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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 <map>
#include <memory>
#include <string>
#include "base/macros.h"
#include "gpu/command_buffer/common/buffer.h"
#include "gpu/command_buffer/common/cmd_buffer_common.h"
#include "gpu/command_buffer/service/async_api_interface.h"
#include "gpu/gpu_export.h"
// Forwardly declare a few GL types to avoid including GL header files.
typedef int GLsizei;
typedef int GLint;
namespace gpu {
class CommandBufferServiceBase;
// This class is a helper base class for implementing the common parts of the
// o3d/gl2 command buffer decoder.
class GPU_EXPORT CommonDecoder {
typedef error::Error Error;
static const unsigned int kMaxStackDepth = 32;
// A bucket is a buffer to help collect memory across a command buffer. When
// creating a command buffer implementation of an existing API, sometimes that
// API has functions that take a pointer to data. A good example is OpenGL's
// glBufferData. Because the data is separated between client and service,
// there are 2 ways to get this data across. 1 is to put all the data in
// shared memory. The problem with this is the data can be arbitarily large
// and the host OS may not support that much shared memory. Another solution
// is to shuffle memory across a little bit at a time, collecting it on the
// service side and when it is all there then call glBufferData. Buckets
// implement this second solution. Using the common commands, SetBucketSize,
// SetBucketData, SetBucketDataImmediate the client can fill a bucket. It can
// then call a command that uses that bucket (like BufferDataBucket in the
// GLES2 command buffer implementation).
// If you are designing an API from scratch you can avoid this need for
// Buckets by making your API always take an offset and a size
// similar to glBufferSubData.
// Buckets also help pass strings to/from the service. To return a string of
// arbitary size, the service puts the string in a bucket. The client can
// then query the size of a bucket and request sections of the bucket to
// be passed across shared memory.
class GPU_EXPORT Bucket {
size_t size() const {
return size_;
// Gets a pointer to a section the bucket. Returns nullptr if offset or size
// is out of range.
void* GetData(size_t offset, size_t size) const;
template <typename T>
T GetDataAs(size_t offset, size_t size) const {
return reinterpret_cast<T>(GetData(offset, size));
// Sets the size of the bucket.
void SetSize(size_t size);
// Sets a part of the bucket.
// Returns false if offset or size is out of range.
bool SetData(const volatile void* src, size_t offset, size_t size);
// Sets the bucket data from a string. Strings are passed NULL terminated to
// distinguish between empty string and no string.
void SetFromString(const char* str);
// Gets the bucket data as a string. Strings are passed NULL terminated to
// distrinquish between empty string and no string. Returns False if there
// is no string.
bool GetAsString(std::string* str);
// Gets the bucket data as strings.
// On success, the number of strings are in |_count|, the string data are
// in |_string|, and string sizes are in |_length|..
bool GetAsStrings(GLsizei* _count,
std::vector<char*>* _string,
std::vector<GLint>* _length);
bool OffsetSizeValid(size_t offset, size_t size) const {
size_t temp = offset + size;
return temp <= size_ && temp >= offset;
size_t size_;
::std::unique_ptr<int8_t[]> data_;
explicit CommonDecoder(CommandBufferServiceBase* command_buffer_service);
CommandBufferServiceBase* command_buffer_service() const {
return command_buffer_service_;
// Sets the maximum size for buckets.
void set_max_bucket_size(size_t max_bucket_size) {
max_bucket_size_ = max_bucket_size;
// Creates a bucket. If the bucket already exists returns that bucket.
Bucket* CreateBucket(uint32_t bucket_id);
// Gets a bucket. Returns nullptr if the bucket does not exist.
Bucket* GetBucket(uint32_t bucket_id) const;
// Gets the address of shared memory data, given a shared memory ID and an
// offset. Also checks that the size is consistent with the shared memory
// size.
// Parameters:
// shm_id: the id of the shared memory buffer.
// offset: the offset of the data in the shared memory buffer.
// size: the size of the data.
// Returns:
// nullptr if shm_id isn't a valid shared memory buffer ID or if the size
// check fails. Return a pointer to the data otherwise.
void* GetAddressAndCheckSize(unsigned int shm_id,
unsigned int offset,
unsigned int size);
// Typed version of GetAddressAndCheckSize.
template <typename T>
T GetSharedMemoryAs(unsigned int shm_id, unsigned int offset,
unsigned int size) {
return static_cast<T>(GetAddressAndCheckSize(shm_id, offset, size));
void* GetAddressAndSize(unsigned int shm_id,
unsigned int offset,
unsigned int minimum_size,
unsigned int* size);
template <typename T>
T GetSharedMemoryAndSizeAs(unsigned int shm_id,
unsigned int offset,
unsigned int minimum_size,
unsigned int* size) {
return static_cast<T>(
GetAddressAndSize(shm_id, offset, minimum_size, size));
unsigned int GetSharedMemorySize(unsigned int shm_id, unsigned int offset);
// Get the actual shared memory buffer.
scoped_refptr<gpu::Buffer> GetSharedMemoryBuffer(unsigned int shm_id);
// Executes a common command.
// Parameters:
// command: the command index.
// arg_count: the number of CommandBufferEntry arguments.
// cmd_data: the command data.
// Returns:
// error::kNoError if no error was found, one of
// error::Error otherwise.
error::Error DoCommonCommand(unsigned int command,
unsigned int arg_count,
const volatile void* cmd_data);
// Gets an name for a common command.
const char* GetCommonCommandName(cmd::CommandId command_id) const;
// Generate a member function prototype for each command in an automated and
// typesafe way.
error::Error Handle##name(uint32_t immediate_data_size, \
const volatile void* data);
CommandBufferServiceBase* command_buffer_service_;
size_t max_bucket_size_;
typedef std::map<uint32_t, std::unique_ptr<Bucket>> BucketMap;
BucketMap buckets_;
typedef Error (CommonDecoder::*CmdHandler)(uint32_t immediate_data_size,
const volatile void* data);
// A struct to hold info about each command.
struct CommandInfo {
CmdHandler cmd_handler;
uint8_t arg_flags; // How to handle the arguments for this command
uint8_t cmd_flags; // How to handle this command
uint16_t arg_count; // How many arguments are expected for this command.
// A table of CommandInfo for all the commands.
static const CommandInfo command_info[];
} // namespace gpu