common/xreadline.c

   1 /* xreadline.c - fgets replacement function
   2  * Copyright (C) 1999, 2004 Free Software Foundation, Inc.
   3  *
   4  * This file is part of GnuPG.
   5  *
   6  * GnuPG is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License as published by
   8  * the Free Software Foundation; either version 3 of the License, or
   9  * (at your option) any later version.
  10  *
  11  * GnuPG is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  * GNU General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU General Public License
  17  * along with this program; if not, see <http://www.gnu.org/licenses/>.
  18  */
  19
  20 #include <config.h>
  21 #include <stdio.h>
  22 #include <stdlib.h>
  23 #include <errno.h>
  24
  25 #include "util.h"
  26
  27
  28 /* Same as fgets() but if the provided buffer is too short a larger
  29    one will be allocated.  This is similar to getline. A line is
  30    considered a byte stream ending in a LF.
  31
  32    If MAX_LENGTH is not NULL, it shall point to a value with the
  33    maximum allowed allocation.
  34
  35    Returns the length of the line. EOF is indicated by a line of
  36    length zero. A truncated line is indicated by setting the value at
  37    MAX_LENGTH to 0.  If the returned value is less then 0 not enough
  38    memory was enable and ERRNO is set accordingly.
  39
  40    If a line has been truncated, the file pointer is moved forward to
  41    the end of the line so that the next read starts with the next
  42    line.  Note that MAX_LENGTH must be re-initialzied in this case.
  43
  44    Note: The returned buffer is allocated with enough extra space to
  45    append a CR,LF,Nul
  46  */
  47 ssize_t
  48 read_line (FILE *fp,
  49            char **addr_of_buffer, size_t *length_of_buffer,
  50            size_t *max_length)
  51 {
  52   int c;
  53   char  *buffer = *addr_of_buffer;
  54   size_t length = *length_of_buffer;
  55   size_t nbytes = 0;
  56   size_t maxlen = max_length? *max_length : 0;
  57   char *p;
  58
  59   if (!buffer)
  60     { /* No buffer given - allocate a new one. */
  61       length = 256;
  62       buffer = xtrymalloc (length);
  63       *addr_of_buffer = buffer;
  64       if (!buffer)
  65         {
  66           *length_of_buffer = 0;
  67           if (max_length)
  68             *max_length = 0;
  69           return -1;
  70         }
  71       *length_of_buffer = length;
  72     }
  73
  74   length -= 3; /* Reserve 3 bytes for CR,LF,EOL. */
  75   p = buffer;
  76   while  ((c = getc (fp)) != EOF)
  77     {
  78       if (nbytes == length)
  79         { /* Enlarge the buffer. */
  80           if (maxlen && length > maxlen) /* But not beyond our limit. */
  81             {
  82               /* Skip the rest of the line. */
  83               while (c != '\n' && (c=getc (fp)) != EOF)
  84                 ;
  85               *p++ = '\n'; /* Always append a LF (we reserved some space). */
  86               nbytes++;
  87               if (max_length)
  88                 *max_length = 0; /* Indicate truncation. */
  89               break; /* the while loop. */
  90             }
  91           length += 3; /* Adjust for the reserved bytes. */
  92           length += length < 1024? 256 : 1024;
  93           *addr_of_buffer = xtryrealloc (buffer, length);
  94           if (!*addr_of_buffer)
  95             {
  96               int save_errno = errno;
  97               xfree (buffer);
  98               *length_of_buffer = *max_length = 0;
  99               errno = save_errno;
 100               return -1;
 101             }
 102           buffer = *addr_of_buffer;
 103           *length_of_buffer = length;
 104           length -= 3;
 105           p = buffer + nbytes;
 106         }
 107       *p++ = c;
 108       nbytes++;
 109       if (c == '\n')
 110         break;
 111     }
 112   *p = 0; /* Make sure the line is a string. */
 113
 114   return nbytes;
 115 }