static int cloop_open(BlockDriverState *bs, QDict *options, int flags,
                      Error **errp)
{
    BDRVCloopState *s = bs->opaque;
    uint32_t offsets_size, max_compressed_block_size = 1, i;
    int ret;
    bs->read_only = 1;
    /* read header */
    ret = bdrv_pread(bs->file, 128, &s->block_size, 4);
    if (ret < 0) {
        return ret;
    s->block_size = be32_to_cpu(s->block_size);
    ret = bdrv_pread(bs->file, 128 + 4, &s->n_blocks, 4);
    if (ret < 0) {
        return ret;
    s->n_blocks = be32_to_cpu(s->n_blocks);
    /* read offsets */
    offsets_size = s->n_blocks * sizeof(uint64_t);
    s->offsets = g_malloc(offsets_size);
    ret = bdrv_pread(bs->file, 128 + 4 + 4, s->offsets, offsets_size);
    if (ret < 0) {
        goto fail;
    for(i=0;i<s->n_blocks;i++) {
        s->offsets[i] = be64_to_cpu(s->offsets[i]);
        if (i > 0) {
            uint32_t size = s->offsets[i] - s->offsets[i - 1];
            if (size > max_compressed_block_size) {
                max_compressed_block_size = size;
    /* initialize zlib engine */
    s->compressed_block = g_malloc(max_compressed_block_size + 1);
    s->uncompressed_block = g_malloc(s->block_size);
    if (inflateInit(&s->zstream) != Z_OK) {
        ret = -EINVAL;
        goto fail;
    s->current_block = s->n_blocks;
    s->sectors_per_block = s->block_size/512;
    bs->total_sectors = s->n_blocks * s->sectors_per_block;
    qemu_co_mutex_init(&s->lock);
    return 0;
fail:
    g_free(s->offsets);
    g_free(s->compressed_block);
    g_free(s->uncompressed_block);
    return ret;