expo-modules-core/src/uuid/lib/bytesToUuid.ts

The core of Expo Modules architecture

/**
 * Convert array of 16 byte values to UUID string format of the form:
 * XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX
 */
const byteToHex: string[] = [];
for (let i = 0; i < 256; ++i) {
  byteToHex[i] = (i + 0x100).toString(16).substr(1);
}

function bytesToUuid(buf: number[], offset?: number) {
  let i = offset || 0;
  const bth = byteToHex;
  // join used to fix memory issue caused by concatenation: https://bugs.chromium.org/p/v8/issues/detail?id=3175#c4
  return [
    bth[buf[i++]],
    bth[buf[i++]],
    bth[buf[i++]],
    bth[buf[i++]],
    '-',
    bth[buf[i++]],
    bth[buf[i++]],
    '-',
    bth[buf[i++]],
    bth[buf[i++]],
    '-',
    bth[buf[i++]],
    bth[buf[i++]],
    '-',
    bth[buf[i++]],
    bth[buf[i++]],
    bth[buf[i++]],
    bth[buf[i++]],
    bth[buf[i++]],
    bth[buf[i++]],
  ].join('');
}

export default bytesToUuid;