Add support for Castagnoli polynomial for CRC32 computation

This is needed for Kafka 0.11 support as the new records' checksum is
computed with Castagnoli polynomial (previous versions of Kafka use
IEEE polynomial).

crc32_field.go

@@ -6,9 +6,17 @@ import (
 	"hash/crc32"
 )
 
+const (
+	crcIEEE = iota
+	crcCastagnoli
+)
+
+var castagnoliTable = crc32.MakeTable(crc32.Castagnoli)
+
 // crc32Field implements the pushEncoder and pushDecoder interfaces for calculating CRC32s.
 type crc32Field struct {
 	startOffset int
+	polynomial  int
 }
 
 func (c *crc32Field) saveOffset(in int) {
@@ -19,14 +27,24 @@ func (c *crc32Field) reserveLength() int {
 	return 4
 }
 
+func newCRC32Field(polynomial int) *crc32Field {
+	return &crc32Field{polynomial: polynomial}
+}
+
 func (c *crc32Field) run(curOffset int, buf []byte) error {
-	crc := crc32.ChecksumIEEE(buf[c.startOffset+4 : curOffset])
+	crc, err := c.crc(curOffset, buf)
+	if err != nil {
+		return err
+	}
 	binary.BigEndian.PutUint32(buf[c.startOffset:], crc)
 	return nil
 }
 
 func (c *crc32Field) check(curOffset int, buf []byte) error {
-	crc := crc32.ChecksumIEEE(buf[c.startOffset+4 : curOffset])
+	crc, err := c.crc(curOffset, buf)
+	if err != nil {
+		return err
+	}
 
 	expected := binary.BigEndian.Uint32(buf[c.startOffset:])
 	if crc != expected {
@@ -35,3 +53,15 @@ func (c *crc32Field) check(curOffset int, buf []byte) error {
 
 	return nil
 }
+func (c *crc32Field) crc(curOffset int, buf []byte) (uint32, error) {
+	var tab *crc32.Table
+	switch c.polynomial {
+	case crcIEEE:
+		tab = crc32.IEEETable
+	case crcCastagnoli:
+		tab = castagnoliTable
+	default:
+		return 0, PacketDecodingError{"invalid CRC type"}
+	}
+	return crc32.Checksum(buf[c.startOffset+4:curOffset], tab), nil
+}

message.go

@@ -37,7 +37,7 @@ type Message struct {
 }
 
 func (m *Message) encode(pe packetEncoder) error {
-	pe.push(&crc32Field{})
+	pe.push(newCRC32Field(crcIEEE))
 
 	pe.putInt8(m.Version)
 
@@ -112,7 +112,7 @@ func (m *Message) encode(pe packetEncoder) error {
 }
 
 func (m *Message) decode(pd packetDecoder) (err error) {
-	err = pd.push(&crc32Field{})
+	err = pd.push(newCRC32Field(crcIEEE))
 	if err != nil {
 		return err
 	}