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// 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.
#include <stdint.h>
#include <string.h>
#include <string>
#include "gpu/gpu_export.h"
// From gl2/gl2ext.h.
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];
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);
// Indicates whether this mailbox is used with the SharedImage system.
bool IsSharedImage() const;
// Generate a unique unguessable mailbox name.
static Mailbox Generate();
// Generate a unique unguessable mailbox name for use with the SharedImage
// system.
static Mailbox GenerateForSharedImage();
// 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