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