush C from the buffer right now.
		     Record that nothing was written from the buffer,
		     and go do clean-up at end.  */
		  buffer_written = 0;
		  goto end;
		}
	      else
		/* We put C in the buffer, so don't write it again later.  */
		flush_only = 1;
	    }
	}

      if (fp->__bufp - fp->__buffer <= buffer_offset && flush_only)
	{
	  /* There is nothing new in the buffer, only data that
	     was read back aligned from the file.  */
	  buffer_written = 0;
	  goto end;
	}
    }

  /* If there is read data in the buffer past what was written,
     write all of that as well.  Otherwise, just write what has been
     written into the buffer.  */
  buffer_written = fp->__bufp - fp->__buffer;
  to_write = (buffer_written == 0 ? 0 :
	      fp->__get_limit > fp->__bufp ?
	      fp->__get_limit - fp->__buffer :
	      buffer_written);

  if (fp->__io_funcs.__write == NULL || (to_write == 0 && flush_only))
    {
      /* There is no writing function or we're coming from an fflush
	 call with nothing in the buffer, so just say the buffer's
	 been flushed, increment the file offset, and return.  */
      fp->__bufp = fp->__buffer;
      fp->__offset += to_write;
      goto end;
    }

  if (to_write > 0)
    {
      int wrote;

      /* Go to the target file position.  Don't bother if appending;
         the write will just ignore the file position anyway.  */
      if (!fp->__mode.__append)
	seek_to_target (fp);

      if (!ferror(fp))
	{
	  /* Write out the buffered data.  */
	  wrote = (*fp->__io_funcs.__write)(fp->__cookie, fp->__buffer,
					    to_write);
	  if (wrote > 0)
	    {
	      if (fp->__mode.__append)
		/* The write has written the data to the end of the file
		   and updated the file position to after the data.  Don't
		   bother to find the current position; we can get it
		   later if we need it.  */
		fp->__offset = fp->__target = -1;
	      else
		/* Record that we've moved forward in the file.  */
		fp->__offset += wrote;
	    }
	  if (wrote < (int) to_write)
	    /* The writing function should always write
	       the whole buffer unless there is an error.  */
	    fp->__error = 1;
	}
    }

  /* Reset the buffer pointer to the beginning of the buffer.  */
  fp->__bufp = fp->__buffer;

  /* If we're not just flushing, write the last character, C.  */
  if (!flush_only && !ferror(fp))
    {
      if (fp->__buffer == NULL || (fp->__linebuf && (unsigned char) c == '\n'))
	{
	  /* Either we're unbuffered, or we're line-buffered and
	     C is a newline, so really write it out immediately.  */
	  char cc = (unsigned char) c;
	  if ((*fp->__io_funcs.__write)(fp->__cookie, &cc, 1) < 1)
	    fp->__error = 1;
	  else
	    {
	      /* Record that we've moved forward in the file.  */
	      ++fp->__offset;
	      ++fp->__target;
	    }
	}
      else
	/* Just put C in the buffer.  */
	*fp->__bufp++ = (unsigned char) c;
    }

 end:

  if (!twiddled)
    {
      /* The new target position moves up as
	 much as the user wrote into the buffer.  */
      fp->__target += buffer_written;

      /* Set the reading limit to the beginning of the buffer,
	 so the next `getc' will call __fillbf.  */
      fp->__get_limit = fp->__buffer;
    }

  if (feof(fp) || ferror(fp))
    fp->__bufp = fp->__put_limit;
}


/* Fill the buffer for FP and return the first character read (or EOF).
   This is the default `input_room' function.  */
static int
DEFUN(fillbuf, (fp), register FILE *fp)
{
  /* How far into the buffer we read we want to start bufp.  */
  size_t buffer_offset = 0;
  register char *buffer;
  register size_t to_read, nread = 0;
  /* This must be unsigned to avoid sign extension in return.  */
  unsigned char c;

  if (fp->__io_funcs.__read == NULL)
    {
      /* There is no read function, so always return EOF.  */
      fp->__eof = 1;
      goto end;
    }

  if (fp->__buffer == NULL)
    {
      /* We're unbuffered, so we want to read only one character.  */
      buffer = (char *) &c;
      to_read = 1;
    }
  else
    {
      /* We're buffered, so try to fill the buffer.  */
      buffer = fp->__buffer;
      to_read = fp->__bufsize;
    }

  /* We're reading, so we're not at the end-of-file.  */
  fp->__eof = 0;

  /* Go to the target file position.  */
  {
    int save = errno;
    if (__stdio_check_offset (fp) == 0 && fp->__target != fp->__offset)
      {
	/* Move to a block (buffer size) boundary.  */
	if (fp->__bufsize != 0)
	  {
	    buffer_offset = fp->__target % fp->__bufsize;
	    fp->__target -= buffer_offset;
	  }
	seek_to_target (fp);
      }
    errno = save;
  }

  while (!ferror(fp) && !feof(fp) && nread <= buffer_offset)
    {
      /* Try to fill the buffer.  */
      int count = (*fp->__io_funcs.__read)(fp->__cookie, buffer, to_read);
      if (count == 0)
	fp->__eof = 1;
      else if (count < 0)
	fp->__error = 1;
      else
	{
	  buffer += count;
	  nread += count;
	  to_read -= count;
	  /* Record that we've moved forward in the file.  */
	  fp->__offset += count;
	}
    }

  if (fp->__buffer == NULL)
    /* There is no buffer, so return the character we read
       without all the buffer pointer diddling.  */
    return (feof(fp) || ferror(fp)) ? EOF : c;

  /* Reset the buffer pointer to the beginning of the buffer
     (plus whatever offset we may have set above).  */
  fp->__bufp = fp->__buffer + buffer_offset;

 end:;

  if (feof(fp) || ferror(fp))
    {
      /* Set both end pointers to the beginning of the buffer so
	 the next i/o call will force a call to __fillbf/__flshfp.  */
      fp->__put_limit = fp->__get_limit = fp->__buffer;
      return EOF;
    }

  /* Set the end pointer to one past the last character we read.  */
  fp->__get_limit = fp->__buffer + nread;

  /* Make it so the next `putc' will call __flshfp.  */
  fp->__put_limit = fp->__buffer;

  /* Return the first character in the buffer.  */
  return *((unsigned char *) (fp->__bufp++));
}


/* Default I/O and room functions.  */

extern __io_read_fn __stdio_read;
extern __io_write_fn __stdio_write;
extern __io_seek_fn __stdio_seek;
extern __io_close_fn __stdio_close;
extern __io_fileno_fn __stdio_fileno;
CONST __io_functions __default_io_functions =
  {
    __stdio_read, __stdio_write, __stdio_seek, __stdio_close, __stdio_fileno
  };

CONST __room_functions __default_room_functions =
  {
    fillbuf, flushbuf
  };


/* Flush the buffer for FP and also write C if FLUSH_ONLY is nonzero.
   This is the function used by putc and fflush.  */
int
DEFUN(__flshfp, (fp, c),
      register FILE *fp AND int c)
{
  int flush_only = c == EOF;

  if (!__validfp(fp) || !fp->__mode.__write)
    {
      errno = EINVAL;
      return EOF;
    }

  if (ferror(fp))
    return EOF;

  if (fp->__pushed_back)
    {
      /* Discard the char pushed back by ungetc.  */
      fp->__bufp = fp->__pushback_bufp;
      fp->__pushed_back = 0;
    }

  /* Make sure the stream is initialized (has functions and buffering).  */
  init_stream(fp);

  /* Do this early, so a `putc' on such a stream will never return success.  */
  if (fp->__room_funcs.__output == NULL)
    {
      /* A NULL `output room' function means
	 to always return an output error.  */
      fp->__error = 1;
      return EOF;
    }

  if (!flush_only &&
      /* Will C fit into the buffer?
	 See below about linebuf_active.  */
      fp->__bufp < (fp->__linebuf_active ? fp->__buffer + fp->__bufsize :
		    fp->__put_limit))
    {
      /* The character will fit in the buffer, so put it there.  */
      *fp->__bufp++ = (unsigned char) c;
      if (fp->__linebuf && (unsigned char) c == '\n')
	flush_only = 1;
      else
	return (unsigned char) c;
    }

  if (fp->__linebuf_active)
    /* This is an active line-buffered stream, so its put-limit is set
       to the beginning of the buffer in order to force a __flshfp call
       on each putc (see below).  We undo this hack here (by setting
       the limit to the end of the buffer) to simplify the interface
       with the output-room function.  */
    fp->__put_limit = fp->__buffer + fp->__bufsize;

  /* Make room in the buffer.  */
  (*fp->__room_funcs.__output) (fp, flush_only ? EOF : (unsigned char) c);

  if (fp->__linebuf)
    {
      /* This is a line-buffered stream, and it is now ready to do
	 some output.  We call this an "active line-buffered stream".
	 We set the put_limit to the beginning of the buffer,
	 so the next `putc' call will force a call to this function.
	 Setting the linebuf_active flag tells the code above
	 (on the next call) to undo this hackery.  */
      fp->__put_limit = fp->__buffer;
      fp->__linebuf_active = 1;
    }

  if (ferror (fp))
    return EOF;
  if (flush_only)
    return 0;
  return (unsigned char) c;
}


/* Fill the buffer for FP and return the first character read.
   This is the function used by getc.  */
int
DEFUN(__fillbf, (fp), register FILE *fp)
{
  register int c;
  fpos_t new_target;

  if (!__validfp(fp) || !fp->__mode.__read)
    {
      errno = EINVAL;
      return EOF;
    }

  if (fp->__pushed_back)
    {
      /* Return the char pushed back by ungetc.  */
      fp->__bufp = fp->__pushback_bufp;
      fp->__pushed_back = 0;
      return fp->__pushback;
    }

  /* Make sure the stream is initialized (has functions and buffering). */
  init_stream(fp);

  /* If we're trying to read the first character of a new
     line of input from an unbuffered or line buffered stream,
     we must flush all line-buffered output streams. */
  if (fp->__buffer == NULL || fp->__linebuf)
    {
      register FILE *f;
      for (f = __stdio_head; f != NULL; f = f->__next)
	if (__validfp (f) && f->__linebuf && f->__mode.__write)
	  (void) __flshfp (f, EOF);
    }

  /* Note we must do this after flushing all line-buffered
     streams, or else __flshfp would undo it!  */
  if (fp->__linebuf_active)
    {
      /* This is an active line-buffered stream, meaning it is in the midst
	 of writing, but has a bogus put_limit.  Restore it to normality.  */
      fp->__put_limit = fp->__buffer + fp->__bufsize;
      fp->__linebuf_active = 0;
    }

  /* We want the beginning of the buffer to now
     map to just past the last data we read.  */
  new_target = fp->__target + (fp->__get_limit - fp->__buffer);

  if (fp->__put_limit > fp->__buffer)
    {
      /* There is written data in the buffer.
	 Flush it out.  */
      if (fp->__room_funcs.__output == NULL)
	fp->__error = 1;
      else
	(*fp->__room_funcs.__output) (fp, EOF);
    }

  fp->__target = new_target;

  if (ferror(fp))
    c = EOF;
  else if (fp->__room_funcs.__input != NULL)
    {
      c = (*fp->__room_funcs.__input)(fp);
      if (fp->__buffer == NULL)
	/* This is an unbuffered stream, so the target sync above
	   won't do anything the next time around.  Instead, note that
	   we have read one character.  The (nonexistent) buffer now
	   maps to the position just past that character.  */
	++fp->__target;
    }
  else
    {
      /* A NULL `input_room' function means always return EOF.  */
      fp->__eof = 1;
      c = EOF;
    }

  return c;
}


/* Nuke a stream, but don't kill its link in the chain.  */
void
DEFUN(__invalidate, (stream), register FILE *stream)
{
  /* Save its link.  */
  register FILE *next = stream->__next;

  /* Pulverize the fucker.  */
  memset((PTR) stream, 0, sizeof(FILE));

  /* Restore the deceased's link.  */
  stream->__next = next;
}