deno.land / std@0.139.0 / encoding / ascii85.ts

ascii85.ts
// Copyright 2018-2022 the Deno authors. All rights reserved. MIT license.// This module is browser compatible.
export type Ascii85Standard = "Adobe" | "btoa" | "RFC 1924" | "Z85";/** * encoding/decoding options * @property standard - characterset and delimiter (if supported and used). Defaults to Adobe * @property delimiter - whether to use a delimiter (if supported) - "<~" and "~>" by default */export interface Ascii85Options { standard?: Ascii85Standard; delimiter?: boolean;}const rfc1924 = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz!#$%&()*+-;<=>?@^_`{|}~";const Z85 = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ.-:+=^!/*?&<>()[]{}@%$#";/** * Encodes a given Uint8Array into ascii85, supports multiple standards * @param uint8 input to encode * @param [options] encoding options * @param [options.standard=Adobe] encoding standard (Adobe, btoa, RFC 1924 or Z85) * @param [options.delimiter] whether to use a delimiter, if supported by encoding standard */export function encode(uint8: Uint8Array, options?: Ascii85Options): string { const standard = options?.standard ?? "Adobe"; let output: string[] = [], v: number, n = 0, 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); for (let i = 0, len = uint8.length; i < len; 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 < len - 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 given ascii85 encoded string. * @param ascii85 input to decode * @param [options] decoding options * @param [options.standard=Adobe] encoding standard used in the input string (Adobe, btoa, RFC 1924 or Z85) */export function decode(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, output = new Uint8Array(len + 4 - (len % 4)); const view = new DataView(output.buffer); let v = 0, n = 0, 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));}
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