From 0104a9335e15779815dcb3a7ff2f7e6f9d7b206f Mon Sep 17 00:00:00 2001
From: assiduous <assiduous@diligentgraphics.com>
Date: Wed, 14 Feb 2024 14:51:17 -0800
Subject: [PATCH] Buffer Suballocator: removed the VirtualSize create info
 parameter

It is redundant as there is the MaxSize
---
 .../interface/BufferSuballocator.h            |  7 ++-
 .../GraphicsTools/src/BufferSuballocator.cpp  | 52 +++++++++----------
 Graphics/GraphicsTools/src/DynamicBuffer.cpp  |  2 +
 .../src/BufferSuballocatorTest.cpp            |  6 ++-
 4 files changed, 34 insertions(+), 33 deletions(-)

diff --git a/Graphics/GraphicsTools/interface/BufferSuballocator.h b/Graphics/GraphicsTools/interface/BufferSuballocator.h
index 111377b33..6b2c9610d 100644
--- a/Graphics/GraphicsTools/interface/BufferSuballocator.h
+++ b/Graphics/GraphicsTools/interface/BufferSuballocator.h
@@ -162,11 +162,10 @@ struct BufferSuballocatorCreateInfo
     /// more space is needed.
     Uint32 ExpansionSize = 0;
 
-    /// If Desc.Usage == USAGE_SPARSE, the virtual buffer size; ignored otherwise.
-    Uint64 VirtualSize = 0;
-
     /// The maximum buffer size, in bytes.
-    /// If zero, the buffer size is not limited.
+    /// If Desc.Usage == USAGE_SPARSE, also the buffer virtual size.
+    ///
+    /// \remarks    If MaxSize is zero, the buffer will not be expanded beyond the initial size.
     Uint64 MaxSize = 0;
 
     /// Whether to disable debug validation of the internal buffer structure.
diff --git a/Graphics/GraphicsTools/src/BufferSuballocator.cpp b/Graphics/GraphicsTools/src/BufferSuballocator.cpp
index 550c08788..5b653d420 100644
--- a/Graphics/GraphicsTools/src/BufferSuballocator.cpp
+++ b/Graphics/GraphicsTools/src/BufferSuballocator.cpp
@@ -128,40 +128,38 @@ class BufferSuballocatorImpl final : public ObjectBase<IBufferSuballocator>
     BufferSuballocatorImpl(IReferenceCounters*                 pRefCounters,
                            IRenderDevice*                      pDevice,
                            const BufferSuballocatorCreateInfo& CreateInfo) :
-        // clang-format off
         TBase{pRefCounters},
-        m_Mgr
-        {
-            VariableSizeAllocationsManager::CreateInfo
-            {
+        m_MaxSize{
+            [](Uint64 Size, Uint64 MaxSize) {
+                if (MaxSize == 0)
+                    MaxSize = Size;
+
+                if (MaxSize < Size)
+                {
+                    LOG_WARNING_MESSAGE("MaxSize (", MaxSize, ") is less than the initial buffer size (", Size, ").");
+                    MaxSize = Size;
+                }
+
+                return MaxSize;
+            }(CreateInfo.Desc.Size, CreateInfo.MaxSize)},
+        m_ExpansionSize{CreateInfo.ExpansionSize},
+        m_Mgr{
+            VariableSizeAllocationsManager::CreateInfo{
                 DefaultRawMemoryAllocator::GetAllocator(),
                 StaticCast<size_t>(CreateInfo.Desc.Size),
-                CreateInfo.DisableDebugValidation
-            }
+                CreateInfo.DisableDebugValidation,
+            },
         },
         m_MgrSize{m_Mgr.GetMaxSize()},
-        m_Buffer
-        {
+        m_Buffer{
             pDevice,
-            DynamicBufferCreateInfo
-            {
+            DynamicBufferCreateInfo{
                 CreateInfo.Desc,
                 CreateInfo.ExpansionSize != 0 ? CreateInfo.ExpansionSize : static_cast<Uint32>(CreateInfo.Desc.Size), // MemoryPageSize
-                CreateInfo.VirtualSize
-            }
+                m_MaxSize,
+            },
         },
         m_BufferSize{m_Buffer.GetDesc().Size},
-        m_ExpansionSize{CreateInfo.ExpansionSize},
-        // clang-format on
-        m_MaxSize{
-            [](Uint64 Size, Uint64 MaxSize) {
-                if (MaxSize != 0 && MaxSize < Size)
-                {
-                    LOG_WARNING_MESSAGE("MaxSize (", MaxSize, ") is less than the initial buffer size (", Size, ").");
-                    MaxSize = Size;
-                }
-                return MaxSize;
-            }(m_BufferSize, CreateInfo.MaxSize)},
         m_SuballocationsAllocator{
             DefaultRawMemoryAllocator::GetAllocator(),
             sizeof(BufferSuballocationImpl),
@@ -305,6 +303,9 @@ class BufferSuballocatorImpl final : public ObjectBase<IBufferSuballocator>
     }
 
 private:
+    const Uint64 m_MaxSize;
+    const Uint32 m_ExpansionSize;
+
     std::mutex                     m_MgrMtx;
     VariableSizeAllocationsManager m_Mgr;
 
@@ -313,9 +314,6 @@ class BufferSuballocatorImpl final : public ObjectBase<IBufferSuballocator>
     DynamicBuffer       m_Buffer;
     std::atomic<Uint64> m_BufferSize{0};
 
-    const Uint32 m_ExpansionSize;
-    const Uint64 m_MaxSize;
-
     std::atomic<Int32>  m_AllocationCount{0};
     std::atomic<Uint64> m_UsedSize{0};
     std::atomic<Uint64> m_MaxFreeBlockSize{0};
diff --git a/Graphics/GraphicsTools/src/DynamicBuffer.cpp b/Graphics/GraphicsTools/src/DynamicBuffer.cpp
index 5dd2cedc7..ae321274c 100644
--- a/Graphics/GraphicsTools/src/DynamicBuffer.cpp
+++ b/Graphics/GraphicsTools/src/DynamicBuffer.cpp
@@ -69,6 +69,8 @@ DynamicBuffer::DynamicBuffer(IRenderDevice*                 pDevice,
     m_VirtualSize{CI.Desc.Usage == USAGE_SPARSE ? CI.VirtualSize : 0},
     m_MemoryPageSize{CI.MemoryPageSize}
 {
+    DEV_CHECK_ERR(CI.Desc.Usage != USAGE_SPARSE || CI.VirtualSize > 0, "Virtual size must not be 0 for sparse buffers");
+
     m_Desc.Name   = m_Name.c_str();
     m_PendingSize = m_Desc.Size;
     m_Desc.Size   = 0; // Current buffer size
diff --git a/Tests/DiligentCoreAPITest/src/BufferSuballocatorTest.cpp b/Tests/DiligentCoreAPITest/src/BufferSuballocatorTest.cpp
index 4abe8a4f4..6c7733d3a 100644
--- a/Tests/DiligentCoreAPITest/src/BufferSuballocatorTest.cpp
+++ b/Tests/DiligentCoreAPITest/src/BufferSuballocatorTest.cpp
@@ -1,5 +1,5 @@
 /*
- *  Copyright 2019-2023 Diligent Graphics LLC
+ *  Copyright 2019-2024 Diligent Graphics LLC
  *  Copyright 2015-2019 Egor Yusov
  *
  *  Licensed under the Apache License, Version 2.0 (the "License");
@@ -80,7 +80,9 @@ TEST(BufferSuballocatorTest, Allocate)
     BufferSuballocatorCreateInfo CI;
     CI.Desc.Name      = "Buffer Suballocator Test";
     CI.Desc.BindFlags = BIND_VERTEX_BUFFER;
-    CI.Desc.Size      = 1024;
+    CI.Desc.Size      = 32;
+    CI.ExpansionSize  = 32;
+    CI.MaxSize        = 1u << 20u;
 
     RefCntAutoPtr<IBufferSuballocator> pAllocator;
     CreateBufferSuballocator(pDevice, CI, &pAllocator);