zstd: Shorten checksum code

zstd/decoder.go

@@ -455,12 +455,7 @@ func (d *Decoder) nextBlock(blocking bool) (ok bool) {
 	}
 
 	if len(next.b) > 0 {
-		n, err := d.current.crc.Write(next.b)
-		if err == nil {
-			if n != len(next.b) {
-				d.current.err = io.ErrShortWrite
-			}
-		}
+		d.current.crc.Write(next.b)
 	}
 	if next.err == nil && next.d != nil && next.d.hasCRC {
 		got := uint32(d.current.crc.Sum64())

zstd/framedec.go

@@ -293,24 +293,16 @@ func (d *frameDec) next(block *blockDec) error {
 	return nil
 }
 
-// checkCRC will check the checksum if the frame has one.
+// checkCRC will check the checksum, assuming the frame has one.
 // Will return ErrCRCMismatch if crc check failed, otherwise nil.
 func (d *frameDec) checkCRC() error {
-	if !d.HasCheckSum {
-		return nil
-	}
-
 	// We can overwrite upper tmp now
 	buf, err := d.rawInput.readSmall(4)
 	if err != nil {
 		println("CRC missing?", err)
 		return err
 	}
 
-	if d.o.ignoreChecksum {
-		return nil
-	}
-
 	want := binary.LittleEndian.Uint32(buf[:4])
 	got := uint32(d.crc.Sum64())
 
@@ -326,17 +318,13 @@ func (d *frameDec) checkCRC() error {
 	return nil
 }
 
-// consumeCRC reads the checksum data if the frame has one.
+// consumeCRC skips over the checksum, assuming the frame has one.
 func (d *frameDec) consumeCRC() error {
-	if d.HasCheckSum {
-		_, err := d.rawInput.readSmall(4)
-		if err != nil {
-			println("CRC missing?", err)
-			return err
-		}
+	_, err := d.rawInput.readSmall(4)
+	if err != nil {
+		println("CRC missing?", err)
 	}
-
-	return nil
+	return err
 }
 
 // runDecoder will run the decoder for the remainder of the frame.
@@ -415,15 +403,8 @@ func (d *frameDec) runDecoder(dst []byte, dec *blockDec) ([]byte, error) {
 			if d.o.ignoreChecksum {
 				err = d.consumeCRC()
 			} else {
-				var n int
-				n, err = d.crc.Write(dst[crcStart:])
-				if err == nil {
-					if n != len(dst)-crcStart {
-						err = io.ErrShortWrite
-					} else {
-						err = d.checkCRC()
-					}
-				}
+				d.crc.Write(dst[crcStart:])
+				err = d.checkCRC()
 			}
 		}
 	}