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xxhash.go
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xxhash.go
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// Go Substrate RPC Client (GSRPC) provides APIs and types around Polkadot and any Substrate-based chain RPC calls
//
// Copyright 2019 Centrifuge GmbH
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package xxhash
import (
"hash"
"github.com/pierrec/xxHash/xxHash64"
)
const (
Typ64 int = iota
Typ64Concat
Typ128
Typ256
)
type state struct {
data []byte
typ int
rounds int
}
// New64 returns a new hash.Hash computing the xxhash checksum with 1 iteration
func New64(b []byte) hash.Hash {
return &state{
data: b,
typ: Typ64,
rounds: 1,
}
}
// New64Concat returns a new hash.Hash computing the xxhash checksum with 1 iteration and appending the data
func New64Concat(b []byte) hash.Hash {
return &state{
data: b,
typ: Typ64Concat,
rounds: 1,
}
}
// New128 returns a new hash.Hash computing the xxhash checksum with 2 iterations
func New128(b []byte) hash.Hash {
return &state{
data: b,
typ: Typ128,
rounds: 2,
}
}
// New256 returns a new hash.Hash computing the xxhash checksum with 4 iterations
func New256(b []byte) hash.Hash {
return &state{
data: b,
typ: Typ256,
rounds: 4,
}
}
// Write (via the embedded io.Writer interface) adds more data to the running hash.
// It never returns an error.
func (s *state) Write(p []byte) (n int, err error) {
s.data = append(s.data, p...)
return len(p), nil
}
// Sum appends the current hash to b and returns the resulting slice.
// It does not change the underlying hash state.
func (s *state) Sum(b []byte) []byte {
res := make([]byte, 0, s.rounds*8)
for i := 0; i < s.rounds; i++ {
h := xxHash64.New(uint64(i))
_, err := h.Write(s.data)
if err != nil {
panic(err)
}
res = append(res, h.Sum(nil)...)
}
if s.typ == Typ64Concat {
res = append(res, s.data...)
}
return append(b, res...)
}
// Reset resets the Hash to its initial state.
func (s *state) Reset() {
s.data = make([]byte, 0)
}
// Size returns the number of bytes Sum will return.
func (s *state) Size() int {
return len(s.Sum(nil))
}
// BlockSize returns the hash's underlying block size.
// The Write method must be able to accept any amount
// of data, but it may operate more efficiently if all writes
// are a multiple of the block size.
func (s *state) BlockSize() int {
return 64
}