kern/file.c

   1 /* file.c - file I/O functions */
   2 /*
   3  *  GRUB  --  GRand Unified Bootloader
   4  *  Copyright (C) 2002,2006,2007  Free Software Foundation, Inc.
   5  *
   6  *  GRUB 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  *  GRUB 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 GRUB.  If not, see <http://www.gnu.org/licenses/>.
  18  */
  19
  20 #include <grub/misc.h>
  21 #include <grub/err.h>
  22 #include <grub/file.h>
  23 #include <grub/mm.h>
  24 #include <grub/fs.h>
  25 #include <grub/device.h>
  26
  27 /* Get the device part of the filename NAME. It is enclosed by parentheses.  */
  28 char *
  29 grub_file_get_device_name (const char *name)
  30 {
  31   if (name[0] == '(')
  32     {
  33       char *p = grub_strchr (name, ')');
  34       char *ret;
  35
  36       if (! p)
  37         {
  38           grub_error (GRUB_ERR_BAD_FILENAME, "missing `)'");
  39           return 0;
  40         }
  41
  42       ret = (char *) grub_malloc (p - name);
  43       if (! ret)
  44         return 0;
  45
  46       grub_memcpy (ret, name + 1, p - name - 1);
  47       ret[p - name - 1] = '\0';
  48       return ret;
  49     }
  50
  51   return 0;
  52 }
  53
  54 grub_file_t
  55 grub_file_open (const char *name)
  56 {
  57   grub_device_t device;
  58   grub_file_t file = 0;
  59   char *device_name;
  60   char *file_name;
  61
  62   device_name = grub_file_get_device_name (name);
  63   if (grub_errno)
  64     return 0;
  65
  66   /* Get the file part of NAME.  */
  67   file_name = grub_strchr (name, ')');
  68   if (file_name)
  69     file_name++;
  70   else
  71     file_name = (char *) name;
  72
  73   device = grub_device_open (device_name);
  74   grub_free (device_name);
  75   if (! device)
  76     goto fail;
  77
  78   file = (grub_file_t) grub_zalloc (sizeof (*file));
  79   if (! file)
  80     goto fail;
  81
  82   file->device = device;
  83
  84   if (device->disk && file_name[0] != '/')
  85     /* This is a block list.  */
  86     file->fs = &grub_fs_blocklist;
  87   else
  88     {
  89       file->fs = grub_fs_probe (device);
  90       if (! file->fs)
  91         goto fail;
  92     }
  93
  94   if ((file->fs->open) (file, file_name) != GRUB_ERR_NONE)
  95     goto fail;
  96
  97   return file;
  98
  99  fail:
 100   if (device)
 101     grub_device_close (device);
 102
 103   /* if (net) grub_net_close (net);  */
 104
 105   grub_free (file);
 106
 107   return 0;
 108 }
 109
 110 grub_ssize_t
 111 grub_file_read (grub_file_t file, void *buf, grub_size_t len)
 112 {
 113   grub_ssize_t res;
 114
 115   if (file->offset > file->size)
 116     {
 117       grub_error (GRUB_ERR_OUT_OF_RANGE,
 118                   "Attempt to read past the end of file.");
 119       return -1;
 120     }
 121
 122   if (len == 0 || len > file->size - file->offset)
 123     len = file->size - file->offset;
 124
 125   /* Prevent an overflow.  */
 126   if ((grub_ssize_t) len < 0)
 127     len >>= 1;
 128
 129   if (len == 0)
 130     return 0;
 131
 132   res = (file->fs->read) (file, buf, len);
 133   if (res > 0)
 134     file->offset += res;
 135
 136   return res;
 137 }
 138
 139 grub_err_t
 140 grub_file_close (grub_file_t file)
 141 {
 142   if (file->fs->close)
 143     (file->fs->close) (file);
 144
 145   if (file->device)
 146     grub_device_close (file->device);
 147   grub_free (file);
 148   return grub_errno;
 149 }
 150
 151 grub_off_t
 152 grub_file_seek (grub_file_t file, grub_off_t offset)
 153 {
 154   grub_off_t old;
 155
 156   if (offset > file->size)
 157     {
 158       grub_error (GRUB_ERR_OUT_OF_RANGE,
 159                   "attempt to seek outside of the file");
 160       return -1;
 161     }
 162
 163   old = file->offset;
 164   file->offset = offset;
 165   return old;
 166 }