Changeset ad34feb in mainline for uspace/lib/ext2/libext2_filesystem.c

Timestamp:

2011-02-23T23:07:28Z (14 years ago)

Author:

Martin Sucha <sucha14@…>

Branches:

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

Children:

102d400

Parents:

a54af66

Message:

Implement reading of blocks from inode in libext2

File:

• uspace/lib/ext2/libext2_filesystem.c (modified) (2 diffs)

uspace/lib/ext2/libext2_filesystem.c

@@ -41 +41 @@
 #include <libblock.h>
 #include <malloc.h>
+#include <assert.h>
 
 /**
@@ -255 +256 @@
 
 /**
+ * Find a filesystem block number where iblock-th data block
+ * of the given inode is located.
+ * 
+ * @return              EOK on success or negative error code on failure
+ */
+int ext2_filesystem_get_inode_data_block_index(ext2_filesystem_t *fs, ext2_inode_t* inode,
+    aoff64_t iblock, uint32_t* fblock)
+{
+        int rc;
+        aoff64_t limits[4];
+        uint32_t block_ids_per_block;
+        aoff64_t blocks_per_level[4];
+        uint32_t offset_in_block;
+        uint32_t current_block;
+        aoff64_t block_offset_in_level;
+        int i;
+        int level;
+        block_t *block;
+        
+        if (iblock < EXT2_INODE_DIRECT_BLOCKS) {
+                current_block = ext2_inode_get_direct_block(inode, (uint32_t)iblock);
+                if (current_block == 0) {
+                        return EIO;
+                }
+                *fblock = current_block;
+                return EOK;
+        }
+        
+        // Compute limits for indirect block levels
+        // TODO: compute this once when loading filesystem and store in ext2_filesystem_t
+        block_ids_per_block = ext2_superblock_get_block_size(fs->superblock) / sizeof(uint32_t);
+        limits[0] = EXT2_INODE_DIRECT_BLOCKS;
+        blocks_per_level[0] = 1;
+        for (i = 1; i < 4; i++) {
+                blocks_per_level[i]  = blocks_per_level[i-1] *
+                    block_ids_per_block;
+                limits[i] = limits[i-1] + blocks_per_level[i];
+        }
+        
+        // Determine the indirection level needed to get the desired block
+        level = -1;
+        for (i = 1; i < 4; i++) {
+                if (iblock < limits[i]) {
+                        level = i;
+                        break;
+                }
+        }
+        
+        if (level == -1) {
+                return EIO;
+        }
+        
+        block_offset_in_level = iblock - limits[level-1];
+        current_block = ext2_inode_get_indirect_block(inode, level-1);
+        offset_in_block = block_offset_in_level / blocks_per_level[level-1];
+        
+        while (level > 0) {
+                rc = block_get(&block, fs->device, current_block, 0);
+                if (rc != EOK) {
+                        return rc;
+                }
+                
+                assert(offset_in_block < block_ids_per_block);
+                current_block = ((uint32_t*)block->data)[offset_in_block];
+                
+                rc = block_put(block);
+                if (rc != EOK) {
+                        return rc;
+                }
+                
+                if (current_block == 0) {
+                        return EIO;
+                }
+                
+                level -= 1;
+                
+                if (level == 0) {
+                        break;
+                }
+                
+                offset_in_block = block_offset_in_level / blocks_per_level[level-1];
+                block_offset_in_level %= blocks_per_level[level-1];
+        }
+        
+        *fblock = current_block;
+        
+        return EOK;
+}
+
+/**
  * Finalize an instance of filesystem
  *