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// Copyright 2017 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package argon2
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import (
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	"encoding/binary"
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	"hash"
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	"golang.org/x/crypto/blake2b"
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)
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// blake2bHash computes an arbitrary long hash value of in
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// and writes the hash to out.
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func blake2bHash(out []byte, in []byte) {
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	var b2 hash.Hash
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	if n := len(out); n < blake2b.Size {
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		b2, _ = blake2b.New(n, nil)
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	} else {
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		b2, _ = blake2b.New512(nil)
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	}
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	var buffer [blake2b.Size]byte
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	binary.LittleEndian.PutUint32(buffer[:4], uint32(len(out)))
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	b2.Write(buffer[:4])
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	b2.Write(in)
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	if len(out) <= blake2b.Size {
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		b2.Sum(out[:0])
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		return
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	}
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	outLen := len(out)
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	b2.Sum(buffer[:0])
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	b2.Reset()
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	copy(out, buffer[:32])
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	out = out[32:]
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	for len(out) > blake2b.Size {
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		b2.Write(buffer[:])
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		b2.Sum(buffer[:0])
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		copy(out, buffer[:32])
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		out = out[32:]
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		b2.Reset()
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	}
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	if outLen%blake2b.Size > 0 { // outLen > 64
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		r := ((outLen + 31) / 32) - 2 // ⌈τ /32⌉-2
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		b2, _ = blake2b.New(outLen-32*r, nil)
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	}
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	b2.Write(buffer[:])
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	b2.Sum(out[:0])
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}
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