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)
65 case FAT12: eoc = EOC_FAT12; break;
66 case FAT16: eoc = EOC_FAT16; break;
67 case FAT32: eoc = EOC_FAT32; break;
72 if( Disk->ClusterCount <= giFAT_MaxCachedClusters )
74 int bFoundCluster = 0;
75 Mutex_Acquire(&Disk->lFAT);
78 for(ret = Previous; ret < Disk->ClusterCount; ret++)
80 if(Disk->FATCache[ret] != 0) {
88 for(ret = 0; ret < Previous; ret++)
90 if(Disk->FATCache[ret] == 0) {
99 Disk->FATCache[ret] = eoc;
101 Disk->FATCache[Previous] = ret;
108 Mutex_Release(&Disk->lFAT);
115 Uint32 base = Disk->bootsect.resvSectCount*512;
116 int block = 0, block_ofs = 0;
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;
126 Mutex_Acquire(&Disk->lFAT);
131 block = Previous / ents_per_block_12;
136 // Search within the same block as the previous cluster first
138 VFS_ReadAt(Disk->fileHandle, base + block, block_size, sector_data);
139 for( block_ofs = 0; block_ofs < ents_per_block_12; block_ofs ++ )
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;
151 // Check for early break from the above loop
152 if( block_ofs != ents_per_block_12 )
157 if( block == block_count_12 )
159 } while( block != first_block );
161 if( ret != 0 ) // TODO: Could cluster 0 be valid?
163 // Write back changes to this part of the FAT
164 VFS_WriteAt(Disk->fileHandle, base + block, block_size, sector_data);
166 // Note the new cluster in the chain
167 VFS_ReadAt(Disk->fileHandle, base + (Previous>>1)*3, 3, &val);
176 VFS_WriteAt(Disk->fileHandle, base + (Previous>>1)*3, 3, &val);
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);
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);
190 Mutex_Release(&Disk->lFAT);
198 * \brief Free's a cluster
199 * \return The original contents of the cluster
201 Uint32 FAT_int_FreeCluster(tFAT_VolInfo *Disk, Uint32 Cluster)
205 Mutex_Acquire(&Disk->lFAT);
207 if( Disk->ClusterCount <= giFAT_MaxCachedClusters )
210 ret = Disk->FATCache[Cluster];
211 Disk->FATCache[Cluster] = 0;
217 Uint32 ofs = Disk->bootsect.resvSectCount*512;
221 VFS_ReadAt(Disk->fileHandle, ofs+(Cluster>>1)*3, 3, &val);
223 ret = val & 0xFFF0000;
230 VFS_WriteAt(Disk->fileHandle, ofs+(Cluster>>1)*3, 3, &val);
233 VFS_ReadAt(Disk->fileHandle, ofs+Cluster*2, 2, &ret);
235 VFS_WriteAt(Disk->fileHandle, ofs+Cluster*2, 2, &val);
238 VFS_ReadAt(Disk->fileHandle, ofs+Cluster*4, 4, &ret);
240 VFS_WriteAt(Disk->fileHandle, ofs+Cluster*2, 2, &val);
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;
255 * ====================
257 * ====================
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
265 void FAT_int_ReadCluster(tFAT_VolInfo *Disk, Uint32 Cluster, int Length, void *Buffer)
267 ENTER("pDisk xCluster iLength pBuffer", Disk, Cluster, Length, Buffer);
270 (Disk->firstDataSect + (Cluster-2)*Disk->bootsect.spc )
271 * Disk->bootsect.bps,
280 * \brief Write a cluster to disk
282 void FAT_int_WriteCluster(tFAT_VolInfo *Disk, Uint32 Cluster, const void *Buffer)
284 ENTER("pDisk xCluster pBuffer", Disk, Cluster, Buffer);
287 (Disk->firstDataSect + (Cluster-2)*Disk->bootsect.spc )
288 * Disk->bootsect.bps,
289 Disk->BytesPerCluster,