ext2: add lseek and L2 read support

fs/ext2/block.c

@@ -126,21 +126,40 @@ uint32_t ext2_inode_get_index(struct fs *ext2, struct ext2_inode *inode, uint32_
     _assert(data);
 
     uint32_t p = data->block_size / sizeof(uint32_t);
-    uint32_t a, b, c, d, e, f, g;
     uint32_t ptrs[p];
 
     if (index < EXT2_DIRECT_BLOCKS) {
         return inode->direct_blocks[index];
-    } else if (index < EXT2_DIRECT_BLOCKS + p) {
+    }
+
+    // Fits in L1?
+    index -= EXT2_DIRECT_BLOCKS;
+    if (index < p) {
         if (!inode->indirect_block_l1) {
-            panic("Read beyond end of file\n");
+            panic("Read beyond end of file (L1.1)\n");
         }
 
         _assert(ext2_read_block(ext2, ptrs, inode->indirect_block_l1) == 0);
-        return ptrs[index - EXT2_DIRECT_BLOCKS];
-    } else {
-        panic("TODO L2+\n");
+        return ptrs[index];
     }
+
+    // Fits in L2?
+    index -= p;
+    if (index < p * p) {
+        uint32_t index_l1 = index / p;
+        uint32_t index_l0 = index % p;
+        if (!inode->indirect_block_l2) {
+            panic("Read beyond end of the file (L2.2)\n");
+        }
+        _assert(ext2_read_block(ext2, ptrs, inode->indirect_block_l2) == 0);
+        if (!ptrs[index_l1]) {
+            panic("Read beyond end of the file (L2.1)\n");
+        }
+        _assert(ext2_read_block(ext2, ptrs, ptrs[index_l1]) == 0);
+        return ptrs[index_l0];
+    }
+
+    panic("TODO: L3 support\n");
 }
 
 int ext2_inode_set_index(struct fs *ext2, struct ext2_inode *inode, uint32_t ino, uint32_t index, uint32_t value) {

fs/ext2/node.c

@@ -18,6 +18,7 @@
 static int ext2_vnode_find(struct vnode *at, const char *name, struct vnode **res);
 static ssize_t ext2_vnode_read(struct ofile *fd, void *buf, size_t count);
 static ssize_t ext2_vnode_write(struct ofile *fd, const void *buf, size_t count);
+static off_t ext2_vnode_lseek(struct ofile *fd, off_t pos, int whence);
 static int ext2_vnode_open(struct ofile *fd, int opt);
 static int ext2_vnode_opendir(struct ofile *fd);
 static int ext2_vnode_chmod(struct vnode *vn, mode_t new_mode);
@@ -48,7 +49,8 @@ struct vnode_operations g_ext2_vnode_ops = {
     .open = ext2_vnode_open,
     .read = ext2_vnode_read,
     .write = ext2_vnode_write,
-    .truncate = ext2_vnode_truncate
+    .truncate = ext2_vnode_truncate,
+    .lseek = ext2_vnode_lseek,
 };
 
 ////
@@ -168,6 +170,33 @@ static ssize_t ext2_vnode_read(struct ofile *fd, void *buf, size_t count) {
     return bread;
 }
 
+static off_t ext2_vnode_lseek(struct ofile *fd, off_t pos, int whence) {
+    off_t calc;
+    struct vnode *node = fd->file.vnode;
+    _assert(node);
+    struct ext2_inode *inode = node->fs_data;
+    _assert(inode);
+
+    switch (whence) {
+    case SEEK_SET:
+        calc = pos;
+        break;
+    case SEEK_CUR:
+        calc = pos + fd->file.pos;
+        break;
+    default:
+        panic("Invalid seek whence: %d\n", whence);
+    }
+
+    if (calc < 0 || calc >= inode->size_lower) {
+        return (off_t) -ESPIPE;
+    }
+
+    fd->file.pos = calc;
+
+    return fd->file.pos;
+}
+
 static int ext2_vnode_opendir(struct ofile *fd) {
     _assert(fd && fd->file.vnode);
     _assert(fd->file.vnode->type == VN_DIR);