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checksum.go
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checksum.go
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package rdiff
import (
"fmt"
"golang.org/x/crypto/blake2b"
"golang.org/x/crypto/md4"
)
type Checksum struct {
checksumType ChecksumType
rollsum *RollingChecksum
rabinkarp *RabinkarpChecksum
}
func NewChecksum(checksumType ChecksumType) (*Checksum, error) {
switch checksumType {
case Rollsum_Md4, Rollsum_Blake2b:
return &Checksum{checksumType: checksumType, rollsum: NewRollingChecksum()}, nil
case Rabinkarp_Md4, Rabinkarp_Blake2b:
return &Checksum{checksumType: checksumType, rabinkarp: NewRabinkarpChecksum()}, nil
default:
return nil, fmt.Errorf("unexpected checksum type %#x", checksumType)
}
}
func (c *Checksum) MaxStrongChecksumSize() uint32 {
switch c.checksumType {
case Rollsum_Md4, Rabinkarp_Md4:
return Md4ChecksumMaxSize
default:
return Blake2bChecksumMaxSize
}
}
func (c *Checksum) CalculateWeakChecksum(data []byte) uint32 {
switch c.checksumType {
case Rollsum_Md4, Rollsum_Blake2b:
rc := NewRollingChecksum()
rc.Update(data)
return rc.Digest()
default:
rc := NewRabinkarpChecksum()
rc.Update(data)
return rc.Digest()
}
}
func (c *Checksum) CalculateStrongChecksum(data []byte, checksumSize uint32) ([]byte, error) {
var checksum []byte
switch c.checksumType {
case Rollsum_Md4, Rabinkarp_Md4:
h := md4.New()
h.Write(data)
checksum = h.Sum(nil)
default:
s := blake2b.Sum256(data)
checksum = s[:]
}
if len(checksum) < int(checksumSize) {
return nil, fmt.Errorf("strong checksum size %d exceeds actual size %d for checksum type %#x", checksumSize, len(checksum), c.checksumType)
}
return checksum[:checksumSize], nil
}
func (c *Checksum) Rollin(in byte) {
switch c.checksumType {
case Rollsum_Md4, Rollsum_Blake2b:
c.rollsum.Rollin(in)
default:
c.rabinkarp.Rollin(in)
}
}
func (c *Checksum) Rollout(out byte) {
switch c.checksumType {
case Rollsum_Md4, Rollsum_Blake2b:
c.rollsum.Rollout(out)
default:
c.rabinkarp.Rollout(out)
}
}
func (c *Checksum) Digest() uint32 {
switch c.checksumType {
case Rollsum_Md4, Rollsum_Blake2b:
return c.rollsum.Digest()
default:
return c.rabinkarp.Digest()
}
}
func (c *Checksum) Reset() {
switch c.checksumType {
case Rollsum_Md4, Rollsum_Blake2b:
c.rollsum.Reset()
default:
c.rabinkarp.Reset()
}
}
func (c *Checksum) Count() uint64 {
switch c.checksumType {
case Rollsum_Md4, Rollsum_Blake2b:
return c.rollsum.count
default:
return c.rabinkarp.count
}
}