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base58/README.md

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+base58
+==========
+
+[![Build Status](http://img.shields.io/travis/btcsuite/btcutil.svg)]
+(https://travis-ci.org/btcsuite/btcutil) [![ISC License]
+(http://img.shields.io/badge/license-ISC-blue.svg)](http://copyfree.org)
+[![GoDoc](https://godoc.org/github.com/btcsuite/btcutil/base58?status.png)]
+(http://godoc.org/github.com/btcsuite/btcutil/base58)
+
+Package base58 provides an API for encoding and decoding to and from the
+modified base58 encoding.  It also provides an API to do Base58Check encoding,
+as described [here](https://en.bitcoin.it/wiki/Base58Check_encoding).
+
+A comprehensive suite of tests is provided to ensure proper functionality.
+
+## Installation and Updating
+
+```bash
+$ go get -u github.com/btcsuite/btcutil/base58
+```
+
+## Examples
+
+* [Decode Example]
+  (http://godoc.org/github.com/btcsuite/btcutil/base58#example-Decode)  
+  Demonstrates how to decode modified base58 encoded data.
+* [Encode Example]
+  (http://godoc.org/github.com/btcsuite/btcutil/base58#example-Encode)  
+  Demonstrates how to encode data using the modified base58 encoding scheme.
+* [CheckDecode Example]
+  (http://godoc.org/github.com/btcsuite/btcutil/base58#example-CheckDecode)  
+  Demonstrates how to decode Base58Check encoded data.
+* [CheckEncode Example]
+  (http://godoc.org/github.com/btcsuite/btcutil/base58#example-CheckEncode)  
+  Demonstrates how to encode data using the Base58Check encoding scheme.
+
+## License
+
+Package base58 is licensed under the [copyfree](http://copyfree.org) ISC
+License.

base58/alphabet.go

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+// Copyright (c) 2015 The btcsuite developers
+// Use of this source code is governed by an ISC
+// license that can be found in the LICENSE file.
+
+// AUTOGENERATED by genalphabet.go; do not edit.
+
+package base58
+
+const (
+	// alphabet is the modified base58 alphabet used by Bitcoin.
+	alphabet = "123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz"
+
+	alphabetIdx0 = '1'
+)
+
+var b58 = [256]byte{
+	255, 255, 255, 255, 255, 255, 255, 255,
+	255, 255, 255, 255, 255, 255, 255, 255,
+	255, 255, 255, 255, 255, 255, 255, 255,
+	255, 255, 255, 255, 255, 255, 255, 255,
+	255, 255, 255, 255, 255, 255, 255, 255,
+	255, 255, 255, 255, 255, 255, 255, 255,
+	255, 0, 1, 2, 3, 4, 5, 6,
+	7, 8, 255, 255, 255, 255, 255, 255,
+	255, 9, 10, 11, 12, 13, 14, 15,
+	16, 255, 17, 18, 19, 20, 21, 255,
+	22, 23, 24, 25, 26, 27, 28, 29,
+	30, 31, 32, 255, 255, 255, 255, 255,
+	255, 33, 34, 35, 36, 37, 38, 39,
+	40, 41, 42, 43, 255, 44, 45, 46,
+	47, 48, 49, 50, 51, 52, 53, 54,
+	55, 56, 57, 255, 255, 255, 255, 255,
+	255, 255, 255, 255, 255, 255, 255, 255,
+	255, 255, 255, 255, 255, 255, 255, 255,
+	255, 255, 255, 255, 255, 255, 255, 255,
+	255, 255, 255, 255, 255, 255, 255, 255,
+	255, 255, 255, 255, 255, 255, 255, 255,
+	255, 255, 255, 255, 255, 255, 255, 255,
+	255, 255, 255, 255, 255, 255, 255, 255,
+	255, 255, 255, 255, 255, 255, 255, 255,
+	255, 255, 255, 255, 255, 255, 255, 255,
+	255, 255, 255, 255, 255, 255, 255, 255,
+	255, 255, 255, 255, 255, 255, 255, 255,
+	255, 255, 255, 255, 255, 255, 255, 255,
+	255, 255, 255, 255, 255, 255, 255, 255,
+	255, 255, 255, 255, 255, 255, 255, 255,
+	255, 255, 255, 255, 255, 255, 255, 255,
+	255, 255, 255, 255, 255, 255, 255, 255,
+}

base58/base58.go

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+// Copyright (c) 2013-2015 The btcsuite developers
+// Use of this source code is governed by an ISC
+// license that can be found in the LICENSE file.
+
+package base58
+
+import (
+	"math/big"
+)
+
+//go:generate go run genalphabet.go
+
+var bigRadix = big.NewInt(58)
+var bigZero = big.NewInt(0)
+
+// Decode decodes a modified base58 string to a byte slice.
+func Decode(b string) []byte {
+	answer := big.NewInt(0)
+	j := big.NewInt(1)
+
+	scratch := new(big.Int)
+	for i := len(b) - 1; i >= 0; i-- {
+		tmp := b58[b[i]]
+		if tmp == 255 {
+			return []byte("")
+		}
+		scratch.SetInt64(int64(tmp))
+		scratch.Mul(j, scratch)
+		answer.Add(answer, scratch)
+		j.Mul(j, bigRadix)
+	}
+
+	tmpval := answer.Bytes()
+
+	var numZeros int
+	for numZeros = 0; numZeros < len(b); numZeros++ {
+		if b[numZeros] != alphabetIdx0 {
+			break
+		}
+	}
+	flen := numZeros + len(tmpval)
+	val := make([]byte, flen, flen)
+	copy(val[numZeros:], tmpval)
+
+	return val
+}
+
+// Encode encodes a byte slice to a modified base58 string.
+func Encode(b []byte) string {
+	x := new(big.Int)
+	x.SetBytes(b)
+
+	answer := make([]byte, 0, len(b)*136/100)
+	for x.Cmp(bigZero) > 0 {
+		mod := new(big.Int)
+		x.DivMod(x, bigRadix, mod)
+		answer = append(answer, alphabet[mod.Int64()])
+	}
+
+	// leading zero bytes
+	for _, i := range b {
+		if i != 0 {
+			break
+		}
+		answer = append(answer, alphabetIdx0)
+	}
+
+	// reverse
+	alen := len(answer)
+	for i := 0; i < alen/2; i++ {
+		answer[i], answer[alen-1-i] = answer[alen-1-i], answer[i]
+	}
+
+	return string(answer)
+}

base58/base58_test.go

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+// Copyright (c) 2013-2014 The btcsuite developers
+// Use of this source code is governed by an ISC
+// license that can be found in the LICENSE file.
+
+package base58_test
+
+import (
+	"bytes"
+	"encoding/hex"
+	"testing"
+
+	"github.com/btcsuite/btcutil/base58"
+)
+
+var stringTests = []struct {
+	in  string
+	out string
+}{
+	{"", ""},
+	{" ", "Z"},
+	{"-", "n"},
+	{"0", "q"},
+	{"1", "r"},
+	{"-1", "4SU"},
+	{"11", "4k8"},
+	{"abc", "ZiCa"},
+	{"1234598760", "3mJr7AoUXx2Wqd"},
+	{"abcdefghijklmnopqrstuvwxyz", "3yxU3u1igY8WkgtjK92fbJQCd4BZiiT1v25f"},
+	{"00000000000000000000000000000000000000000000000000000000000000", "3sN2THZeE9Eh9eYrwkvZqNstbHGvrxSAM7gXUXvyFQP8XvQLUqNCS27icwUeDT7ckHm4FUHM2mTVh1vbLmk7y"},
+}
+
+var invalidStringTests = []struct {
+	in  string
+	out string
+}{
+	{"0", ""},
+	{"O", ""},
+	{"I", ""},
+	{"l", ""},
+	{"3mJr0", ""},
+	{"O3yxU", ""},
+	{"3sNI", ""},
+	{"4kl8", ""},
+	{"0OIl", ""},
+	{"!@#$%^&*()-_=+~`", ""},
+}
+
+var hexTests = []struct {
+	in  string
+	out string
+}{
+	{"61", "2g"},
+	{"626262", "a3gV"},
+	{"636363", "aPEr"},
+	{"73696d706c792061206c6f6e6720737472696e67", "2cFupjhnEsSn59qHXstmK2ffpLv2"},
+	{"00eb15231dfceb60925886b67d065299925915aeb172c06647", "1NS17iag9jJgTHD1VXjvLCEnZuQ3rJDE9L"},
+	{"516b6fcd0f", "ABnLTmg"},
+	{"bf4f89001e670274dd", "3SEo3LWLoPntC"},
+	{"572e4794", "3EFU7m"},
+	{"ecac89cad93923c02321", "EJDM8drfXA6uyA"},
+	{"10c8511e", "Rt5zm"},
+	{"00000000000000000000", "1111111111"},
+}
+
+func TestBase58(t *testing.T) {
+	// Encode tests
+	for x, test := range stringTests {
+		tmp := []byte(test.in)
+		if res := base58.Encode(tmp); res != test.out {
+			t.Errorf("Encode test #%d failed: got: %s want: %s",
+				x, res, test.out)
+			continue
+		}
+	}
+
+	// Decode tests
+	for x, test := range hexTests {
+		b, err := hex.DecodeString(test.in)
+		if err != nil {
+			t.Errorf("hex.DecodeString failed failed #%d: got: %s", x, test.in)
+			continue
+		}
+		if res := base58.Decode(test.out); bytes.Equal(res, b) != true {
+			t.Errorf("Decode test #%d failed: got: %q want: %q",
+				x, res, test.in)
+			continue
+		}
+	}
+
+	// Decode with invalid input
+	for x, test := range invalidStringTests {
+		if res := base58.Decode(test.in); string(res) != test.out {
+			t.Errorf("Decode invalidString test #%d failed: got: %q want: %q",
+				x, res, test.out)
+			continue
+		}
+	}
+}

base58/base58bench_test.go

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+// Copyright (c) 2013-2014 The btcsuite developers
+// Use of this source code is governed by an ISC
+// license that can be found in the LICENSE file.
+
+package base58_test
+
+import (
+	"bytes"
+	"testing"
+
+	"github.com/btcsuite/btcutil/base58"
+)
+
+func BenchmarkBase58Encode(b *testing.B) {
+	b.StopTimer()
+	data := bytes.Repeat([]byte{0xff}, 5000)
+	b.SetBytes(int64(len(data)))
+	b.StartTimer()
+
+	for i := 0; i < b.N; i++ {
+		base58.Encode(data)
+	}
+}
+
+func BenchmarkBase58Decode(b *testing.B) {
+	b.StopTimer()
+	data := bytes.Repeat([]byte{0xff}, 5000)
+	encoded := base58.Encode(data)
+	b.SetBytes(int64(len(encoded)))
+	b.StartTimer()
+
+	for i := 0; i < b.N; i++ {
+		base58.Decode(encoded)
+	}
+}

base58/base58check.go

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+// Copyright (c) 2013-2014 The btcsuite developers
+// Use of this source code is governed by an ISC
+// license that can be found in the LICENSE file.
+
+package base58
+
+import (
+	"crypto/sha256"
+	"errors"
+)
+
+// ErrChecksum indicates that the checksum of a check-encoded string does not verify against
+// the checksum.
+var ErrChecksum = errors.New("checksum error")
+
+// ErrInvalidFormat indicates that the check-encoded string has an invalid format.
+var ErrInvalidFormat = errors.New("invalid format: version and/or checksum bytes missing")
+
+// checksum: first four bytes of sha256^2
+func checksum(input []byte) (cksum [4]byte) {
+	h := sha256.Sum256(input)
+	h2 := sha256.Sum256(h[:])
+	copy(cksum[:], h2[:4])
+	return
+}
+
+// CheckEncode prepends two version bytes and appends a four byte checksum.
+func CheckEncode(input []byte, version [2]byte) string {
+	b := make([]byte, 0, 2+len(input)+4)
+	b = append(b, version[:]...)
+	b = append(b, input[:]...)
+	cksum := checksum(b)
+	b = append(b, cksum[:]...)
+	return Encode(b)
+}
+
+// CheckDecode decodes a string that was encoded with CheckEncode and verifies
+// the checksum.
+func CheckDecode(input string) (result []byte, version [2]byte, err error) {
+	decoded := Decode(input)
+	if len(decoded) < 6 {
+		return nil, [2]byte{0, 0}, ErrInvalidFormat
+	}
+	version = [2]byte{decoded[0], decoded[1]}
+	var cksum [4]byte
+	copy(cksum[:], decoded[len(decoded)-4:])
+	if checksum(decoded[:len(decoded)-4]) != cksum {
+		return nil, [2]byte{0, 0}, ErrChecksum
+	}
+	payload := decoded[2 : len(decoded)-4]
+	result = append(result, payload...)
+	return
+}