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 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., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */
  20
  21 /* Originally written by Jan Brittenson, bson@gnu.ai.mit.edu.  */
  22
  23 #if HAVE_CONFIG_H
  24 # include <config.h>
  25 #endif
  26
  27 /* Specification.  */
  28 #include "getndelim2.h"
  29
  30 #include <stdlib.h>
  31
  32 #include "unlocked-io.h"
  33
  34 /* Always add at least this many bytes when extending the buffer.  */
  35 #define MIN_CHUNK 64
  36
  37 ssize_t
  38 getndelim2 (char **lineptr, size_t *linesize, size_t nmax,
  39             FILE *stream, int delim1, int delim2, size_t offset)
  40 {
  41   size_t nbytes_avail;          /* Allocated but unused chars in *LINEPTR.  */
  42   char *read_pos;               /* Where we're reading into *LINEPTR. */
  43
  44   if (!lineptr || !linesize || !nmax || !stream)
  45     return -1;
  46
  47   if (!*lineptr)
  48     {
  49       size_t newlinesize = MIN_CHUNK;
  50
  51       if (newlinesize > nmax)
  52         newlinesize = nmax;
  53
  54       *linesize = newlinesize;
  55       *lineptr = malloc (*linesize);
  56       if (!*lineptr)
  57         return -1;
  58     }
  59
  60   if (*linesize < offset)
  61     return -1;
  62
  63   nbytes_avail = *linesize - offset;
  64   read_pos = *lineptr + offset;
  65
  66   if (nbytes_avail == 0 && *linesize >= nmax)
  67     return -1;
  68
  69   for (;;)
  70     {
  71       /* Here always *lineptr + *linesize == read_pos + nbytes_avail.  */
  72
  73       register int c;
  74
  75       /* We always want at least one char left in the buffer, since we
  76          always (unless we get an error while reading the first char)
  77          NUL-terminate the line buffer.  */
  78
  79       if (nbytes_avail < 2 && *linesize < nmax)
  80         {
  81           size_t newlinesize =
  82             (*linesize > MIN_CHUNK ? 2 * *linesize : *linesize + MIN_CHUNK);
  83
  84           if (newlinesize > nmax)
  85             newlinesize = nmax;
  86
  87           if (newlinesize > *linesize)
  88             {
  89               *linesize = newlinesize;
  90               nbytes_avail = *linesize + *lineptr - read_pos;
  91               *lineptr = realloc (*lineptr, *linesize);
  92               if (!*lineptr)
  93                 return -1;
  94               read_pos = *linesize - nbytes_avail + *lineptr;
  95             }
  96         }
  97
  98       c = getc (stream);
  99       if (c == EOF)
 100         {
 101           /* Return partial line, if any.  */
 102           if (read_pos == *lineptr)
 103             return -1;
 104           else
 105             break;
 106         }
 107
 108       if (nbytes_avail >= 2)
 109         {
 110           *read_pos++ = c;
 111           nbytes_avail--;
 112         }
 113
 114       if (c == delim1 || (delim2 && c == delim2))
 115         /* Return the line.  */
 116         break;
 117     }
 118
 119   /* Done - NUL terminate and return the number of chars read.
 120      At this point we know that nbytes_avail >= 1.  */
 121   *read_pos = '\0';
 122
 123   return read_pos - (*lineptr + offset);
 124 }