Speed up IdAllocator.

gpu/command_buffer/common/id_allocator_test.cc

 // Copyright (c) 2009 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.
 
 // This file has the unit tests for the IdAllocator class.
 
 #include "gpu/command_buffer/common/id_allocator.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 namespace gpu {
@@ skipping 31 matching lines @@
 
   // Frees the other ID, check that it's not in use any more.
   allocator->FreeID(id2);
   EXPECT_FALSE(allocator->InUse(id2));
 }
 
 // Checks that the resource IDs are re-used after being freed.
 TEST_F(IdAllocatorTest, TestAdvanced) {
   IdAllocator *allocator = id_allocator();
 
+  // Allocate the highest possible ID, to make life awkward.
+  allocator->AllocateIDAtOrAbove(-1);
+
   // Allocate a significant number of resources.
   const unsigned int kNumResources = 100;
   ResourceId ids[kNumResources];
   for (unsigned int i = 0; i < kNumResources; ++i) {
     ids[i] = allocator->AllocateID();
     EXPECT_TRUE(allocator->InUse(ids[i]));
   }
 
   // Check that a new allocation re-uses the resource we just freed.
   ResourceId id1 = ids[kNumResources / 2];
@@ skipping 26 matching lines @@
   const ResourceId kOffset = 123456;
   IdAllocator* allocator = id_allocator();
   ResourceId id1 = allocator->AllocateIDAtOrAbove(kOffset);
   EXPECT_EQ(kOffset, id1);
   ResourceId id2 = allocator->AllocateIDAtOrAbove(kOffset);
   EXPECT_GT(id2, kOffset);
   ResourceId id3 = allocator->AllocateIDAtOrAbove(kOffset);
   EXPECT_GT(id3, kOffset);
 }
 
+// Checks that AllocateIdAtOrAbove wraps around at the maximum 32-bit value.
+TEST_F(IdAllocatorTest, AllocateIdAtOrAboveWrapsAround) {
+  const ResourceId kMaxPossibleOffset = -1;
+  IdAllocator* allocator = id_allocator();
+  ResourceId id1 = allocator->AllocateIDAtOrAbove(kMaxPossibleOffset);
+  EXPECT_EQ(kMaxPossibleOffset, id1);
+  ResourceId id2 = allocator->AllocateIDAtOrAbove(kMaxPossibleOffset);
+  EXPECT_EQ(1u, id2);
+  ResourceId id3 = allocator->AllocateIDAtOrAbove(kMaxPossibleOffset);
+  EXPECT_EQ(2u, id3);
+}
+
 }  // namespace gpu