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/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#ifndef WEBGLELEMENTARRAYCACHE_H
#define WEBGLELEMENTARRAYCACHE_H

#include "mozilla/MemoryReporting.h"
#include "mozilla/Scoped.h"
#include "nsTArray.h"
#include <stdint.h>
#include "nscore.h"
#include "GLDefs.h"

namespace mozilla {

template<typename T>
struct WebGLElementArrayCacheTree;

/*
 * WebGLElementArrayCache implements WebGL element array buffer validation for drawElements.
 *
 * Its exposes methods meant to be called by WebGL method implementations:
 *  - Validate, to be called by WebGLContext::DrawElements, is where we use the cache
 *  - BufferData and BufferSubData, to be called by eponymous WebGL methods, are how
 *    data is fed into the cache
 *
 * Most of the implementation is hidden in the auxilary class template, WebGLElementArrayCacheTree.
 * Refer to its code for design comments.
 */
class WebGLElementArrayCache {

public:
  bool BufferData(const void* ptr, size_t byteLength);
  bool BufferSubData(size_t pos, const void* ptr, size_t updateByteSize);

  bool Validate(GLenum type, uint32_t maxAllowed, size_t first, size_t count,
                uint32_t* out_upperBound);

  template<typename T>
  T Element(size_t i) const { return Elements<T>()[i]; }

  WebGLElementArrayCache();

  ~WebGLElementArrayCache();

  size_t SizeOfIncludingThis(mozilla::MallocSizeOf aMallocSizeOf) const;

  bool BeenUsedWithMultipleTypes() const;

private:

  /*
   * Returns true if a drawElements call with the given parameters should succeed,
   * false otherwise.
   *
   * In other words, this returns true if all entries in the element array at positions
   *
   *    first .. first+count-1
   *
   * are less than or equal to maxAllowed.
   *
   * Input parameters:
   *   maxAllowed: maximum value to be allowed in the specificied portion of the element array.
   *   first: start of the portion of the element array to consume.
   *   count: number of entries from the element array to consume.
   *
   * Output parameter:
   *   out_upperBound: upon success, is set to the actual maximum value in the specified range,
   *                   which is then guaranteed to be less than or equal to maxAllowed.
   *                   upon failure, is set to the first value in the specified range, that
   *                   is greater than maxAllowed.
   */
  template<typename T>
  bool Validate(uint32_t maxAllowed, size_t first, size_t count,
                uint32_t* out_upperBound);

  template<typename T>
  const T* Elements() const { return reinterpret_cast<const T*>(mBytes.Elements()); }
  template<typename T>
  T* Elements() { return reinterpret_cast<T*>(mBytes.Elements()); }

  bool UpdateTrees(size_t firstByte, size_t lastByte);

  template<typename T>
  friend struct WebGLElementArrayCacheTree;
  template<typename T>
  friend struct TreeForType;

  FallibleTArray<uint8_t> mBytes;
  ScopedDeletePtr<WebGLElementArrayCacheTree<uint8_t>> mUint8Tree;
  ScopedDeletePtr<WebGLElementArrayCacheTree<uint16_t>> mUint16Tree;
  ScopedDeletePtr<WebGLElementArrayCacheTree<uint32_t>> mUint32Tree;
};


} // end namespace mozilla

#endif // WEBGLELEMENTARRAYCACHE_H