disk-utils/cramfs_common.c

   1 /*
   2  * cramfs_common - cramfs common code
   3  *
   4  * Copyright (c) 2008 Roy Peled, the.roy.peled  -at-  gmail.com
   5  * Copyright (c) 2004-2006 by Juliane Holzt, kju -at- fqdn.org
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License as published by
   9  * the Free Software Foundation; either version 2 of the License, or
  10  * (at your option) any later version.
  11  *
  12  * This program is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15  * GNU General Public License for more details.
  16  *
  17  */
  18
  19 #include <string.h>
  20 #include "cramfs.h"
  21 #include "../include/bitops.h"
  22
  23 uint32_t u32_toggle_endianness(int big_endian, uint32_t what)
  24 {
  25         return big_endian == HOST_IS_BIG_ENDIAN ? what : swab32(what);
  26 }
  27
  28 void super_toggle_endianness(int big_endian, struct cramfs_super *super)
  29 {
  30         if (big_endian != HOST_IS_BIG_ENDIAN) {
  31                 super->magic = swab32(super->magic);
  32                 super->size = swab32(super->size);
  33                 super->flags = swab32(super->flags);
  34                 super->future = swab32(super->future);
  35                 super->fsid.crc = swab32(super->fsid.crc);
  36                 super->fsid.edition = swab32(super->fsid.edition);
  37                 super->fsid.blocks = swab32(super->fsid.blocks);
  38                 super->fsid.files = swab32(super->fsid.files);
  39         }
  40 }
  41
  42 static void inode_toggle_endianness(int input_big_endian, int output_big_endian,
  43                              struct cramfs_inode *inode_in,
  44                              struct cramfs_inode *inode_out)
  45 {
  46         if (input_big_endian == output_big_endian) {
  47                 memmove(inode_out, inode_in, sizeof(*inode_out));
  48         } else {
  49                 unsigned char inode_out_buf[sizeof(*inode_in)];
  50                 unsigned char *inode_in_buf = (unsigned char*)inode_in;
  51
  52                 inode_out_buf[0] = inode_in_buf[1]; /* 16 bit: mode */
  53                 inode_out_buf[1] = inode_in_buf[0];
  54
  55                 inode_out_buf[2] = inode_in_buf[3]; /* 16 bit: uid */
  56                 inode_out_buf[3] = inode_in_buf[2];
  57
  58                 inode_out_buf[4] = inode_in_buf[6]; /* 24 bit: size */
  59                 inode_out_buf[5] = inode_in_buf[5];
  60                 inode_out_buf[6] = inode_in_buf[4];
  61
  62                 inode_out_buf[7] = inode_in_buf[7]; /* 8 bit: gid width */
  63
  64                 /*
  65                  * Stop the madness! Outlaw C bitfields! They are unportable
  66                  * and nasty! See for yourself what a mess this is:
  67                  */
  68                 if (output_big_endian) {
  69                         inode_out_buf[ 8] = ( (inode_in_buf[ 8]&0x3F) << 2 ) |
  70                                 ( (inode_in_buf[11]&0xC0) >> 6 );
  71
  72                         inode_out_buf[ 9] = ( (inode_in_buf[11]&0x3F) << 2 ) |
  73                                 ( (inode_in_buf[10]&0xC0) >> 6 );
  74
  75                         inode_out_buf[10] = ( (inode_in_buf[10]&0x3F) << 2 ) |
  76                                 ( (inode_in_buf[ 9]&0xC0) >> 6 );
  77
  78                         inode_out_buf[11] = ( (inode_in_buf[ 9]&0x3F) << 2 ) |
  79                                 ( (inode_in_buf[ 8]&0xC0) >> 6 );
  80                 } else {
  81                         inode_out_buf[ 8] = ( (inode_in_buf[ 8]&0xFD) >> 2 ) |
  82                                 ( (inode_in_buf[11]&0x03) << 6 );
  83
  84                         inode_out_buf[ 9] = ( (inode_in_buf[11]&0xFD) >> 2 ) |
  85                                 ( (inode_in_buf[10]&0x03) << 6 );
  86
  87                         inode_out_buf[10] = ( (inode_in_buf[10]&0xFD) >> 2 ) |
  88                                 ( (inode_in_buf[ 9]&0x03) << 6 );
  89
  90                         inode_out_buf[11] = ( (inode_in_buf[ 9]&0xFD) >> 2 ) |
  91                                 ( (inode_in_buf[ 8]&0x03) << 6 );
  92                 }
  93                 memmove(inode_out, inode_out_buf, sizeof(*inode_out));
  94         }
  95 }
  96
  97 void inode_to_host(int from_big_endian, struct cramfs_inode *inode_in,
  98                    struct cramfs_inode *inode_out)
  99 {
 100         inode_toggle_endianness(from_big_endian, HOST_IS_BIG_ENDIAN, inode_in,
 101                                 inode_out);
 102 }
 103
 104 void inode_from_host(int to_big_endian, struct cramfs_inode *inode_in,
 105                      struct cramfs_inode *inode_out)
 106 {
 107         inode_toggle_endianness(HOST_IS_BIG_ENDIAN, to_big_endian, inode_in,
 108                                 inode_out);
 109 }