Bound Vulkan host buffer pool memory (#201)

Co-authored-by: Dafenx <196083014+Dafenxz0@users.noreply.github.com>

tests/SharpEmu.Libs.Tests/VideoOut/VulkanHostBufferPoolTests.cs

@@ -0,0 +1,60 @@
+// Copyright (C) 2026 SharpEmu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+using SharpEmu.Libs.VideoOut;
+using Silk.NET.Vulkan;
+using VkBuffer = Silk.NET.Vulkan.Buffer;
+using Xunit;
+
+namespace SharpEmu.Libs.Tests.VideoOut;
+
+public sealed class VulkanHostBufferPoolTests
+{
+    [Fact]
+    public void ReturnedAllocationCanBeRentedAgain()
+    {
+        var destroyed = new List<VulkanHostBufferAllocation>();
+        using var pool = new VulkanHostBufferPool(1024, destroyed.Add);
+        var key = new VulkanHostBufferPoolKey(BufferUsageFlags.StorageBufferBit, 256);
+        var allocation = Allocation(1, 2, key);
+
+        pool.Register(allocation);
+        Assert.True(pool.Return(allocation.Buffer, allocation.Memory));
+        Assert.Equal(256UL, pool.CachedBytes);
+
+        Assert.True(pool.TryRent(key, out var rented));
+        Assert.Equal(allocation, rented);
+        Assert.Equal(0UL, pool.CachedBytes);
+        Assert.Empty(destroyed);
+    }
+
+    [Fact]
+    public void ReturnDestroysAllocationThatWouldExceedBudget()
+    {
+        var destroyed = new List<VulkanHostBufferAllocation>();
+        using var pool = new VulkanHostBufferPool(256, destroyed.Add);
+        var key = new VulkanHostBufferPoolKey(BufferUsageFlags.VertexBufferBit, 512);
+        var allocation = Allocation(3, 4, key);
+
+        pool.Register(allocation);
+
+        Assert.True(pool.Return(allocation.Buffer, allocation.Memory));
+        Assert.Equal(0UL, pool.CachedBytes);
+        Assert.Equal([allocation], destroyed);
+        Assert.False(pool.TryRent(key, out _));
+    }
+
+    [Fact]
+    public void UnknownAllocationIsNotClaimedByPool()
+    {
+        using var pool = new VulkanHostBufferPool(1024, _ => { });
+
+        Assert.False(pool.Return(new VkBuffer(9), new DeviceMemory(10)));
+    }
+
+    private static VulkanHostBufferAllocation Allocation(
+        ulong buffer,
+        ulong memory,
+        VulkanHostBufferPoolKey key) =>
+        new(new VkBuffer(buffer), new DeviceMemory(memory), key, 0);
+}