93 lines
2.6 KiB
Go
93 lines
2.6 KiB
Go
// Copyright 2018 The go-ethereum Authors
|
|
// This file is part of the go-ethereum library.
|
|
//
|
|
// The go-ethereum library is free software: you can redistribute it and/or modify
|
|
// it under the terms of the GNU Lesser General Public License as published by
|
|
// the Free Software Foundation, either version 3 of the License, or
|
|
// (at your option) any later version.
|
|
//
|
|
// The go-ethereum library is distributed in the hope that it will be useful,
|
|
// but WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
|
|
// GNU Lesser General Public License for more details.
|
|
//
|
|
// You should have received a copy of the GNU Lesser General Public License
|
|
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
|
|
|
|
package multihash
|
|
|
|
import (
|
|
"bytes"
|
|
"encoding/binary"
|
|
"errors"
|
|
"fmt"
|
|
)
|
|
|
|
const (
|
|
defaultMultihashLength = 32
|
|
defaultMultihashTypeCode = 0x1b
|
|
)
|
|
|
|
var (
|
|
multihashTypeCode uint8
|
|
MultihashLength = defaultMultihashLength
|
|
)
|
|
|
|
func init() {
|
|
multihashTypeCode = defaultMultihashTypeCode
|
|
MultihashLength = defaultMultihashLength
|
|
}
|
|
|
|
// check if valid swarm multihash
|
|
func isSwarmMultihashType(code uint8) bool {
|
|
return code == multihashTypeCode
|
|
}
|
|
|
|
// GetMultihashLength returns the digest length of the provided multihash
|
|
// It will fail if the multihash is not a valid swarm mulithash
|
|
func GetMultihashLength(data []byte) (int, int, error) {
|
|
cursor := 0
|
|
typ, c := binary.Uvarint(data)
|
|
if c <= 0 {
|
|
return 0, 0, errors.New("unreadable hashtype field")
|
|
}
|
|
if !isSwarmMultihashType(uint8(typ)) {
|
|
return 0, 0, fmt.Errorf("hash code %x is not a swarm hashtype", typ)
|
|
}
|
|
cursor += c
|
|
hashlength, c := binary.Uvarint(data[cursor:])
|
|
if c <= 0 {
|
|
return 0, 0, errors.New("unreadable length field")
|
|
}
|
|
cursor += c
|
|
|
|
// we cheekily assume hashlength < maxint
|
|
inthashlength := int(hashlength)
|
|
if len(data[c:]) < inthashlength {
|
|
return 0, 0, errors.New("length mismatch")
|
|
}
|
|
return inthashlength, cursor, nil
|
|
}
|
|
|
|
// FromMulithash returns the digest portion of the multihash
|
|
// It will fail if the multihash is not a valid swarm multihash
|
|
func FromMultihash(data []byte) ([]byte, error) {
|
|
hashLength, _, err := GetMultihashLength(data)
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
return data[len(data)-hashLength:], nil
|
|
}
|
|
|
|
// ToMulithash wraps the provided digest data with a swarm mulithash header
|
|
func ToMultihash(hashData []byte) []byte {
|
|
buf := bytes.NewBuffer(nil)
|
|
b := make([]byte, 8)
|
|
c := binary.PutUvarint(b, uint64(multihashTypeCode))
|
|
buf.Write(b[:c])
|
|
c = binary.PutUvarint(b, uint64(len(hashData)))
|
|
buf.Write(b[:c])
|
|
buf.Write(hashData)
|
|
return buf.Bytes()
|
|
}
|