Mojo: Optimize VerifyUserPointer().

mojo/public/tests/system_core_perftest.cc

 // Copyright 2013 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 "mojo/public/system/core.h"
 
 #include "base/basictypes.h"
 #include "base/bind.h"
 #include "base/logging.h"
 #include "mojo/public/tests/test_support.h"
@@ skipping 27 matching lines @@
                           MOJO_WRITE_MESSAGE_FLAG_NONE);
     DCHECK_EQ(result, MOJO_RESULT_OK);
     uint32_t read_bytes = bytes;
     result = ReadMessage(h_1_,
                          buffer, &read_bytes,
                          NULL, NULL,
                          MOJO_READ_MESSAGE_FLAG_NONE);
     DCHECK_EQ(result, MOJO_RESULT_OK);
   }
 
+  void MessagePipe_EmptyRead() {
+    MojoResult result;
+    result = ReadMessage(h_0_,
+                         NULL, NULL,
+                         NULL, NULL,
+                         MOJO_READ_MESSAGE_FLAG_MAY_DISCARD);
+    DCHECK_EQ(result, MOJO_RESULT_NOT_FOUND);
+  }
+
  protected:
   Handle h_0_;
   Handle h_1_;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(SystemPerftest);
 };
 
 // A no-op test so we can compare performance.
 TEST_F(SystemPerftest, NoOp) {
@@ skipping 30 matching lines @@
                  static_cast<void*>(buffer), static_cast<uint32_t>(1000)));
   test::IterateAndReportPerf(
       "MessagePipe_WriteAndRead_10000bytes",
       base::Bind(&SystemPerftest::MessagePipe_WriteAndRead,
                  base::Unretained(this),
                  static_cast<void*>(buffer), static_cast<uint32_t>(10000)));
   CHECK_EQ(Close(h_0_), MOJO_RESULT_OK);
   CHECK_EQ(Close(h_1_), MOJO_RESULT_OK);
 }
 
+TEST_F(SystemPerftest, MessagePipe_EmptyRead) {
+  CHECK_EQ(CreateMessagePipe(&h_0_, &h_1_), MOJO_RESULT_OK);
+  test::IterateAndReportPerf(
+      "MessagePipe_EmptyRead",
+      base::Bind(&SystemPerftest::MessagePipe_EmptyRead,
+                 base::Unretained(this)));
+  CHECK_EQ(Close(h_0_), MOJO_RESULT_OK);
+  CHECK_EQ(Close(h_1_), MOJO_RESULT_OK);
+}
+
 }  // namespace
 }  // namespace mojo