Function bidirectionalIndexOf

stackgl_modules/index.js:619–670

(buffer, val, byteOffset, encoding, dir)

// - encoding - an optional encoding, relevant is val is a string
// - dir - true for indexOf, false for lastIndexOf
function bidirectionalIndexOf(buffer, val, byteOffset, encoding, dir) {
  // Empty buffer means no match
  if (buffer.length === 0) return -1;

  // Normalize byteOffset
  if (typeof byteOffset === 'string') {
    encoding = byteOffset;
    byteOffset = 0;
  } else if (byteOffset > 0x7fffffff) {
    byteOffset = 0x7fffffff;
  } else if (byteOffset < -0x80000000) {
    byteOffset = -0x80000000;
  }
  byteOffset = +byteOffset; // Coerce to Number.
  if (numberIsNaN(byteOffset)) {
    // byteOffset: it it's undefined, null, NaN, "foo", etc, search whole buffer
    byteOffset = dir ? 0 : buffer.length - 1;
  }

  // Normalize byteOffset: negative offsets start from the end of the buffer
  if (byteOffset < 0) byteOffset = buffer.length + byteOffset;
  if (byteOffset >= buffer.length) {
    if (dir) return -1;else byteOffset = buffer.length - 1;
  } else if (byteOffset < 0) {
    if (dir) byteOffset = 0;else return -1;
  }

  // Normalize val
  if (typeof val === 'string') {
    val = Buffer.from(val, encoding);
  }

  // Finally, search either indexOf (if dir is true) or lastIndexOf
  if (Buffer.isBuffer(val)) {
    // Special case: looking for empty string/buffer always fails
    if (val.length === 0) {
      return -1;
    }
    return arrayIndexOf(buffer, val, byteOffset, encoding, dir);
  } else if (typeof val === 'number') {
    val = val & 0xFF; // Search for a byte value [0-255]
    if (typeof Uint8Array.prototype.indexOf === 'function') {
      if (dir) {
        return Uint8Array.prototype.indexOf.call(buffer, val, byteOffset);
      } else {
        return Uint8Array.prototype.lastIndexOf.call(buffer, val, byteOffset);
      }
    }
    return arrayIndexOf(buffer, [val], byteOffset, encoding, dir);
  }
  throw new TypeError('val must be string, number or Buffer');
}
function arrayIndexOf(arr, val, byteOffset, encoding, dir) {
  var indexSize = 1;
  var arrLength = arr.length;