mirror of
https://github.com/denoland/std.git
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219 lines
6.8 KiB
TypeScript
219 lines
6.8 KiB
TypeScript
// Copyright 2018-2024 the Deno authors. All rights reserved. MIT license.
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// Copyright (c) 2014 Jameson Little. MIT License.
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// This module is browser compatible.
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/**
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* common code for base32 and base32hex encodings.
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*/
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import { validateBinaryLike } from "./_validate_binary_like.ts";
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const placeHolderPadLookup = [0, 1, , 2, 3, , 4];
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function getPadLength(placeHoldersLen: number): number {
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const maybeLen = placeHolderPadLookup[placeHoldersLen];
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if (typeof maybeLen !== "number") {
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throw new Error("Invalid pad length");
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}
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return maybeLen;
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}
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function getLens(b32: string): [number, number] {
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const len = b32.length;
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if (len % 8 > 0) {
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throw new Error(
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`Cannot decode base32 string as the length must be a multiple of 8: received length ${len}`,
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);
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}
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let validLen = b32.indexOf("=");
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if (validLen === -1) validLen = len;
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const placeHoldersLen = validLen === len ? 0 : 8 - (validLen % 8);
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return [validLen, placeHoldersLen];
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}
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function getByteLength(validLen: number, placeHoldersLen: number): number {
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return ((validLen + placeHoldersLen) * 5) / 8 - getPadLength(placeHoldersLen);
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}
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/**
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* Decodes an encoded string with the given lookup table.
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*
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* @param b32 The string to encode.
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* @param lookup The lookup table
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* @returns The encoded string.
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*/
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export function decode(b32: string, lookup: ReadonlyArray<string>): Uint8Array {
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const revLookup: number[] = [];
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lookup.forEach((c, i) => (revLookup[c.charCodeAt(0)] = i));
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let tmp: number;
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const [validLen, placeHoldersLen] = getLens(b32);
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const arr = new Uint8Array(getByteLength(validLen, placeHoldersLen));
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let curByte = 0;
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// if there are placeholders, only get up to the last complete 8 chars
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const len = placeHoldersLen > 0 ? validLen - 8 : validLen;
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let i: number;
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for (i = 0; i < len; i += 8) {
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tmp = (revLookup[b32.charCodeAt(i)]! << 20) |
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(revLookup[b32.charCodeAt(i + 1)]! << 15) |
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(revLookup[b32.charCodeAt(i + 2)]! << 10) |
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(revLookup[b32.charCodeAt(i + 3)]! << 5) |
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revLookup[b32.charCodeAt(i + 4)]!;
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arr[curByte++] = (tmp >> 17) & 0xff;
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arr[curByte++] = (tmp >> 9) & 0xff;
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arr[curByte++] = (tmp >> 1) & 0xff;
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tmp = ((tmp & 1) << 15) |
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(revLookup[b32.charCodeAt(i + 5)]! << 10) |
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(revLookup[b32.charCodeAt(i + 6)]! << 5) |
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revLookup[b32.charCodeAt(i + 7)]!;
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arr[curByte++] = (tmp >> 8) & 0xff;
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arr[curByte++] = tmp & 0xff;
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}
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if (placeHoldersLen === 1) {
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tmp = (revLookup[b32.charCodeAt(i)]! << 20) |
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(revLookup[b32.charCodeAt(i + 1)]! << 15) |
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(revLookup[b32.charCodeAt(i + 2)]! << 10) |
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(revLookup[b32.charCodeAt(i + 3)]! << 5) |
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revLookup[b32.charCodeAt(i + 4)]!;
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arr[curByte++] = (tmp >> 17) & 0xff;
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arr[curByte++] = (tmp >> 9) & 0xff;
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arr[curByte++] = (tmp >> 1) & 0xff;
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tmp = ((tmp & 1) << 7) |
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(revLookup[b32.charCodeAt(i + 5)]! << 2) |
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(revLookup[b32.charCodeAt(i + 6)]! >> 3);
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arr[curByte++] = tmp & 0xff;
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} else if (placeHoldersLen === 3) {
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tmp = (revLookup[b32.charCodeAt(i)]! << 19) |
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(revLookup[b32.charCodeAt(i + 1)]! << 14) |
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(revLookup[b32.charCodeAt(i + 2)]! << 9) |
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(revLookup[b32.charCodeAt(i + 3)]! << 4) |
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(revLookup[b32.charCodeAt(i + 4)]! >> 1);
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arr[curByte++] = (tmp >> 16) & 0xff;
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arr[curByte++] = (tmp >> 8) & 0xff;
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arr[curByte++] = tmp & 0xff;
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} else if (placeHoldersLen === 4) {
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tmp = (revLookup[b32.charCodeAt(i)]! << 11) |
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(revLookup[b32.charCodeAt(i + 1)]! << 6) |
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(revLookup[b32.charCodeAt(i + 2)]! << 1) |
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(revLookup[b32.charCodeAt(i + 3)]! >> 4);
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arr[curByte++] = (tmp >> 8) & 0xff;
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arr[curByte++] = tmp & 0xff;
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} else if (placeHoldersLen === 6) {
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tmp = (revLookup[b32.charCodeAt(i)]! << 3) |
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(revLookup[b32.charCodeAt(i + 1)]! >> 2);
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arr[curByte++] = tmp & 0xff;
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}
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return arr;
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}
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function encodeChunk(
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uint8: Uint8Array,
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start: number,
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end: number,
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lookup: ReadonlyArray<string>,
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): string {
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let tmp: number;
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const output = [];
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for (let i = start; i < end; i += 5) {
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tmp = ((uint8[i]! << 16) & 0xff0000) |
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((uint8[i + 1]! << 8) & 0xff00) |
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(uint8[i + 2]! & 0xff);
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output.push(lookup[(tmp >> 19) & 0x1f]);
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output.push(lookup[(tmp >> 14) & 0x1f]);
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output.push(lookup[(tmp >> 9) & 0x1f]);
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output.push(lookup[(tmp >> 4) & 0x1f]);
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tmp = ((tmp & 0xf) << 16) |
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((uint8[i + 3]! << 8) & 0xff00) |
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(uint8[i + 4]! & 0xff);
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output.push(lookup[(tmp >> 15) & 0x1f]);
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output.push(lookup[(tmp >> 10) & 0x1f]);
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output.push(lookup[(tmp >> 5) & 0x1f]);
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output.push(lookup[tmp & 0x1f]);
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}
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return output.join("");
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}
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/**
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* Encodes the given data using the lookup table.
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*
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* @param data The data to encode.
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* @param lookup The lookup table.
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* @returns The encoded string.
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*/
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export function encode(
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data: ArrayBuffer | Uint8Array | string,
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lookup: ReadonlyArray<string>,
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): string {
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const uint8 = validateBinaryLike(data);
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let tmp: number;
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const len = uint8.length;
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const extraBytes = len % 5;
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const parts = [];
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const maxChunkLength = 16385; // must be multiple of 5
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const len2 = len - extraBytes;
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// go through the array every 5 bytes, we'll deal with trailing stuff later
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for (let i = 0; i < len2; i += maxChunkLength) {
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parts.push(
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encodeChunk(
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uint8,
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i,
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i + maxChunkLength > len2 ? len2 : i + maxChunkLength,
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lookup,
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),
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);
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}
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// pad the end with zeros, but make sure to not forget the extra bytes
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if (extraBytes === 4) {
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tmp = ((uint8[len2]! & 0xff) << 16) |
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((uint8[len2 + 1]! & 0xff) << 8) |
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(uint8[len2 + 2]! & 0xff);
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parts.push(lookup[(tmp >> 19) & 0x1f]);
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parts.push(lookup[(tmp >> 14) & 0x1f]);
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parts.push(lookup[(tmp >> 9) & 0x1f]);
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parts.push(lookup[(tmp >> 4) & 0x1f]);
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tmp = ((tmp & 0xf) << 11) | (uint8[len2 + 3]! << 3);
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parts.push(lookup[(tmp >> 10) & 0x1f]);
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parts.push(lookup[(tmp >> 5) & 0x1f]);
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parts.push(lookup[tmp & 0x1f]);
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parts.push("=");
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} else if (extraBytes === 3) {
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tmp = ((uint8[len2]! & 0xff) << 17) |
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((uint8[len2 + 1]! & 0xff) << 9) |
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((uint8[len2 + 2]! & 0xff) << 1);
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parts.push(lookup[(tmp >> 20) & 0x1f]);
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parts.push(lookup[(tmp >> 15) & 0x1f]);
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parts.push(lookup[(tmp >> 10) & 0x1f]);
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parts.push(lookup[(tmp >> 5) & 0x1f]);
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parts.push(lookup[tmp & 0x1f]);
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parts.push("===");
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} else if (extraBytes === 2) {
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tmp = ((uint8[len2]! & 0xff) << 12) | ((uint8[len2 + 1]! & 0xff) << 4);
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parts.push(lookup[(tmp >> 15) & 0x1f]);
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parts.push(lookup[(tmp >> 10) & 0x1f]);
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parts.push(lookup[(tmp >> 5) & 0x1f]);
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parts.push(lookup[tmp & 0x1f]);
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parts.push("====");
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} else if (extraBytes === 1) {
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tmp = (uint8[len2]! & 0xff) << 2;
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parts.push(lookup[(tmp >> 5) & 0x1f]);
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parts.push(lookup[tmp & 0x1f]);
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parts.push("======");
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}
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return parts.join("");
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}
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