When clearing the priority message queue, don't copy an item to itself.

This avoids a memcpy to overlapping---in this case the same---memory locations.

BUG=4100
R=juberti@webrtc.org, pthatcher@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/33019004

Cr-Commit-Position: refs/heads/master@{#8449}
git-svn-id: http://webrtc.googlecode.com/svn/trunk@8449 4adac7df-926f-26a2-2b94-8c16560cd09d
diff --git a/webrtc/base/messagequeue.cc b/webrtc/base/messagequeue.cc
index 74b1024..e5d69a3 100644
--- a/webrtc/base/messagequeue.cc
+++ b/webrtc/base/messagequeue.cc
@@ -361,7 +361,6 @@
   }
 
   // Remove from priority queue. Not directly iterable, so use this approach
-
   PriorityQueue::container_type::iterator new_end = dmsgq_.container().begin();
   for (PriorityQueue::container_type::iterator it = new_end;
        it != dmsgq_.container().end(); ++it) {
@@ -372,7 +371,10 @@
         delete it->msg_.pdata;
       }
     } else {
-      *new_end++ = *it;
+      if (new_end != it) {
+        *new_end = *it;
+      }
+      new_end++;
     }
   }
   dmsgq_.container().erase(new_end, dmsgq_.container().end());
diff --git a/webrtc/base/messagequeue_unittest.cc b/webrtc/base/messagequeue_unittest.cc
index 871542d..ac9affe 100644
--- a/webrtc/base/messagequeue_unittest.cc
+++ b/webrtc/base/messagequeue_unittest.cc
@@ -20,7 +20,7 @@
 
 using namespace rtc;
 
-class MessageQueueTest: public testing::Test, public MessageQueue {
+class MessageQueueForTest : public MessageQueue {
  public:
   bool IsLocked_Worker() {
     if (!crit_.TryEnter()) {
@@ -29,24 +29,38 @@
     crit_.Leave();
     return false;
   }
+
   bool IsLocked() {
     // We have to do this on a worker thread, or else the TryEnter will
     // succeed, since our critical sections are reentrant.
     Thread worker;
     worker.Start();
     return worker.Invoke<bool>(
-        rtc::Bind(&MessageQueueTest::IsLocked_Worker, this));
+        rtc::Bind(&MessageQueueForTest::IsLocked_Worker, this));
+  }
+
+  size_t GetDmsgqSize() {
+    return dmsgq_.size();
+  }
+
+  const DelayedMessage& GetDmsgqTop() {
+    return dmsgq_.top();
   }
 };
 
+class MessageQueueTest : public testing::Test {
+ protected:
+  MessageQueueForTest q_;
+};
+
 struct DeletedLockChecker {
-  DeletedLockChecker(MessageQueueTest* test, bool* was_locked, bool* deleted)
-      : test(test), was_locked(was_locked), deleted(deleted) { }
+  DeletedLockChecker(MessageQueueForTest* q, bool* was_locked, bool* deleted)
+      : q_(q), was_locked(was_locked), deleted(deleted) { }
   ~DeletedLockChecker() {
     *deleted = true;
-    *was_locked = test->IsLocked();
+    *was_locked = q_->IsLocked();
   }
-  MessageQueueTest* test;
+  MessageQueueForTest* q_;
   bool* was_locked;
   bool* deleted;
 };
@@ -73,8 +87,7 @@
 
 TEST_F(MessageQueueTest,
        DelayedPostsWithIdenticalTimesAreProcessedInFifoOrder) {
-  MessageQueue q;
-  DelayedPostsWithIdenticalTimesAreProcessedInFifoOrder(&q);
+  DelayedPostsWithIdenticalTimesAreProcessedInFifoOrder(&q_);
   NullSocketServer nullss;
   MessageQueue q_nullss(&nullss);
   DelayedPostsWithIdenticalTimesAreProcessedInFifoOrder(&q_nullss);
@@ -83,10 +96,10 @@
 TEST_F(MessageQueueTest, DisposeNotLocked) {
   bool was_locked = true;
   bool deleted = false;
-  DeletedLockChecker* d = new DeletedLockChecker(this, &was_locked, &deleted);
-  Dispose(d);
+  DeletedLockChecker* d = new DeletedLockChecker(&q_, &was_locked, &deleted);
+  q_.Dispose(d);
   Message msg;
-  EXPECT_FALSE(Get(&msg, 0));
+  EXPECT_FALSE(q_.Get(&msg, 0));
   EXPECT_TRUE(deleted);
   EXPECT_FALSE(was_locked);
 }
@@ -102,18 +115,138 @@
   bool* deleted_;
 };
 
-TEST_F(MessageQueueTest, DiposeHandlerWithPostedMessagePending) {
+// TODO(decurtis): Test that ordering of elements is done properly.
+// TODO(decurtis): Test that timestamps are being properly set.
+
+TEST_F(MessageQueueTest, DisposeHandlerWithPostedMessagePending) {
   bool deleted = false;
   DeletedMessageHandler *handler = new DeletedMessageHandler(&deleted);
   // First, post a dispose.
-  Dispose(handler);
+  q_.Dispose(handler);
   // Now, post a message, which should *not* be returned by Get().
-  Post(handler, 1);
+  q_.Post(handler, 1);
   Message msg;
-  EXPECT_FALSE(Get(&msg, 0));
+  EXPECT_FALSE(q_.Get(&msg, 0));
   EXPECT_TRUE(deleted);
 }
 
+// Test Clear for removing messages that have been posted for times in
+// the past.
+TEST_F(MessageQueueTest, ClearPast) {
+  TimeStamp now = Time();
+  Message msg;
+
+  // Test removing the only element.
+  q_.PostAt(now - 4, NULL, 1);
+  q_.Clear(NULL, 1, NULL);
+
+  // Make sure the queue is empty now.
+  EXPECT_FALSE(q_.Get(&msg, 0));
+
+  // Test removing the one element with a two element list.
+  q_.PostAt(now - 4, NULL, 1);
+  q_.PostAt(now - 2, NULL, 3);
+
+  q_.Clear(NULL, 1, NULL);
+
+  EXPECT_TRUE(q_.Get(&msg, 0));
+  EXPECT_EQ(3U, msg.message_id);
+
+  // Make sure the queue is empty now.
+  EXPECT_FALSE(q_.Get(&msg, 0));
+
+
+  // Test removing the three element with a two element list.
+  q_.PostAt(now - 4, NULL, 1);
+  q_.PostAt(now - 2, NULL, 3);
+
+  q_.Clear(NULL, 3, NULL);
+
+  EXPECT_TRUE(q_.Get(&msg, 0));
+  EXPECT_EQ(1U, msg.message_id);
+
+  // Make sure the queue is empty now.
+  EXPECT_FALSE(q_.Get(&msg, 0));
+
+
+  // Test removing the two element in a three element list.
+  q_.PostAt(now - 4, NULL, 1);
+  q_.PostAt(now - 3, NULL, 2);
+  q_.PostAt(now - 2, NULL, 3);
+
+  q_.Clear(NULL, 2, NULL);
+
+  EXPECT_TRUE(q_.Get(&msg, 0));
+  EXPECT_EQ(1U, msg.message_id);
+
+  EXPECT_TRUE(q_.Get(&msg, 0));
+  EXPECT_EQ(3U, msg.message_id);
+
+  // Make sure the queue is empty now.
+  EXPECT_FALSE(q_.Get(&msg, 0));
+
+
+  // Test not clearing any messages.
+  q_.PostAt(now - 4, NULL, 1);
+  q_.PostAt(now - 3, NULL, 2);
+  q_.PostAt(now - 2, NULL, 3);
+
+  // Remove nothing.
+  q_.Clear(NULL, 0, NULL);
+  q_.Clear(NULL, 4, NULL);
+
+  EXPECT_TRUE(q_.Get(&msg, 0));
+  EXPECT_EQ(1U, msg.message_id);
+
+  EXPECT_TRUE(q_.Get(&msg, 0));
+  EXPECT_EQ(2U, msg.message_id);
+
+  EXPECT_TRUE(q_.Get(&msg, 0));
+  EXPECT_EQ(3U, msg.message_id);
+
+  // Make sure the queue is empty now.
+  EXPECT_FALSE(q_.Get(&msg, 0));
+}
+
+// Test clearing messages that have been posted for the future.
+TEST_F(MessageQueueTest, ClearFuture) {
+  EXPECT_EQ(0U, q_.GetDmsgqSize());
+  q_.PostDelayed(10, NULL, 4);
+  EXPECT_EQ(1U, q_.GetDmsgqSize());
+  q_.PostDelayed(13, NULL, 4);
+  EXPECT_EQ(2U, q_.GetDmsgqSize());
+  q_.PostDelayed(9, NULL, 2);
+  EXPECT_EQ(3U, q_.GetDmsgqSize());
+  q_.PostDelayed(11, NULL, 10);
+  EXPECT_EQ(4U, q_.GetDmsgqSize());
+
+  EXPECT_EQ(9, q_.GetDmsgqTop().cmsDelay_);
+
+  MessageList removed;
+  q_.Clear(NULL, 10, &removed);
+  EXPECT_EQ(1U, removed.size());
+  EXPECT_EQ(3U, q_.GetDmsgqSize());
+
+  removed.clear();
+  q_.Clear(NULL, 4, &removed);
+  EXPECT_EQ(2U, removed.size());
+  EXPECT_EQ(1U, q_.GetDmsgqSize());
+
+  removed.clear();
+  q_.Clear(NULL, 4, &removed);
+  EXPECT_EQ(0U, removed.size());
+  EXPECT_EQ(1U, q_.GetDmsgqSize());
+
+  removed.clear();
+  q_.Clear(NULL, 2, &removed);
+  EXPECT_EQ(1U, removed.size());
+  EXPECT_EQ(0U, q_.GetDmsgqSize());
+
+  Message msg;
+  EXPECT_FALSE(q_.Get(&msg, 0));
+}
+
+
 struct UnwrapMainThreadScope {
   UnwrapMainThreadScope() : rewrap_(Thread::Current() != NULL) {
     if (rewrap_) ThreadManager::Instance()->UnwrapCurrentThread();
@@ -125,7 +258,7 @@
   bool rewrap_;
 };
 
-TEST(MessageQueueManager, Clear) {
+TEST(MessageQueueManager, DeletedHandler) {
   UnwrapMainThreadScope s;
   if (MessageQueueManager::IsInitialized()) {
     LOG(LS_INFO) << "Unable to run MessageQueueManager::Clear test, since the "