74 lines
2.0 KiB
TypeScript
74 lines
2.0 KiB
TypeScript
/**
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* The [Base58 Encoding](link-base58) scheme allows a **numeric** value
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* to be encoded as a compact string using a radix of 58 using only
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* alpha-numeric characters. Confusingly similar characters are omitted
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* (i.e. ``"l0O"``).
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*
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* Note that Base58 encodes a **numeric** value, not arbitrary bytes,
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* since any zero-bytes on the left would get removed. To mitigate this
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* issue most schemes that use Base58 choose specific high-order values
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* to ensure non-zero prefixes.
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*
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* @_subsection: api/utils:Base58 Encoding [about-base58]
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*/
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import { getBytes } from "./data.js";
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import { assertArgument } from "./errors.js";
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import { toBigInt } from "./maths.js";
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import type { BytesLike } from "./index.js";
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const Alphabet = "123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz";
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let Lookup: null | Record<string, bigint> = null;
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function getAlpha(letter: string): bigint {
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if (Lookup == null) {
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Lookup = { };
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for (let i = 0; i < Alphabet.length; i++) {
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Lookup[Alphabet[i]] = BigInt(i);
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}
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}
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const result = Lookup[letter];
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assertArgument(result != null, `invalid base58 value`, "letter", letter);
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return result;
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}
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const BN_0 = BigInt(0);
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const BN_58 = BigInt(58);
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/**
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* Encode %%value%% as a Base58-encoded string.
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*/
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export function encodeBase58(_value: BytesLike): string {
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const bytes = getBytes(_value);
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let value = toBigInt(bytes);
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let result = "";
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while (value) {
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result = Alphabet[Number(value % BN_58)] + result;
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value /= BN_58;
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}
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// Account for leading padding zeros
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for (let i = 0; i < bytes.length; i++) {
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if (bytes[i]) { break; }
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result = Alphabet[0] + result;
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}
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return result;
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}
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/**
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* Decode the Base58-encoded %%value%%.
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*/
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export function decodeBase58(value: string): bigint {
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let result = BN_0;
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for (let i = 0; i < value.length; i++) {
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result *= BN_58;
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result += getAlpha(value[i]);
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}
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return result;
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}
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