LinuxGUI/Ventoy2Disk/Lib/exfat/src/mkfs/fat.c

   1 /*
   2         fat.c (09.11.10)
   3         File Allocation Table creation code.
   4
   5         Free exFAT implementation.
   6         Copyright (C) 2011-2018  Andrew Nayenko
   7
   8         This program is free software; you can redistribute it and/or modify
   9         it under the terms of the GNU General Public License as published by
  10         the Free Software Foundation, either version 2 of the License, or
  11         (at your option) any later version.
  12
  13         This program is distributed in the hope that it will be useful,
  14         but WITHOUT ANY WARRANTY; without even the implied warranty of
  15         MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16         GNU General Public License for more details.
  17
  18         You should have received a copy of the GNU General Public License along
  19         with this program; if not, write to the Free Software Foundation, Inc.,
  20         51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  21 */
  22
  23 #include "fat.h"
  24 #include "cbm.h"
  25 #include "uct.h"
  26 #include "rootdir.h"
  27 #include <unistd.h>
  28
  29 static off_t fat_alignment(void)
  30 {
  31         return (off_t) 128 * get_sector_size();
  32 }
  33
  34 static off_t fat_size(void)
  35 {
  36         return get_volume_size() / get_cluster_size() * sizeof(cluster_t);
  37 }
  38
  39 static cluster_t fat_write_entry(struct exfat_dev* dev, cluster_t cluster,
  40                 cluster_t value)
  41 {
  42         le32_t fat_entry = cpu_to_le32(value);
  43         if (exfat_write(dev, &fat_entry, sizeof(fat_entry)) < 0)
  44         {
  45                 exfat_error("failed to write FAT entry 0x%x", value);
  46                 return 0;
  47         }
  48         return cluster + 1;
  49 }
  50
  51 static cluster_t fat_write_entries(struct exfat_dev* dev, cluster_t cluster,
  52                 uint64_t length)
  53 {
  54         cluster_t end = cluster + DIV_ROUND_UP(length, get_cluster_size());
  55
  56         while (cluster < end - 1)
  57         {
  58                 cluster = fat_write_entry(dev, cluster, cluster + 1);
  59                 if (cluster == 0)
  60                         return 0;
  61         }
  62         return fat_write_entry(dev, cluster, EXFAT_CLUSTER_END);
  63 }
  64
  65 static int fat_write(struct exfat_dev* dev)
  66 {
  67         cluster_t c = 0;
  68
  69         if (!(c = fat_write_entry(dev, c, 0xfffffff8))) /* media type */
  70                 return 1;
  71         if (!(c = fat_write_entry(dev, c, 0xffffffff))) /* some weird constant */
  72                 return 1;
  73         if (!(c = fat_write_entries(dev, c, cbm.get_size())))
  74                 return 1;
  75         if (!(c = fat_write_entries(dev, c, uct.get_size())))
  76                 return 1;
  77         if (!(c = fat_write_entries(dev, c, rootdir.get_size())))
  78                 return 1;
  79
  80         return 0;
  81 }
  82
  83 const struct fs_object fat =
  84 {
  85         .get_alignment = fat_alignment,
  86         .get_size = fat_size,
  87         .write = fat_write,
  88 };