Update documentation comments.

lib/src/sha1.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library crypto.sha1;
 
 import 'dart:typed_data';
 
 import 'hash.dart';
 import 'hash_base.dart';
 import 'utils.dart';
 
-/**
- * SHA1 hash function implementation.
- */
+/// An implementation of the [SHA-1][rfc] hash function.
+///
+/// [rfc]: http://tools.ietf.org/html/rfc3174
 abstract class SHA1 implements Hash {
   factory SHA1() = _SHA1;
 
   SHA1 newInstance();
 }
 
+/// The concrete implementation of [SHA1].
+///
+/// This is separate so that it can extend [HashBase] without leaking additional
+/// public memebers.
 class _SHA1 extends HashBase implements SHA1 {
+  /// The sixteen words from the original chunk, extended to 80 words.
+  ///
+  /// This is an instance variable to avoid re-allocating, but its data isn't
+  /// used across invocations of [updateHash].
   final Uint32List _w;
 
-  // Construct a SHA1 hasher object.
   _SHA1()
       : _w = new Uint32List(80),
         super(16, 5, true) {
     h[0] = 0x67452301;
     h[1] = 0xEFCDAB89;
     h[2] = 0x98BADCFE;
     h[3] = 0x10325476;
     h[4] = 0xC3D2E1F0;
   }
 
-  // Returns a new instance of this Hash.
   SHA1 newInstance() {
     return new _SHA1();
   }
 
-  // Compute one iteration of the SHA1 algorithm with a chunk of
-  // 16 32-bit pieces.
   void updateHash(Uint32List m) {
     assert(m.length == 16);
 
     var a = h[0];
     var b = h[1];
     var c = h[2];
     var d = h[3];
     var e = h[4];
 
     for (var i = 0; i < 80; i++) {
@@ skipping 21 matching lines @@
       a = t & MASK_32;
     }
 
     h[0] = add32(a, h[0]);
     h[1] = add32(b, h[1]);
     h[2] = add32(c, h[2]);
     h[3] = add32(d, h[3]);
     h[4] = add32(e, h[4]);
   }
 }