@airgap/coinlib-core/dependencies/src/bech32-1.1.3/index.js

The @airgap/coinlib-core is a protocol agnostic library to prepare, sign and broadcast cryptocurrency transactions.

'use strict'
var ALPHABET = 'qpzry9x8gf2tvdw0s3jn54khce6mua7l'

// pre-compute lookup table
var ALPHABET_MAP = {}
for (var z = 0; z < ALPHABET.length; z++) {
  var x = ALPHABET.charAt(z)

  if (ALPHABET_MAP[x] !== undefined) throw new TypeError(x + ' is ambiguous')
  ALPHABET_MAP[x] = z
}

function polymodStep (pre) {
  var b = pre >> 25
  return ((pre & 0x1FFFFFF) << 5) ^
    (-((b >> 0) & 1) & 0x3b6a57b2) ^
    (-((b >> 1) & 1) & 0x26508e6d) ^
    (-((b >> 2) & 1) & 0x1ea119fa) ^
    (-((b >> 3) & 1) & 0x3d4233dd) ^
    (-((b >> 4) & 1) & 0x2a1462b3)
}

function prefixChk (prefix) {
  var chk = 1
  for (var i = 0; i < prefix.length; ++i) {
    var c = prefix.charCodeAt(i)
    if (c < 33 || c > 126) throw new Error('Invalid prefix (' + prefix + ')')

    chk = polymodStep(chk) ^ (c >> 5)
  }
  chk = polymodStep(chk)

  for (i = 0; i < prefix.length; ++i) {
    var v = prefix.charCodeAt(i)
    chk = polymodStep(chk) ^ (v & 0x1f)
  }
  return chk
}

function encode (prefix, words, LIMIT) {
  LIMIT = LIMIT || 90
  if ((prefix.length + 7 + words.length) > LIMIT) throw new TypeError('Exceeds length limit')

  prefix = prefix.toLowerCase()

  // determine chk mod
  var chk = prefixChk(prefix)
  var result = prefix + '1'
  for (var i = 0; i < words.length; ++i) {
    var x = words[i]
    if ((x >> 5) !== 0) throw new Error('Non 5-bit word')

    chk = polymodStep(chk) ^ x
    result += ALPHABET.charAt(x)
  }

  for (i = 0; i < 6; ++i) {
    chk = polymodStep(chk)
  }
  chk ^= 1

  for (i = 0; i < 6; ++i) {
    var v = (chk >> ((5 - i) * 5)) & 0x1f
    result += ALPHABET.charAt(v)
  }

  return result
}

function decode (str, LIMIT) {
  LIMIT = LIMIT || 90
  if (str.length < 8) throw new TypeError(str + ' too short')
  if (str.length > LIMIT) throw new TypeError('Exceeds length limit')

  // don't allow mixed case
  var lowered = str.toLowerCase()
  var uppered = str.toUpperCase()
  if (str !== lowered && str !== uppered) throw new Error('Mixed-case string ' + str)
  str = lowered

  var split = str.lastIndexOf('1')
  if (split === -1) throw new Error('No separator character for ' + str)
  if (split === 0) throw new Error('Missing prefix for ' + str)

  var prefix = str.slice(0, split)
  var wordChars = str.slice(split + 1)
  if (wordChars.length < 6) throw new Error('Data too short')

  var chk = prefixChk(prefix)
  var words = []
  for (var i = 0; i < wordChars.length; ++i) {
    var c = wordChars.charAt(i)
    var v = ALPHABET_MAP[c]
    if (v === undefined) throw new Error('Unknown character ' + c)
    chk = polymodStep(chk) ^ v

    // not in the checksum?
    if (i + 6 >= wordChars.length) continue
    words.push(v)
  }

  if (chk !== 1) throw new Error('Invalid checksum for ' + str)
  return { prefix: prefix, words: words }
}

function convert (data, inBits, outBits, pad) {
  var value = 0
  var bits = 0
  var maxV = (1 << outBits) - 1

  var result = []
  for (var i = 0; i < data.length; ++i) {
    value = (value << inBits) | data[i]
    bits += inBits

    while (bits >= outBits) {
      bits -= outBits
      result.push((value >> bits) & maxV)
    }
  }

  if (pad) {
    if (bits > 0) {
      result.push((value << (outBits - bits)) & maxV)
    }
  } else {
    if (bits >= inBits) throw new Error('Excess padding')
    if ((value << (outBits - bits)) & maxV) throw new Error('Non-zero padding')
  }

  return result
}

function toWords (bytes) {
  return convert(bytes, 8, 5, true)
}

function fromWords (words) {
  return convert(words, 5, 8, false)
}

module.exports = {
  decode: decode,
  encode: encode,
  toWords: toWords,
  fromWords: fromWords
}