Revert "*,sstable: upgrade zstd to v1.5.6"

This reverts commit 975fbcb.

The CockroachDB build process is unable to build zstd at v1.5.6 on Linux.
Resolving this issue is tracked in cockroachdb/cockroach#105568.

go.mod

@@ -1,7 +1,7 @@
 module github.com/cockroachdb/pebble
 
 require (
-	github.com/DataDog/zstd v1.5.6-0.20230622172052-ea68dcab66c0
+	github.com/DataDog/zstd v1.4.5
 	github.com/HdrHistogram/hdrhistogram-go v1.1.2
 	github.com/cespare/xxhash/v2 v2.2.0
 	github.com/cockroachdb/datadriven v1.0.3-0.20230413201302-be42291fc80f

go.sum

@@ -38,8 +38,8 @@ github.com/BurntSushi/toml v0.3.1/go.mod h1:xHWCNGjB5oqiDr8zfno3MHue2Ht5sIBksp03
 github.com/BurntSushi/xgb v0.0.0-20160522181843-27f122750802/go.mod h1:IVnqGOEym/WlBOVXweHU+Q+/VP0lqqI8lqeDx9IjBqo=
 github.com/CloudyKit/fastprinter v0.0.0-20170127035650-74b38d55f37a/go.mod h1:EFZQ978U7x8IRnstaskI3IysnWY5Ao3QgZUKOXlsAdw=
 github.com/CloudyKit/jet v2.1.3-0.20180809161101-62edd43e4f88+incompatible/go.mod h1:HPYO+50pSWkPoj9Q/eq0aRGByCL6ScRlUmiEX5Zgm+w=
-github.com/DataDog/zstd v1.5.6-0.20230622172052-ea68dcab66c0 h1:ye3LRgDs6Og7SKC1wBQH8oMaGczhCRpPpnU74l4rma8=
-github.com/DataDog/zstd v1.5.6-0.20230622172052-ea68dcab66c0/go.mod h1:g4AWEaM3yOg3HYfnJ3YIawPnVdXJh9QME85blwSAmyw=
+github.com/DataDog/zstd v1.4.5 h1:EndNeuB0l9syBZhut0wns3gV1hL8zX8LIu6ZiVHWLIQ=
+github.com/DataDog/zstd v1.4.5/go.mod h1:1jcaCB/ufaK+sKp1NBhlGmpz41jOoPQ35bpF36t7BBo=
 github.com/GoogleCloudPlatform/cloudsql-proxy v0.0.0-20190129172621-c8b1d7a94ddf/go.mod h1:aJ4qN3TfrelA6NZ6AXsXRfmEVaYin3EDbSPJrKS8OXo=
 github.com/HdrHistogram/hdrhistogram-go v1.1.2 h1:5IcZpTvzydCQeHzK4Ef/D5rrSqwxob0t8PQPMybUNFM=
 github.com/HdrHistogram/hdrhistogram-go v1.1.2/go.mod h1:yDgFjdqOqDEKOvasDdhWNXYg9BVp4O+o5f6V/ehm6Oo=

sstable/compression.go

@@ -33,24 +33,23 @@ func decompressedLen(blockType blockType, b []byte) (int, int, error) {
 	}
 }
 
-func decompressInto(blockType blockType, compressed []byte, buf []byte) error {
+func decompressInto(blockType blockType, compressed []byte, buf []byte) ([]byte, error) {
 	var result []byte
 	var err error
 	switch blockType {
 	case snappyCompressionBlockType:
 		result, err = snappy.Decode(buf, compressed)
 	case zstdCompressionBlockType:
-		err = decodeZstd(buf, compressed)
-		result = buf
+		result, err = decodeZstd(buf, compressed)
 	}
 	if err != nil {
-		return base.MarkCorruptionError(err)
+		return nil, base.MarkCorruptionError(err)
 	}
 	if len(result) != 0 && (len(result) != len(buf) || &result[0] != &buf[0]) {
-		return base.CorruptionErrorf("pebble/table: decompressed into unexpected buffer: %p != %p",
+		return nil, base.CorruptionErrorf("pebble/table: decompressed into unexpected buffer: %p != %p",
 			errors.Safe(result), errors.Safe(buf))
 	}
-	return nil
+	return result, nil
 }
 
 // decompressBlock decompresses an SST block, with space allocated from a cache.
@@ -69,7 +68,7 @@ func decompressBlock(cache *cache.Cache, blockType blockType, b []byte) (*cache.
 	// Allocate sufficient space from the cache.
 	decoded := cache.Alloc(decodedLen)
 	decodedBuf := decoded.Buf()
-	if err := decompressInto(blockType, b, decodedBuf); err != nil {
+	if _, err := decompressInto(blockType, b, decodedBuf); err != nil {
 		cache.Free(decoded)
 		return nil, err
 	}

sstable/compression_cgo.go

@@ -13,11 +13,11 @@ import (
 	"github.com/DataDog/zstd"
 )
 
-// decodeZstd decompresses src with the Zstandard algorithm. The destination
-// buffer must already be sufficiently sized, otherwise decodeZstd may error.
-func decodeZstd(dst, src []byte) error {
-	_, err := zstd.DecompressInto(dst, src)
-	return err
+// decodeZstd decompresses b with the Zstandard algorithm.
+// It reuses the preallocated capacity of decodedBuf if it is sufficient.
+// On success, it returns the decoded byte slice.
+func decodeZstd(decodedBuf, b []byte) ([]byte, error) {
+	return zstd.Decompress(decodedBuf, b)
 }
 
 // encodeZstd compresses b with the Zstandard algorithm at default compression

sstable/compression_nocgo.go

@@ -9,13 +9,13 @@ package sstable
 
 import "github.com/klauspost/compress/zstd"
 
-// decodeZstd decompresses src with the Zstandard algorithm. The destination
-// buffer must already be sufficiently sized, otherwise decodeZstd may error.
-func decodeZstd(dst, src []byte) error {
+// decodeZstd decompresses b with the Zstandard algorithm.
+// It reuses the preallocated capacity of decodedBuf if it is sufficient.
+// On success, it returns the decoded byte slice.
+func decodeZstd(decodedBuf, b []byte) ([]byte, error) {
 	decoder, _ := zstd.NewReader(nil)
 	defer decoder.Close()
-	_, err := decoder.DecodeAll(src, dst[:0])
-	return err
+	return decoder.DecodeAll(b, decodedBuf[:0])
 }
 
 // encodeZstd compresses b with the Zstandard algorithm at default compression

sstable/suffix_rewriter.go

@@ -540,9 +540,8 @@ func readBlockBuf(r *Reader, bh BlockHandle, buf []byte) ([]byte, []byte, error)
 	if cap(buf) < decompressedLen {
 		buf = make([]byte, decompressedLen)
 	}
-	dst := buf[:decompressedLen]
-	err = decompressInto(typ, raw[prefix:], dst)
-	return dst, buf, err
+	res, err := decompressInto(typ, raw[prefix:], buf[:decompressedLen])
+	return res, buf, err
 }
 
 // memReader is a thin wrapper around a []byte such that it can be passed to