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A Kotlin multiplatform REST client utilizing secret network's gRPC gateway endpoints.
package io.eqoty.secretk.utils.bech32
import io.eqoty.secretk.utils.bech32.BitConverter.from5BitArray
import io.eqoty.secretk.utils.bech32.BitConverter.to5BitArray
import kotlin.experimental.and
sealed class Bech32Error(override val message: String) : Error()
class InvalidDataLength(message: String) : Bech32Error(message)
class InvalidCharacter(character: Char, index: Int) : Bech32Error("Invalid char:$character, at index: $index")
class InvalidPrefix(message: String) : Bech32Error(message)
class InvalidChecksum : Bech32Error("InvalidChecksum")
class RangeError(message: String) : Bech32Error(message)
// Based on:
//https://github.com/bitcoinj/bitcoinj/tree/master/core/src/main/java/org/bitcoinj/core
//https://github.com/slowli/bech32-buffer
//https://github.com/bitcoinjs/bech32/blob/master/src/index.ts
/**
*
* Implementation of the Bech32 encoding.
*
*
* See [BIP350](https://github.com/bitcoin/bips/blob/master/bip-0350.mediawiki) and
* [BIP173](https://github.com/bitcoin/bips/blob/master/bip-0173.mediawiki) for details.
*/
object Bech32 {
/** The Bech32 character set for encoding. */
val CHARSET = "qpzry9x8gf2tvdw0s3jn54khce6mua7l"
/** The Bech32 character set for decoding. */
val CHARSET_REV = byteArrayOf(
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
15, -1, 10, 17, 21, 20, 26, 30, 7, 5, -1, -1, -1, -1, -1, -1,
-1, 29, -1, 24, 13, 25, 9, 8, 23, -1, 18, 22, 31, 27, 19, -1,
1, 0, 3, 16, 11, 28, 12, 14, 6, 4, 2, -1, -1, -1, -1, -1,
-1, 29, -1, 24, 13, 25, 9, 8, 23, -1, 18, 22, 31, 27, 19, -1,
1, 0, 3, 16, 11, 28, 12, 14, 6, 4, 2, -1, -1, -1, -1, -1
)
val CHECKSUM_LENGTH = 6
// Minimum char code that could be present in the encoded message
private val MIN_CHAR_CODE = 33
// Maximum char code that could be present in the encoded message
private val MAX_CHAR_CODE = 126
// Maximum encoded message length
private val MAX_ENC_LENGTH = 90
/** Encode a Bech32 string. */
fun encode(bech32: Bech32Data): String {
return encode(bech32.encoding, bech32.hrp, bech32.data)
}
/**
* Encodes binary data into Bech32 encoding.
*
* @param {string} prefix
* Human-readable prefix to place at the beginning of the encoding
* @param {ByteArray} data
* Binary data to encode
* @param {Encoding} encoding
* Encoding to use influences the checksum computation. If not specified,
* Bech32 encoding will be used.
* @returns {string}
* Bech32 encoding of data in the form `1`
*
* @api public
*/
fun encode(encoding: Encoding = Encoding.BECH32, prefix: String, data: ByteArray): String =
encode5BitArray(prefix, to5BitArray(data), encoding)
/**
* Based on: https://github.com/bitcoinjs/bech32/blob/master/src/index.ts
*/
private fun encode5BitArray(prefix: String, data: ByteArray, encoding: Encoding): String {
// 1. Allocate buffer for all operations
// expanded prefix + five-bit data encoding + CHECKSUM_LENGTH
val len = 2 * prefix.length + 1 + data.size + CHECKSUM_LENGTH
if (len - prefix.length > MAX_ENC_LENGTH) {
throw Error("Message to be produced is too long (max $MAX_ENC_LENGTH supported)")
}
// determine chk mod
var chk = prefixChk(prefix)
var result = prefix + "1"
for (i in data.indices) {
val x = data[i].toInt()
if (x shr 5 != 0) throw Error("Non 5-bit word")
chk = polymodStep(chk) xor x
result += CHARSET[x]
}
for (i in 0 until CHECKSUM_LENGTH) {
chk = polymodStep(chk)
}
chk = chk xor encoding.checksum
for (i in 0 until CHECKSUM_LENGTH) {
val v = (chk shr ((5 - i) * 5)) and 0x1f
result += CHARSET[v]
}
return result
}
fun decode(message: String): Bech32Data {
val fiveBitBech32Data = decodeTo5BitArray(message)
return Bech32Data(fiveBitBech32Data.encoding, fiveBitBech32Data.hrp, from5BitArray(fiveBitBech32Data.data))
}
/** Decode a Bech32 string. */
fun decodeTo5BitArray(str: String): Bech32Data {
var lower = false
var upper = false
if (str.length < 8) throw InvalidDataLength("Input too short: " + str.length)
if (str.length > 90) throw InvalidDataLength("Input too long: " + str.length)
for (i in 0 until str.length) {
val c = str[i]
if (c.code < 33 || c.code > 126) throw InvalidCharacter(c, i)
if (c >= 'a' && c <= 'z') {
if (upper) throw InvalidCharacter(c, i)
lower = true
}
if (c >= 'A' && c <= 'Z') {
if (lower) throw InvalidCharacter(c, i)
upper = true
}
}
val pos = str.lastIndexOf('1')
if (pos < 1) throw InvalidPrefix("Missing human-readable part")
val dataPartLength = str.length - 1 - pos
if (dataPartLength < 6) throw InvalidDataLength("Data part too short: $dataPartLength")
val values = ByteArray(dataPartLength)
for (i in 0 until dataPartLength) {
val c = str[i + pos + 1]
if (CHARSET_REV[c.code].toInt() == -1) throw InvalidCharacter(c, i + pos + 1)
values[i] = CHARSET_REV[c.code]
}
val hrp = str.substring(0, pos).lowercase()
val encoding = verifyChecksum(hrp, values) ?: throw InvalidChecksum()
return Bech32Data(encoding, hrp, values.copyOfRange(0, values.size - 6))
}
fun prefixChk(prefix: String): Int {
var chk = 1
for (i in prefix.indices) {
val c = prefix[i].code
if (c < MIN_CHAR_CODE || c > MAX_CHAR_CODE) {
throw RangeError("Invalid char in prefix: $c should be in ASCII range $MIN_CHAR_CODE-$MAX_CHAR_CODE")
}
chk = polymodStep(chk) xor (c shr 5)
}
chk = polymodStep(chk)
for (i in prefix.indices) {
val v = prefix[i].code
chk = polymodStep(chk) xor (v and 0x1f)
}
return chk
}
fun polymodStep(pre: Int): Int {
val b = pre shr 25
return (
((pre and 0x1ffffff) shl 5) xor
(-((b shr 0) and 1) and 0x3b6a57b2) xor
(-((b shr 1) and 1) and 0x26508e6d) xor
(-((b shr 2) and 1) and 0x1ea119fa) xor
(-((b shr 3) and 1) and 0x3d4233dd) xor
(-((b shr 4) and 1) and 0x2a1462b3)
)
}
/** Find the polynomial with value coefficients mod the generator as 30-bit. */
private fun polymod(values: ByteArray): Int {
var c = 1
for (v_i in values) {
val c0 = c ushr 25 and 0xff
c = c and 0x1ffffff shl 5 xor (v_i and 0xff.toByte()).toInt()
if (c0 and 1 != 0) c = c xor 0x3b6a57b2
if (c0 and 2 != 0) c = c xor 0x26508e6d
if (c0 and 4 != 0) c = c xor 0x1ea119fa
if (c0 and 8 != 0) c = c xor 0x3d4233dd
if (c0 and 16 != 0) c = c xor 0x2a1462b3
}
return c
}
/** Expand a HRP for use in checksum computation. */
private fun expandHrp(hrp: String): ByteArray {
val hrpLength = hrp.length
val ret = ByteArray(hrpLength * 2 + 1)
for (i in 0 until hrpLength) {
val c = hrp[i].code and 0x7f // Limit to standard 7-bit ASCII
ret[i] = (c ushr 5 and 0x07).toByte()
ret[i + hrpLength + 1] = (c and 0x1f).toByte()
}
ret[hrpLength] = 0
return ret
}
/** Verify a checksum. */
fun verifyChecksum(hrp: String, values: ByteArray): Encoding? {
val hrpExpanded = expandHrp(hrp)
val combined = ByteArray(hrpExpanded.size + values.size)
hrpExpanded.copyInto(combined, 0, 0, hrpExpanded.size)
values.copyInto(combined, hrpExpanded.size, 0, values.size)
val check = polymod(combined)
return when (check) {
Encoding.BECH32.checksum -> Encoding.BECH32
Encoding.BECH32M.checksum -> Encoding.BECH32M
else -> null
}
}
enum class Encoding(val checksum: Int) {
BECH32(1),
BECH32M(0x2bc830a3)
}
class Bech32Data constructor(val encoding: Encoding, val hrp: String, val data: ByteArray)
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