gpu/command_buffer/common/mailbox.h

// Copyright 2013 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef GPU_COMMAND_BUFFER_MAILBOX_H_
#define GPU_COMMAND_BUFFER_MAILBOX_H_

#include <stdint.h>
#include <string.h>

#include <string>

#include "gpu/gpu_export.h"

// From gl2/gl2ext.h.
#ifndef GL_MAILBOX_SIZE_CHROMIUM
#define GL_MAILBOX_SIZE_CHROMIUM 16
#endif

namespace gpu {

// A mailbox is an unguessable name that references texture image data.
// This name can be passed across processes permitting one context to share
// texture image data with another. The mailbox name consists of a random
// set of bytes, optionally with a checksum (in debug mode) to verify the
// name is valid.
// See src/gpu/GLES2/extensions/CHROMIUM/CHROMIUM_texture_mailbox.txt for more
// details.
struct GPU_EXPORT Mailbox {
  using Name = int8_t[GL_MAILBOX_SIZE_CHROMIUM];

  Mailbox();

  static Mailbox FromVolatile(const volatile Mailbox& other) {
    // Because the copy constructor is trivial, const_cast is safe.
    return const_cast<const Mailbox&>(other);
  }

  bool IsZero() const;
  void SetZero();
  void SetName(const int8_t* name);

  // Generate a unique unguessable mailbox name.
  static Mailbox Generate();

  // Verify that the mailbox was created through Mailbox::Generate. This only
  // works in Debug (always returns true in Release). This is not a secure
  // check, only to catch bugs where clients forgot to call Mailbox::Generate.
  bool Verify() const;

  std::string ToDebugString() const;

  Name name;

  bool operator<(const Mailbox& other) const {
    return memcmp(this, &other, sizeof other) < 0;
  }
  bool operator==(const Mailbox& other) const {
    return memcmp(this, &other, sizeof other) == 0;
  }
  bool operator!=(const Mailbox& other) const {
    return !operator==(other);
  }
};

}  // namespace gpu

#endif  // GPU_COMMAND_BUFFER_MAILBOX_H_