Function arrayBufferToBase64

packages/ai-utils/src/base64.ts:27–56

(buffer: ArrayBuffer)

 * isolate.
 */
export function arrayBufferToBase64(buffer: ArrayBuffer): string {
  const bytes = new Uint8Array(buffer)

  const fast = (bytes as Uint8ArrayInstanceWithBase64).toBase64
  if (typeof fast === 'function') {
    return fast.call(bytes)
  }

  if (typeof Buffer !== 'undefined' && typeof Buffer.from === 'function') {
    return Buffer.from(buffer).toString('base64')
  }

  if (typeof btoa === 'function') {
    let binary = ''
    // 32KB chunks keep us well under V8's argument-count limits for
    // String.fromCharCode.apply on large buffers.
    const chunkSize = 0x8000
    for (let i = 0; i < bytes.length; i += chunkSize) {
      const chunk = bytes.subarray(i, i + chunkSize)
      binary += String.fromCharCode.apply(
        null,
        // eslint-disable-next-line no-restricted-syntax -- TS lib types String.fromCharCode.apply as Array<number> but runtime accepts any ArrayLike
        chunk as unknown as Array<number>,
      )
    }
    return btoa(binary)
  }

  throw new Error('No base64 encoder available in this environment.')
}

/**
 * Decode a base64 string into an `ArrayBuffer`.