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nobs/hash/shake/xor_generic.go
Henry Case 49bf0db8fd SHAKE: Don't use function pointers (#20)
* xorIn and copyOut function pointers cause input and output data
  to be moved to heap. This degrades performance of calling code.

* This change removes usage of those function pointers. We will always
  use unaligned implementation as it's faster (but may crash on some
  systems)

* Benchmark compares generic vs unaligned xorIn and copyOut

benchmark                          old ns/op     new ns/op     delta
BenchmarkPermutationFunction-4     463           815           +76.03%
BenchmarkShake128_MTU-4            4443          8180          +84.11%
BenchmarkShake256_MTU-4            4739          9060          +91.18%
BenchmarkShake256_16x-4            71886         132629        +84.50%
BenchmarkShake256_1MiB-4           3695138       6649012       +79.94%
BenchmarkCShake128_448_16x-4       21210         24611         +16.03%
BenchmarkCShake128_1MiB-4          3009342       3396496       +12.87%
BenchmarkCShake256_448_16x-4       26034         27785         +6.73%
BenchmarkCShake256_1MiB-4          3654713       3829404       +4.78%
2019-05-14 17:08:33 +01:00

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725 B
Go

// Copyright 2015 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package shake
import "encoding/binary"
// xorInGeneric xors the bytes in buf into the state; it
// makes no non-portable assumptions about memory layout
// or alignment.
func xorInGeneric(d *state, buf []byte) {
n := len(buf) / 8
for i := 0; i < n; i++ {
a := binary.LittleEndian.Uint64(buf)
d.a[i] ^= a
buf = buf[8:]
}
}
// copyOutGeneric copies ulint64s to a byte buffer.
func copyOutGeneric(d *state, b []byte) {
for i := 0; len(b) >= 8; i++ {
binary.LittleEndian.PutUint64(b, d.a[i])
b = b[8:]
}
}
const xorImplementationGeneric = "generic"