stdio/internals.c

   1 /* Copyright (C) 1991, 92, 93, 94, 95, 96 Free Software Foundation, Inc.
   2 This file is part of the GNU C Library.
   3
   4 The GNU C Library is free software; you can redistribute it and/or
   5 modify it under the terms of the GNU Library General Public License as
   6 published by the Free Software Foundation; either version 2 of the
   7 License, or (at your option) any later version.
   8
   9 The GNU C Library is distributed in the hope that it will be useful,
  10 but WITHOUT ANY WARRANTY; without even the implied warranty of
  11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12 Library General Public License for more details.
  13
  14 You should have received a copy of the GNU Library General Public
  15 License along with the GNU C Library; see the file COPYING.LIB.  If
  16 not, write to the Free Software Foundation, Inc., 675 Mass Ave,
  17 Cambridge, MA 02139, USA.  */
  18
  19 #include <errno.h>
  20 #include <stdio.h>
  21 #include <stdlib.h>
  22 #include <string.h>
  23
  24
  25 /* Make sure that FP has its functions set.  */
  26 void
  27 __stdio_check_funcs (register FILE *fp)
  28 {
  29   if (!fp->__seen)
  30     {
  31       /* Initialize the stream's info, including buffering info.
  32          This may give a buffer, change I/O functions, etc.
  33          If no buffer is set (and the stream is not made explicitly
  34          unbuffered), we allocate a buffer below, using the bufsize
  35          set by this function.  */
  36       extern void __stdio_init_stream __P ((FILE *));
  37       fp->__room_funcs = __default_room_functions;
  38       fp->__io_funcs = __default_io_functions;
  39       __stdio_init_stream (fp);
  40       fp->__seen = 1;
  41     }
  42 }
  43
  44
  45 /* Minimum size of a buffer we will allocate by default.
  46    If this much memory is not available,
  47    the stream in question will be made unbuffered instead.  */
  48 #define MIN_BUFSIZE     128
  49
  50 /* Figure out what kind of buffering (none, line, or full)
  51    and what buffer size to give FP.  */
  52 static void
  53 init_stream (register FILE *fp)
  54 {
  55   __stdio_check_funcs (fp);
  56
  57   if (fp->__buffer == NULL && !fp->__userbuf)
  58     {
  59       int save;
  60
  61       if (fp->__bufsize == 0)
  62         fp->__bufsize = BUFSIZ;
  63
  64       /* Try to get however many bytes of buffering __stdio_pickbuf
  65          specified, but if that much memory isn't available,
  66          try half as much each time until it succeeds or the buffer
  67          size becomes too small to be useful.  */
  68       save = errno;
  69       while (fp->__bufsize >= MIN_BUFSIZE)
  70         {
  71           fp->__buffer = (char *) malloc (fp->__bufsize);
  72           if (fp->__buffer == NULL)
  73             fp->__bufsize /= 2;
  74           else
  75             break;
  76         }
  77       __set_errno (save);
  78
  79       if (fp->__buffer == NULL)
  80         {
  81           /* We can't get space for the buffer, so make it unbuffered.  */
  82           fp->__userbuf = 1;
  83           fp->__bufsize = 0;
  84         }
  85     }
  86
  87   if (fp->__bufp == NULL)
  88     {
  89       /* Set the buffer pointer to the beginning of the buffer.  */
  90       fp->__bufp = fp->__buffer;
  91       fp->__put_limit = fp->__get_limit = fp->__buffer;
  92     }
  93 }
  94
  95
  96 /* Determine the current file position of STREAM if it is unknown.  */
  97 int
  98 __stdio_check_offset (stream)
  99      FILE *stream;
 100 {
 101   init_stream (stream);
 102
 103   if (stream->__offset == (fpos_t) -1)
 104     {
 105       /* This stream's offset is unknown or unknowable.  */
 106       if (stream->__io_funcs.__seek == NULL)
 107         {
 108           /* Unknowable.  */
 109           __set_errno (ESPIPE);
 110           return EOF;
 111         }
 112       else
 113         {
 114           /* Unknown.  Find it out.  */
 115           fpos_t pos = (fpos_t) 0;
 116           if ((*stream->__io_funcs.__seek) (stream->__cookie,
 117                                             &pos, SEEK_CUR) < 0)
 118             {
 119               if (errno == ESPIPE)
 120                 /* Object is incapable of seeking.  */
 121                 stream->__io_funcs.__seek = NULL;
 122               return EOF;
 123             }
 124           stream->__offset = pos;
 125         }
 126     }
 127
 128   if (stream->__target == (fpos_t) -1)
 129     /* This stream was opened on an existing object with
 130        an unknown file position.  The position is now known.
 131        Make this the target position.  */
 132     stream->__target = stream->__offset;
 133
 134   return 0;
 135 }
 136
 137
 138 /* Move FP's file position to its target file position,
 139    seeking as necessary and updating its `offset' field.
 140    Sets ferror(FP) (and possibly errno) for errors.  */
 141 static void
 142 seek_to_target (FILE *fp)
 143 {
 144   int save = errno;
 145   if (__stdio_check_offset (fp) == EOF)
 146     {
 147       if (errno == ESPIPE)
 148         __set_errno (save);
 149       else
 150         fp->__error = 1;
 151     }
 152   else if (fp->__target != fp->__offset)
 153     {
 154       /* We are not at the target file position.
 155          Seek to that position.  */
 156       if (fp->__io_funcs.__seek == NULL)
 157         {
 158           /* We can't seek!  */
 159           __set_errno (ESPIPE);
 160           fp->__error = 1;
 161         }
 162       else
 163         {
 164           fpos_t pos = fp->__target;
 165           if ((*fp->__io_funcs.__seek) (fp->__cookie, &pos, SEEK_SET) < 0)
 166             /* Seek failed!  */
 167             fp->__error = 1;
 168           else
 169             {
 170               fp->__offset = pos;
 171               if (pos != fp->__target)
 172                 {
 173                   /* Seek didn't go to the right place!
 174                      This should never happen.  */
 175 #ifdef EGRATUITOUS
 176                   /* It happens in the Hurd when the io server doesn't
 177                      obey the protocol for io_seek.  */
 178                   __set_errno (EGRATUITOUS);
 179 #else
 180                   /* I don't think this can happen in Unix.  */
 181                   __set_errno (ESPIPE); /* ??? */
 182 #endif
 183                   fp->__error = 1;
 184                 }
 185             }
 186         }
 187     }
 188 }
 189
 190 /* Flush the buffer for FP.
 191    If C is not EOF, it is also to be written.
 192    If the stream is line buffered and C is a newline, it is written
 193    to the output, otherwise it is put in the buffer after it has been
 194    flushed to avoid a system call for a single character.
 195    This is the default `output room' function.  */
 196 static void
 197 flushbuf (register FILE *fp, int c)
 198 {
 199   int flush_only = c == EOF;
 200   size_t buffer_written;
 201   size_t to_write;
 202
 203   /* Set if target and get_limit have already been twiddled appropriately.  */
 204   int twiddled = 0;
 205
 206   if (fp->__put_limit == fp->__buffer)
 207     {
 208       /* The stream needs to be primed for writing.  */
 209
 210       size_t buffer_offset = 0;
 211
 212       if (fp->__target == -1)
 213         /* For an unseekable object, data recently read bears no relation
 214            to data we will write later.  Discard the buffer.  */
 215         fp->__get_limit = fp->__buffer;
 216       else
 217         /* If the user has read some of the buffer, the target position
 218            is incremented for each character he has read.  */
 219         fp->__target += fp->__bufp - fp->__buffer;
 220
 221       if (fp->__mode.__read && fp->__room_funcs.__input != NULL &&
 222           !fp->__mode.__append)
 223         {
 224           int save = errno;
 225           const int aligned = (fp->__buffer == NULL ||
 226                                __stdio_check_offset (fp) == EOF ||
 227                                fp->__target % fp->__bufsize == 0);
 228           __set_errno (save);
 229
 230           if (!aligned)
 231             {
 232               /* Move to a block (buffer size) boundary and read in a block.
 233                  Then the output will be written as a whole block, too.  */
 234               const size_t o = fp->__target % fp->__bufsize;
 235               fp->__target -= o;
 236               if ((*fp->__room_funcs.__input) (fp) == EOF && ferror (fp))
 237                 return;
 238               else
 239                 __clearerr (fp);
 240
 241               if (fp->__get_limit - fp->__buffer < o)
 242                 /* Oops.  We didn't read enough (probably because we got EOF).
 243                    Forget we even mentioned it.  */
 244                 fp->__target += o;
 245               else
 246                 /* Start bufp as far into the buffer as we were into
 247                    this block before we read it.  */
 248                 buffer_offset = o;
 249
 250               /* The target position is now set to where the beginning of the
 251                  buffer maps to; and the get_limit was set by the input-room
 252                  function.  */
 253               twiddled = 1;
 254             }
 255         }
 256
 257       if (fp->__buffer != NULL)
 258         {
 259           /* Set up to write output into the buffer.  */
 260           fp->__put_limit = fp->__buffer + fp->__bufsize;
 261           fp->__bufp = fp->__buffer + buffer_offset;
 262
 263           if (!flush_only)
 264             {
 265               /* Put C in the buffer to be written out.
 266                  We only need to actually write it out now if
 267                  it is a newline on a line-buffered stream.  */
 268               *fp->__bufp++ = (unsigned char) c;
 269               if (!fp->__linebuf || (unsigned char) c != '\n')
 270                 {
 271                   /* There is no need to flush C from the buffer right now.
 272                      Record that nothing was written from the buffer,
 273                      and go do clean-up at end.  */
 274                   buffer_written = 0;
 275                   goto end;
 276                 }
 277               else
 278                 /* We put C in the buffer, so don't write it again later.  */
 279                 flush_only = 1;
 280             }
 281         }
 282
 283       if (fp->__bufp - fp->__buffer <= buffer_offset && flush_only)
 284         {
 285           /* There is nothing new in the buffer, only data that
 286              was read back aligned from the file.  */
 287           buffer_written = 0;
 288           goto end;
 289         }
 290     }
 291
 292   /* If there is read data in the buffer past what was written,
 293      write all of that as well.  Otherwise, just write what has been
 294      written into the buffer.  */
 295   buffer_written = fp->__bufp - fp->__buffer;
 296   to_write = (buffer_written == 0 ? 0 :
 297               fp->__get_limit > fp->__bufp ?
 298               fp->__get_limit - fp->__buffer :
 299               buffer_written);
 300
 301   if (fp->__io_funcs.__write == NULL || (to_write == 0 && flush_only))
 302     {
 303       /* There is no writing function or we're coming from an fflush
 304          call with nothing in the buffer, so just say the buffer's
 305          been flushed, increment the file offset, and return.  */
 306       fp->__bufp = fp->__buffer;
 307       if (fp->__offset != -1)
 308         fp->__offset += to_write;
 309       goto end;
 310     }
 311
 312   if (to_write > 0)
 313     {
 314       int wrote;
 315
 316       /* Go to the target file position.  Don't bother if appending;
 317          the write will just ignore the file position anyway.  */
 318       if (!fp->__mode.__append)
 319         seek_to_target (fp);
 320
 321       if (!ferror(fp))
 322         {
 323           /* Write out the buffered data.  */
 324           wrote = (*fp->__io_funcs.__write) (fp->__cookie, fp->__buffer,
 325                                              to_write);
 326           if (wrote > 0)
 327             {
 328               if (fp->__mode.__append)
 329                 /* The write has written the data to the end of the file
 330                    and updated the file position to after the data.  Don't
 331                    bother to find the current position; we can get it
 332                    later if we need it.  */
 333                 fp->__offset = fp->__target = -1;
 334               else if (fp->__offset != -1)
 335                 /* Record that we've moved forward in the file.  */
 336                 fp->__offset += wrote;
 337             }
 338           if (wrote < (int) to_write)
 339             /* The writing function should always write
 340                the whole buffer unless there is an error.  */
 341             fp->__error = 1;
 342         }
 343     }
 344
 345   /* Reset the buffer pointer to the beginning of the buffer.  */
 346   fp->__bufp = fp->__buffer;
 347
 348   /* If we're not just flushing, write the last character, C.  */
 349   if (!flush_only && !ferror (fp))
 350     {
 351       if (fp->__buffer == NULL || (fp->__linebuf && (unsigned char) c == '\n'))
 352         {
 353           /* Either we're unbuffered, or we're line-buffered and
 354              C is a newline, so really write it out immediately.  */
 355           char cc = (unsigned char) c;
 356           if ((*fp->__io_funcs.__write)(fp->__cookie, &cc, 1) < 1)
 357             fp->__error = 1;
 358           else if (fp->__offset != -1)
 359             {
 360               /* Record that we've moved forward in the file.  */
 361               ++fp->__offset;
 362               ++fp->__target;
 363             }
 364         }
 365       else
 366         /* Just put C in the buffer.  */
 367         *fp->__bufp++ = (unsigned char) c;
 368     }
 369
 370  end:
 371
 372   if (!twiddled)
 373     {
 374       if (fp->__target != -1)
 375         /* The new target position moves up as
 376            much as the user wrote into the buffer.  */
 377         fp->__target += buffer_written;
 378
 379       /* Set the reading limit to the beginning of the buffer,
 380          so the next `getc' will call __fillbf.  */
 381       fp->__get_limit = fp->__buffer;
 382     }
 383
 384   if (feof (fp) || ferror (fp))
 385     fp->__bufp = fp->__put_limit;
 386 }
 387
 388
 389 /* Fill the buffer for FP and return the first character read (or EOF).
 390    This is the default `input_room' function.  */
 391 static int
 392 fillbuf (register FILE *fp)
 393 {
 394   /* How far into the buffer we read we want to start bufp.  */
 395   size_t buffer_offset = 0;
 396   register char *buffer;
 397   register size_t to_read, nread = 0;
 398   /* This must be unsigned to avoid sign extension in return.  */
 399   unsigned char c;
 400
 401   if (fp->__io_funcs.__read == NULL)
 402     {
 403       /* There is no read function, so always return EOF.  */
 404       fp->__eof = 1;
 405       goto end;
 406     }
 407
 408   if (fp->__buffer == NULL)
 409     {
 410       /* We're unbuffered, so we want to read only one character.  */
 411       buffer = (char *) &c;
 412       to_read = 1;
 413     }
 414   else
 415     {
 416       /* We're buffered, so try to fill the buffer.  */
 417       buffer = fp->__buffer;
 418       to_read = fp->__bufsize;
 419     }
 420
 421   /* We're reading, so we're not at the end-of-file.  */
 422   fp->__eof = 0;
 423
 424   /* Go to the target file position.  */
 425   {
 426     int save = errno;
 427     if (__stdio_check_offset (fp) == 0 && fp->__target != fp->__offset)
 428       {
 429         /* Move to a block (buffer size) boundary.  */
 430         if (fp->__bufsize != 0)
 431           {
 432             buffer_offset = fp->__target % fp->__bufsize;
 433             fp->__target -= buffer_offset;
 434           }
 435         seek_to_target (fp);
 436       }
 437     __set_errno (save);
 438   }
 439
 440   while (!ferror (fp) && !feof (fp) && nread <= buffer_offset)
 441     {
 442       /* Try to fill the buffer.  */
 443       int count = (*fp->__io_funcs.__read) (fp->__cookie, buffer, to_read);
 444       if (count == 0)
 445         fp->__eof = 1;
 446       else if (count < 0)
 447         fp->__error = 1;
 448       else
 449         {
 450           buffer += count;
 451           nread += count;
 452           to_read -= count;
 453           if (fp->__offset != -1)
 454             /* Record that we've moved forward in the file.  */
 455             fp->__offset += count;
 456         }
 457     }
 458
 459   if (fp->__buffer == NULL)
 460     /* There is no buffer, so return the character we read
 461        without all the buffer pointer diddling.  */
 462     return (feof (fp) || ferror (fp)) ? EOF : c;
 463
 464   /* Reset the buffer pointer to the beginning of the buffer
 465      (plus whatever offset we may have set above).  */
 466   fp->__bufp = fp->__buffer + buffer_offset;
 467
 468  end:;
 469
 470   if (feof (fp) || ferror (fp))
 471     {
 472       /* Set both end pointers to the beginning of the buffer so
 473          the next i/o call will force a call to __fillbf/__flshfp.  */
 474       fp->__put_limit = fp->__get_limit = fp->__buffer;
 475       return EOF;
 476     }
 477
 478   /* Set the end pointer to one past the last character we read.  */
 479   fp->__get_limit = fp->__buffer + nread;
 480
 481   /* Make it so the next `putc' will call __flshfp.  */
 482   fp->__put_limit = fp->__buffer;
 483
 484   /* Return the first character in the buffer.  */
 485   return *((unsigned char *) (fp->__bufp++));
 486 }
 487
 488
 489 /* Default I/O and room functions.  */
 490
 491 extern __io_read_fn __stdio_read;
 492 extern __io_write_fn __stdio_write;
 493 extern __io_seek_fn __stdio_seek;
 494 extern __io_close_fn __stdio_close;
 495 extern __io_fileno_fn __stdio_fileno;
 496 const __io_functions __default_io_functions =
 497   {
 498     __stdio_read, __stdio_write, __stdio_seek, __stdio_close, __stdio_fileno
 499   };
 500
 501 const __room_functions __default_room_functions =
 502   {
 503     fillbuf, flushbuf
 504   };
 505
 506
 507 /* Flush the buffer for FP and also write C if FLUSH_ONLY is nonzero.
 508    This is the function used by putc and fflush.  */
 509 int
 510 __flshfp (fp, c)
 511      register FILE *fp;
 512      int c;
 513 {
 514   int flush_only = c == EOF;
 515
 516   if (!__validfp (fp) || !fp->__mode.__write)
 517     {
 518       __set_errno (EINVAL);
 519       return EOF;
 520     }
 521
 522   if (ferror (fp))
 523     return EOF;
 524
 525   if (fp->__pushed_back)
 526     {
 527       /* Discard the char pushed back by ungetc.  */
 528       fp->__bufp = fp->__pushback_bufp;
 529       fp->__pushed_back = 0;
 530     }
 531
 532   /* Make sure the stream is initialized (has functions and buffering).  */
 533   init_stream (fp);
 534
 535   /* Do this early, so a `putc' on such a stream will never return success.  */
 536   if (fp->__room_funcs.__output == NULL)
 537     {
 538       /* A NULL `output room' function means
 539          to always return an output error.  */
 540       fp->__error = 1;
 541       return EOF;
 542     }
 543
 544   if (!flush_only &&
 545       /* Will C fit into the buffer?
 546          See below about linebuf_active.  */
 547       fp->__bufp < (fp->__linebuf_active ? fp->__buffer + fp->__bufsize :
 548                     fp->__put_limit))
 549     {
 550       /* The character will fit in the buffer, so put it there.  */
 551       *fp->__bufp++ = (unsigned char) c;
 552       if (fp->__linebuf && (unsigned char) c == '\n')
 553         flush_only = 1;
 554       else
 555         return (unsigned char) c;
 556     }
 557
 558   if (fp->__linebuf_active)
 559     /* This is an active line-buffered stream, so its put-limit is set
 560        to the beginning of the buffer in order to force a __flshfp call
 561        on each putc (see below).  We undo this hack here (by setting
 562        the limit to the end of the buffer) to simplify the interface
 563        with the output-room function.  */
 564     fp->__put_limit = fp->__buffer + fp->__bufsize;
 565
 566   /* Make room in the buffer.  */
 567   (*fp->__room_funcs.__output) (fp, flush_only ? EOF : (unsigned char) c);
 568
 569   if (fp->__linebuf)
 570     {
 571       /* This is a line-buffered stream, and it is now ready to do
 572          some output.  We call this an "active line-buffered stream".
 573          We set the put_limit to the beginning of the buffer,
 574          so the next `putc' call will force a call to this function.
 575          Setting the linebuf_active flag tells the code above
 576          (on the next call) to undo this hackery.  */
 577       fp->__put_limit = fp->__buffer;
 578       fp->__linebuf_active = 1;
 579     }
 580
 581   if (ferror (fp))
 582     return EOF;
 583   if (flush_only)
 584     return 0;
 585   return (unsigned char) c;
 586 }
 587
 588
 589 /* Fill the buffer for FP and return the first character read.
 590    This is the function used by getc.  */
 591 int
 592 __fillbf (fp)
 593      register FILE *fp;
 594 {
 595   register int c;
 596   fpos_t new_target;
 597
 598   if (!__validfp (fp) || !fp->__mode.__read)
 599     {
 600       __set_errno (EINVAL);
 601       return EOF;
 602     }
 603
 604   if (fp->__pushed_back)
 605     {
 606       /* Return the char pushed back by ungetc.  */
 607       fp->__bufp = fp->__pushback_bufp;
 608       fp->__pushed_back = 0;
 609       return fp->__pushback;
 610     }
 611
 612   /* Make sure the stream is initialized (has functions and buffering). */
 613   init_stream (fp);
 614
 615   /* If we're trying to read the first character of a new
 616      line of input from an unbuffered or line buffered stream,
 617      we must flush all line-buffered output streams. */
 618   if (fp->__buffer == NULL || fp->__linebuf)
 619     {
 620       register FILE *f;
 621       for (f = __stdio_head; f != NULL; f = f->__next)
 622         if (__validfp (f) && f->__linebuf && f->__mode.__write)
 623           (void) __flshfp (f, EOF);
 624     }
 625
 626   /* Note we must do this after flushing all line-buffered
 627      streams, or else __flshfp would undo it!  */
 628   if (fp->__linebuf_active)
 629     {
 630       /* This is an active line-buffered stream, meaning it is in the midst
 631          of writing, but has a bogus put_limit.  Restore it to normality.  */
 632       fp->__put_limit = fp->__buffer + fp->__bufsize;
 633       fp->__linebuf_active = 0;
 634     }
 635
 636   /* We want the beginning of the buffer to now
 637      map to just past the last data we read.  */
 638   new_target = fp->__target + (fp->__get_limit - fp->__buffer);
 639
 640   if (fp->__put_limit > fp->__buffer)
 641     {
 642       /* There is written data in the buffer.
 643          Flush it out.  */
 644       if (fp->__room_funcs.__output == NULL)
 645         fp->__error = 1;
 646       else
 647         (*fp->__room_funcs.__output) (fp, EOF);
 648     }
 649
 650   fp->__target = new_target;
 651
 652   if (ferror (fp))
 653     c = EOF;
 654   else if (fp->__room_funcs.__input != NULL)
 655     {
 656       c = (*fp->__room_funcs.__input) (fp);
 657       if (fp->__buffer == NULL)
 658         /* This is an unbuffered stream, so the target sync above
 659            won't do anything the next time around.  Instead, note that
 660            we have read one character.  The (nonexistent) buffer now
 661            maps to the position just past that character.  */
 662         ++fp->__target;
 663     }
 664   else
 665     {
 666       /* A NULL `input_room' function means always return EOF.  */
 667       fp->__eof = 1;
 668       c = EOF;
 669     }
 670
 671   return c;
 672 }
 673
 674
 675 /* Nuke a stream, but don't kill its link in the chain.  */
 676 void
 677 __invalidate (stream)
 678      register FILE *stream;
 679 {
 680   /* Save its link.  */
 681   register FILE *next = stream->__next;
 682
 683   /* Pulverize the deceased.  */
 684   memset((void *) stream, 0, sizeof(FILE));
 685
 686   /* Restore the deceased's link.  */
 687   stream->__next = next;
 688 }