ZSTD_IOBUF_SIZE
in_allocated = large_malloc(ZSTD_IOBUF_SIZE);
in_len = fill(in_buf, ZSTD_IOBUF_SIZE);
out_allocated = large_malloc(ZSTD_IOBUF_SIZE);
out_len = ZSTD_IOBUF_SIZE;
in_len = fill ? fill(in_buf, ZSTD_IOBUF_SIZE) : -1;