fse, huff0, zstd: Remove always-nil error returns (#857)

fse/bitwriter.go

@@ -152,12 +152,11 @@ func (b *bitWriter) flushAlign() {
 
 // close will write the alignment bit and write the final byte(s)
 // to the output.
-func (b *bitWriter) close() error {
+func (b *bitWriter) close() {
 	// End mark
 	b.addBits16Clean(1, 1)
 	// flush until next byte.
 	b.flushAlign()
-	return nil
 }
 
 // reset and continue writing by appending to out.

fse/compress.go

@@ -199,7 +199,8 @@ func (s *Scratch) compress(src []byte) error {
 	c2.flush(s.actualTableLog)
 	c1.flush(s.actualTableLog)
 
-	return s.bw.close()
+	s.bw.close()
+	return nil
 }
 
 // writeCount will write the normalized histogram count to header.

huff0/bitwriter.go

@@ -94,10 +94,9 @@ func (b *bitWriter) flushAlign() {
 
 // close will write the alignment bit and write the final byte(s)
 // to the output.
-func (b *bitWriter) close() error {
+func (b *bitWriter) close() {
 	// End mark
 	b.addBits16Clean(1, 1)
 	// flush until next byte.
 	b.flushAlign()
-	return nil
 }

huff0/compress.go

@@ -227,10 +227,10 @@ func EstimateSizes(in []byte, s *Scratch) (tableSz, dataSz, reuseSz int, err err
 }
 
 func (s *Scratch) compress1X(src []byte) ([]byte, error) {
-	return s.compress1xDo(s.Out, src)
+	return s.compress1xDo(s.Out, src), nil
 }
 
-func (s *Scratch) compress1xDo(dst, src []byte) ([]byte, error) {
+func (s *Scratch) compress1xDo(dst, src []byte) []byte {
 	var bw = bitWriter{out: dst}
 
 	// N is length divisible by 4.
@@ -260,8 +260,8 @@ func (s *Scratch) compress1xDo(dst, src []byte) ([]byte, error) {
 			bw.encTwoSymbols(cTable, tmp[1], tmp[0])
 		}
 	}
-	err := bw.close()
-	return bw.out, err
+	bw.close()
+	return bw.out
 }
 
 var sixZeros [6]byte
@@ -283,12 +283,8 @@ func (s *Scratch) compress4X(src []byte) ([]byte, error) {
 		}
 		src = src[len(toDo):]
 
-		var err error
 		idx := len(s.Out)
-		s.Out, err = s.compress1xDo(s.Out, toDo)
-		if err != nil {
-			return nil, err
-		}
+		s.Out = s.compress1xDo(s.Out, toDo)
 		if len(s.Out)-idx > math.MaxUint16 {
 			// We cannot store the size in the jump table
 			return nil, ErrIncompressible
@@ -315,7 +311,6 @@ func (s *Scratch) compress4Xp(src []byte) ([]byte, error) {
 
 	segmentSize := (len(src) + 3) / 4
 	var wg sync.WaitGroup
-	var errs [4]error
 	wg.Add(4)
 	for i := 0; i < 4; i++ {
 		toDo := src
@@ -326,15 +321,12 @@ func (s *Scratch) compress4Xp(src []byte) ([]byte, error) {
 
 		// Separate goroutine for each block.
 		go func(i int) {
-			s.tmpOut[i], errs[i] = s.compress1xDo(s.tmpOut[i][:0], toDo)
+			s.tmpOut[i] = s.compress1xDo(s.tmpOut[i][:0], toDo)
 			wg.Done()
 		}(i)
 	}
 	wg.Wait()
 	for i := 0; i < 4; i++ {
-		if errs[i] != nil {
-			return nil, errs[i]
-		}
 		o := s.tmpOut[i]
 		if len(o) > math.MaxUint16 {
 			// We cannot store the size in the jump table

zstd/bitwriter.go

@@ -97,12 +97,11 @@ func (b *bitWriter) flushAlign() {
 
 // close will write the alignment bit and write the final byte(s)
 // to the output.
-func (b *bitWriter) close() error {
+func (b *bitWriter) close() {
 	// End mark
 	b.addBits16Clean(1, 1)
 	// flush until next byte.
 	b.flushAlign()
-	return nil
 }
 
 // reset and continue writing by appending to out.

zstd/blockenc.go

@@ -791,10 +791,7 @@ func (b *blockEnc) encode(org []byte, raw, rawAllLits bool) error {
 	ml.flush(mlEnc.actualTableLog)
 	of.flush(ofEnc.actualTableLog)
 	ll.flush(llEnc.actualTableLog)
-	err = wr.close()
-	if err != nil {
-		return err
-	}
+	wr.close()
 	b.output = wr.out
 
 	// Maybe even add a bigger margin.

zstd/encoder.go

@@ -227,10 +227,7 @@ func (e *Encoder) nextBlock(final bool) error {
 			DictID:        e.o.dict.ID(),
 		}
 
-		dst, err := fh.appendTo(tmp[:0])
-		if err != nil {
-			return err
-		}
+		dst := fh.appendTo(tmp[:0])
 		s.headerWritten = true
 		s.wWg.Wait()
 		var n2 int
@@ -483,7 +480,7 @@ func (e *Encoder) EncodeAll(src, dst []byte) []byte {
 				Checksum: false,
 				DictID:   0,
 			}
-			dst, _ = fh.appendTo(dst)
+			dst = fh.appendTo(dst)
 
 			// Write raw block as last one only.
 			var blk blockHeader
@@ -518,10 +515,7 @@ func (e *Encoder) EncodeAll(src, dst []byte) []byte {
 	if len(dst) == 0 && cap(dst) == 0 && len(src) < 1<<20 && !e.o.lowMem {
 		dst = make([]byte, 0, len(src))
 	}
-	dst, err := fh.appendTo(dst)
-	if err != nil {
-		panic(err)
-	}
+	dst = fh.appendTo(dst)
 
 	// If we can do everything in one block, prefer that.
 	if len(src) <= e.o.blockSize {
@@ -581,6 +575,7 @@ func (e *Encoder) EncodeAll(src, dst []byte) []byte {
 	// Add padding with content from crypto/rand.Reader
 	if e.o.pad > 0 {
 		add := calcSkippableFrame(int64(len(dst)), int64(e.o.pad))
+		var err error
 		dst, err = skippableFrame(dst, add, rand.Reader)
 		if err != nil {
 			panic(err)

zstd/frameenc.go

@@ -22,7 +22,7 @@ type frameHeader struct {
 
 const maxHeaderSize = 14
 
-func (f frameHeader) appendTo(dst []byte) ([]byte, error) {
+func (f frameHeader) appendTo(dst []byte) []byte {
 	dst = append(dst, frameMagic...)
 	var fhd uint8
 	if f.Checksum {
@@ -88,7 +88,7 @@ func (f frameHeader) appendTo(dst []byte) ([]byte, error) {
 	default:
 		panic("invalid fcs")
 	}
-	return dst, nil
+	return dst
 }
 
 const skippableFrameHeader = 4 + 4

zstd/snappy.go

@@ -95,10 +95,9 @@ func (r *SnappyConverter) Convert(in io.Reader, w io.Writer) (int64, error) {
 	var written int64
 	var readHeader bool
 	{
-		var header []byte
-		var n int
-		header, r.err = frameHeader{WindowSize: snappyMaxBlockSize}.appendTo(r.buf[:0])
+		header := frameHeader{WindowSize: snappyMaxBlockSize}.appendTo(r.buf[:0])
 
+		var n int
 		n, r.err = w.Write(header)
 		if r.err != nil {
 			return written, r.err