aplfw/volume/fat/fatvol_getnextcluster.c

   1
   2 #include <string.h>
   3 #include "fatvol_local.h"
   4
   5
   6 FATVOL_UINT FatVol_GetNextCluster(C_FATVOL *self, FATVOL_UINT uiCluster)
   7 {
   8         FATVOL_UINT uiNextCluster = FATVOL_CLUSTER_ENDMARKER;
   9
  10         switch ( self->iFatType )
  11         {
  12         case FATVOL_TYPE_FAT12:
  13                 /* 0xffff0000 からルートディレクトリをマップ */
  14                 if ( uiCluster >= 0xffff0000 )
  15                 {
  16                         return uiCluster + 1;
  17                 }
  18
  19                 /* FAT検索 */
  20                 if ( uiCluster % 2 == 0 )
  21                 {
  22                         uiNextCluster = self->pubFatBuf[(uiCluster / 2) * 3 + 0]
  23                                                         + ((self->pubFatBuf[(uiCluster / 2) * 3 + 1] & 0x0f) << 8);
  24                 }
  25                 else
  26                 {
  27                         uiNextCluster = ((self->pubFatBuf[(uiCluster / 2) * 3 + 1] >> 4) & 0xf)
  28                                                         + (self->pubFatBuf[(uiCluster / 2) * 3 + 2] << 4);
  29                 }
  30
  31                 if ( uiNextCluster >= 0x0ff7 )
  32                 {
  33                         uiNextCluster = FATVOL_CLUSTER_ENDMARKER;
  34                 }
  35                 break;
  36
  37         case FATVOL_TYPE_FAT16:
  38                 /* 0xffff0000 からルートディレクトリをマップ */
  39                 if ( uiCluster >= 0xffff0000 )
  40                 {
  41                         return uiCluster + 1;
  42                 }
  43
  44                 /* FAT検索 */
  45                 uiNextCluster = self->pubFatBuf[uiCluster * 2] + self->pubFatBuf[uiCluster * 2 + 1] * 256;
  46                 if ( uiNextCluster >= 0xfff7 )
  47                 {
  48                         uiNextCluster = FATVOL_CLUSTER_ENDMARKER;
  49                 }
  50                 break;
  51
  52         case FATVOL_TYPE_FAT32:
  53                 uiNextCluster = self->pubFatBuf[uiCluster * 4]
  54                                 + self->pubFatBuf[uiCluster * 4 + 1] * 256
  55                                 + self->pubFatBuf[uiCluster * 4 + 2] * 256 * 256
  56                                 + self->pubFatBuf[uiCluster * 4 + 3] * 256 * 256 * 256;
  57                 break;
  58         }
  59
  60         return uiNextCluster;
  61 }
  62
  63
  64 /* end of file */