Function decode

packages/effect/src/internal/encoding/base64.ts:38–74

(str: string)

/** @internal */
export const decode = (str: string): Either.Either<Uint8Array, Encoding.DecodeException> => {
  const stripped = stripCrlf(str)
  const length = stripped.length
  if (length % 4 !== 0) {
    return Either.left(
      DecodeException(stripped, `Length must be a multiple of 4, but is ${length}`)
    )
  }

  const index = stripped.indexOf("=")
  if (index !== -1 && ((index < length - 2) || (index === length - 2 && stripped[length - 1] !== "="))) {
    return Either.left(
      DecodeException(stripped, "Found a '=' character, but it is not at the end")
    )
  }

  try {
    const missingOctets = stripped.endsWith("==") ? 2 : stripped.endsWith("=") ? 1 : 0
    const result = new Uint8Array(3 * (length / 4) - missingOctets)
    for (let i = 0, j = 0; i < length; i += 4, j += 3) {
      const buffer = getBase64Code(stripped.charCodeAt(i)) << 18 |
        getBase64Code(stripped.charCodeAt(i + 1)) << 12 |
        getBase64Code(stripped.charCodeAt(i + 2)) << 6 |
        getBase64Code(stripped.charCodeAt(i + 3))

      result[j] = buffer >> 16
      result[j + 1] = (buffer >> 8) & 0xff
      result[j + 2] = buffer & 0xff
    }

    return Either.right(result)
  } catch (e) {
    return Either.left(
      DecodeException(stripped, e instanceof Error ? e.message : "Invalid input")
    )
  }
}

/** @internal */
export const stripCrlf = (str: string) => str.replace(/[\n\r]/g, "")