Make peeking before the head of OffsetByteQueue a hard error.

media/mp4/offset_byte_queue_unittest.cc

 // Copyright (c) 2012 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 <string.h>
 
 #include "base/basictypes.h"
 #include "base/memory/scoped_ptr.h"
 #include "media/mp4/offset_byte_queue.h"
 #include "testing/gtest/include/gtest/gtest.h"
@@ skipping 26 matching lines @@
 
   const uint8* buf;
   int size;
 
   queue_->Peek(&buf, &size);
   EXPECT_EQ(128, size);
   EXPECT_EQ(128, buf[0]);
   EXPECT_EQ(255, buf[size-1]);
 }
 
-TEST_F(OffsetByteQueueTest, TestPeekAt) {
+TEST_F(OffsetByteQueueTest, PeekAtDeathTest) {
   const uint8* buf;
   int size;
 
-  queue_->PeekAt(128, &buf, &size);
-  EXPECT_EQ(NULL, buf);
-  EXPECT_EQ(0, size);
-
   queue_->PeekAt(400, &buf, &size);
   EXPECT_EQ(queue_->tail() - 400, size);
   EXPECT_EQ(400 - 256, buf[0]);
 
   queue_->PeekAt(512, &buf, &size);
   EXPECT_EQ(NULL, buf);
   EXPECT_EQ(0, size);
+
+  // Peeking before current head should be an error
+  ASSERT_DEATH(queue_->PeekAt(128, &buf, &size), "offset >= head");

[acolwell GONE FROM CHROMIUM, 2012/07/31 19:27:44]

Remove this since you said this situation only happens as a result of a coding
error. No need to test that the DCHECK is there.

 }
 
 TEST_F(OffsetByteQueueTest, TestTrim) {
   EXPECT_TRUE(queue_->Trim(128));
   EXPECT_TRUE(queue_->Trim(384));
   EXPECT_EQ(384, queue_->head());
   EXPECT_EQ(512, queue_->tail());
 
   EXPECT_TRUE(queue_->Trim(400));
   EXPECT_EQ(400, queue_->head());
@@ skipping 15 matching lines @@
   // Trimming past the end of the buffer should return 'false'; we haven't seen
   // the preceeding bytes.
   EXPECT_FALSE(queue_->Trim(513));
 
   // However, doing that shouldn't affect the EOS case. Only adding new data
   // should alter this behavior.
   EXPECT_TRUE(queue_->Trim(512));
 }
 
 }  // namespace media