zstd: Add stream encoding without goroutines (#505)

* zstd: Add stream encoding without goroutines

Does not use goroutines when encoder concurrency is 1.

Fixes #264

Can probably be clean up a bit.

* Reduce allocs for concurrent buffers when not used.

zstd/decoder.go

@@ -238,7 +238,9 @@ func (d *Decoder) Reset(r io.Reader) error {
 // drainOutput will drain the output until errEndOfStream is sent.
 func (d *Decoder) drainOutput() {
 	if d.current.cancel != nil {
-		println("cancelling current")
+		if debugDecoder {
+			println("cancelling current")
+		}
 		d.current.cancel()
 		d.current.cancel = nil
 	}
@@ -816,7 +818,9 @@ func (d *Decoder) startStreamDecoder(ctx context.Context, r io.Reader, output ch
 					do.err = ErrFrameSizeMismatch
 					hasErr = true
 				} else {
-					println("fcs ok", block.Last, fcs, decodedFrame)
+					if debugDecoder {
+						println("fcs ok", block.Last, fcs, decodedFrame)
+					}
 				}
 			}
 			output <- do

zstd/encoder.go

@@ -98,23 +98,25 @@ func (e *Encoder) Reset(w io.Writer) {
 	if cap(s.filling) == 0 {
 		s.filling = make([]byte, 0, e.o.blockSize)
 	}
-	if cap(s.current) == 0 {
-		s.current = make([]byte, 0, e.o.blockSize)
-	}
-	if cap(s.previous) == 0 {
-		s.previous = make([]byte, 0, e.o.blockSize)
+	if e.o.concurrent > 1 {
+		if cap(s.current) == 0 {
+			s.current = make([]byte, 0, e.o.blockSize)
+		}
+		if cap(s.previous) == 0 {
+			s.previous = make([]byte, 0, e.o.blockSize)
+		}
+		s.current = s.current[:0]
+		s.previous = s.previous[:0]
+		if s.writing == nil {
+			s.writing = &blockEnc{lowMem: e.o.lowMem}
+			s.writing.init()
+		}
+		s.writing.initNewEncode()
 	}
 	if s.encoder == nil {
 		s.encoder = e.o.encoder()
 	}
-	if s.writing == nil {
-		s.writing = &blockEnc{lowMem: e.o.lowMem}
-		s.writing.init()
-	}
-	s.writing.initNewEncode()
 	s.filling = s.filling[:0]
-	s.current = s.current[:0]
-	s.previous = s.previous[:0]
 	s.encoder.Reset(e.o.dict, false)
 	s.headerWritten = false
 	s.eofWritten = false
@@ -258,6 +260,46 @@ func (e *Encoder) nextBlock(final bool) error {
 		return s.err
 	}
 
+	// SYNC:
+	if e.o.concurrent == 1 {
+		src := s.filling
+		s.nInput += int64(len(s.filling))
+		if debugEncoder {
+			println("Adding sync block,", len(src), "bytes, final:", final)
+		}
+		enc := s.encoder
+		blk := enc.Block()
+		blk.reset(nil)
+		enc.Encode(blk, src)
+		blk.last = final
+		if final {
+			s.eofWritten = true
+		}
+
+		err := errIncompressible
+		// If we got the exact same number of literals as input,
+		// assume the literals cannot be compressed.
+		if len(src) != len(blk.literals) || len(src) != e.o.blockSize {
+			err = blk.encode(src, e.o.noEntropy, !e.o.allLitEntropy)
+		}
+		switch err {
+		case errIncompressible:
+			if debugEncoder {
+				println("Storing incompressible block as raw")
+			}
+			blk.encodeRaw(src)
+			// In fast mode, we do not transfer offsets, so we don't have to deal with changing the.
+		case nil:
+		default:
+			s.err = err
+			return err
+		}
+		_, s.err = s.w.Write(blk.output)
+		s.nWritten += int64(len(blk.output))
+		s.filling = s.filling[:0]
+		return s.err
+	}
+
 	// Move blocks forward.
 	s.filling, s.current, s.previous = s.previous[:0], s.filling, s.current
 	s.nInput += int64(len(s.current))

zstd/encoder_options.go

@@ -76,6 +76,7 @@ func WithEncoderCRC(b bool) EOption {
 // WithEncoderConcurrency will set the concurrency,
 // meaning the maximum number of encoders to run concurrently.
 // The value supplied must be at least 1.
+// For streams, setting a value of 1 will disable async compression.
 // By default this will be set to GOMAXPROCS.
 func WithEncoderConcurrency(n int) EOption {
 	return func(o *encoderOptions) error {

zstd/encoder_test.go

@@ -506,7 +506,7 @@ func testEncoderRoundtrip(t *testing.T, file string, wantCRC []byte) {
 	for _, opt := range getEncOpts(1) {
 		t.Run(opt.name, func(t *testing.T) {
 			opt := opt
-			t.Parallel()
+			//t.Parallel()
 			f, err := os.Open(file)
 			if err != nil {
 				if os.IsNotExist(err) {
@@ -851,7 +851,7 @@ func TestEncoder_EncodeAllEmpty(t *testing.T) {
 }
 
 func TestEncoder_EncodeAllEnwik9(t *testing.T) {
-	if false || testing.Short() {
+	if testing.Short() {
 		t.SkipNow()
 	}
 	file := "testdata/enwik9.zst"
@@ -873,8 +873,11 @@ func TestEncoder_EncodeAllEnwik9(t *testing.T) {
 	}
 
 	start := time.Now()
-	var e Encoder
+	e, err := NewWriter(nil)
 	dst := e.EncodeAll(in, nil)
+	if err != nil {
+		t.Fatal(err)
+	}
 	t.Log("Simple Encoder len", len(in), "-> zstd len", len(dst))
 	mbpersec := (float64(len(in)) / (1024 * 1024)) / (float64(time.Since(start)) / (float64(time.Second)))
 	t.Logf("Encoded %d bytes with %.2f MB/s", len(in), mbpersec)
@@ -889,6 +892,52 @@ func TestEncoder_EncodeAllEnwik9(t *testing.T) {
 	t.Log("Encoded content matched")
 }
 
+func TestEncoder_EncoderStreamEnwik9(t *testing.T) {
+	if testing.Short() {
+		t.SkipNow()
+	}
+	file := "testdata/enwik9.zst"
+	f, err := os.Open(file)
+	if err != nil {
+		if os.IsNotExist(err) {
+			t.Skip("To run extended tests, download http://mattmahoney.net/dc/enwik9.zip unzip it \n" +
+				"compress it with 'zstd -15 -T0 enwik9' and place it in " + file)
+		}
+	}
+	dec, err := NewReader(f)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer dec.Close()
+	in, err := ioutil.ReadAll(dec)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	start := time.Now()
+	var dst bytes.Buffer
+	e, err := NewWriter(&dst)
+	_, err = io.Copy(e, bytes.NewBuffer(in))
+	if err != nil {
+		t.Fatal(err)
+	}
+	e.Close()
+	t.Log("Full Encoder len", len(in), "-> zstd len", dst.Len())
+	mbpersec := (float64(len(in)) / (1024 * 1024)) / (float64(time.Since(start)) / (float64(time.Second)))
+	t.Logf("Encoded %d bytes with %.2f MB/s", len(in), mbpersec)
+	if false {
+		decoded, err := dec.DecodeAll(dst.Bytes(), nil)
+		if err != nil {
+			t.Error(err, len(decoded))
+		}
+		if !bytes.Equal(decoded, in) {
+			ioutil.WriteFile("testdata/"+t.Name()+"-enwik9.got", decoded, os.ModePerm)
+			t.Fatal("Decoded does not match")
+		}
+		t.Log("Encoded content matched")
+	}
+}
+
 func BenchmarkEncoder_EncodeAllXML(b *testing.B) {
 	f, err := os.Open("testdata/xml.zst")
 	if err != nil {