crypto/hash: impl Writer for Hasher to allow use of Reader-Writer convenience functions

src/crypto/hash.rs

@@ -1,5 +1,6 @@
 use libc::c_uint;
 use std::ptr;
+use std::io;
 
 use ffi;
 
@@ -34,6 +35,13 @@ pub struct Hasher {
     len: uint,
 }
 
+impl io::Writer for Hasher {
+    fn write(&mut self, buf: &[u8]) -> io::IoResult<()> {
+        self.update(buf);
+        Ok(())
+    }
+}
+
 impl Hasher {
     pub fn new(ht: HashType) -> Hasher {
         ffi::init();