base::Hash: Minor improvements to documentation and testing.

base/hash_unittest.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "base/hash.h"
 
 #include <string>
 #include <vector>
 
 #include "testing/gtest/include/gtest/gtest.h"
 
 namespace base {
 
 TEST(HashTest, String) {
   std::string str;
   // Empty string (should hash to 0).
   str = "";
   EXPECT_EQ(0u, Hash(str));
 
   // Simple test.
   str = "hello world";
   EXPECT_EQ(2794219650u, Hash(str));
 
   // Change one bit.
   str = "helmo world";
   EXPECT_EQ(1006697176u, Hash(str));
 
+  // Add a null byte.

[Noel Gordon, 2014/03/05 04:47:01]

nit: maybe s/Add/Insert/ ?

[Matt Giuca, 2014/03/05 04:49:17]

Done.

+  str = "hello  world";
+  str[5] = '\0';
+  EXPECT_EQ(2319902537u, Hash(str));
+
+  // Test that the bytes after the null contribute to the hash.
+  str = "hello  worle";
+  str[5] = '\0';
+  EXPECT_EQ(553904462u, Hash(str));
+
   // Extremely long string.
   // Also tests strings with high bit set, and null byte.
   std::vector<char> long_string_buffer;
   for (int i = 0; i < 4096; ++i)
     long_string_buffer.push_back((i % 256) - 128);
   str.assign(&long_string_buffer.front(), long_string_buffer.size());
   EXPECT_EQ(2797962408u, Hash(str));
 
   // All possible lengths (mod 4). Tests separate code paths. Also test with
   // final byte high bit set (regression test for http://crbug.com/90659).
@@ skipping 25 matching lines @@
   str = "hello world";
   EXPECT_EQ(2794219650u, Hash(str, strlen(str)));
 
   // Ensure that it stops reading after the given length, and does not expect a
   // null byte.
   str = "hello world; don't read this part";
   EXPECT_EQ(2794219650u, Hash(str, strlen("hello world")));
 }
 
 }  // namespace base