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std/encoding/ascii85.ts

The Deno Standard Library
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// Copyright 2018-2024 the Deno authors. All rights reserved. MIT license.// This module is browser compatible.
/** * Utilities for working with {@link https://en.wikipedia.org/wiki/Ascii85 | ascii85} encoding. * * This module is browser compatible. * * ## Specifying a standard and delimiter * * By default, all functions are using the most popular Adobe version of ascii85 * and not adding any delimiter. However, there are three more standards * supported - btoa (different delimiter and additional compression of 4 bytes * equal to 32), {@link https://rfc.zeromq.org/spec/32/ | Z85} and * {@link https://tools.ietf.org/html/rfc1924 | RFC 1924}. It's possible to use a * different encoding by specifying it in `options` object as a second parameter. * * Similarly, it's possible to make `encode` add a delimiter (`<~` and `~>` for * Adobe, `xbtoa Begin` and `xbtoa End` with newlines between the delimiters and * encoded data for btoa. Checksums for btoa are not supported. Delimiters are not * supported by other encodings.) * * @module */
import { validateBinaryLike } from "./_util.ts";
/** Supported ascii85 standards for {@linkcode Ascii85Options}. */export type Ascii85Standard = "Adobe" | "btoa" | "RFC 1924" | "Z85";
/** Options for {@linkcode encodeAscii85} and {@linkcode decodeAscii85}. */export interface Ascii85Options { /** * Character set and delimiter (if supported and used). * * @default {"Adobe"} */ standard?: Ascii85Standard; /** * Whether to use a delimiter (if supported). * * @default {false} */ delimiter?: boolean;}const rfc1924 = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz!#$%&()*+-;<=>?@^_`{|}~" as const;const Z85 = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ.-:+=^!/*?&<>()[]{}@%$#" as const;
/** * Converts data into an ascii58-encoded string. * * @example * ```ts * import { encodeAscii85 } from "https://deno.land/std@$STD_VERSION/encoding/ascii85.ts"; * * encodeAscii85("Hello world!"); // "87cURD]j7BEbo80" * ``` */export function encodeAscii85( data: ArrayBuffer | Uint8Array | string, options?: Ascii85Options,): string { let uint8 = validateBinaryLike(data);
const standard = options?.standard ?? "Adobe"; let output: string[] = []; let v: number; let n = 0; let difference = 0; if (uint8.length % 4 !== 0) { const tmp = uint8; difference = 4 - (tmp.length % 4); uint8 = new Uint8Array(tmp.length + difference); uint8.set(tmp); } const view = new DataView(uint8.buffer, uint8.byteOffset, uint8.byteLength); for (let i = 0; i < uint8.length; i += 4) { v = view.getUint32(i); // Adobe and btoa standards compress 4 zeroes to single "z" character if ( (standard === "Adobe" || standard === "btoa") && v === 0 && i < uint8.length - difference - 3 ) { output[n++] = "z"; continue; } // btoa compresses 4 spaces - that is, bytes equal to 32 - into single "y" character if (standard === "btoa" && v === 538976288) { output[n++] = "y"; continue; } for (let j = 4; j >= 0; j--) { output[n + j] = String.fromCharCode((v % 85) + 33); v = Math.trunc(v / 85); } n += 5; } switch (standard) { case "Adobe": if (options?.delimiter) { return `<~${output.slice(0, output.length - difference).join("")}~>`; } break; case "btoa": if (options?.delimiter) { return `xbtoa Begin\n${ output .slice(0, output.length - difference) .join("") }\nxbtoa End`; } break; case "RFC 1924": output = output.map((val) => rfc1924[val.charCodeAt(0) - 33]!); break; case "Z85": output = output.map((val) => Z85[val.charCodeAt(0) - 33]!); break; } return output.slice(0, output.length - difference).join("");}
/** * Decodes a ascii85-encoded string. * * @param ascii85 The ascii85-encoded string to decode. * @param options Options for decoding. * @returns The decoded data. * * @example * ```ts * import { decodeAscii85 } from "https://deno.land/std@$STD_VERSION/encoding/ascii85.ts"; * * decodeAscii85("87cURD]j7BEbo80"); * // Uint8Array(12) [ 72, 101, 108, 108, 111, 32, 119, 111, 114, 108, 100, 33 ] * ``` */export function decodeAscii85( ascii85: string, options?: Ascii85Options,): Uint8Array { const encoding = options?.standard ?? "Adobe"; // translate all encodings to most basic adobe/btoa one and decompress some special characters ("z" and "y") switch (encoding) { case "Adobe": ascii85 = ascii85.replaceAll(/(<~|~>)/g, "").replaceAll("z", "!!!!!"); break; case "btoa": ascii85 = ascii85 .replaceAll(/(xbtoa Begin|xbtoa End|\n)/g, "") .replaceAll("z", "!!!!!") .replaceAll("y", "+<VdL"); break; case "RFC 1924": ascii85 = ascii85.replaceAll( /./g, (match) => String.fromCharCode(rfc1924.indexOf(match) + 33), ); break; case "Z85": ascii85 = ascii85.replaceAll( /./g, (match) => String.fromCharCode(Z85.indexOf(match) + 33), ); break; } // remove all invalid characters ascii85 = ascii85.replaceAll(/[^!-u]/g, ""); const len = ascii85.length; const output = new Uint8Array(len + 4 - (len % 4)); const view = new DataView(output.buffer); let v = 0; let n = 0; let max = 0; for (let i = 0; i < len;) { for (max += 5; i < max; i++) { v = v * 85 + (i < len ? ascii85.charCodeAt(i) : 117) - 33; } view.setUint32(n, v); v = 0; n += 4; } return output.slice(0, Math.trunc(len * 0.8));}