KernelLand/Modules/Filesystems/FAT/fatio.c

   1 /*
   2  * Acess2 FAT12/16/32 Driver
   3  * - By John Hodge (thePowersGang)
   4  *
   5  * fatio.c
   6  * - FAT Manipulation and Cluster IO
   7  */
   8 #define DEBUG   1
   9 #include <acess.h>
  10 #include <vfs.h>
  11 #include "common.h"
  12
  13 // === CODE ===
  14 /**
  15  * \fn Uint32 FAT_int_GetFatValue(tFAT_VolInfo *Disk, Uint32 cluster)
  16  * \brief Fetches a value from the FAT
  17  */
  18 Uint32 FAT_int_GetFatValue(tFAT_VolInfo *Disk, Uint32 cluster)
  19 {
  20         Uint32  val = 0;
  21         Uint32  ofs;
  22         ENTER("pDisk xCluster", Disk, cluster);
  23         Mutex_Acquire( &Disk->lFAT );
  24         #if CACHE_FAT
  25         if( Disk->ClusterCount <= giFAT_MaxCachedClusters )
  26         {
  27                 val = Disk->FATCache[cluster];
  28                 if(Disk->type == FAT12 && val == EOC_FAT12)     val = -1;
  29                 if(Disk->type == FAT16 && val == EOC_FAT16)     val = -1;
  30                 if(Disk->type == FAT32 && val == EOC_FAT32)     val = -1;
  31         }
  32         else
  33         {
  34         #endif
  35                 ofs = Disk->bootsect.resvSectCount*512;
  36                 if(Disk->type == FAT12) {
  37                         VFS_ReadAt(Disk->fileHandle, ofs+(cluster/2)*3, 3, &val);
  38                         val = (cluster & 1 ? val>>12 : val & 0xFFF);
  39                         if(val == EOC_FAT12)    val = -1;
  40                 } else if(Disk->type == FAT16) {
  41                         VFS_ReadAt(Disk->fileHandle, ofs+cluster*2, 2, &val);
  42                         if(val == EOC_FAT16)    val = -1;
  43                 } else {
  44                         VFS_ReadAt(Disk->fileHandle, ofs+cluster*4, 4, &val);
  45                         if(val == EOC_FAT32)    val = -1;
  46                 }
  47         #if CACHE_FAT
  48         }
  49         #endif /*CACHE_FAT*/
  50         Mutex_Release( &Disk->lFAT );
  51         LEAVE('x', val);
  52         return val;
  53 }
  54
  55 #if SUPPORT_WRITE
  56 /**
  57  * \brief Allocate a new cluster
  58  */
  59 Uint32 FAT_int_AllocateCluster(tFAT_VolInfo *Disk, Uint32 Previous)
  60 {
  61         Uint32  ret = -1, eoc;
  62
  63         switch(Disk->type)
  64         {
  65         case FAT12:     eoc = EOC_FAT12;        break;
  66         case FAT16:     eoc = EOC_FAT16;        break;
  67         case FAT32:     eoc = EOC_FAT32;        break;
  68         default:        return 0;
  69         }
  70
  71         #if CACHE_FAT
  72         if( Disk->ClusterCount <= giFAT_MaxCachedClusters )
  73         {
  74                  int    bFoundCluster = 0;
  75                 Mutex_Acquire(&Disk->lFAT);
  76                 if( Previous != -1 )
  77                 {
  78                         for(ret = Previous; ret < Disk->ClusterCount; ret++)
  79                         {
  80                                 if(Disk->FATCache[ret] != 0) {
  81                                         bFoundCluster = 1;
  82                                         break;
  83                                 }
  84                         }
  85                 }
  86                 if( !bFoundCluster )
  87                 {
  88                         for(ret = 0; ret < Previous; ret++)
  89                         {
  90                                 if(Disk->FATCache[ret] == 0) {
  91                                         bFoundCluster = 1;
  92                                         break;
  93                                 }
  94                         }
  95                 }
  96
  97                 if(bFoundCluster)
  98                 {
  99                         Disk->FATCache[ret] = eoc;
 100                         if( Previous != -1 )
 101                                 Disk->FATCache[Previous] = ret;
 102                 }
 103                 else
 104                 {
 105                         ret = 0;
 106                 }
 107
 108                 Mutex_Release(&Disk->lFAT);
 109                 return ret;
 110         }
 111         else
 112         {
 113         #endif
 114                 Uint32  val = 0;
 115                 Uint32  base = Disk->bootsect.resvSectCount*512;
 116                  int    block = 0, block_ofs = 0;
 117                  int    first_block;
 118                 const int       block_size = 512*3;
 119                 const int       ents_per_block_12 = block_size * 2 / 3; // 1.5 bytes per entry
 120 //              const int       ents_per_block_16 = block_size / 2;     // 2 bytes per entry
 121 //              const int       ents_per_block_32 = block_size / 4;     // 4 bytes per entry
 122                  int    block_count_12 = DivUp(Disk->ClusterCount, ents_per_block_12);
 123                 Uint8   sector_data[block_size+1];
 124                 sector_data[block_size] = 0;
 125
 126                 Mutex_Acquire(&Disk->lFAT);
 127                 switch(Disk->type)
 128                 {
 129                 case FAT12:
 130                         if( Previous != -1 )
 131                                 block = Previous / ents_per_block_12;
 132                         else
 133                                 block = 0;
 134                         first_block = block;
 135
 136                         // Search within the same block as the previous cluster first
 137                         do {
 138                                 VFS_ReadAt(Disk->fileHandle, base + block, block_size, sector_data);
 139                                 for( block_ofs = 0; block_ofs < ents_per_block_12; block_ofs ++ )
 140                                 {
 141                                         Uint32  *valptr = (void*)( sector_data + block_ofs / 2 * 3 );
 142                                          int    bitofs = 12 * (block_ofs % 2);
 143 //                                      LOG("%i:%i - FAT Ent 0x%03x", block, block_ofs, (*valptr>>bitofs) & 0xFFF);
 144                                         if( ((*valptr >> bitofs) & 0xFFF) == 0 ) {
 145                                                 // Found a free cluster
 146                                                 *valptr |= EOC_FAT12 << bitofs;
 147                                                 ret = block * ents_per_block_12 + block_ofs;
 148                                                 break;
 149                                         }
 150                                 }
 151                                 // Check for early break from the above loop
 152                                 if( block_ofs != ents_per_block_12 )
 153                                         break;
 154
 155                                 // Next block please
 156                                 block ++;
 157                                 if( block == block_count_12 )
 158                                         block = 0;
 159                         } while( block != first_block );
 160
 161                         if( ret != 0 )  // TODO: Could cluster 0 be valid?
 162                         {
 163                                 // Write back changes to this part of the FAT
 164                                 VFS_WriteAt(Disk->fileHandle, base + block, block_size, sector_data);
 165
 166                                 // Note the new cluster in the chain
 167                                 VFS_ReadAt(Disk->fileHandle, base + (Previous>>1)*3, 3, &val);
 168                                 if( ret & 1 ) {
 169                                         val &= 0x000FFF;
 170                                         val |= ret << 12;
 171                                 }
 172                                 else {
 173                                         val &= 0xFFF000;
 174                                         val |= ret << 0;
 175                                 }
 176                                 VFS_WriteAt(Disk->fileHandle, base + (Previous>>1)*3, 3, &val);
 177                         }
 178                         break;
 179                 case FAT16:
 180                         Log_Warning("FAT", "TODO: Implement cluster allocation with FAT16");
 181 //                      VFS_ReadAt(Disk->fileHandle, ofs+Previous*2, 2, &ret);
 182 //                      VFS_WriteAt(Disk->fileHandle, ofs+ret*2, 2, &eoc);
 183                         break;
 184                 case FAT32:
 185                         Log_Warning("FAT", "TODO: Implement cluster allocation with FAT32");
 186 //                      VFS_ReadAt(Disk->fileHandle, ofs+Previous*4, 4, &ret);
 187 //                      VFS_WriteAt(Disk->fileHandle, ofs+ret*4, 4, &eoc);
 188                         break;
 189                 }
 190                 Mutex_Release(&Disk->lFAT);
 191                 return ret;
 192         #if CACHE_FAT
 193         }
 194         #endif
 195 }
 196
 197 /**
 198  * \brief Free's a cluster
 199  * \return The original contents of the cluster
 200  */
 201 Uint32 FAT_int_FreeCluster(tFAT_VolInfo *Disk, Uint32 Cluster)
 202 {
 203         Uint32  ret;
 204
 205         Mutex_Acquire(&Disk->lFAT);
 206         #if CACHE_FAT
 207         if( Disk->ClusterCount <= giFAT_MaxCachedClusters )
 208         {
 209
 210                 ret = Disk->FATCache[Cluster];
 211                 Disk->FATCache[Cluster] = 0;
 212         }
 213         else
 214         {
 215         #endif
 216                 Uint32  val;
 217                 Uint32  ofs = Disk->bootsect.resvSectCount*512;
 218                 switch(Disk->type)
 219                 {
 220                 case FAT12:
 221                         VFS_ReadAt(Disk->fileHandle, ofs+(Cluster>>1)*3, 3, &val);
 222                         if( Cluster & 1 ) {
 223                                 ret = val & 0xFFF0000;
 224                                 val &= 0xFFF;
 225                         }
 226                         else {
 227                                 ret = val & 0xFFF;
 228                                 val &= 0xFFF000;
 229                         }
 230                         VFS_WriteAt(Disk->fileHandle, ofs+(Cluster>>1)*3, 3, &val);
 231                         break;
 232                 case FAT16:
 233                         VFS_ReadAt(Disk->fileHandle, ofs+Cluster*2, 2, &ret);
 234                         val = 0;
 235                         VFS_WriteAt(Disk->fileHandle, ofs+Cluster*2, 2, &val);
 236                         break;
 237                 case FAT32:
 238                         VFS_ReadAt(Disk->fileHandle, ofs+Cluster*4, 4, &ret);
 239                         val = 0;
 240                         VFS_WriteAt(Disk->fileHandle, ofs+Cluster*2, 2, &val);
 241                         break;
 242                 }
 243         #if CACHE_FAT
 244         }
 245         #endif
 246         Mutex_Release(&Disk->lFAT);
 247         if(Disk->type == FAT12 && ret == EOC_FAT12)     ret = -1;
 248         if(Disk->type == FAT16 && ret == EOC_FAT16)     ret = -1;
 249         if(Disk->type == FAT32 && ret == EOC_FAT32)     ret = -1;
 250         return ret;
 251 }
 252 #endif
 253
 254 /*
 255  * ====================
 256  *      Cluster IO
 257  * ====================
 258  */
 259 /**
 260  * \brief Read a cluster
 261  * \param Disk  Disk (Volume) to read from
 262  * \param Length        Length to read
 263  * \param Buffer        Destination for read data
 264  */
 265 void FAT_int_ReadCluster(tFAT_VolInfo *Disk, Uint32 Cluster, int Length, void *Buffer)
 266 {
 267         ENTER("pDisk xCluster iLength pBuffer", Disk, Cluster, Length, Buffer);
 268         VFS_ReadAt(
 269                 Disk->fileHandle,
 270                 (Disk->firstDataSect + (Cluster-2)*Disk->bootsect.spc )
 271                         * Disk->bootsect.bps,
 272                 Length,
 273                 Buffer
 274                 );
 275         LEAVE('-');
 276 }
 277
 278 #if SUPPORT_WRITE
 279 /**
 280  * \brief Write a cluster to disk
 281  */
 282 void FAT_int_WriteCluster(tFAT_VolInfo *Disk, Uint32 Cluster, const void *Buffer)
 283 {
 284         ENTER("pDisk xCluster pBuffer", Disk, Cluster, Buffer);
 285         VFS_WriteAt(
 286                 Disk->fileHandle,
 287                 (Disk->firstDataSect + (Cluster-2)*Disk->bootsect.spc )
 288                         * Disk->bootsect.bps,
 289                 Disk->BytesPerCluster,
 290                 Buffer
 291                 );
 292         LEAVE('-');
 293 }
 294 #endif