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//! Extendable-Output Function (XOF) support use crate::Reset; #[cfg(feature = "alloc")] use alloc::boxed::Box; /// Trait for describing readers which are used to extract extendable output /// from XOF (extendable-output function) result. pub trait XofReader { /// Read output into the `buffer`. Can be called an unlimited number of times. fn read(&mut self, buffer: &mut [u8]); /// Read output into a boxed slice of the specified size. /// /// Can be called an unlimited number of times in combination with `read`. /// /// `Box<[u8]>` is used instead of `Vec<u8>` to save stack space, since /// they have size of 2 and 3 words respectively. #[cfg(feature = "alloc")] #[cfg_attr(docsrs, doc(cfg(feature = "alloc")))] fn read_boxed(&mut self, n: usize) -> Box<[u8]> { let mut buf = vec![0u8; n].into_boxed_slice(); self.read(&mut buf); buf } } /// Trait which describes extendable-output functions (XOF). pub trait ExtendableOutput: Sized { /// Reader type Reader: XofReader; /// Retrieve XOF reader and consume hasher instance. fn finalize_xof(self) -> Self::Reader; /// Retrieve XOF reader and reset hasher instance state. fn finalize_xof_reset(&mut self) -> Self::Reader; /// Retrieve result into a boxed slice of the specified size and consume /// the hasher. /// /// `Box<[u8]>` is used instead of `Vec<u8>` to save stack space, since /// they have size of 2 and 3 words respectively. #[cfg(feature = "alloc")] #[cfg_attr(docsrs, doc(cfg(feature = "alloc")))] fn finalize_boxed(self, n: usize) -> Box<[u8]> { let mut buf = vec![0u8; n].into_boxed_slice(); self.finalize_xof().read(&mut buf); buf } /// Retrieve result into a boxed slice of the specified size and reset /// the hasher's state. /// /// `Box<[u8]>` is used instead of `Vec<u8>` to save stack space, since /// they have size of 2 and 3 words respectively. #[cfg(feature = "alloc")] #[cfg_attr(docsrs, doc(cfg(feature = "alloc")))] fn finalize_boxed_reset(&mut self, n: usize) -> Box<[u8]> { let mut buf = vec![0u8; n].into_boxed_slice(); self.finalize_xof_reset().read(&mut buf); buf } } /// Trait for extendable-output function (XOF) implementations to use to /// retrieve the hash output. /// /// Usage of this trait in user code is discouraged. Instead use the /// [`ExtendableOutput::finalize_xof`] or /// [`ExtendableOutput::finalize_xof_reset`] methods. /// /// Types which impl this trait along with [`Reset`] will receive a blanket /// impl of [`ExtendableOutput`]. pub trait ExtendableOutputDirty: Sized { /// Reader type Reader: XofReader; /// Retrieve XOF reader. /// /// This method is expected to only be called once unless /// [`Reset::reset`] is called, after which point it can be /// called again and reset again (and so on). fn finalize_xof_dirty(&mut self) -> Self::Reader; } impl<X: ExtendableOutputDirty + Reset> ExtendableOutput for X { type Reader = X::Reader; #[inline] fn finalize_xof(mut self) -> Self::Reader { self.finalize_xof_dirty() } #[inline] fn finalize_xof_reset(&mut self) -> Self::Reader { let reader = self.finalize_xof_dirty(); self.reset(); reader } }