zstd: Fix ReadFrom with small blocks (#278)

Two 'last' blocks was added on small payloads when using ReadFrom.

Fixes #277

zstd/blockenc.go

@@ -295,7 +295,7 @@ func (b *blockEnc) encodeRaw(a []byte) {
 	b.output = bh.appendTo(b.output[:0])
 	b.output = append(b.output, a...)
 	if debug {
-		println("Adding RAW block, length", len(a))
+		println("Adding RAW block, length", len(a), "last:", b.last)
 	}
 }
 
@@ -308,7 +308,7 @@ func (b *blockEnc) encodeRawTo(dst, src []byte) []byte {
 	dst = bh.appendTo(dst)
 	dst = append(dst, src...)
 	if debug {
-		println("Adding RAW block, length", len(src))
+		println("Adding RAW block, length", len(src), "last:", b.last)
 	}
 	return dst
 }
@@ -322,7 +322,7 @@ func (b *blockEnc) encodeLits(raw bool) error {
 	// Don't compress extremely small blocks
 	if len(b.literals) < 32 || raw {
 		if debug {
-			println("Adding RAW block, length", len(b.literals))
+			println("Adding RAW block, length", len(b.literals), "last:", b.last)
 		}
 		bh.setType(blockTypeRaw)
 		b.output = bh.appendTo(b.output)
@@ -349,7 +349,7 @@ func (b *blockEnc) encodeLits(raw bool) error {
 	switch err {
 	case huff0.ErrIncompressible:
 		if debug {
-			println("Adding RAW block, length", len(b.literals))
+			println("Adding RAW block, length", len(b.literals), "last:", b.last)
 		}
 		bh.setType(blockTypeRaw)
 		b.output = bh.appendTo(b.output)

zstd/encoder.go

@@ -190,6 +190,7 @@ func (e *Encoder) nextBlock(final bool) error {
 			s.filling = s.filling[:0]
 			s.headerWritten = true
 			s.fullFrameWritten = true
+			s.eofWritten = true
 			return nil
 		}
 

zstd/encoder_test.go

@@ -667,6 +667,34 @@ func TestEncoder_EncodeAllSilesia(t *testing.T) {
 	t.Log("Encoded content matched")
 }
 
+func TestEncoderReadFrom(t *testing.T) {
+	buffer := bytes.NewBuffer(nil)
+	encoder, err := NewWriter(buffer)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if _, err := encoder.ReadFrom(strings.NewReader("0")); err != nil {
+		t.Fatal(err)
+	}
+	if err := encoder.Close(); err != nil {
+		t.Fatal(err)
+	}
+
+	dec, _ := NewReader(nil)
+	toDec := buffer.Bytes()
+	toDec = append(toDec, toDec...)
+	decoded, err := dec.DecodeAll(toDec, nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if !bytes.Equal([]byte("00"), decoded) {
+		t.Logf("encoded: % x\n", buffer.Bytes())
+		t.Fatalf("output mismatch, got %s", string(decoded))
+	}
+	dec.Close()
+}
+
 func TestEncoder_EncodeAllEmpty(t *testing.T) {
 	if testing.Short() {
 		t.SkipNow()