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Arc
@@ -0,0 +1,236 @@
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//TODO - A reader MUST check that the signature is valid (see the n tagged field)
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//TODO - Tagged part of type f: the fallback on-chain address should be decoded into an address format
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//TODO - A reader MUST check that the SHA-2 256 in the h field exactly matches the hashed description.
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//TODO - A reader MUST use the n field to validate the signature instead of performing signature recovery if a valid n field is provided.
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function decode(paymentRequest) {
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let input = paymentRequest.toLowerCase();
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let splitPosition = input.lastIndexOf('1');
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let humanReadablePart = input.substring(0, splitPosition);
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let data = input.substring(splitPosition + 1, input.length - 6);
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let checksum = input.substring(input.length - 6, input.length);
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if (!verify_checksum(humanReadablePart, bech32ToFiveBitArray(data + checksum))) {
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throw 'Malformed request: checksum is incorrect'; // A reader MUST fail if the checksum is incorrect.
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}
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return {
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'human_readable_part': decodeHumanReadablePart(humanReadablePart),
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'data': decodeData(data, humanReadablePart),
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'checksum': checksum
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}
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}
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function decodeHumanReadablePart(humanReadablePart) {
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let prefixes = ['lnbc', 'lntb', 'lnbcrt', 'lnsb'];
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let prefix;
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prefixes.forEach(value => {
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if (humanReadablePart.substring(0, value.length) === value) {
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prefix = value;
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}
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});
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if (prefix == null) throw 'Malformed request: unknown prefix'; // A reader MUST fail if it does not understand the prefix.
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let amount = decodeAmount(humanReadablePart.substring(prefix.length, humanReadablePart.length));
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return {
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'prefix': prefix,
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'amount': amount
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}
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}
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function decodeData(data, humanReadablePart) {
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let date32 = data.substring(0, 7);
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let dateEpoch = bech32ToInt(date32);
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let signature = data.substring(data.length - 104, data.length);
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let tagData = data.substring(7, data.length - 104);
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let decodedTags = decodeTags(tagData);
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let value = bech32ToFiveBitArray(date32 + tagData);
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value = fiveBitArrayTo8BitArray(value, true);
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value = textToHexString(humanReadablePart).concat(byteArrayToHexString(value));
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return {
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'time_stamp': dateEpoch,
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'tags': decodedTags,
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'signature': decodeSignature(signature),
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'signing_data': value
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}
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}
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function decodeSignature(signature) {
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let data = fiveBitArrayTo8BitArray(bech32ToFiveBitArray(signature));
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let recoveryFlag = data[data.length - 1];
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let r = byteArrayToHexString(data.slice(0, 32));
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let s = byteArrayToHexString(data.slice(32, data.length - 1));
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return {
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'r': r,
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's': s,
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'recovery_flag': recoveryFlag
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}
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}
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function decodeAmount(str) {
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let multiplier = str.charAt(str.length - 1);
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let amount = str.substring(0, str.length - 1);
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if (amount.substring(0, 1) === '0') {
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throw 'Malformed request: amount cannot contain leading zeros';
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}
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amount = Number(amount);
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if (amount < 0 || !Number.isInteger(amount)) {
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throw 'Malformed request: amount must be a positive decimal integer'; // A reader SHOULD fail if amount contains a non-digit
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}
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switch (multiplier) {
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case '':
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return 'Any amount'; // A reader SHOULD indicate if amount is unspecified
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case 'p':
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return amount / 10;
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case 'n':
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return amount * 100;
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case 'u':
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return amount * 100000;
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case 'm':
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return amount * 100000000;
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default:
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// A reader SHOULD fail if amount is followed by anything except a defined multiplier.
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throw 'Malformed request: undefined amount multiplier';
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}
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}
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function decodeTags(tagData) {
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let tags = extractTags(tagData);
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let decodedTags = [];
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tags.forEach(value => decodedTags.push(decodeTag(value.type, value.length, value.data)));
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return decodedTags;
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}
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function extractTags(str) {
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let tags = [];
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while (str.length > 0) {
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let type = str.charAt(0);
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let dataLength = bech32ToInt(str.substring(1, 3));
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let data = str.substring(3, dataLength + 3);
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tags.push({
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'type': type,
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'length': dataLength,
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'data': data
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});
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str = str.substring(3 + dataLength, str.length);
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}
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return tags;
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}
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function decodeTag(type, length, data) {
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switch (type) {
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case 'p':
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if (length !== 52) break; // A reader MUST skip over a 'p' field that does not have data_length 52
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return {
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'type': type,
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'length': length,
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'description': 'payment_hash',
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'value': byteArrayToHexString(fiveBitArrayTo8BitArray(bech32ToFiveBitArray(data)))
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};
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case 'd':
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return {
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'type': type,
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'length': length,
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'description': 'description',
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'value': bech32ToUTF8String(data)
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};
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case 'n':
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if (length !== 53) break; // A reader MUST skip over a 'n' field that does not have data_length 53
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return {
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'type': type,
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'length': length,
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'description': 'payee_public_key',
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'value': byteArrayToHexString(fiveBitArrayTo8BitArray(bech32ToFiveBitArray(data)))
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};
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case 'h':
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if (length !== 52) break; // A reader MUST skip over a 'h' field that does not have data_length 52
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return {
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'type': type,
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'length': length,
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'description': 'description_hash',
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'value': data
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};
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case 'x':
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return {
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'type': type,
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'length': length,
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'description': 'expiry',
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'value': bech32ToInt(data)
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};
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case 'c':
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return {
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'type': type,
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'length': length,
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'description': 'min_final_cltv_expiry',
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'value': bech32ToInt(data)
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};
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case 'f':
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let version = bech32ToFiveBitArray(data.charAt(0))[0];
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if (version < 0 || version > 18) break; // a reader MUST skip over an f field with unknown version.
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data = data.substring(1, data.length);
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return {
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'type': type,
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'length': length,
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'description': 'fallback_address',
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'value': {
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'version': version,
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'fallback_address': data
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}
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};
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case 'r':
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data = fiveBitArrayTo8BitArray(bech32ToFiveBitArray(data));
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let pubkey = data.slice(0, 33);
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let shortChannelId = data.slice(33, 41);
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let feeBaseMsat = data.slice(41, 45);
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let feeProportionalMillionths = data.slice(45, 49);
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let cltvExpiryDelta = data.slice(49, 51);
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return {
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'type': type,
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'length': length,
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'description': 'routing_information',
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'value': {
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'public_key': byteArrayToHexString(pubkey),
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'short_channel_id': byteArrayToHexString(shortChannelId),
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'fee_base_msat': byteArrayToInt(feeBaseMsat),
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'fee_proportional_millionths': byteArrayToInt(feeProportionalMillionths),
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'cltv_expiry_delta': byteArrayToInt(cltvExpiryDelta)
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}
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};
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default:
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// reader MUST skip over unknown fields
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}
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}
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function polymod(values) {
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let GEN = [0x3b6a57b2, 0x26508e6d, 0x1ea119fa, 0x3d4233dd, 0x2a1462b3];
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let chk = 1;
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values.forEach((value) => {
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let b = (chk >> 25);
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chk = (chk & 0x1ffffff) << 5 ^ value;
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for (let i = 0; i < 5; i++) {
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if (((b >> i) & 1) === 1) {
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chk ^= GEN[i];
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} else {
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chk ^= 0;
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}
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}
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});
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return chk;
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}
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function expand(str) {
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let array = [];
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for (let i = 0; i < str.length; i++) {
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array.push(str.charCodeAt(i) >> 5);
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}
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array.push(0);
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for (let i = 0; i < str.length; i++) {
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array.push(str.charCodeAt(i) & 31);
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}
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return array;
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}
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function verify_checksum(hrp, data) {
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hrp = expand(hrp);
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let all = hrp.concat(data);
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let bool = polymod(all);
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return bool === 1;
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}
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