gl/read-file.c

   1 /* read-file.c -- read file contents into a string
   2    Copyright (C) 2006 Free Software Foundation, Inc.
   3    Written by Simon Josefsson and Bruno Haible.
   4
   5    This program is free software; you can redistribute it and/or modify
   6    it under the terms of the GNU General Public License as published by
   7    the Free Software Foundation; either version 2, or (at your option)
   8    any later version.
   9
  10    This program is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13    GNU 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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.  */
  18
  19 #include <config.h>
  20
  21 #include "read-file.h"
  22
  23 /* Get realloc, free. */
  24 #include <stdlib.h>
  25
  26 /* Get errno. */
  27 #include <errno.h>
  28
  29 /* Read a STREAM and return a newly allocated string with the content,
  30    and set *LENGTH to the length of the string.  The string is
  31    zero-terminated, but the terminating zero byte is not counted in
  32    *LENGTH.  On errors, *LENGTH is undefined, errno preserves the
  33    values set by system functions (if any), and NULL is returned. */
  34 char *
  35 fread_file (FILE * stream, size_t * length)
  36 {
  37   char *buf = NULL;
  38   size_t alloc = 0;
  39   size_t size = 0;
  40   int save_errno;
  41
  42   for (;;)
  43     {
  44       size_t count;
  45       size_t requested;
  46
  47       if (size + BUFSIZ + 1 > alloc)
  48         {
  49           char *new_buf;
  50
  51           alloc += alloc / 2;
  52           if (alloc < size + BUFSIZ + 1)
  53             alloc = size + BUFSIZ + 1;
  54
  55           new_buf = realloc (buf, alloc);
  56           if (!new_buf)
  57             {
  58               save_errno = errno;
  59               break;
  60             }
  61
  62           buf = new_buf;
  63         }
  64
  65       requested = alloc - size - 1;
  66       count = fread (buf + size, 1, requested, stream);
  67       size += count;
  68
  69       if (count != requested)
  70         {
  71           save_errno = errno;
  72           if (ferror (stream))
  73             break;
  74           buf[size] = '\0';
  75           *length = size;
  76           return buf;
  77         }
  78     }
  79
  80   free (buf);
  81   errno = save_errno;
  82   return NULL;
  83 }
  84
  85 static char *
  86 internal_read_file (const char *filename, size_t * length, const char *mode)
  87 {
  88   FILE *stream = fopen (filename, mode);
  89   char *out;
  90   int save_errno;
  91
  92   if (!stream)
  93     return NULL;
  94
  95   out = fread_file (stream, length);
  96
  97   save_errno = errno;
  98
  99   if (fclose (stream) != 0)
 100     {
 101       if (out)
 102         {
 103           save_errno = errno;
 104           free (out);
 105         }
 106       errno = save_errno;
 107       return NULL;
 108     }
 109
 110   return out;
 111 }
 112
 113 /* Open and read the contents of FILENAME, and return a newly
 114    allocated string with the content, and set *LENGTH to the length of
 115    the string.  The string is zero-terminated, but the terminating
 116    zero byte is not counted in *LENGTH.  On errors, *LENGTH is
 117    undefined, errno preserves the values set by system functions (if
 118    any), and NULL is returned.  */
 119 char *
 120 read_file (const char *filename, size_t * length)
 121 {
 122   return internal_read_file (filename, length, "r");
 123 }
 124
 125 /* Open (on non-POSIX systems, in binary mode) and read the contents
 126    of FILENAME, and return a newly allocated string with the content,
 127    and set LENGTH to the length of the string.  The string is
 128    zero-terminated, but the terminating zero byte is not counted in
 129    the LENGTH variable.  On errors, *LENGTH is undefined, errno
 130    preserves the values set by system functions (if any), and NULL is
 131    returned.  */
 132 char *
 133 read_binary_file (const char *filename, size_t * length)
 134 {
 135   return internal_read_file (filename, length, "rb");
 136 }