Function zfs_zstd_compress

freebsd/contrib/openzfs/module/zstd/zfs_zstd.c:365–466

Compress block using zstd */

/* Compress block using zstd */
size_t
zfs_zstd_compress(void *s_start, void *d_start, size_t s_len, size_t d_len,
    int level)
{
	size_t c_len;
	int16_t zstd_level;
	zfs_zstdhdr_t *hdr;
	ZSTD_CCtx *cctx;

	hdr = (zfs_zstdhdr_t *)d_start;

	/* Skip compression if the specified level is invalid */
	if (zstd_enum_to_level(level, &zstd_level)) {
		ZSTDSTAT_BUMP(zstd_stat_com_inval);
		return (s_len);
	}

	ASSERT3U(d_len, >=, sizeof (*hdr));
	ASSERT3U(d_len, <=, s_len);
	ASSERT3U(zstd_level, !=, 0);

	cctx = ZSTD_createCCtx_advanced(zstd_malloc);

	/*
	 * Out of kernel memory, gently fall through - this will disable
	 * compression in zio_compress_data
	 */
	if (!cctx) {
		ZSTDSTAT_BUMP(zstd_stat_com_alloc_fail);
		return (s_len);
	}

	/* Set the compression level */
	ZSTD_CCtx_setParameter(cctx, ZSTD_c_compressionLevel, zstd_level);

	/* Use the "magicless" zstd header which saves us 4 header bytes */
	ZSTD_CCtx_setParameter(cctx, ZSTD_c_format, ZSTD_f_zstd1_magicless);

	/*
	 * Disable redundant checksum calculation and content size storage since
	 * this is already done by ZFS itself.
	 */
	ZSTD_CCtx_setParameter(cctx, ZSTD_c_checksumFlag, 0);
	ZSTD_CCtx_setParameter(cctx, ZSTD_c_contentSizeFlag, 0);

	c_len = ZSTD_compress2(cctx,
	    hdr->data,
	    d_len - sizeof (*hdr),
	    s_start, s_len);

	ZSTD_freeCCtx(cctx);

	/* Error in the compression routine, disable compression. */
	if (ZSTD_isError(c_len)) {
		/*
		 * If we are aborting the compression because the saves are
		 * too small, that is not a failure. Everything else is a
		 * failure, so increment the compression failure counter.