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package sarama
import (
"encoding/binary"
"fmt"
"hash/crc32"
)
type crcPolynomial int8
const (
crcIEEE crcPolynomial = iota
crcCastagnoli
)
var castagnoliTable = crc32.MakeTable(crc32.Castagnoli)
// crc32Field implements the pushEncoder and pushDecoder interfaces for calculating CRC32s.
type crc32Field struct {
startOffset int
polynomial crcPolynomial
}
func (c *crc32Field) saveOffset(in int) {
c.startOffset = in
}
func (c *crc32Field) reserveLength() int {
return 4
}
func newCRC32Field(polynomial crcPolynomial) *crc32Field {
return &crc32Field{polynomial: polynomial}
}
func (c *crc32Field) run(curOffset int, buf []byte) error {
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, err := c.crc(curOffset, buf)
if err != nil {
return err
}
expected := binary.BigEndian.Uint32(buf[c.startOffset:])
if crc != expected {
return PacketDecodingError{fmt.Sprintf("CRC didn't match expected %#x got %#x", expected, crc)}
}
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
}
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