From 5dd63ff5b888f8d861aa2327507fcefa7103ffeb Mon Sep 17 00:00:00 2001
From: assiduous <assiduous@diligentgraphics.com>
Date: Wed, 1 Jul 2020 20:59:18 -0700
Subject: VariableSizeAllocationsManager: added Extend method

---
 .../interface/VariableSizeAllocationsManager.hpp   | 40 +++++++++++++++++++++
 .../VariableSizeGPUAllocationsManagerTest.cpp      | 41 ++++++++++++++++++++++
 2 files changed, 81 insertions(+)

diff --git a/Graphics/GraphicsAccessories/interface/VariableSizeAllocationsManager.hpp b/Graphics/GraphicsAccessories/interface/VariableSizeAllocationsManager.hpp
index c1fc083f..0788db23 100644
--- a/Graphics/GraphicsAccessories/interface/VariableSizeAllocationsManager.hpp
+++ b/Graphics/GraphicsAccessories/interface/VariableSizeAllocationsManager.hpp
@@ -175,6 +175,12 @@ public:
             return UnalignedOffset != InvalidAllocation().UnalignedOffset;
         }
 
+        bool operator==(const Allocation& rhs) const
+        {
+            return UnalignedOffset == rhs.UnalignedOffset &&
+                Size == rhs.Size;
+        }
+
         OffsetType UnalignedOffset = InvalidOffset;
         OffsetType Size            = 0;
     };
@@ -357,6 +363,40 @@ public:
         return m_FreeBlocksByOffset.size();
     }
 
+    void Extend(size_t ExtraSize)
+    {
+        size_t NewBlockOffset = m_MaxSize;
+        size_t NewBlockSize   = ExtraSize;
+
+        if (!m_FreeBlocksByOffset.empty())
+        {
+            auto LastBlockIt = m_FreeBlocksByOffset.end();
+            --LastBlockIt;
+
+            const auto LastBlockOffset = LastBlockIt->first;
+            const auto LastBlockSize   = LastBlockIt->second.Size;
+            if (LastBlockOffset + LastBlockSize == m_MaxSize)
+            {
+                // Extend the last block
+                NewBlockOffset = LastBlockOffset;
+                NewBlockSize += LastBlockSize;
+
+                VERIFY_EXPR(LastBlockIt->second.OrderBySizeIt->first == LastBlockOffset);
+                m_FreeBlocksBySize.erase(LastBlockIt->second.OrderBySizeIt);
+                m_FreeBlocksByOffset.erase(LastBlockIt);
+            }
+        }
+
+        AddNewBlock(NewBlockOffset, NewBlockSize);
+
+        m_MaxSize += ExtraSize;
+        m_FreeSize += ExtraSize;
+
+#ifdef DILIGENT_DEBUG
+        DbgVerifyList();
+#endif
+    }
+
 private:
     void AddNewBlock(OffsetType Offset, OffsetType Size)
     {
diff --git a/Tests/DiligentCoreTest/src/GraphicsAccessories/VariableSizeGPUAllocationsManagerTest.cpp b/Tests/DiligentCoreTest/src/GraphicsAccessories/VariableSizeGPUAllocationsManagerTest.cpp
index 3fa579da..45711497 100644
--- a/Tests/DiligentCoreTest/src/GraphicsAccessories/VariableSizeGPUAllocationsManagerTest.cpp
+++ b/Tests/DiligentCoreTest/src/GraphicsAccessories/VariableSizeGPUAllocationsManagerTest.cpp
@@ -128,6 +128,47 @@ TEST(GraphicsAccessories_VariableSizeGPUAllocationsManager, AllocateFree)
 
         EXPECT_TRUE(ListMgr.IsEmpty());
     }
+
+    {
+        VariableSizeAllocationsManager ListMgr(128, Allocator);
+
+        auto a1 = ListMgr.Allocate(64, 1);
+        EXPECT_EQ(a1.UnalignedOffset, OffsetType{0});
+        EXPECT_EQ(a1.Size, OffsetType{64});
+        EXPECT_EQ(ListMgr.GetNumFreeBlocks(), size_t{1});
+
+        auto a2 = ListMgr.Allocate(128, 1);
+        EXPECT_EQ(a2, VariableSizeAllocationsManager::Allocation::InvalidAllocation());
+
+        ListMgr.Extend(128);
+        EXPECT_EQ(ListMgr.GetNumFreeBlocks(), size_t{1});
+
+        a2 = ListMgr.Allocate(128, 1);
+        EXPECT_EQ(a2.UnalignedOffset, 64);
+        EXPECT_EQ(a2.Size, 128);
+
+        auto a3 = ListMgr.Allocate(64, 1);
+        EXPECT_TRUE(ListMgr.IsFull());
+
+        ListMgr.Extend(32);
+        EXPECT_EQ(ListMgr.GetNumFreeBlocks(), size_t{1});
+
+        auto a4 = ListMgr.Allocate(32, 1);
+        EXPECT_TRUE(ListMgr.IsFull());
+
+        ListMgr.Free(std::move(a1));
+        EXPECT_EQ(ListMgr.GetNumFreeBlocks(), size_t{1});
+
+        ListMgr.Extend(1024);
+        EXPECT_EQ(ListMgr.GetNumFreeBlocks(), size_t{2});
+
+        auto a5 = ListMgr.Allocate(512, 1);
+
+        ListMgr.Free(std::move(a4));
+        ListMgr.Free(std::move(a2));
+        ListMgr.Free(std::move(a5));
+        ListMgr.Free(std::move(a3));
+    }
 }
 
 TEST(GraphicsAccessories_VariableSizeGPUAllocationsManager, FreeOrder)
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