Add base to the repository.

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@8 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 74 insertions, 0 deletions

diff --git a/base/spin_wait.h b/base/spin_wait.h
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+// Copyright 2008, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//    * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//    * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//    * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// This file provides a macro ONLY for use in testing.
+// DO NOT USE IN PRODUCTION CODE.  There are much better ways to wait.
+
+// This code is very helpful in testing multi-threaded code, without depending
+// on almost any primitives.  This is especially helpful if you are testing
+// those primitive multi-threaded constructs.
+
+// We provide a simple one argument spin wait (for 1 second), and a generic
+// spin wait (for longer periods of time).
+
+#ifndef BASE_SPIN_WAIT_H__
+#define BASE_SPIN_WAIT_H__
+
+#include "base/time.h"
+
+// Provide a macro that will wait no longer than 1 second for an asynchronous
+// change is the value of an expression.
+// A typical use would be:
+//
+//   SPIN_FOR_1_SECOND_OR_UNTIL_TRUE(0 == f(x));
+//
+// The expression will be evaluated repeatedly until it is true, or until
+// the time (1 second) expires.
+// Since tests generally have a 5 second watch dog timer, this spin loop is
+// typically used to get the padding needed on a given test platform to assure
+// that the test passes, even if load varies, and external events vary.
+
+#define SPIN_FOR_1_SECOND_OR_UNTIL_TRUE(expression) \
+    SPIN_FOR_TIMEDELTA_OR_UNTIL_TRUE(TimeDelta::FromSeconds(1), (expression))
+
+#define SPIN_FOR_TIMEDELTA_OR_UNTIL_TRUE(delta, expression) do { \
+  Time start = Time::Now(); \
+  const TimeDelta kTimeout = delta; \
+    while(!(expression)) { \
+      if (kTimeout < Time::Now() - start) { \
+      EXPECT_LE((Time::Now() - start).InMilliseconds(), \
+                kTimeout.InMilliseconds()) << "Timed out"; \
+        break; \
+      } \
+      Sleep(50); \
+    } \
+  } \
+  while(0)
+
+#endif  // BASE_SPIN_WAIT_H__