contrib/cvs-1.12/lib/getndelim2.c

   1 /* getndelim2 - Read a line from a stream, stopping at one of 2 delimiters,
   2    with bounded memory allocation.
   3
   4    Copyright (C) 1993, 1996, 1997, 1998, 2000, 2003, 2004 Free Software
   5    Foundation, Inc.
   6
   7    This program is free software; you can redistribute it and/or modify
   8    it under the terms of the GNU General Public License as published by
   9    the Free Software Foundation; either version 2, or (at your option)
  10    any later version.
  11
  12    This program is distributed in the hope that it will be useful,
  13    but WITHOUT ANY WARRANTY; without even the implied warranty of
  14    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15    GNU General Public License for more details.
  16
  17    You should have received a copy of the GNU General Public License
  18    along with this program; if not, write to the Free Software Foundation,
  19    Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.  */
  20
  21 /* Originally written by Jan Brittenson, bson@gnu.ai.mit.edu.  */
  22
  23 #ifdef HAVE_CONFIG_H
  24 # include <config.h>
  25 #endif
  26
  27 #include "getndelim2.h"
  28
  29 #include <stdlib.h>
  30 #include <stddef.h>
  31
  32 #if USE_UNLOCKED_IO
  33 # include "unlocked-io.h"
  34 #endif
  35
  36 #include <limits.h>
  37 #if HAVE_INTTYPES_H
  38 # include <inttypes.h>
  39 #endif
  40 #if HAVE_STDINT_H
  41 # include <stdint.h>
  42 #endif
  43 #ifndef PTRDIFF_MAX
  44 # define PTRDIFF_MAX ((ptrdiff_t) (SIZE_MAX / 2))
  45 #endif
  46 #ifndef SIZE_MAX
  47 # define SIZE_MAX ((size_t) -1)
  48 #endif
  49 #ifndef SSIZE_MAX
  50 # define SSIZE_MAX ((ssize_t) (SIZE_MAX / 2))
  51 #endif
  52
  53 /* The maximum value that getndelim2 can return without suffering from
  54    overflow problems, either internally (because of pointer
  55    subtraction overflow) or due to the API (because of ssize_t).  */
  56 #define GETNDELIM2_MAXIMUM (PTRDIFF_MAX < SSIZE_MAX ? PTRDIFF_MAX : SSIZE_MAX)
  57
  58 /* Try to add at least this many bytes when extending the buffer.
  59    MIN_CHUNK must be no greater than GETNDELIM2_MAXIMUM.  */
  60 #define MIN_CHUNK 64
  61
  62 ssize_t
  63 getndelim2 (char **lineptr, size_t *linesize, size_t offset, size_t nmax,
  64             int delim1, int delim2, FILE *stream)
  65 {
  66   size_t nbytes_avail;          /* Allocated but unused bytes in *LINEPTR.  */
  67   char *read_pos;               /* Where we're reading into *LINEPTR. */
  68   ssize_t bytes_stored = -1;
  69   char *ptr = *lineptr;
  70   size_t size = *linesize;
  71
  72   if (!ptr)
  73     {
  74       size = nmax < MIN_CHUNK ? nmax : MIN_CHUNK;
  75       ptr = malloc (size);
  76       if (!ptr)
  77         return -1;
  78     }
  79
  80   if (size < offset)
  81     goto done;
  82
  83   nbytes_avail = size - offset;
  84   read_pos = ptr + offset;
  85
  86   if (nbytes_avail == 0 && nmax <= size)
  87     goto done;
  88
  89   for (;;)
  90     {
  91       /* Here always ptr + size == read_pos + nbytes_avail.  */
  92
  93       int c;
  94
  95       /* We always want at least one byte left in the buffer, since we
  96          always (unless we get an error while reading the first byte)
  97          NUL-terminate the line buffer.  */
  98
  99       if (nbytes_avail < 2 && size < nmax)
 100         {
 101           size_t newsize = size < MIN_CHUNK ? size + MIN_CHUNK : 2 * size;
 102           char *newptr;
 103
 104           if (! (size < newsize && newsize <= nmax))
 105             newsize = nmax;
 106
 107           if (GETNDELIM2_MAXIMUM < newsize - offset)
 108             {
 109               size_t newsizemax = offset + GETNDELIM2_MAXIMUM + 1;
 110               if (size == newsizemax)
 111                 goto done;
 112               newsize = newsizemax;
 113             }
 114
 115           nbytes_avail = newsize - (read_pos - ptr);
 116           newptr = realloc (ptr, newsize);
 117           if (!newptr)
 118             goto done;
 119           ptr = newptr;
 120           size = newsize;
 121           read_pos = size - nbytes_avail + ptr;
 122         }
 123
 124       c = getc (stream);
 125       if (c == EOF)
 126         {
 127           /* Return partial line, if any.  */
 128           if (read_pos == ptr)
 129             goto done;
 130           else
 131             break;
 132         }
 133
 134       if (nbytes_avail >= 2)
 135         {
 136           *read_pos++ = c;
 137           nbytes_avail--;
 138         }
 139
 140       if (c == delim1 || c == delim2)
 141         /* Return the line.  */
 142         break;
 143     }
 144
 145   /* Done - NUL terminate and return the number of bytes read.
 146      At this point we know that nbytes_avail >= 1.  */
 147   *read_pos = '\0';
 148
 149   bytes_stored = read_pos - (ptr + offset);
 150
 151  done:
 152   *lineptr = ptr;
 153   *linesize = size;
 154   return bytes_stored;
 155 }