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utils.go
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/
utils.go
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////////////////////////////////////////////////////////////////////////////////
package tfutils
////////////////////////////////////////////////////////////////////////////////
import (
"bytes"
"encoding/binary"
"errors"
"hash/crc32"
)
////////////////////////////////////////////////////////////////////////////////
const (
crc32Polynomial = crc32.Castagnoli
crc32MaskDelta = uint32(0xa282ead8)
)
var (
crc = crc32.MakeTable(crc32Polynomial)
)
func CrcMask(v uint32) uint32 {
return ((v >> 15) | (v << 17)) + crc32MaskDelta
}
func CrcUnmask(v uint32) uint32 {
r := v - crc32MaskDelta
return (r >> 17) | (r << 15)
}
func MaskedCrc(bs []byte, n int64) uint32 {
return CrcMask(crc32.Checksum(bs[:n], crc))
}
////////////////////////////////////////////////////////////////////////////////
type recordEntry struct {
length uint64
lengthCrc uint32
data []byte
dataCrc uint32
}
func newEntry(data []byte) (*recordEntry, error) {
length := uint64(len(data))
if length == 0 {
return nil, errors.New("data array is empty")
}
bs := make([]byte, 8)
binary.LittleEndian.PutUint64(bs[0:], length)
return &recordEntry{
length: length,
lengthCrc: MaskedCrc(bs, 8),
data: data,
dataCrc: MaskedCrc(data, int64(length)),
}, nil
}
func (re *recordEntry) Marshal() ([]byte, error) {
b := bytes.NewBuffer(make([]byte, 0, re.length+8+4+4))
err := binary.Write(b, binary.LittleEndian, re.length)
if err != nil {
return nil, err
}
err = binary.Write(b, binary.LittleEndian, re.lengthCrc)
if err != nil {
return nil, err
}
_, err = b.Write(re.data[:])
if err != nil {
return nil, err
}
err = binary.Write(b, binary.LittleEndian, re.dataCrc)
if err != nil {
return nil, err
}
return b.Bytes(), nil
}
////////////////////////////////////////////////////////////////////////////////
type CompressionType int
const (
CompressionTypeNone CompressionType = iota
CompressionTypeZlib
)
////////////////////////////////////////////////////////////////////////////////