2 * Acess2 FAT12/16/32 Driver
3 * - By John Hodge (thePowersGang)
6 * - FAT Manipulation and Cluster IO
15 * \fn Uint32 FAT_int_GetFatValue(tFAT_VolInfo *Disk, Uint32 cluster)
16 * \brief Fetches a value from the FAT
18 Uint32 FAT_int_GetFatValue(tFAT_VolInfo *Disk, Uint32 cluster)
22 ENTER("pDisk xCluster", Disk, cluster);
23 Mutex_Acquire( &Disk->lFAT );
25 if( Disk->ClusterCount <= giFAT_MaxCachedClusters )
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;
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;
44 VFS_ReadAt(Disk->fileHandle, ofs+cluster*4, 4, &val);
45 if(val == EOC_FAT32) val = -1;
50 Mutex_Release( &Disk->lFAT );
57 * \brief Allocate a new cluster
59 Uint32 FAT_int_AllocateCluster(tFAT_VolInfo *Disk, Uint32 Previous)
64 if( Disk->ClusterCount <= giFAT_MaxCachedClusters )
66 int bFoundCluster = 0;
71 case FAT12: eoc = EOC_FAT12; break;
72 case FAT16: eoc = EOC_FAT16; break;
73 case FAT32: eoc = EOC_FAT32; break;
77 Mutex_Acquire(&Disk->lFAT);
80 for(ret = Previous; ret < Disk->ClusterCount; ret++)
82 if(Disk->FATCache[ret] != 0) {
90 for(ret = 0; ret < Previous; ret++)
92 if(Disk->FATCache[ret] == 0) {
101 Disk->FATCache[ret] = eoc;
103 Disk->FATCache[Previous] = ret;
110 Mutex_Release(&Disk->lFAT);
117 Uint32 base = Disk->bootsect.resvSectCount*512;
118 int block = 0, block_ofs = 0;
120 const int block_size = 512*3;
121 const int ents_per_block_12 = block_size * 2 / 3; // 1.5 bytes per entry
122 // const int ents_per_block_16 = block_size / 2; // 2 bytes per entry
123 // const int ents_per_block_32 = block_size / 4; // 4 bytes per entry
124 int block_count_12 = DivUp(Disk->ClusterCount, ents_per_block_12);
125 Uint8 sector_data[block_size+1];
126 sector_data[block_size] = 0;
128 Mutex_Acquire(&Disk->lFAT);
133 block = Previous / ents_per_block_12;
138 // Search within the same block as the previous cluster first
140 VFS_ReadAt(Disk->fileHandle, base + block, block_size, sector_data);
141 for( block_ofs = 0; block_ofs < ents_per_block_12; block_ofs ++ )
143 Uint32 *valptr = (void*)( sector_data + block_ofs / 2 * 3 );
144 int bitofs = 12 * (block_ofs % 2);
145 // LOG("%i:%i - FAT Ent 0x%03x", block, block_ofs, (*valptr>>bitofs) & 0xFFF);
146 if( ((*valptr >> bitofs) & 0xFFF) == 0 ) {
147 // Found a free cluster
148 *valptr |= EOC_FAT12 << bitofs;
149 ret = block * ents_per_block_12 + block_ofs;
153 // Check for early break from the above loop
154 if( block_ofs != ents_per_block_12 )
159 if( block == block_count_12 )
161 } while( block != first_block );
163 if( ret != 0 ) // TODO: Could cluster 0 be valid?
165 // Write back changes to this part of the FAT
166 VFS_WriteAt(Disk->fileHandle, base + block, block_size, sector_data);
168 // Note the new cluster in the chain
169 VFS_ReadAt(Disk->fileHandle, base + (Previous>>1)*3, 3, &val);
178 VFS_WriteAt(Disk->fileHandle, base + (Previous>>1)*3, 3, &val);
182 Log_Warning("FAT", "TODO: Implement cluster allocation with FAT16");
183 // VFS_ReadAt(Disk->fileHandle, ofs+Previous*2, 2, &ret);
184 // VFS_WriteAt(Disk->fileHandle, ofs+ret*2, 2, &eoc);
187 Log_Warning("FAT", "TODO: Implement cluster allocation with FAT32");
188 // VFS_ReadAt(Disk->fileHandle, ofs+Previous*4, 4, &ret);
189 // VFS_WriteAt(Disk->fileHandle, ofs+ret*4, 4, &eoc);
192 Mutex_Release(&Disk->lFAT);
200 * \brief Free's a cluster
201 * \return The original contents of the cluster
203 Uint32 FAT_int_FreeCluster(tFAT_VolInfo *Disk, Uint32 Cluster)
207 if( Cluster < 2 || Cluster > Disk->ClusterCount ) // oops?
209 Log_Notice("FAT", "Cluster 0x%x is out of range (2 ... 0x%x)",
210 Cluster, Disk->ClusterCount-1);
214 Mutex_Acquire(&Disk->lFAT);
216 if( Disk->ClusterCount <= giFAT_MaxCachedClusters )
219 ret = Disk->FATCache[Cluster];
220 Disk->FATCache[Cluster] = 0;
226 Uint32 ofs = Disk->bootsect.resvSectCount*512;
230 VFS_ReadAt(Disk->fileHandle, ofs+(Cluster>>1)*3, 3, &val);
231 val = LittleEndian32(val);
233 ret = (val >> 12) & 0xFFF;
240 val = LittleEndian32(val);
241 VFS_WriteAt(Disk->fileHandle, ofs+(Cluster>>1)*3, 3, &val);
244 VFS_ReadAt(Disk->fileHandle, ofs+Cluster*2, 2, &ret);
245 ret = LittleEndian16(ret);
247 VFS_WriteAt(Disk->fileHandle, ofs+Cluster*2, 2, &val);
250 VFS_ReadAt(Disk->fileHandle, ofs+Cluster*4, 4, &ret);
251 ret = LittleEndian32(ret);
253 VFS_WriteAt(Disk->fileHandle, ofs+Cluster*2, 4, &val);
259 Mutex_Release(&Disk->lFAT);
260 LOG("ret = %07x, eoc = %07x", ret, EOC_FAT12);
262 Log_Notice("FAT", "Cluster 0x%x was already free", Cluster);
265 if(Disk->type == FAT12 && ret == EOC_FAT12) ret = -1;
266 if(Disk->type == FAT16 && ret == EOC_FAT16) ret = -1;
267 if(Disk->type == FAT32 && ret == EOC_FAT32) ret = -1;
268 LOG("ret = %07x", ret);
274 * ====================
276 * ====================
279 * \brief Read a cluster
280 * \param Disk Disk (Volume) to read from
281 * \param Length Length to read
282 * \param Buffer Destination for read data
284 void FAT_int_ReadCluster(tFAT_VolInfo *Disk, Uint32 Cluster, int Length, void *Buffer)
286 ENTER("pDisk xCluster iLength pBuffer", Disk, Cluster, Length, Buffer);
289 (Disk->firstDataSect + (Cluster-2)*Disk->bootsect.spc )
290 * Disk->bootsect.bps,
299 * \brief Write a cluster to disk
301 void FAT_int_WriteCluster(tFAT_VolInfo *Disk, Uint32 Cluster, const void *Buffer)
303 ENTER("pDisk xCluster pBuffer", Disk, Cluster, Buffer);
306 (Disk->firstDataSect + (Cluster-2)*Disk->bootsect.spc )
307 * Disk->bootsect.bps,
308 Disk->BytesPerCluster,