Remove cgo zstd package

Switch from cgo package to pure Go implementation. This will (when fixed) work even if no cgo is present.

https://github.com/klauspost/compress/tree/master/zstd#zstd

Compression level is removed. It could be made so the first request determines the compression level. But since there is currently only two levels (fast and default) I am not sure it is worth it.

This does NOT fix IBM#1252 - only updates the code used for compression/decompression.

compress.go

@@ -68,7 +68,7 @@ func compress(cc CompressionCodec, level int, data []byte) ([]byte, error) {
 		}
 		return buf.Bytes(), nil
 	case CompressionZSTD:
-		return zstdCompressLevel(nil, data, level)
+		return zstdCompress(nil, data)
 	default:
 		return nil, PacketEncodingError{fmt.Sprintf("unsupported compression codec (%d)", cc)}
 	}

go.mod

@@ -1,7 +1,6 @@
 module github.com/Shopify/sarama
 
 require (
-	github.com/DataDog/zstd v1.4.0
 	github.com/Shopify/toxiproxy v2.1.4+incompatible
 	github.com/davecgh/go-spew v1.1.1
 	github.com/eapache/go-resiliency v1.1.0
@@ -12,6 +11,7 @@ require (
 	github.com/golang/snappy v0.0.1 // indirect
 	github.com/hashicorp/go-uuid v1.0.1 // indirect
 	github.com/jcmturner/gofork v0.0.0-20190328161633-dc7c13fece03 // indirect
+	github.com/klauspost/compress v1.8.1
 	github.com/pierrec/lz4 v2.2.6+incompatible
 	github.com/rcrowley/go-metrics v0.0.0-20181016184325-3113b8401b8a
 	github.com/stretchr/testify v1.3.0

zstd.go

@@ -0,0 +1,28 @@
+package sarama
+
+import (
+	"github.com/klauspost/compress/zstd"
+	"sync"
+)
+
+var (
+	zstdDec *zstd.Decoder
+	zstdEnc *zstd.Encoder
+
+	zstdEncOnce, zstdDecOnce sync.Once
+)
+
+
+func zstdDecompress(dst, src []byte) ([]byte, error) {
+	zstdDecOnce.Do(func() {
+		zstdDec, _ = zstd.NewReader(nil)
+	})
+	return zstdDec.DecodeAll(src, dst)
+}
+
+func zstdCompress(dst, src []byte) ([]byte, error) {
+	zstdEncOnce.Do(func() {
+		zstdEnc, _ = zstd.NewWriter(nil)
+	})
+	return zstdEnc.EncodeAll(src, dst), nil
+}