@statewalker/webrun-devtools/src/libs/serd.js

DevTools Extension for the StateWalker WebRun framework

export async function* serd(encoder, input) {
  for await (const chunk of input) {
    yield encoder(chunk);
  }
}
export async function* encode(input) {
  // yield* serd(btoa, input);
  yield* serd(binaryToBase64, input);
}
export async function* decode(input) {
  yield* serd(base64ToBinary, input);
}

// https://github.com/niklasvh/base64-arraybuffer/blob/master/src/index.ts
const chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";

// Use a lookup table to find the index.
const lookup = typeof Uint8Array === "undefined" ? [] : new Uint8Array(256);
for (let i = 0; i < chars.length; i++) {
  lookup[chars.charCodeAt(i)] = i;
}

function binaryToBase64(arraybuffer) {
  let bytes = new Uint8Array(arraybuffer),
    i,
    len = bytes.length,
    base64 = "";

  for (i = 0; i < len; i += 3) {
    base64 += chars[bytes[i] >> 2];
    base64 += chars[((bytes[i] & 3) << 4) | (bytes[i + 1] >> 4)];
    base64 += chars[((bytes[i + 1] & 15) << 2) | (bytes[i + 2] >> 6)];
    base64 += chars[bytes[i + 2] & 63];
  }

  if (len % 3 === 2) {
    base64 = base64.substring(0, base64.length - 1) + "=";
  } else if (len % 3 === 1) {
    base64 = base64.substring(0, base64.length - 2) + "==";
  }

  return base64;
}

function base64ToBinary(base64) {
  let bufferLength = base64.length * 0.75,
    len = base64.length,
    i,
    p = 0,
    encoded1,
    encoded2,
    encoded3,
    encoded4;

  if (base64[base64.length - 1] === "=") {
    bufferLength--;
    if (base64[base64.length - 2] === "=") {
      bufferLength--;
    }
  }

  const arraybuffer = new ArrayBuffer(bufferLength),
    bytes = new Uint8Array(arraybuffer);

  for (i = 0; i < len; i += 4) {
    encoded1 = lookup[base64.charCodeAt(i)];
    encoded2 = lookup[base64.charCodeAt(i + 1)];
    encoded3 = lookup[base64.charCodeAt(i + 2)];
    encoded4 = lookup[base64.charCodeAt(i + 3)];

    bytes[p++] = (encoded1 << 2) | (encoded2 >> 4);
    bytes[p++] = ((encoded2 & 15) << 4) | (encoded3 >> 2);
    bytes[p++] = ((encoded3 & 3) << 6) | (encoded4 & 63);
  }

  return bytes;
}