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use ring::hkdf;

/// Generic newtype wrapper that lets us implement traits for externally-defined
/// types.

// BORROWED FROM RING Itself.
// LICENSE: https://github.com/briansmith/ring/blob/master/LICENSE
pub struct CustomKeyWrapper<T>(pub T);

impl hkdf::KeyType for CustomKeyWrapper<usize> {
  fn len(&self) -> usize {
    self.0
  }
}

impl From<hkdf::Okm<'_, CustomKeyWrapper<usize>>> for CustomKeyWrapper<Vec<u8>> {
  fn from(okm: hkdf::Okm<CustomKeyWrapper<usize>>) -> Self {
    let mut r = vec![0u8; okm.len().0];
    okm.fill(&mut r).unwrap();
    CustomKeyWrapper(r)
  }
}