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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 <stddef.h>
#include <stdint.h>
#include "base/macros.h"
#include "gpu/command_buffer/common/buffer.h"
#include "gpu/command_buffer/common/constants.h"
#include "gpu/gpu_export.h"
namespace gpu {
// Common interface for CommandBuffer implementations.
class GPU_EXPORT CommandBuffer {
struct State {
: get_offset(0),
set_get_buffer_count(0) {}
// The offset (in entries) from which the reader is reading.
int32_t get_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_t token;
// The fence sync release count. Incremented by InsertFenceSync commands.
// Used by the client to monitor sync token progress.
uint64_t release_count;
// 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_t generation;
// Number of times SetGetBuffer was called. This allows the client to verify
// that |get| corresponds (or not) to the last buffer it set.
uint32_t set_get_buffer_count;
struct ConsoleMessage {
// An user supplied id.
int32_t id;
// The message.
std::string message;
CommandBuffer() = default;
virtual ~CommandBuffer() = default;
// Check if a value is between a start and end value, inclusive, allowing
// for wrapping if start > end.
static bool InRange(int32_t start, int32_t end, int32_t value) {
if (start <= end)
return start <= value && value <= end;
return start <= value || value <= end;
// Returns the last state without synchronizing with the service.
virtual State GetLastState() = 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_t put_offset) = 0;
// As Flush, ensures that on the service side, commands up to put_offset
// are processed but before subsequent commands on the same GpuChannel but
// flushing to the service may be deferred.
virtual void OrderingBarrier(int32_t 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 State WaitForTokenInRange(int32_t start, int32_t end) = 0;
// The writer calls this to wait until the current get offset is within a
// specific range, inclusive, after SetGetBuffer was called exactly
// set_get_buffer_count times. Can return early if an error is generated.
virtual State WaitForGetOffsetInRange(uint32_t set_get_buffer_count,
int32_t start,
int32_t end) = 0;
// Sets the buffer commands are read from.
// Also resets the get and put offsets to 0, and increments
// set_get_buffer_count.
virtual void SetGetBuffer(int32_t 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(uint32_t size,
int32_t* id) = 0;
// Destroy a transfer buffer. The ID must be positive.
// An ordering barrier must be placed after any commands that use the buffer
// before it is safe to call this function to destroy it.
virtual void DestroyTransferBuffer(int32_t id) = 0;
} // namespace gpu