cubefs

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package sarama
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import (
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	"encoding/binary"
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	"fmt"
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	"hash/crc32"
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	"sync"
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)
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type crcPolynomial int8
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const (
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	crcIEEE crcPolynomial = iota
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	crcCastagnoli
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)
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var crc32FieldPool = sync.Pool{}
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func acquireCrc32Field(polynomial crcPolynomial) *crc32Field {
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	val := crc32FieldPool.Get()
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	if val != nil {
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		c := val.(*crc32Field)
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		c.polynomial = polynomial
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		return c
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	}
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	return newCRC32Field(polynomial)
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}
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func releaseCrc32Field(c *crc32Field) {
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	crc32FieldPool.Put(c)
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}
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var castagnoliTable = crc32.MakeTable(crc32.Castagnoli)
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// crc32Field implements the pushEncoder and pushDecoder interfaces for calculating CRC32s.
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type crc32Field struct {
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	startOffset int
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	polynomial  crcPolynomial
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}
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func (c *crc32Field) saveOffset(in int) {
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	c.startOffset = in
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}
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func (c *crc32Field) reserveLength() int {
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	return 4
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}
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func newCRC32Field(polynomial crcPolynomial) *crc32Field {
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	return &crc32Field{polynomial: polynomial}
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}
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func (c *crc32Field) run(curOffset int, buf []byte) error {
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	crc, err := c.crc(curOffset, buf)
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	if err != nil {
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		return err
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	}
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	binary.BigEndian.PutUint32(buf[c.startOffset:], crc)
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	return nil
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}
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func (c *crc32Field) check(curOffset int, buf []byte) error {
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	crc, err := c.crc(curOffset, buf)
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	if err != nil {
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		return err
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	}
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	expected := binary.BigEndian.Uint32(buf[c.startOffset:])
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	if crc != expected {
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		return PacketDecodingError{fmt.Sprintf("CRC didn't match expected %#x got %#x", expected, crc)}
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	}
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	return nil
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}
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func (c *crc32Field) crc(curOffset int, buf []byte) (uint32, error) {
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	var tab *crc32.Table
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	switch c.polynomial {
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	case crcIEEE:
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		tab = crc32.IEEETable
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	case crcCastagnoli:
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		tab = castagnoliTable
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	default:
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		return 0, PacketDecodingError{"invalid CRC type"}
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	}
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	return crc32.Checksum(buf[c.startOffset+4:curOffset], tab), nil
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}
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