contrib/tar/lib/getstr.c

   1 /* getstr.c -- core function for GNU C library getline replacement function
   2
   3    Copyright (C) 1993, 1996-2000 Free Software Foundation, Inc.
   4
   5    This program is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU General Public License as
   7    published by the Free Software Foundation; either version 2 of the
   8    License, or (at your option) any later version.
   9
  10    This program is distributed in the hope that it will be useful, but
  11    WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    General Public License for more details.
  14
  15    You should have received a copy of the GNU General Public License
  16    along with this program; if not, write to the Free Software Foundation,
  17    Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */
  18
  19 /* Written by Jan Brittenson, bson@gnu.ai.mit.edu.  */
  20
  21 #if HAVE_CONFIG_H
  22 # include <config.h>
  23 #endif
  24
  25 #include <stdio.h>
  26 #include <sys/types.h>
  27
  28 #include <assert.h>
  29
  30 #if STDC_HEADERS
  31 # include <stdlib.h>
  32 #else
  33 char *malloc (), *realloc ();
  34 #endif
  35
  36 /* Always add at least this many bytes when extending the buffer.  */
  37 #define MIN_CHUNK 64
  38
  39 /* Read up to (and including) a delimiter DELIM1 from STREAM into *LINEPTR
  40    + OFFSET (and NUL-terminate it).  If DELIM2 is non-zero, then read up
  41    and including the first occurrence of DELIM1 or DELIM2.  *LINEPTR is
  42    a pointer returned from malloc (or NULL), pointing to *N characters of
  43    space.  It is realloc'd as necessary.  Return the number of characters
  44    read (not including the NUL terminator), or -1 on error or EOF.  */
  45
  46 int
  47 getstr (char **lineptr, size_t *n, FILE *stream, int delim1, int delim2,
  48         size_t offset)
  49 {
  50   int nchars_avail;             /* Allocated but unused chars in *LINEPTR.  */
  51   char *read_pos;               /* Where we're reading into *LINEPTR. */
  52   int ret;
  53
  54   if (!lineptr || !n || !stream)
  55     return -1;
  56
  57   if (!*lineptr)
  58     {
  59       *n = MIN_CHUNK;
  60       *lineptr = malloc (*n);
  61       if (!*lineptr)
  62         return -1;
  63     }
  64
  65   nchars_avail = *n - offset;
  66   read_pos = *lineptr + offset;
  67
  68   for (;;)
  69     {
  70       register int c = getc (stream);
  71
  72       /* We always want at least one char left in the buffer, since we
  73          always (unless we get an error while reading the first char)
  74          NUL-terminate the line buffer.  */
  75
  76       assert(*n - nchars_avail == read_pos - *lineptr);
  77       if (nchars_avail < 2)
  78         {
  79           if (*n > MIN_CHUNK)
  80             *n *= 2;
  81           else
  82             *n += MIN_CHUNK;
  83
  84           nchars_avail = *n + *lineptr - read_pos;
  85           *lineptr = realloc (*lineptr, *n);
  86           if (!*lineptr)
  87             return -1;
  88           read_pos = *n - nchars_avail + *lineptr;
  89           assert(*n - nchars_avail == read_pos - *lineptr);
  90         }
  91
  92       if (c == EOF || ferror (stream))
  93         {
  94           /* Return partial line, if any.  */
  95           if (read_pos == *lineptr)
  96             return -1;
  97           else
  98             break;
  99         }
 100
 101       *read_pos++ = c;
 102       nchars_avail--;
 103
 104       if (c == delim1 || (delim2 && c == delim2))
 105         /* Return the line.  */
 106         break;
 107     }
 108
 109   /* Done - NUL terminate and return the number of chars read.  */
 110   *read_pos = '\0';
 111
 112   ret = read_pos - (*lineptr + offset);
 113   return ret;
 114 }