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Add support for Castagnoli polynomial for CRC32 computation #971

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merged 2 commits into from
Oct 25, 2017
Merged

Add support for Castagnoli polynomial for CRC32 computation #971

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0d4d83d
Add support for Castagnoli polynomial for CRC32 computation
vlad-arista Oct 24, 2017
07a5840
Make polynomial a type
vlad-arista Oct 25, 2017
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34 changes: 32 additions & 2 deletions crc32_field.go
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Original file line number Diff line number Diff line change
Expand Up @@ -6,9 +6,17 @@ import (
"hash/crc32"
)

const (
crcIEEE = iota
crcCastagnoli
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Why define these? you can just have newCRC32Field take the crc32-defined constant directly?

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Do you mean I should use the polynomial constants directly? I could, as they are just ints, but it didn't seem very clean to me as the intent here is to represent an enumeration of supported polynomials in the context of Kafka protocol, not the polynomial itself.
But if you feel strongly about it, I can remove them.

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That's what I meant, but I see your point. In that case it probably makes sense to explicitly type it (e.g. the way that compression codecs are) rather than using ints, since the polynomials themselves are just ints.

)

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) {
Expand All @@ -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 {
Expand All @@ -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
}
4 changes: 2 additions & 2 deletions message.go
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Expand Up @@ -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)

Expand Down Expand Up @@ -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
}
Expand Down