unsigned int a_inode_index = FS_MAXFILEBLOCKS;

unsigned int b_inode_index = FS_MAXFILEBLOCKS;

unsigned int a_dir_index = FS_DIRENTRIES;

fs_direntry dir_block[FS_DIRENTRIES];

fs_direntry dir_a[FS_DIRENTRIES];

fs_direntry dir_b[FS_DIRENTRIES];

for ( int i = 0; i < dir_inode.size / FS_BLOCKSIZE; i++ ) {

disk_readblock(dir_inode.blocks[i], dir_block);

for ( int j = 0; j < FS_DIRENTRIES; j++ ) {

if ( dir_block[j].inode_block != 0 ) {

if ( strcmp(dir_block[j].name, a) ) {

a_inode_index = i;

a_dir_index = j;

memcpy(dir_a, dir_block, FS_BLOCKSIZE);

strcpy(dir_a[j].name, b);

}

if ( strcmp(dir_block[j].name, b) ) {

b_inode_index = i;

memcpy(dir_b, dir_block, FS_BLOCKSIZE);

mark_all_file_blocks_free(dir_b[j].inode_block);

dir_b[j].inode_block = 0;

}

}

}

if ( a_inode_index != FS_MAXFILEBLOCKS && b_inode_index != FS_MAXFILEBLOCKS

&& a_inode_index == b_inode_index ) {

strcpy(dir_b[a_dir_index].name, b);

disk_writeblock(dir_inode.blocks[b_inode_index], dir_b);

return 0;

}

}

if ( a_inode_index == FS_MAXFILEBLOCKS ) {

return -1;

}

if ( b_inode_index == FS_MAXFILEBLOCKS ) {

disk_writeblock(dir_inode.blocks[a_inode_index], dir_a);

return 0;

}

unsigned int old_a_dir_block = dir_inode.blocks[a_inode_index];

unsigned int old_b_dir_block = dir_inode.blocks[b_inode_index];

unsigned int new_a_dir_block = get_free_block();

unsigned int new_b_dir_block = get_free_block();

dir_inode.blocks[a_inode_index] = new_a_dir_block;

dir_inode.blocks[b_inode_index] = new_b_dir_block;

disk_writeblock(new_a_dir_block, dir_a);

disk_writeblock(new_b_dir_block, dir_b);

disk_writeblock(dir_inode, 0);

mark_block_free(old_a_dir_block);

mark_block_free(old_b_dir_block);

return 0;

}