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use std::hash::{Hash, Hasher};
use std::io::{Result, Write};
use content::{Content, Sink, Source};
pub trait ContentHasher where Self: Write + Sized {
type Digest: Eq + Hash + Clone + Content<Self> + AsRef<[u8]>;
fn new() -> Self;
fn fin(self) -> Self::Digest;
fn null() -> Self::Digest {
Self::new().fin()
}
}
struct VoidHasher;
#[derive(PartialEq, Eq, Clone)]
struct VoidHash;
impl ContentHasher for VoidHasher {
type Digest = VoidHash;
fn new() -> Self {
VoidHasher
}
fn fin(self) -> Self::Digest {
VoidHash
}
}
impl AsRef<[u8]> for VoidHash {
fn as_ref(&self) -> &[u8] {
&[]
}
}
impl Hash for VoidHash {
fn hash<H>(&self, _: &mut H) where H: Hasher {}
}
impl<H> Content<H> for VoidHash where H: ContentHasher {
fn to_content(&self, _: &mut Sink<H>) -> Result<()> {
Ok(())
}
fn from_content(_: &mut Source<H>) -> Result<Self> {
Ok(VoidHash)
}
}
impl Write for VoidHasher {
fn write(&mut self, buf: &[u8]) -> Result<usize> {
Ok(buf.len())
}
fn flush(&mut self) -> Result<()> {
Ok(())
}
}