blob: 3217b5ff8a663927af793dd61c5ab02c6f157c86 [file] [log] [blame]
// Copyright (c) 2012 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 <stddef.h>
#include <stdint.h>
#include "base/macros.h"
#include "base/memory/shared_memory.h"
#include "build/build_config.h"
#include "ui/surface/surface_export.h"
#if defined(OS_WIN)
#include <windows.h>
#include <memory>
class SkCanvas;
// -----------------------------------------------------------------------------
// A TransportDIB is a block of memory that is used to transport pixels
// between processes: from the renderer process to the browser, and
// between renderer and plugin processes.
// -----------------------------------------------------------------------------
class SURFACE_EXPORT TransportDIB {
// A Handle is the type which can be sent over the wire so that the remote
// side can map the transport DIB.
typedef base::SharedMemoryHandle Handle;
// Returns a default, invalid handle, that is meant to indicate a missing
// Transport DIB.
static Handle DefaultHandleValue() {
return base::SharedMemory::NULLHandle();
// Create a new TransportDIB, returning NULL on failure.
// The size is the minimum size in bytes of the memory backing the transport
// DIB (we may actually allocate more than that to give us better reuse when
// cached).
// The sequence number is used to uniquely identify the transport DIB. It
// should be unique for all transport DIBs ever created in the same
// renderer.
static TransportDIB* Create(size_t size, uint32_t sequence_num);
// Map the referenced transport DIB. The caller owns the returned object.
// Returns NULL on failure.
static TransportDIB* Map(Handle transport_dib);
// Create a new |TransportDIB| with a handle to the shared memory. This
// always returns a valid pointer. The DIB is not mapped.
static TransportDIB* CreateWithHandle(Handle handle);
// Returns true if the handle is valid.
static bool is_valid_handle(Handle dib);
// Returns a canvas using the memory of this TransportDIB. The returned
// pointer will be owned by the caller. The bitmap will be of the given size,
// which should fit inside this memory. Bitmaps returned will be either
// opaque or have premultiplied alpha.
// On POSIX, this |TransportDIB| will be mapped if not already. On Windows,
// this |TransportDIB| will NOT be mapped and should not be mapped prior,
// because PlatformCanvas will map the file internally.
// Will return NULL on allocation failure. This could be because the image
// is too large to map into the current process' address space.
std::unique_ptr<SkCanvas> GetPlatformCanvas(int w, int h, bool opaque);
// Map the DIB into the current process if it is not already. This is used to
// map a DIB that has already been created. Returns true if the DIB is mapped.
bool Map();
// Return a pointer to the shared memory.
void* memory() const;
// Return the maximum size of the shared memory. This is not the amount of
// data which is valid, you have to know that via other means, this is simply
// the maximum amount that /could/ be valid.
size_t size() const { return size_; }
// Returns a pointer to the SharedMemory object that backs the transport dib.
base::SharedMemory* shared_memory();
// Verifies that the dib can hold a canvas of the requested dimensions.
bool VerifyCanvasSize(int w, int h);
explicit TransportDIB(base::SharedMemoryHandle dib);
base::SharedMemory shared_memory_;
uint32_t sequence_num_;
size_t size_; // length, in bytes