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// 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 "gpu/command_buffer/common/buffer.h"
#include "gpu/command_buffer/common/constants.h"
#include "gpu/gpu_export.h"
namespace base {
class SharedMemory;
namespace gpu {
// Common interface for CommandBuffer implementations.
class GPU_EXPORT CommandBuffer {
struct State {
: num_entries(0),
generation(0) {
// Size of the command buffer in command buffer entries.
int32 num_entries;
// The offset (in entries) from which the reader is reading.
int32 get_offset;
// The offset (in entries) at which the writer is writing.
int32 put_offset;
// The current token value. This is used by the writer to defer
// changes to shared memory objects until the reader has reached a certain
// point in the command buffer. The reader is responsible for updating the
// token value, for example in response to an asynchronous set token command
// embedded in the command buffer. The default token value is zero.
int32 token;
// Error status.
error::Error error;
// Lost context detail information.
error::ContextLostReason context_lost_reason;
// Generation index of this state. The generation index is incremented every
// time a new state is retrieved from the command processor, so that
// consistency can be kept even if IPC messages are processed out-of-order.
uint32 generation;
struct ConsoleMessage {
// An user supplied id.
int32 id;
// The message.
std::string message;
CommandBuffer() {
virtual ~CommandBuffer() {
// Check if a value is between a start and end value, inclusive, allowing
// for wrapping if start > end.
static bool InRange(int32 start, int32 end, int32 value) {
if (start <= end)
return start <= value && value <= end;
return start <= value || value <= end;
// Initialize the command buffer with the given size.
virtual bool Initialize() = 0;
// Returns the last state without synchronizing with the service.
virtual State GetLastState() = 0;
// Returns the last token without synchronizing with the service. Note that
// while you could just call GetLastState().token, GetLastState needs to be
// fast as it is called for every command where GetLastToken is only called
// by code that needs to know the last token so it can be slower but more up
// to date than GetLastState.
virtual int32 GetLastToken() = 0;
// The writer calls this to update its put offset. This ensures the reader
// sees the latest added commands, and will eventually process them. On the
// service side, commands are processed up to the given put_offset before
// subsequent Flushes on the same GpuChannel.
virtual void Flush(int32 put_offset) = 0;
// The writer calls this to wait until the current token is within a
// specific range, inclusive. Can return early if an error is generated.
virtual void WaitForTokenInRange(int32 start, int32 end) = 0;
// The writer calls this to wait until the current get offset is within a
// specific range, inclusive. Can return early if an error is generated.
virtual void WaitForGetOffsetInRange(int32 start, int32 end) = 0;
// Sets the buffer commands are read from.
// Also resets the get and put offsets to 0.
virtual void SetGetBuffer(int32 transfer_buffer_id) = 0;
// Create a transfer buffer of the given size. Returns its ID or -1 on
// error.
virtual scoped_refptr<gpu::Buffer> CreateTransferBuffer(size_t size,
int32* id) = 0;
// Destroy a transfer buffer. The ID must be positive.
virtual void DestroyTransferBuffer(int32 id) = 0;
// The NaCl Win64 build only really needs the struct definitions above; having
// GetLastError declared would mean we'd have to also define it, and pull more
// of gpu in to the NaCl Win64 build.
#if !defined(NACL_WIN64)
// TODO(apatrick): this is a temporary optimization while skia is calling
// RendererGLContext::MakeCurrent prior to every GL call. It saves returning 6
// ints redundantly when only the error is needed for the CommandBufferProxy
// implementation.
virtual error::Error GetLastError();
} // namespace gpu