[Pisces] / base64.js

// ♓🌟 Piscēs ∷ base64.js
// ====================================================================
//
// Copyright © 2020–2022 Lady [@ Lady’s Computer].
//
// This Source Code Form is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this
// file, You can obtain one at <https://mozilla.org/MPL/2.0/>.

import { fill, map, reduce } from "./collection.js";
import { bind, call } from "./function.js";
import { ceil, floor } from "./numeric.js";
import { hasOwnProperty, objectCreate } from "./object.js";
import {
  getCodeUnit,
  rawString,
  stringFromCodeUnits,
  stringReplace,
} from "./string.js";

const Buffer = ArrayBuffer;
const View = DataView;
const TypedArray = Object.getPrototypeOf(Uint8Array);
const { prototype: arrayPrototype } = Array;
const { prototype: bufferPrototype } = Buffer;
const { iterator: iteratorSymbol } = Symbol;
const { prototype: rePrototype } = RegExp;
const { prototype: typedArrayPrototype } = TypedArray;
const { prototype: viewPrototype } = View;

const { [iteratorSymbol]: arrayIterator } = arrayPrototype;
const {
  next: arrayIteratorNext,
} = Object.getPrototypeOf([][iteratorSymbol]());
const getBufferByteLength =
  Object.getOwnPropertyDescriptor(bufferPrototype, "byteLength").get;
const getTypedArrayBuffer =
  Object.getOwnPropertyDescriptor(typedArrayPrototype, "buffer").get;
const getViewBuffer =
  Object.getOwnPropertyDescriptor(viewPrototype, "buffer").get;
const { exec: reExec } = rePrototype;
const {
  getUint8: viewGetUint8,
  setUint8: viewSetUint8,
  setUint16: viewSetUint16,
} = viewPrototype;

const base64CodeUnitIterablePrototype = {
  [iteratorSymbol]() {
    return {
      next: bind(
        arrayIteratorNext,
        call(arrayIterator, this, []),
        [],
      ),
    };
  },
};

/**
 * Returns an ArrayBuffer generated from the provided Base64.
 *
 * This function can also be used as a tag for a template literal. The
 * literal will be interpreted akin to `String.raw`.
 */
export const a2b = ($, ...$s) => {
  const source = stringReplace(
    typeof $ == "string"
      ? $
      : hasOwnProperty($, "raw")
      ? rawString($, ...$s)
      : `${$}`,
    /[\t\n\f\r ]+/gu,
    "",
  );
  const u6s = map(
    source.length % 4 == 0
      ? stringReplace(source, /={1,2}$/u, "")
      : source,
    (ucsCharacter) => {
      const code = getCodeUnit(ucsCharacter, 0);
      const result = code >= 0x41 && code <= 0x5A
        ? code - 65
        : code >= 0x61 && code <= 0x7A
        ? code - 71
        : code >= 0x30 && code <= 0x39
        ? code + 4
        : code == 0x2B
        ? 62
        : code == 0x2F
        ? 63
        : -1;
      if (result < 0) {
        throw new RangeError(
          `Piscēs: Invalid character in Base64: ${character}.`,
        );
      } else {
        return result;
      }
    },
  );
  const { length } = u6s;
  const dataView = new View(new Buffer(floor(length * 3 / 4)));
  for (let index = 0; index < length - 1;) {
    const dataIndex = ceil(index * 3 / 4);
    const remainder = index % 3;
    if (remainder == 0) {
      call(viewSetUint8, dataView, [
        dataIndex,
        (u6s[index] << 2) + (u6s[++index] >> 4),
      ]);
    } else if (remainder == 1) {
      call(viewSetUint8, dataView, [
        dataIndex,
        ((u6s[index] & 0xF) << 4) + (u6s[++index] >> 2),
      ]);
    } else {
      call(viewSetUint8, dataView, [
        dataIndex,
        ((u6s[index] & 0x3) << 6) + u6s[++index],
      ]);
    }
  }
  return call(getViewBuffer, dataView, []);
};

/**
 * Returns a (big‐endian) base64 string created from a typed array,
 * buffer, or string.
 *
 * This function can also be used as a tag for a template literal. The
 * literal will be interpreted akin to `String.raw`.
 */
export const b2a = ($, ...$s) => {
  const buffer = $ instanceof Buffer
    ? $
    : $ instanceof View
    ? call(getViewBuffer, $, [])
    : $ instanceof TypedArray
    ? call(getTypedArrayBuffer, $, [])
    : ((string) =>
      call(
        getViewBuffer,
        reduce(
          string,
          (result, ucsCharacter, index) => (
            call(viewSetUint16, result, [
              index * 2,
              getCodeUnit(ucsCharacter, 0),
            ]), result
          ),
          new View(new Buffer(string.length * 2)),
        ),
        [],
      ))(
        typeof $ == "string"
          ? $
          : hasOwnProperty($, "raw")
          ? rawString($, ...$s)
          : `${$}`,
      );
  const dataView = new View(buffer);
  const byteLength = call(getBufferByteLength, buffer, []);
  const minimumLengthOfResults = ceil(byteLength * 4 / 3);
  const resultingCodeUnits = fill(
    objectCreate(
      base64CodeUnitIterablePrototype,
      {
        length: {
          value: minimumLengthOfResults +
            (4 - (minimumLengthOfResults % 4)) % 4,
        },
      },
    ),
    0x3D,
  );
  for (let index = 0; index < byteLength;) {
    const codeUnitIndex = ceil(index * 4 / 3);
    const currentIndex = codeUnitIndex + +(
      index % 3 == 0 && resultingCodeUnits[codeUnitIndex] != 0x3D
    );
    const remainder = currentIndex % 4;
    const u6 = remainder == 0
      ? call(viewGetUint8, dataView, [index]) >> 2
      : remainder == 1
      ? ((call(viewGetUint8, dataView, [index++]) & 0x3) << 4) +
        (index < byteLength
          ? call(viewGetUint8, dataView, [index]) >> 4
          : 0)
      : remainder == 2
      ? ((call(viewGetUint8, dataView, [index++]) & 0xF) << 2) +
        (index < byteLength
          ? call(viewGetUint8, dataView, [index]) >> 6
          : 0)
      : call(viewGetUint8, dataView, [index++]) & 0x3F;
    const result = u6 < 26
      ? u6 + 65
      : u6 < 52
      ? u6 + 71
      : u6 < 62
      ? u6 - 4
      : u6 < 63
      ? 43
      : u6 < 64
      ? 47
      : -1;
    if (result < 0) {
      throw new RangeError(`Piscēs: Unexpected Base64 value: ${u6}.`);
    } else {
      resultingCodeUnits[currentIndex] = result;
    }
  }
  return stringFromCodeUnits(...resultingCodeUnits);
};

/**
 * Returns whether the provided value is a Base64 string.
 *
 * Returns false if the provided value is not a string primitive.
 */
export const isBase64 = ($) => {
  if (typeof $ !== "string") {
    return false;
  } else {
    const source = stringReplace($, /[\t\n\f\r ]+/gu, "");
    const trimmed = source.length % 4 == 0
      ? stringReplace(source, /={1,2}$/u, "")
      : source;
    return trimmed.length % 4 != 1 &&
      call(reExec, /[^0-9A-Za-z+\/]/u, [trimmed]) == null;
  }
};