Further performance improvements

Further removed multiple pointer instances
Re-use decompression readers (except zstd due to bugs)

internal/decompress/lz4.go

@@ -3,13 +3,28 @@ package decompress
 import (
 	"bytes"
 	"io"
+	"sync"
 
 	"github.com/pierrec/lz4/v4"
 )
 
-type Lz4 struct{}
+type Lz4 struct {
+	pool sync.Pool
+}
 
-func (l Lz4) Decompress(data []byte) ([]byte, error) {
-	rdr := lz4.NewReader(bytes.NewReader(data))
+func NewLz4() *Lz4 {
+	return &Lz4{
+		pool: sync.Pool{
+			New: func() any {
+				return lz4.NewReader(nil)
+			},
+		},
+	}
+}
+
+func (l *Lz4) Decompress(data []byte) ([]byte, error) {
+	rdr := l.pool.Get().(*lz4.Reader)
+	defer l.pool.Put(rdr)
+	rdr.Reset(bytes.NewReader(data))
 	return io.ReadAll(rdr)
 }

internal/decompress/xz.go

@@ -3,14 +3,30 @@ package decompress
 import (
 	"bytes"
 	"io"
+	"sync"
 
 	"github.com/therootcompany/xz"
 )
 
-type Xz struct{}
+type Xz struct {
+	pool sync.Pool
+}
 
-func (x Xz) Decompress(data []byte) ([]byte, error) {
-	rdr, err := xz.NewReader(bytes.NewReader(data), 0)
+func NewXz() *Xz {
+	return &Xz{
+		pool: sync.Pool{
+			New: func() any {
+				rdr, _ := xz.NewReader(nil, 0)
+				return rdr
+			},
+		},
+	}
+}
+
+func (x *Xz) Decompress(data []byte) ([]byte, error) {
+	rdr := x.pool.Get().(*xz.Reader)
+	defer x.pool.Put(rdr)
+	err := rdr.Reset(bytes.NewReader(data))
 	if err != nil {
 		return nil, err
 	}

internal/decompress/zstd.go

@@ -1,19 +1,16 @@
 package decompress
 
 import (
-	"bytes"
-	"io"
-
 	"github.com/klauspost/compress/zstd"
 )
 
 type Zstd struct{}
 
 func (z Zstd) Decompress(data []byte) ([]byte, error) {
-	rdr, err := zstd.NewReader(bytes.NewReader(data))
+	rdr, err := zstd.NewReader(nil, zstd.WithDecoderLowmem(true), zstd.WithDecoderConcurrency(1))
 	if err != nil {
 		return nil, err
 	}
 	defer rdr.Close()
-	return io.ReadAll(rdr)
+	return rdr.DecodeAll(data, nil)
 }

internal/metadata/reader.go

@@ -14,8 +14,8 @@ type Reader struct {
 	curOffset uint16
 }
 
-func NewReader(r io.Reader, d decompress.Decompressor) *Reader {
-	return &Reader{
+func NewReader(r io.Reader, d decompress.Decompressor) Reader {
+	return Reader{
 		r: r,
 		d: d,
 	}