Changeset 9a5f0cb in mainline

Timestamp:

2008-04-15T06:09:32Z (17 years ago)

Author:

Jakub Jermar <jakub@…>

Branches:

lfn, master, serial, ticket/834-toolchain-update, topic/msim-upgrade, topic/simplify-dev-export

Children:

ecc83bd

Parents:

45f244b

Message:

Add fat_block_get().

File:

• uspace/srv/fs/fat/fat_ops.c (modified) (2 diffs)

uspace/srv/fs/fat/fat_ops.c

@@ -111 +111 @@
 }
 
+static void block_put(block_t *block)
+{
+        /* TODO */
+}
+
+
+#define FAT_BS(b)               ((fat_bs_t *)((b)->data))
+
+#define FAT_CLST_FIRST  0x0002
+#define FAT_CLST_BAD    0xfff7
+#define FAT_CLST_LAST1  0xfff8
+#define FAT_CLST_LAST8  0xffff
+
+/** Convert cluster number to an index within a FAT.
+ *
+ * Format Identifier and cluster numbering is considered.
+ */
+#define C2FAT_IDX(c)    (1 + (c) - FAT_CLST_FIRST)
+
 static block_t *fat_block_get(dev_handle_t dev_handle, fs_index_t index,
-    off_t offset) {
-        return NULL;    /* TODO */
-}
-
-static void block_put(block_t *block)
-{
-        /* TODO */
+    off_t offset)
+{
+        block_t *bb;
+        block_t *b;
+        unsigned bps;
+        unsigned spc;
+        unsigned rscnt;         /* block address of the first FAT */
+        unsigned fatcnt;
+        unsigned rde;
+        unsigned rds;           /* root directory size */
+        unsigned sf;
+        unsigned ssa;           /* size of the system area */
+        unsigned clusters;
+        unsigned clst = index;
+        unsigned i;
+
+        bb = block_get(dev_handle, BS_BLOCK);
+        bps = uint16_t_le2host(FAT_BS(bb)->bps);
+        spc = FAT_BS(bb)->spc;
+        rscnt = uint16_t_le2host(FAT_BS(bb)->rscnt);
+        fatcnt = FAT_BS(bb)->fatcnt;
+        rde = uint16_t_le2host(FAT_BS(bb)->root_ent_max);
+        sf = uint16_t_le2host(FAT_BS(bb)->sec_per_fat);
+        block_put(bb);
+
+        rds = (sizeof(fat_dentry_t) * rde) / bps;
+        rds += ((sizeof(fat_dentry_t) * rde) % bps != 0);
+        ssa = rscnt + fatcnt * sf + rds;
+
+        if (!index) {
+                /* root directory special case */
+                assert(offset < rds);
+                b = block_get(dev_handle, rscnt + fatcnt * sf + offset);
+                return b;
+        }
+
+        clusters = offset / spc; 
+        for (i = 0; i < clusters; i++) {
+                unsigned fsec;  /* sector offset relative to FAT1 */
+                unsigned fidx;  /* FAT1 entry index */
+
+                assert(clst >= FAT_CLST_FIRST && clst < FAT_CLST_BAD);
+                fsec = (C2FAT_IDX(clst) * sizeof(uint16_t)) / bps;
+                fidx = C2FAT_IDX(clst) % (bps / sizeof(uint16_t));
+                /* read FAT1 */
+                b = block_get(dev_handle, rscnt + fsec);
+                clst = uint16_t_le2host(((uint16_t *)b->data)[fidx]);
+                assert(clst != FAT_CLST_BAD);
+                assert(clst < FAT_CLST_LAST1);
+                block_put(b);
+        }
+
+        b = block_get(dev_handle, ssa + (clst - FAT_CLST_FIRST) * spc +
+            offset % spc);
+
+        return b;
 }
 
@@ -143 +211 @@
         bb = block_get(dev_handle, BS_BLOCK);
         assert(bb != NULL);
-        bps = uint16_t_le2host(((fat_bs_t *)bb->data)->bps);
+        bps = uint16_t_le2host(FAT_BS(bb)->bps);
         block_put(bb);