well-goknown/vendor/github.com/btcsuite/btcd/chaincfg/chainhash/hashfuncs.go

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// Copyright (c) 2015 The Decred developers
// Copyright (c) 2016-2017 The btcsuite developers
// Use of this source code is governed by an ISC
// license that can be found in the LICENSE file.
package chainhash
import (
"crypto/sha256"
"io"
)
// HashB calculates hash(b) and returns the resulting bytes.
func HashB(b []byte) []byte {
hash := sha256.Sum256(b)
return hash[:]
}
// HashH calculates hash(b) and returns the resulting bytes as a Hash.
func HashH(b []byte) Hash {
return Hash(sha256.Sum256(b))
}
// DoubleHashB calculates hash(hash(b)) and returns the resulting bytes.
func DoubleHashB(b []byte) []byte {
first := sha256.Sum256(b)
second := sha256.Sum256(first[:])
return second[:]
}
// DoubleHashH calculates hash(hash(b)) and returns the resulting bytes as a
// Hash.
func DoubleHashH(b []byte) Hash {
first := sha256.Sum256(b)
return Hash(sha256.Sum256(first[:]))
}
// DoubleHashRaw calculates hash(hash(w)) where w is the resulting bytes from
// the given serialize function and returns the resulting bytes as a Hash.
func DoubleHashRaw(serialize func(w io.Writer) error) Hash {
// Encode the transaction into the hash. Ignore the error returns
// since the only way the encode could fail is being out of memory
// or due to nil pointers, both of which would cause a run-time panic.
h := sha256.New()
_ = serialize(h)
// This buf is here because Sum() will append the result to the passed
// in byte slice. Pre-allocating here saves an allocation on the second
// hash as we can reuse it. This allocation also does not escape to the
// heap, saving an allocation.
buf := make([]byte, 0, HashSize)
first := h.Sum(buf)
h.Reset()
h.Write(first)
res := h.Sum(buf)
return *(*Hash)(res)
}