reserve_size += sizeof(struct alt_chunk_table_header_disk);
memset(ctx->chunk_csizes, 0, reserve_size);
ret = full_write(ctx->out_fd, ctx->chunk_csizes, reserve_size);
reserve_size += sizeof(struct alt_chunk_table_header_disk);
memset(ctx->chunk_csizes, 0, reserve_size);
ret = full_write(ctx->out_fd, ctx->chunk_csizes, reserve_size);