[UI] UploadBufferPool common code

src/xenia/ui/graphics_upload_buffer_pool.h

@@ -0,0 +1,79 @@
+/**
+ ******************************************************************************
+ * Xenia : Xbox 360 Emulator Research Project                                 *
+ ******************************************************************************
+ * Copyright 2020 Ben Vanik. All rights reserved.                             *
+ * Released under the BSD license - see LICENSE in the root for more details. *
+ ******************************************************************************
+ */
+
+#ifndef XENIA_UI_GRAPHICS_UPLOAD_BUFFER_POOL_H_
+#define XENIA_UI_GRAPHICS_UPLOAD_BUFFER_POOL_H_
+
+#include <cstdint>
+
+namespace xe {
+namespace ui {
+
+// Submission index is the fence value or a value derived from it (if reclaiming
+// less often than once per fence value, for instance).
+
+class GraphicsUploadBufferPool {
+ public:
+  // Taken from the Direct3D 12 MiniEngine sample (LinearAllocator
+  // kCpuAllocatorPageSize). Large enough for most cases.
+  static constexpr size_t kDefaultPageSize = 2 * 1024 * 1024;
+
+  virtual ~GraphicsUploadBufferPool();
+
+  void Reclaim(uint64_t completed_submission_index);
+  void ClearCache();
+
+  // Should be called before submitting anything using this pool, unless the
+  // implementation doesn't require explicit flushing.
+  void FlushWrites();
+
+ protected:
+  // Extended by the implementation.
+  struct Page {
+    virtual ~Page();
+    uint64_t last_submission_index_;
+    Page* next_;
+  };
+
+  GraphicsUploadBufferPool(size_t page_size) : page_size_(page_size) {}
+
+  // Request to write data in a single piece, creating a new page if the current
+  // one doesn't have enough free space.
+  Page* Request(uint64_t submission_index, size_t size, size_t alignment,
+                size_t& offset_out);
+  // Request to write data in multiple parts, filling the buffer entirely.
+  Page* RequestPartial(uint64_t submission_index, size_t size, size_t alignment,
+                       size_t& offset_out, size_t& size_out);
+
+  virtual Page* CreatePageImplementation() = 0;
+
+  virtual void FlushPageWrites(Page* page, size_t offset, size_t size);
+
+  // May be increased by the implementation on creation or on first allocation
+  // to avoid wasting space if the real allocation turns out to be bigger than
+  // the specified page size.
+  size_t page_size_;
+
+  // A list of buffers with free space, with the first buffer being the one
+  // currently being filled.
+  Page* writable_first_ = nullptr;
+  Page* writable_last_ = nullptr;
+  // A list of full buffers that can be reclaimed when the GPU doesn't use them
+  // anymore.
+  Page* submitted_first_ = nullptr;
+  Page* submitted_last_ = nullptr;
+
+  size_t current_page_used_ = 0;
+  size_t current_page_flushed_ = 0;
+};
+
+}  // namespace ui
+}  // namespace xe
+
+#endif  // XENIA_UI_GRAPHICS_UPLOAD_BUFFER_POOL_H_