Re-use zstd and zlib readers

internal/decompress/zlib.go

@@ -2,17 +2,31 @@ package decompress
 
 import (
 	"bytes"
-	"compress/zlib"
 	"io"
+	"sync"
+
+	"github.com/klauspost/compress/zlib"
 )
 
-type Zlib struct{}
+type Zlib struct {
+	pool sync.Pool
+}
 
-func (z Zlib) Decompress(data []byte) ([]byte, error) {
-	rdr, err := zlib.NewReader(bytes.NewReader(data))
+func NewZlib() *Zlib {
+	return &Zlib{}
+}
+
+func (z *Zlib) Decompress(data []byte) ([]byte, error) {
+	rdr := z.pool.Get()
+	defer z.pool.Put(rdr)
+	var err error
+	if rdr == nil {
+		rdr, err = zlib.NewReader(bytes.NewReader(data))
+	} else {
+		err = rdr.(zlib.Resetter).Reset(bytes.NewReader(data), nil)
+	}
 	if err != nil {
 		return nil, err
 	}
-	defer rdr.Close()
-	return io.ReadAll(rdr)
+	return io.ReadAll(rdr.(io.ReadCloser))
 }

internal/decompress/zstd.go

@@ -1,16 +1,31 @@
 package decompress
 
 import (
+	"sync"
+
 	"github.com/klauspost/compress/zstd"
 )
 
-type Zstd struct{}
+type Zstd struct {
+	pool sync.Pool
+}
 
-func (z Zstd) Decompress(data []byte) ([]byte, error) {
-	rdr, err := zstd.NewReader(nil, zstd.WithDecoderLowmem(true), zstd.WithDecoderConcurrency(1))
-	if err != nil {
-		return nil, err
+func NewZstd() *Zstd {
+	return &Zstd{
+		pool: sync.Pool{
+			New: func() any {
+				rdr, _ := zstd.NewReader(nil, zstd.WithDecoderLowmem(true), zstd.WithDecoderConcurrency(1))
+				return rdr
+			},
+		},
 	}
-	defer rdr.Close()
+}
+
+func (z *Zstd) Decompress(data []byte) ([]byte, error) {
+	rdr := z.pool.Get().(*zstd.Decoder)
+	defer func() {
+		rdr.Reset(nil)
+		z.pool.Put(rdr)
+	}()
 	return rdr.DecodeAll(data, nil)
 }

low/reader.go

@@ -56,7 +56,7 @@ func NewReader(r io.ReaderAt) (rdr Reader, err error) {
 	}
 	switch rdr.Superblock.CompType {
 	case ZlibCompression:
-		rdr.d = decompress.Zlib{}
+		rdr.d = decompress.NewZlib()
 	case LZMACompression:
 		rdr.d, err = decompress.NewLzma()
 		if err != nil {
@@ -72,7 +72,7 @@ func NewReader(r io.ReaderAt) (rdr Reader, err error) {
 	case LZ4Compression:
 		rdr.d = decompress.NewLz4()
 	case ZSTDCompression:
-		rdr.d = decompress.Zstd{}
+		rdr.d = decompress.NewZstd()
 	default:
 		return rdr, errors.New("invalid compression type. possible corrupted archive")
 	}