Implement basic classes for HPACK (HTTP/2 compression)

net/spdy/hpack_string_util_test.cc

+#include "net/spdy/hpack_string_util.h"
+
+#include <cstddef>
+#include <cstring>
+
+#include "base/basictypes.h"
+#include "base/logging.h"
+#include "base/strings/string_piece.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace net {
+
+namespace {
+
+using std::string;
+
+// Make sure StringPiecesEqualConstantTime() behaves like the regular
+// string equality operator.
+TEST(HpackStringUtilTest, StringPiecesEqualConstantTime) {
+  EXPECT_TRUE(StringPiecesEqualConstantTime("foo", "foo"));
+  EXPECT_FALSE(StringPiecesEqualConstantTime("foo", "foox"));
+  EXPECT_FALSE(StringPiecesEqualConstantTime("foo", "bar"));
+}
+
+// TODO(jgraettinger): Support this benchmark.

[akalin, 2014/01/14 20:54:10]

Out of curiosity, what's the issue here? Does Chromium's gtest not support
benchmarks?

[Johnny, 2014/01/14 21:11:21]

Correct, not that I can tell.

On 2014/01/14 20:54:10, akalin wrote:

+/*
+enum BM_StringPieceEqualityType {
+  STRCMP_EQUAL,
+  STRCMP_FIRST_CHAR_DIFFERS,
+  STRING_PIECES_EQUAL_CONSTANT_TIME_EQUAL,
+  STRING_PIECES_EQUAL_CONSTANT_TIME_FIRST_CHAR_DIFFERS,
+};
+
+void BM_StringPieceEquality(int iters, int size, int type_int) {
+  BM_StringPieceEqualityType type =
+      static_cast<BM_StringPieceEqualityType>(type_int);
+  string str_a(size, 'x');
+  string str_b(size, 'x');
+  int result = 0;
+  switch (type) {
+    case STRCMP_EQUAL:
+      for (int i = 0; i < iters; ++i) {
+        result |= std::strcmp(str_a.c_str(), str_b.c_str());
+      }
+      CHECK_EQ(result, 0);
+      return;
+
+    case STRCMP_FIRST_CHAR_DIFFERS:
+      str_b[0] = 'y';
+      for (int i = 0; i < iters; ++i) {
+        result |= std::strcmp(str_a.c_str(), str_b.c_str());
+      }
+      CHECK_LT(result, 0);
+      return;
+
+    case STRING_PIECES_EQUAL_CONSTANT_TIME_EQUAL:
+      for (int i = 0; i < iters; ++i) {
+        result |= StringPiecesEqualConstantTime(str_a, str_b);
+      }
+      CHECK_EQ(result, 1);
+      return;
+
+    case STRING_PIECES_EQUAL_CONSTANT_TIME_FIRST_CHAR_DIFFERS:
+      str_b[0] = 'y';
+      for (int i = 0; i < iters; ++i) {
+        result |= StringPiecesEqualConstantTime(str_a, str_b);
+      }
+      CHECK_EQ(result, 0);
+      return;
+  }
+
+  DCHECK(false);
+}
+
+// Results should resemble the table below, where 0 and 1 are clearly
+// different (STRCMP), but 2 and 3 are roughly the same
+// (STRING_PIECES_EQUAL_CONSTANT_TIME).
+//
+// DEBUG: Benchmark                     Time(ns)    CPU(ns) Iterations
+// -------------------------------------------------------------------
+// DEBUG: BM_StringPieceEquality/1M/0      77796      77141       7778
+// DEBUG: BM_StringPieceEquality/1M/1         10         10   70000000
+// DEBUG: BM_StringPieceEquality/1M/2    7729735    7700000        100
+// DEBUG: BM_StringPieceEquality/1M/3    7803051    7800000        100
+BENCHMARK(BM_StringPieceEquality)
+  ->ArgPair(1<<20, STRCMP_EQUAL)
+  ->ArgPair(1<<20, STRCMP_FIRST_CHAR_DIFFERS)
+  ->ArgPair(1<<20, STRING_PIECES_EQUAL_CONSTANT_TIME_EQUAL)
+  ->ArgPair(1<<20, STRING_PIECES_EQUAL_CONSTANT_TIME_FIRST_CHAR_DIFFERS);
+*/
+
+}  // namespace
+
+}  // namespace net