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      1 // Copyright 2014 The Chromium Authors. All rights reserved.
      2 // Use of this source code is governed by a BSD-style license that can be
      3 // found in the LICENSE file.
      4 
      5 #include "net/spdy/hpack_string_util.h"
      6 
      7 #include <cstddef>
      8 #include <cstring>
      9 
     10 #include "base/basictypes.h"
     11 #include "base/logging.h"
     12 #include "base/strings/string_piece.h"
     13 #include "testing/gtest/include/gtest/gtest.h"
     14 
     15 namespace net {
     16 
     17 namespace {
     18 
     19 using std::string;
     20 
     21 // Make sure StringPiecesEqualConstantTime() behaves like the regular
     22 // string equality operator.
     23 TEST(HpackStringUtilTest, StringPiecesEqualConstantTime) {
     24   EXPECT_TRUE(StringPiecesEqualConstantTime("foo", "foo"));
     25   EXPECT_FALSE(StringPiecesEqualConstantTime("foo", "foox"));
     26   EXPECT_FALSE(StringPiecesEqualConstantTime("foo", "bar"));
     27 }
     28 
     29 // TODO(jgraettinger): Support this benchmark.
     30 /*
     31 enum BM_StringPieceEqualityType {
     32   STRCMP_EQUAL,
     33   STRCMP_FIRST_CHAR_DIFFERS,
     34   STRING_PIECES_EQUAL_CONSTANT_TIME_EQUAL,
     35   STRING_PIECES_EQUAL_CONSTANT_TIME_FIRST_CHAR_DIFFERS,
     36 };
     37 
     38 void BM_StringPieceEquality(int iters, int size, int type_int) {
     39   BM_StringPieceEqualityType type =
     40       static_cast<BM_StringPieceEqualityType>(type_int);
     41   string str_a(size, 'x');
     42   string str_b(size, 'x');
     43   int result = 0;
     44   switch (type) {
     45     case STRCMP_EQUAL:
     46       for (int i = 0; i < iters; ++i) {
     47         result |= std::strcmp(str_a.c_str(), str_b.c_str());
     48       }
     49       CHECK_EQ(result, 0);
     50       return;
     51 
     52     case STRCMP_FIRST_CHAR_DIFFERS:
     53       str_b[0] = 'y';
     54       for (int i = 0; i < iters; ++i) {
     55         result |= std::strcmp(str_a.c_str(), str_b.c_str());
     56       }
     57       CHECK_LT(result, 0);
     58       return;
     59 
     60     case STRING_PIECES_EQUAL_CONSTANT_TIME_EQUAL:
     61       for (int i = 0; i < iters; ++i) {
     62         result |= StringPiecesEqualConstantTime(str_a, str_b);
     63       }
     64       CHECK_EQ(result, 1);
     65       return;
     66 
     67     case STRING_PIECES_EQUAL_CONSTANT_TIME_FIRST_CHAR_DIFFERS:
     68       str_b[0] = 'y';
     69       for (int i = 0; i < iters; ++i) {
     70         result |= StringPiecesEqualConstantTime(str_a, str_b);
     71       }
     72       CHECK_EQ(result, 0);
     73       return;
     74   }
     75 
     76   DCHECK(false);
     77 }
     78 
     79 // Results should resemble the table below, where 0 and 1 are clearly
     80 // different (STRCMP), but 2 and 3 are roughly the same
     81 // (STRING_PIECES_EQUAL_CONSTANT_TIME).
     82 //
     83 // DEBUG: Benchmark                     Time(ns)    CPU(ns) Iterations
     84 // -------------------------------------------------------------------
     85 // DEBUG: BM_StringPieceEquality/1M/0      77796      77141       7778
     86 // DEBUG: BM_StringPieceEquality/1M/1         10         10   70000000
     87 // DEBUG: BM_StringPieceEquality/1M/2    7729735    7700000        100
     88 // DEBUG: BM_StringPieceEquality/1M/3    7803051    7800000        100
     89 BENCHMARK(BM_StringPieceEquality)
     90   ->ArgPair(1<<20, STRCMP_EQUAL)
     91   ->ArgPair(1<<20, STRCMP_FIRST_CHAR_DIFFERS)
     92   ->ArgPair(1<<20, STRING_PIECES_EQUAL_CONSTANT_TIME_EQUAL)
     93   ->ArgPair(1<<20, STRING_PIECES_EQUAL_CONSTANT_TIME_FIRST_CHAR_DIFFERS);
     94 */
     95 
     96 }  // namespace
     97 
     98 }  // namespace net
     99