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// Copyright 2018-2022 the Deno authors. All rights reserved. MIT license.
/** * {@linkcode encode} and {@linkcode decode} for * [Ascii85/base85](https://en.wikipedia.org/wiki/Ascii85) encoding. * * This module is browser compatible. * * @module */
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));}