53 lines
1.5 KiB
Go
53 lines
1.5 KiB
Go
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// Copyright (c) 2013-2014 Conformal Systems LLC.
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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 base58
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import (
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"crypto/sha256"
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"errors"
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)
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// ErrChecksum indicates that the checksum of a check-encoded string does not verify against
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// the checksum.
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var ErrChecksum = errors.New("checksum error")
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// ErrInvalidFormat indicates that the check-encoded string has an invalid format.
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var ErrInvalidFormat = errors.New("invalid format: version and/or checksum bytes missing")
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// checksum: first four bytes of sha256^2
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func checksum(input []byte) (cksum [4]byte) {
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h := sha256.Sum256(input)
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h2 := sha256.Sum256(h[:])
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copy(cksum[:], h2[:4])
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return
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}
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// CheckEncode prepends a version byte and appends a four byte checksum.
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func CheckEncode(input []byte, version byte) string {
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b := make([]byte, 0, 1+len(input)+4)
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b = append(b, version)
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b = append(b, input[:]...)
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cksum := checksum(b)
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b = append(b, cksum[:]...)
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return Encode(b)
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}
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// CheckDecode decodes a string that was encoded with CheckEncode and verifies the checksum.
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func CheckDecode(input string) (result []byte, version byte, err error) {
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decoded := Decode(input)
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if len(decoded) < 5 {
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return nil, 0, ErrInvalidFormat
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}
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version = decoded[0]
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var cksum [4]byte
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copy(cksum[:], decoded[len(decoded)-4:])
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if checksum(decoded[:len(decoded)-4]) != cksum {
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return nil, 0, ErrChecksum
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}
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payload := decoded[1 : len(decoded)-4]
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result = append(result, payload...)
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return
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}
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