static int qcow_create(const char *filename, int64_t total_size,

                      const char *backing_file, int flags)

{

    int fd, header_size, backing_filename_len, l1_size, i, shift, l2_bits;

    QCowHeader header;

    uint64_t tmp, offset;

    QCowCreateState s1, *s = &s1;



    memset(s, 0, sizeof(*s));



    fd = open(filename, O_WRONLY | O_CREAT | O_TRUNC | O_BINARY, 0644);

    if (fd < 0)

        return -1;

    memset(&header, 0, sizeof(header));

    header.magic = cpu_to_be32(QCOW_MAGIC);

    header.version = cpu_to_be32(QCOW_VERSION);

    header.size = cpu_to_be64(total_size * 512);

    header_size = sizeof(header);

    backing_filename_len = 0;

    if (backing_file) {

        header.backing_file_offset = cpu_to_be64(header_size);

        backing_filename_len = strlen(backing_file);

        header.backing_file_size = cpu_to_be32(backing_filename_len);

        header_size += backing_filename_len;

    }

    s->cluster_bits = 12;  /* 4 KB clusters */

    s->cluster_size = 1 << s->cluster_bits;

    header.cluster_bits = cpu_to_be32(s->cluster_bits);

    header_size = (header_size + 7) & ~7;

    if (flags & BLOCK_FLAG_ENCRYPT) {

        header.crypt_method = cpu_to_be32(QCOW_CRYPT_AES);

    } else {

        header.crypt_method = cpu_to_be32(QCOW_CRYPT_NONE);

    }

    l2_bits = s->cluster_bits - 3;

    shift = s->cluster_bits + l2_bits;

    l1_size = (((total_size * 512) + (1LL << shift) - 1) >> shift);

    offset = align_offset(header_size, s->cluster_size);

    s->l1_table_offset = offset;

    header.l1_table_offset = cpu_to_be64(s->l1_table_offset);

    header.l1_size = cpu_to_be32(l1_size);

    offset += align_offset(l1_size * sizeof(uint64_t), s->cluster_size);



    s->refcount_table = qemu_mallocz(s->cluster_size);

    s->refcount_block = qemu_mallocz(s->cluster_size);



    s->refcount_table_offset = offset;

    header.refcount_table_offset = cpu_to_be64(offset);

    header.refcount_table_clusters = cpu_to_be32(1);

    offset += s->cluster_size;



    s->refcount_table[0] = cpu_to_be64(offset);

    s->refcount_block_offset = offset;

    offset += s->cluster_size;



    /* update refcounts */

    create_refcount_update(s, 0, header_size);

    create_refcount_update(s, s->l1_table_offset, l1_size * sizeof(uint64_t));

    create_refcount_update(s, s->refcount_table_offset, s->cluster_size);

    create_refcount_update(s, s->refcount_block_offset, s->cluster_size);



    /* write all the data */

    write(fd, &header, sizeof(header));

    if (backing_file) {

        write(fd, backing_file, backing_filename_len);

    }

    lseek(fd, s->l1_table_offset, SEEK_SET);

    tmp = 0;

    for(i = 0;i < l1_size; i++) {

        write(fd, &tmp, sizeof(tmp));

    }

    lseek(fd, s->refcount_table_offset, SEEK_SET);

    write(fd, s->refcount_table, s->cluster_size);



    lseek(fd, s->refcount_block_offset, SEEK_SET);

    write(fd, s->refcount_block, s->cluster_size);



    qemu_free(s->refcount_table);

    qemu_free(s->refcount_block);

    close(fd);

    return 0;

}
