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use std::io::Read;
use std::path::PathBuf;
use std::result::Result as RResult;
use crypto::sha1::Sha1;
use crypto::digest::Digest;
use libimagerror::into::IntoError;
use hasher::Hasher;
use result::Result;
use error::RefErrorKind as REK;
use error::MapErrInto;
pub struct NBytesHasher {
hasher: Sha1,
n: usize,
}
impl NBytesHasher {
pub fn new(n: usize) -> NBytesHasher {
NBytesHasher {
hasher: Sha1::new(),
n: n,
}
}
}
impl Hasher for NBytesHasher {
fn hash_name(&self) -> &'static str {
"n-bytes-hasher"
}
fn create_hash<R: Read>(&mut self, _: &PathBuf, contents: &mut R) -> Result<String> {
let s = contents
.bytes()
.take(self.n)
.collect::<RResult<Vec<u8>, _>>()
.map_err_into(REK::IOError)
.and_then(|v| String::from_utf8(v).map_err_into(REK::IOError))
.map_err(Box::new)
.map_err(|e| REK::UTF8Error.into_error_with_cause(e))
.map_err_into(REK::IOError);
self.hasher.input_str(&try!(s)[..]);
Ok(self.hasher.result_str())
}
}