711f33450c
This is a backport of the chainhash package made in Decred along with a few additional things cleaned up, finished test coverage, and rewording of some documentation to make it more generic. In particular, the new package provides the definition of the hash type and associated hashing functions which will allow the rest of the code to be agnostic to the specific hash algorithm. This only implements the package and does not change any of the code base over to use it.
119 lines
3.2 KiB
Go
119 lines
3.2 KiB
Go
// Copyright (c) 2013-2016 The btcsuite developers
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// Copyright (c) 2015 The Decred developers
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// Use of this source code is governed by an ISC
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// license that can be found in the LICENSE file.
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package chainhash
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import (
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"encoding/hex"
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"fmt"
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)
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// HashSize of array used to store hashes. See Hash.
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const HashSize = 32
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// MaxHashStringSize is the maximum length of a Hash hash string.
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const MaxHashStringSize = HashSize * 2
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// ErrHashStrSize describes an error that indicates the caller specified a hash
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// string that has too many characters.
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var ErrHashStrSize = fmt.Errorf("max hash string length is %v bytes", MaxHashStringSize)
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// Hash is used in several of the bitcoin messages and common structures. It
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// typically represents the double sha256 of data.
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type Hash [HashSize]byte
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// String returns the Hash as the hexadecimal string of the byte-reversed
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// hash.
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func (hash Hash) String() string {
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for i := 0; i < HashSize/2; i++ {
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hash[i], hash[HashSize-1-i] = hash[HashSize-1-i], hash[i]
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}
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return hex.EncodeToString(hash[:])
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}
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// CloneBytes returns a copy of the bytes which represent the hash as a byte
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// slice.
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//
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// NOTE: It is generally cheaper to just slice the hash directly thereby reusing
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// the same bytes rather than calling this method.
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func (hash *Hash) CloneBytes() []byte {
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newHash := make([]byte, HashSize)
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copy(newHash, hash[:])
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return newHash
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}
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// SetBytes sets the bytes which represent the hash. An error is returned if
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// the number of bytes passed in is not HashSize.
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func (hash *Hash) SetBytes(newHash []byte) error {
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nhlen := len(newHash)
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if nhlen != HashSize {
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return fmt.Errorf("invalid hash length of %v, want %v", nhlen,
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HashSize)
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}
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copy(hash[:], newHash)
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return nil
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}
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// IsEqual returns true if target is the same as hash.
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func (hash *Hash) IsEqual(target *Hash) bool {
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if hash == nil && target == nil {
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return true
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}
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if hash == nil || target == nil {
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return false
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}
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return *hash == *target
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}
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// NewHash returns a new Hash from a byte slice. An error is returned if
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// the number of bytes passed in is not HashSize.
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func NewHash(newHash []byte) (*Hash, error) {
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var sh Hash
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err := sh.SetBytes(newHash)
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if err != nil {
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return nil, err
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}
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return &sh, err
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}
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// NewHashFromStr creates a Hash from a hash string. The string should be
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// the hexadecimal string of a byte-reversed hash, but any missing characters
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// result in zero padding at the end of the Hash.
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func NewHashFromStr(hash string) (*Hash, error) {
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// Return error if hash string is too long.
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if len(hash) > MaxHashStringSize {
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return nil, ErrHashStrSize
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}
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// Hex decoder expects the hash to be a multiple of two.
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if len(hash)%2 != 0 {
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hash = "0" + hash
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}
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// Convert string hash to bytes.
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buf, err := hex.DecodeString(hash)
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if err != nil {
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return nil, err
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}
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// Un-reverse the decoded bytes, copying into in leading bytes of a
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// Hash. There is no need to explicitly pad the result as any
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// missing (when len(buf) < HashSize) bytes from the decoded hex string
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// will remain zeros at the end of the Hash.
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var ret Hash
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blen := len(buf)
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mid := blen / 2
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if blen%2 != 0 {
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mid++
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}
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blen--
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for i, b := range buf[:mid] {
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ret[i], ret[blen-i] = buf[blen-i], b
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}
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return &ret, nil
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}
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