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// Copyright (c) 2017 Takatoshi Nakagawa
// Copyright (c) 2019 The age Authors
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.
// Package bech32 is a modified version of the reference implementation of BIP173.
package bech32
import (
"fmt"
"strings"
)
var charset = "qpzry9x8gf2tvdw0s3jn54khce6mua7l"
var generator = []uint32{0x3b6a57b2, 0x26508e6d, 0x1ea119fa, 0x3d4233dd, 0x2a1462b3}
func polymod(values []byte) uint32 {
chk := uint32(1)
for _, v := range values {
top := chk >> 25
chk = (chk & 0x1ffffff) << 5
chk = chk ^ uint32(v)
for i := 0; i < 5; i++ {
bit := top >> i & 1
if bit == 1 {
chk ^= generator[i]
}
}
}
return chk
}
func hrpExpand(hrp string) []byte {
h := []byte(strings.ToLower(hrp))
var ret []byte
for _, c := range h {
ret = append(ret, c>>5)
}
ret = append(ret, 0)
for _, c := range h {
ret = append(ret, c&31)
}
return ret
}
func verifyChecksum(hrp string, data []byte) bool {
return polymod(append(hrpExpand(hrp), data...)) == 1
}
func createChecksum(hrp string, data []byte) []byte {
values := append(hrpExpand(hrp), data...)
values = append(values, []byte{0, 0, 0, 0, 0, 0}...)
mod := polymod(values) ^ 1
ret := make([]byte, 6)
for p := range ret {
shift := 5 * (5 - p)
ret[p] = byte(mod>>shift) & 31
}
return ret
}
func convertBits(data []byte, frombits, tobits byte, pad bool) ([]byte, error) {
var ret []byte
acc := uint32(0)
bits := byte(0)
maxv := byte(1<<tobits - 1)
for idx, value := range data {
if value>>frombits != 0 {
return nil, fmt.Errorf("invalid data range: data[%d]=%d (frombits=%d)", idx, value, frombits)
}
acc = acc<<frombits | uint32(value)
bits += frombits
for bits >= tobits {
bits -= tobits
ret = append(ret, byte(acc>>bits)&maxv)
}
}
if pad {
if bits > 0 {
ret = append(ret, byte(acc<<(tobits-bits))&maxv)
}
} else if bits >= frombits {
return nil, fmt.Errorf("illegal zero padding")
} else if byte(acc<<(tobits-bits))&maxv != 0 {
return nil, fmt.Errorf("non-zero padding")
}
return ret, nil
}
// Encode encodes the HRP and a bytes slice to Bech32. If the HRP is uppercase,
// the output will be uppercase.
func Encode(hrp string, data []byte) (string, error) {
values, err := convertBits(data, 8, 5, true)
if err != nil {
return "", err
}
if len(hrp) < 1 {
return "", fmt.Errorf("invalid HRP: %q", hrp)
}
for p, c := range hrp {
if c < 33 || c > 126 {
return "", fmt.Errorf("invalid HRP character: hrp[%d]=%d", p, c)
}
}
if strings.ToUpper(hrp) != hrp && strings.ToLower(hrp) != hrp {
return "", fmt.Errorf("mixed case HRP: %q", hrp)
}
lower := strings.ToLower(hrp) == hrp
hrp = strings.ToLower(hrp)
var ret strings.Builder
ret.WriteString(hrp)
ret.WriteString("1")
for _, p := range values {
ret.WriteByte(charset[p])
}
for _, p := range createChecksum(hrp, values) {
ret.WriteByte(charset[p])
}
if lower {
return ret.String(), nil
}
return strings.ToUpper(ret.String()), nil
}
// Decode decodes a Bech32 string. If the string is uppercase, the HRP will be uppercase.
func Decode(s string) (hrp string, data []byte, err error) {
if strings.ToLower(s) != s && strings.ToUpper(s) != s {
return "", nil, fmt.Errorf("mixed case")
}
pos := strings.LastIndex(s, "1")
if pos < 1 || pos+7 > len(s) {
return "", nil, fmt.Errorf("separator '1' at invalid position: pos=%d, len=%d", pos, len(s))
}
hrp = s[:pos]
for p, c := range hrp {
if c < 33 || c > 126 {
return "", nil, fmt.Errorf("invalid character human-readable part: s[%d]=%d", p, c)
}
}
s = strings.ToLower(s)
for p, c := range s[pos+1:] {
d := strings.IndexRune(charset, c)
if d == -1 {
return "", nil, fmt.Errorf("invalid character data part: s[%d]=%v", p, c)
}
data = append(data, byte(d))
}
if !verifyChecksum(hrp, data) {
return "", nil, fmt.Errorf("invalid checksum")
}
data, err = convertBits(data[:len(data)-6], 5, 8, false)
if err != nil {
return "", nil, err
}
return hrp, data, nil
}
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