gpu/command_buffer/common/cmd_buffer_common.h - mojo-tools - Git at Google

 // 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.

 // This file contains the common parts of command buffer formats.

 #ifndef GPU_COMMAND_BUFFER_COMMON_CMD_BUFFER_COMMON_H_
 #define GPU_COMMAND_BUFFER_COMMON_CMD_BUFFER_COMMON_H_

 #include <stddef.h>
 #include <stdint.h>

 #include "base/logging.h"
 #include "base/macros.h"
 #include "gpu/command_buffer/common/bitfield_helpers.h"
 #include "gpu/gpu_export.h"

 namespace gpu {

 namespace cmd {
   enum ArgFlags {
     kFixed = 0x0,
     kAtLeastN = 0x1
   };
 }  // namespace cmd

 // Pack & unpack Command cmd_flags
 #define CMD_FLAG_SET_TRACE_LEVEL(level)     ((level & 3) << 0)
 #define CMD_FLAG_GET_TRACE_LEVEL(cmd_flags) ((cmd_flags >> 0) & 3)

 // Computes the number of command buffer entries needed for a certain size. In
 // other words it rounds up to a multiple of entries.
 inline uint32_t ComputeNumEntries(size_t size_in_bytes) {
   return static_cast<uint32_t>(
       (size_in_bytes + sizeof(uint32_t) - 1) / sizeof(uint32_t));  // NOLINT
 }

 // Rounds up to a multiple of entries in bytes.
 inline size_t RoundSizeToMultipleOfEntries(size_t size_in_bytes) {
   return ComputeNumEntries(size_in_bytes) * sizeof(uint32_t);  // NOLINT
 }

 // Struct that defines the command header in the command buffer.
 struct CommandHeader {
   uint32_t size:21;
   uint32_t command:11;

   GPU_EXPORT static const int32_t kMaxSize = (1 << 21) - 1;

   void Init(uint32_t _command, int32_t _size) {
     DCHECK_LE(_size, kMaxSize);
     command = _command;
     size = _size;
   }

   // Sets the header based on the passed in command. Can not be used for
   // variable sized commands like immediate commands or Noop.
   template <typename T>
   void SetCmd() {
     static_assert(T::kArgFlags == cmd::kFixed,
                   "T::kArgFlags should equal cmd::kFixed");
     Init(T::kCmdId, ComputeNumEntries(sizeof(T)));  // NOLINT
   }

   // Sets the header by a size in bytes of the immediate data after the command.
   template <typename T>
   void SetCmdBySize(uint32_t size_of_data_in_bytes) {
     static_assert(T::kArgFlags == cmd::kAtLeastN,
                   "T::kArgFlags should equal cmd::kAtLeastN");
     Init(T::kCmdId,
          ComputeNumEntries(sizeof(T) + size_of_data_in_bytes));  // NOLINT
   }

   // Sets the header by a size in bytes.
   template <typename T>
   void SetCmdByTotalSize(uint32_t size_in_bytes) {
     static_assert(T::kArgFlags == cmd::kAtLeastN,
                   "T::kArgFlags should equal cmd::kAtLeastN");
     DCHECK_GE(size_in_bytes, sizeof(T));  // NOLINT
     Init(T::kCmdId, ComputeNumEntries(size_in_bytes));
   }
 };

 static_assert(sizeof(CommandHeader) == 4,
               "size of CommandHeader should equal 4");

 // Union that defines possible command buffer entries.
 union CommandBufferEntry {
   CommandHeader value_header;
   uint32_t value_uint32;
   int32_t value_int32;
   float value_float;
 };

 #define GPU_COMMAND_BUFFER_ENTRY_ALIGNMENT 4
 const size_t kCommandBufferEntrySize = GPU_COMMAND_BUFFER_ENTRY_ALIGNMENT;

 static_assert(sizeof(CommandBufferEntry) == kCommandBufferEntrySize,
               "size of CommandBufferEntry should equal "
               "kCommandBufferEntrySize");

 // Command buffer is GPU_COMMAND_BUFFER_ENTRY_ALIGNMENT byte aligned.
 #pragma pack(push, GPU_COMMAND_BUFFER_ENTRY_ALIGNMENT)

 // Gets the address of memory just after a structure in a typesafe way. This is
 // used for IMMEDIATE commands to get the address of the place to put the data.
 // Immediate command put their data direclty in the command buffer.
 // Parameters:
 //   cmd: Address of command.
 template <typename T>
 void* ImmediateDataAddress(T* cmd) {
   static_assert(T::kArgFlags == cmd::kAtLeastN,
                 "T::kArgFlags should equal cmd::kAtLeastN");
   return reinterpret_cast<char*>(cmd) + sizeof(*cmd);
 }

 // Gets the address of the place to put the next command in a typesafe way.
 // This can only be used for fixed sized commands.
 template <typename T>
 // Parameters:
 //   cmd: Address of command.
 void* NextCmdAddress(void* cmd) {
   static_assert(T::kArgFlags == cmd::kFixed,
                 "T::kArgFlags should equal cmd::kFixed");
   return reinterpret_cast<char*>(cmd) + sizeof(T);
 }

 // Gets the address of the place to put the next command in a typesafe way.
 // This can only be used for variable sized command like IMMEDIATE commands.
 // Parameters:
 //   cmd: Address of command.
 //   size_of_data_in_bytes: Size of the data for the command.
 template <typename T>
 void* NextImmediateCmdAddress(void* cmd, uint32_t size_of_data_in_bytes) {
   static_assert(T::kArgFlags == cmd::kAtLeastN,
                 "T::kArgFlags should equal cmd::kAtLeastN");
   return reinterpret_cast<char*>(cmd) + sizeof(T) +   // NOLINT
       RoundSizeToMultipleOfEntries(size_of_data_in_bytes);
 }

 // Gets the address of the place to put the next command in a typesafe way.
 // This can only be used for variable sized command like IMMEDIATE commands.
 // Parameters:
 //   cmd: Address of command.
 //   size_of_cmd_in_bytes: Size of the cmd and data.
 template <typename T>
 void* NextImmediateCmdAddressTotalSize(void* cmd,
                                        uint32_t total_size_in_bytes) {
   static_assert(T::kArgFlags == cmd::kAtLeastN,
                 "T::kArgFlags should equal cmd::kAtLeastN");
   DCHECK_GE(total_size_in_bytes, sizeof(T));  // NOLINT
   return reinterpret_cast<char*>(cmd) +
       RoundSizeToMultipleOfEntries(total_size_in_bytes);
 }

 namespace cmd {

 // This macro is used to safely and convienently expand the list of commnad
 // buffer commands in to various lists and never have them get out of sync. To
 // add a new command, add it this list, create the corresponding structure below
 // and then add a function in gapi_decoder.cc called Handle_COMMAND_NAME where
 // COMMAND_NAME is the name of your command structure.
 //
 // NOTE: THE ORDER OF THESE MUST NOT CHANGE (their id is derived by order)
 #define COMMON_COMMAND_BUFFER_CMDS(OP) \
   OP(Noop)                          /*  0 */ \
   OP(SetToken)                      /*  1 */ \
   OP(SetBucketSize)                 /*  2 */ \
   OP(SetBucketData)                 /*  3 */ \
   OP(SetBucketDataImmediate)        /*  4 */ \
   OP(GetBucketStart)                /*  5 */ \
   OP(GetBucketData)                 /*  6 */ \

 // Common commands.
 enum CommandId {
   #define COMMON_COMMAND_BUFFER_CMD_OP(name) k ## name,

   COMMON_COMMAND_BUFFER_CMDS(COMMON_COMMAND_BUFFER_CMD_OP)

   #undef COMMON_COMMAND_BUFFER_CMD_OP

   kNumCommands,
   kLastCommonId = 255  // reserve 256 spaces for common commands.
 };

 static_assert(kNumCommands - 1 <= kLastCommonId, "too many commands");

 const char* GetCommandName(CommandId id);

 // A Noop command.
 struct Noop {
   typedef Noop ValueType;
   static const CommandId kCmdId = kNoop;
   static const cmd::ArgFlags kArgFlags = cmd::kAtLeastN;
   static const uint8_t cmd_flags = CMD_FLAG_SET_TRACE_LEVEL(3);

   void SetHeader(uint32_t skip_count) {
     DCHECK_GT(skip_count, 0u);
     header.Init(kCmdId, skip_count);
   }

   void Init(uint32_t skip_count) {
     SetHeader(skip_count);
   }

   static void* Set(void* cmd, uint32_t skip_count) {
     static_cast<ValueType*>(cmd)->Init(skip_count);
     return NextImmediateCmdAddress<ValueType>(
         cmd, skip_count * sizeof(CommandBufferEntry));  // NOLINT
   }

   CommandHeader header;
 };

 static_assert(sizeof(Noop) == 4, "size of Noop should equal 4");
 static_assert(offsetof(Noop, header) == 0,
               "offset of Noop.header should equal 0");

 // The SetToken command puts a token in the command stream that you can
 // use to check if that token has been passed in the command stream.
 struct SetToken {
   typedef SetToken ValueType;
   static const CommandId kCmdId = kSetToken;
   static const cmd::ArgFlags kArgFlags = cmd::kFixed;
   static const uint8_t cmd_flags = CMD_FLAG_SET_TRACE_LEVEL(3);

   void SetHeader() {
     header.SetCmd<ValueType>();
   }

   void Init(uint32_t _token) {
     SetHeader();
     token = _token;
   }
   static void* Set(void* cmd, uint32_t token) {
     static_cast<ValueType*>(cmd)->Init(token);
     return NextCmdAddress<ValueType>(cmd);
   }

   CommandHeader header;
   uint32_t token;
 };

 static_assert(sizeof(SetToken) == 8, "size of SetToken should equal 8");
 static_assert(offsetof(SetToken, header) == 0,
               "offset of SetToken.header should equal 0");
 static_assert(offsetof(SetToken, token) == 4,
               "offset of SetToken.token should equal 4");

 // Sets the size of a bucket for collecting data on the service side.
 // This is a utility for gathering data on the service side so it can be used
 // all at once when some service side API is called. It removes the need to add
 // special commands just to support a particular API. For example, any API
 // command that needs a string needs a way to send that string to the API over
 // the command buffers. While you can require that the command buffer or
 // transfer buffer be large enough to hold the largest string you can send,
 // using this command removes that restriction by letting you send smaller
 // pieces over and build up the data on the service side.
 //
 // You can clear a bucket on the service side and thereby free memory by sending
 // a size of 0.
 struct SetBucketSize {
   typedef SetBucketSize ValueType;
   static const CommandId kCmdId = kSetBucketSize;
   static const cmd::ArgFlags kArgFlags = cmd::kFixed;
   static const uint8_t cmd_flags = CMD_FLAG_SET_TRACE_LEVEL(3);

   void SetHeader() {
     header.SetCmd<ValueType>();
   }

   void Init(uint32_t _bucket_id, uint32_t _size) {
     SetHeader();
     bucket_id = _bucket_id;
     size = _size;
   }
   static void* Set(void* cmd, uint32_t _bucket_id, uint32_t _size) {
     static_cast<ValueType*>(cmd)->Init(_bucket_id, _size);
     return NextCmdAddress<ValueType>(cmd);
   }

   CommandHeader header;
   uint32_t bucket_id;
   uint32_t size;
 };

 static_assert(sizeof(SetBucketSize) == 12,
               "size of SetBucketSize should equal 12");
 static_assert(offsetof(SetBucketSize, header) == 0,
               "offset of SetBucketSize.header should equal 0");
 static_assert(offsetof(SetBucketSize, bucket_id) == 4,
               "offset of SetBucketSize.bucket_id should equal 4");
 static_assert(offsetof(SetBucketSize, size) == 8,
               "offset of SetBucketSize.size should equal 8");

 // Sets the contents of a portion of a bucket on the service side from data in
 // shared memory.
 // See SetBucketSize.
 struct SetBucketData {
   typedef SetBucketData ValueType;
   static const CommandId kCmdId = kSetBucketData;
   static const cmd::ArgFlags kArgFlags = cmd::kFixed;
   static const uint8_t cmd_flags = CMD_FLAG_SET_TRACE_LEVEL(3);

   void SetHeader() {
     header.SetCmd<ValueType>();
   }

   void Init(uint32_t _bucket_id,
             uint32_t _offset,
             uint32_t _size,
             uint32_t _shared_memory_id,
             uint32_t _shared_memory_offset) {
     SetHeader();
     bucket_id = _bucket_id;
     offset = _offset;
     size = _size;
     shared_memory_id = _shared_memory_id;
     shared_memory_offset = _shared_memory_offset;
   }
   static void* Set(void* cmd,
                    uint32_t _bucket_id,
                    uint32_t _offset,
                    uint32_t _size,
                    uint32_t _shared_memory_id,
                    uint32_t _shared_memory_offset) {
     static_cast<ValueType*>(cmd)->Init(
         _bucket_id,
         _offset,
         _size,
         _shared_memory_id,
         _shared_memory_offset);
     return NextCmdAddress<ValueType>(cmd);
   }

   CommandHeader header;
   uint32_t bucket_id;
   uint32_t offset;
   uint32_t size;
   uint32_t shared_memory_id;
   uint32_t shared_memory_offset;
 };

 static_assert(sizeof(SetBucketData) == 24,
               "size of SetBucketData should be 24");
 static_assert(offsetof(SetBucketData, header) == 0,
               "offset of SetBucketData.header should be 0");
 static_assert(offsetof(SetBucketData, bucket_id) == 4,
               "offset of SetBucketData.bucket_id should be 4");
 static_assert(offsetof(SetBucketData, offset) == 8,
               "offset of SetBucketData.offset should be 8");
 static_assert(offsetof(SetBucketData, size) == 12,
               "offset of SetBucketData.size should be 12");
 static_assert(offsetof(SetBucketData, shared_memory_id) == 16,
               "offset of SetBucketData.shared_memory_id should be 16");
 static_assert(offsetof(SetBucketData, shared_memory_offset) == 20,
               "offset of SetBucketData.shared_memory_offset should be 20");

 // Sets the contents of a portion of a bucket on the service side from data in
 // the command buffer.
 // See SetBucketSize.
 struct SetBucketDataImmediate {
   typedef SetBucketDataImmediate ValueType;
   static const CommandId kCmdId = kSetBucketDataImmediate;
   static const cmd::ArgFlags kArgFlags = cmd::kAtLeastN;
   static const uint8_t cmd_flags = CMD_FLAG_SET_TRACE_LEVEL(3);

   void SetHeader(uint32_t size) {
     header.SetCmdBySize<ValueType>(size);
   }

   void Init(uint32_t _bucket_id,
             uint32_t _offset,
             uint32_t _size) {
     SetHeader(_size);
     bucket_id = _bucket_id;
     offset = _offset;
     size = _size;
   }
   static void* Set(void* cmd,
                    uint32_t _bucket_id,
                    uint32_t _offset,
                    uint32_t _size) {
     static_cast<ValueType*>(cmd)->Init(
         _bucket_id,
         _offset,
         _size);
     return NextImmediateCmdAddress<ValueType>(cmd, _size);
   }

   CommandHeader header;
   uint32_t bucket_id;
   uint32_t offset;
   uint32_t size;
 };

 static_assert(sizeof(SetBucketDataImmediate) == 16,
               "size of SetBucketDataImmediate should be 16");
 static_assert(offsetof(SetBucketDataImmediate, header) == 0,
               "offset of SetBucketDataImmediate.header should be 0");
 static_assert(offsetof(SetBucketDataImmediate, bucket_id) == 4,
               "offset of SetBucketDataImmediate.bucket_id should be 4");
 static_assert(offsetof(SetBucketDataImmediate, offset) == 8,
               "offset of SetBucketDataImmediate.offset should be 8");
 static_assert(offsetof(SetBucketDataImmediate, size) == 12,
               "offset of SetBucketDataImmediate.size should be 12");

 // Gets the start of a bucket the service has available. Sending a variable size
 // result back to the client and the portion of that result that fits in the
 // supplied shared memory. If the size of the result is larger than the supplied
 // shared memory the rest of the bucket's contents can be retrieved with
 // GetBucketData.
 //
 // This is used for example for any API that returns a string. The problem is
 // the largest thing you can send back in 1 command is the size of your shared
 // memory. This command along with GetBucketData implements a way to get a
 // result a piece at a time to help solve that problem in a generic way.
 struct GetBucketStart {
   typedef GetBucketStart ValueType;
   static const CommandId kCmdId = kGetBucketStart;
   static const cmd::ArgFlags kArgFlags = cmd::kFixed;
   static const uint8_t cmd_flags = CMD_FLAG_SET_TRACE_LEVEL(3);

   typedef uint32_t Result;

   void SetHeader() {
     header.SetCmd<ValueType>();
   }

   void Init(uint32_t _bucket_id,
             uint32_t _result_memory_id,
             uint32_t _result_memory_offset,
             uint32_t _data_memory_size,
             uint32_t _data_memory_id,
             uint32_t _data_memory_offset) {
     SetHeader();
     bucket_id = _bucket_id;
     result_memory_id = _result_memory_id;
     result_memory_offset = _result_memory_offset;
     data_memory_size = _data_memory_size;
     data_memory_id = _data_memory_id;
     data_memory_offset = _data_memory_offset;
   }
   static void* Set(void* cmd,
                    uint32_t _bucket_id,
                    uint32_t _result_memory_id,
                    uint32_t _result_memory_offset,
                    uint32_t _data_memory_size,
                    uint32_t _data_memory_id,
                    uint32_t _data_memory_offset) {
     static_cast<ValueType*>(cmd)->Init(
         _bucket_id,
         _result_memory_id,
         _result_memory_offset,
         _data_memory_size,
         _data_memory_id,
         _data_memory_offset);
     return NextCmdAddress<ValueType>(cmd);
   }

   CommandHeader header;
   uint32_t bucket_id;
   uint32_t result_memory_id;
   uint32_t result_memory_offset;
   uint32_t data_memory_size;
   uint32_t data_memory_id;
   uint32_t data_memory_offset;
 };

 static_assert(sizeof(GetBucketStart) == 28,
               "size of GetBucketStart should be 28");
 static_assert(offsetof(GetBucketStart, header) == 0,
               "offset of GetBucketStart.header should be 0");
 static_assert(offsetof(GetBucketStart, bucket_id) == 4,
               "offset of GetBucketStart.bucket_id should be 4");
 static_assert(offsetof(GetBucketStart, result_memory_id) == 8,
               "offset of GetBucketStart.result_memory_id should be 8");
 static_assert(offsetof(GetBucketStart, result_memory_offset) == 12,
               "offset of GetBucketStart.result_memory_offset should be 12");
 static_assert(offsetof(GetBucketStart, data_memory_size) == 16,
               "offset of GetBucketStart.data_memory_size should be 16");
 static_assert(offsetof(GetBucketStart, data_memory_id) == 20,
               "offset of GetBucketStart.data_memory_id should be 20");
 static_assert(offsetof(GetBucketStart, data_memory_offset) == 24,
               "offset of GetBucketStart.data_memory_offset should be 24");

 // Gets a piece of a result the service as available.
 // See GetBucketSize.
 struct GetBucketData {
   typedef GetBucketData ValueType;
   static const CommandId kCmdId = kGetBucketData;
   static const cmd::ArgFlags kArgFlags = cmd::kFixed;
   static const uint8_t cmd_flags = CMD_FLAG_SET_TRACE_LEVEL(3);

   void SetHeader() {
     header.SetCmd<ValueType>();
   }

   void Init(uint32_t _bucket_id,
             uint32_t _offset,
             uint32_t _size,
             uint32_t _shared_memory_id,
             uint32_t _shared_memory_offset) {
     SetHeader();
     bucket_id = _bucket_id;
     offset = _offset;
     size = _size;
     shared_memory_id = _shared_memory_id;
     shared_memory_offset = _shared_memory_offset;
   }
   static void* Set(void* cmd,
                    uint32_t _bucket_id,
                    uint32_t _offset,
                    uint32_t _size,
                    uint32_t _shared_memory_id,
                    uint32_t _shared_memory_offset) {
     static_cast<ValueType*>(cmd)->Init(
         _bucket_id,
         _offset,
         _size,
         _shared_memory_id,
         _shared_memory_offset);
     return NextCmdAddress<ValueType>(cmd);
   }

   CommandHeader header;
   uint32_t bucket_id;
   uint32_t offset;
   uint32_t size;
   uint32_t shared_memory_id;
   uint32_t shared_memory_offset;
 };

 static_assert(sizeof(GetBucketData) == 24,
               "size of GetBucketData should be 24");
 static_assert(offsetof(GetBucketData, header) == 0,
               "offset of GetBucketData.header should be 0");
 static_assert(offsetof(GetBucketData, bucket_id) == 4,
               "offset of GetBucketData.bucket_id should be 4");
 static_assert(offsetof(GetBucketData, offset) == 8,
               "offset of GetBucketData.offset should be 8");
 static_assert(offsetof(GetBucketData, size) == 12,
               "offset of GetBucketData.size should be 12");
 static_assert(offsetof(GetBucketData, shared_memory_id) == 16,
               "offset of GetBucketData.shared_memory_id should be 16");
 static_assert(offsetof(GetBucketData, shared_memory_offset) == 20,
               "offset of GetBucketData.shared_memory_offset should be 20");

 }  // namespace cmd

 #pragma pack(pop)

 }  // namespace gpu

 #endif  // GPU_COMMAND_BUFFER_COMMON_CMD_BUFFER_COMMON_H_
	// 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.

	// This file contains the common parts of command buffer formats.

	#ifndef GPU_COMMAND_BUFFER_COMMON_CMD_BUFFER_COMMON_H_
	#define GPU_COMMAND_BUFFER_COMMON_CMD_BUFFER_COMMON_H_

	#include <stddef.h>
	#include <stdint.h>

	#include "base/logging.h"
	#include "base/macros.h"
	#include "gpu/command_buffer/common/bitfield_helpers.h"
	#include "gpu/gpu_export.h"

	namespace gpu {

	namespace cmd {
	enum ArgFlags {
	kFixed = 0x0,
	kAtLeastN = 0x1
	};
	} // namespace cmd

	// Pack & unpack Command cmd_flags
	#define CMD_FLAG_SET_TRACE_LEVEL(level) ((level & 3) << 0)
	#define CMD_FLAG_GET_TRACE_LEVEL(cmd_flags) ((cmd_flags >> 0) & 3)

	// Computes the number of command buffer entries needed for a certain size. In
	// other words it rounds up to a multiple of entries.
	inline uint32_t ComputeNumEntries(size_t size_in_bytes) {
	return static_cast<uint32_t>(
	(size_in_bytes + sizeof(uint32_t) - 1) / sizeof(uint32_t)); // NOLINT
	}

	// Rounds up to a multiple of entries in bytes.
	inline size_t RoundSizeToMultipleOfEntries(size_t size_in_bytes) {
	return ComputeNumEntries(size_in_bytes) * sizeof(uint32_t); // NOLINT
	}

	// Struct that defines the command header in the command buffer.
	struct CommandHeader {
	uint32_t size:21;
	uint32_t command:11;

	GPU_EXPORT static const int32_t kMaxSize = (1 << 21) - 1;

	void Init(uint32_t _command, int32_t _size) {
	DCHECK_LE(_size, kMaxSize);
	command = _command;
	size = _size;
	}

	// Sets the header based on the passed in command. Can not be used for
	// variable sized commands like immediate commands or Noop.
	template <typename T>
	void SetCmd() {
	static_assert(T::kArgFlags == cmd::kFixed,
	"T::kArgFlags should equal cmd::kFixed");
	Init(T::kCmdId, ComputeNumEntries(sizeof(T))); // NOLINT
	}

	// Sets the header by a size in bytes of the immediate data after the command.
	template <typename T>
	void SetCmdBySize(uint32_t size_of_data_in_bytes) {
	static_assert(T::kArgFlags == cmd::kAtLeastN,
	"T::kArgFlags should equal cmd::kAtLeastN");
	Init(T::kCmdId,
	ComputeNumEntries(sizeof(T) + size_of_data_in_bytes)); // NOLINT
	}

	// Sets the header by a size in bytes.
	template <typename T>
	void SetCmdByTotalSize(uint32_t size_in_bytes) {
	static_assert(T::kArgFlags == cmd::kAtLeastN,
	"T::kArgFlags should equal cmd::kAtLeastN");
	DCHECK_GE(size_in_bytes, sizeof(T)); // NOLINT
	Init(T::kCmdId, ComputeNumEntries(size_in_bytes));
	}
	};

	static_assert(sizeof(CommandHeader) == 4,
	"size of CommandHeader should equal 4");

	// Union that defines possible command buffer entries.
	union CommandBufferEntry {
	CommandHeader value_header;
	uint32_t value_uint32;
	int32_t value_int32;
	float value_float;
	};

	#define GPU_COMMAND_BUFFER_ENTRY_ALIGNMENT 4
	const size_t kCommandBufferEntrySize = GPU_COMMAND_BUFFER_ENTRY_ALIGNMENT;

	static_assert(sizeof(CommandBufferEntry) == kCommandBufferEntrySize,
	"size of CommandBufferEntry should equal "
	"kCommandBufferEntrySize");

	// Command buffer is GPU_COMMAND_BUFFER_ENTRY_ALIGNMENT byte aligned.
	#pragma pack(push, GPU_COMMAND_BUFFER_ENTRY_ALIGNMENT)

	// Gets the address of memory just after a structure in a typesafe way. This is
	// used for IMMEDIATE commands to get the address of the place to put the data.
	// Immediate command put their data direclty in the command buffer.
	// Parameters:
	// cmd: Address of command.
	template <typename T>
	void* ImmediateDataAddress(T* cmd) {
	static_assert(T::kArgFlags == cmd::kAtLeastN,
	"T::kArgFlags should equal cmd::kAtLeastN");
	return reinterpret_cast<char>(cmd) + sizeof(cmd);
	}

	// Gets the address of the place to put the next command in a typesafe way.
	// This can only be used for fixed sized commands.
	template <typename T>
	// Parameters:
	// cmd: Address of command.
	void* NextCmdAddress(void* cmd) {
	static_assert(T::kArgFlags == cmd::kFixed,
	"T::kArgFlags should equal cmd::kFixed");
	return reinterpret_cast<char*>(cmd) + sizeof(T);
	}

	// Gets the address of the place to put the next command in a typesafe way.
	// This can only be used for variable sized command like IMMEDIATE commands.
	// Parameters:
	// cmd: Address of command.
	// size_of_data_in_bytes: Size of the data for the command.
	template <typename T>
	void* NextImmediateCmdAddress(void* cmd, uint32_t size_of_data_in_bytes) {
	static_assert(T::kArgFlags == cmd::kAtLeastN,
	"T::kArgFlags should equal cmd::kAtLeastN");
	return reinterpret_cast<char*>(cmd) + sizeof(T) + // NOLINT
	RoundSizeToMultipleOfEntries(size_of_data_in_bytes);
	}

	// Gets the address of the place to put the next command in a typesafe way.
	// This can only be used for variable sized command like IMMEDIATE commands.
	// Parameters:
	// cmd: Address of command.
	// size_of_cmd_in_bytes: Size of the cmd and data.
	template <typename T>
	void* NextImmediateCmdAddressTotalSize(void* cmd,
	uint32_t total_size_in_bytes) {
	static_assert(T::kArgFlags == cmd::kAtLeastN,
	"T::kArgFlags should equal cmd::kAtLeastN");
	DCHECK_GE(total_size_in_bytes, sizeof(T)); // NOLINT
	return reinterpret_cast<char*>(cmd) +
	RoundSizeToMultipleOfEntries(total_size_in_bytes);
	}

	namespace cmd {

	// This macro is used to safely and convienently expand the list of commnad
	// buffer commands in to various lists and never have them get out of sync. To
	// add a new command, add it this list, create the corresponding structure below
	// and then add a function in gapi_decoder.cc called Handle_COMMAND_NAME where
	// COMMAND_NAME is the name of your command structure.
	//
	// NOTE: THE ORDER OF THESE MUST NOT CHANGE (their id is derived by order)
	#define COMMON_COMMAND_BUFFER_CMDS(OP) \
	OP(Noop) /* 0 */ \
	OP(SetToken) /* 1 */ \
	OP(SetBucketSize) /* 2 */ \
	OP(SetBucketData) /* 3 */ \
	OP(SetBucketDataImmediate) /* 4 */ \
	OP(GetBucketStart) /* 5 */ \
	OP(GetBucketData) /* 6 */ \

	// Common commands.
	enum CommandId {
	#define COMMON_COMMAND_BUFFER_CMD_OP(name) k ## name,

	COMMON_COMMAND_BUFFER_CMDS(COMMON_COMMAND_BUFFER_CMD_OP)

	#undef COMMON_COMMAND_BUFFER_CMD_OP

	kNumCommands,
	kLastCommonId = 255 // reserve 256 spaces for common commands.
	};

	static_assert(kNumCommands - 1 <= kLastCommonId, "too many commands");

	const char* GetCommandName(CommandId id);

	// A Noop command.
	struct Noop {
	typedef Noop ValueType;
	static const CommandId kCmdId = kNoop;
	static const cmd::ArgFlags kArgFlags = cmd::kAtLeastN;
	static const uint8_t cmd_flags = CMD_FLAG_SET_TRACE_LEVEL(3);

	void SetHeader(uint32_t skip_count) {
	DCHECK_GT(skip_count, 0u);
	header.Init(kCmdId, skip_count);
	}

	void Init(uint32_t skip_count) {
	SetHeader(skip_count);
	}

	static void* Set(void* cmd, uint32_t skip_count) {
	static_cast<ValueType*>(cmd)->Init(skip_count);
	return NextImmediateCmdAddress<ValueType>(
	cmd, skip_count * sizeof(CommandBufferEntry)); // NOLINT
	}

	CommandHeader header;
	};

	static_assert(sizeof(Noop) == 4, "size of Noop should equal 4");
	static_assert(offsetof(Noop, header) == 0,
	"offset of Noop.header should equal 0");

	// The SetToken command puts a token in the command stream that you can
	// use to check if that token has been passed in the command stream.
	struct SetToken {
	typedef SetToken ValueType;
	static const CommandId kCmdId = kSetToken;
	static const cmd::ArgFlags kArgFlags = cmd::kFixed;
	static const uint8_t cmd_flags = CMD_FLAG_SET_TRACE_LEVEL(3);

	void SetHeader() {
	header.SetCmd<ValueType>();
	}

	void Init(uint32_t _token) {
	SetHeader();
	token = _token;
	}
	static void* Set(void* cmd, uint32_t token) {
	static_cast<ValueType*>(cmd)->Init(token);
	return NextCmdAddress<ValueType>(cmd);
	}

	CommandHeader header;
	uint32_t token;
	};

	static_assert(sizeof(SetToken) == 8, "size of SetToken should equal 8");
	static_assert(offsetof(SetToken, header) == 0,
	"offset of SetToken.header should equal 0");
	static_assert(offsetof(SetToken, token) == 4,
	"offset of SetToken.token should equal 4");

	// Sets the size of a bucket for collecting data on the service side.
	// This is a utility for gathering data on the service side so it can be used
	// all at once when some service side API is called. It removes the need to add
	// special commands just to support a particular API. For example, any API
	// command that needs a string needs a way to send that string to the API over
	// the command buffers. While you can require that the command buffer or
	// transfer buffer be large enough to hold the largest string you can send,
	// using this command removes that restriction by letting you send smaller
	// pieces over and build up the data on the service side.
	//
	// You can clear a bucket on the service side and thereby free memory by sending
	// a size of 0.
	struct SetBucketSize {
	typedef SetBucketSize ValueType;
	static const CommandId kCmdId = kSetBucketSize;
	static const cmd::ArgFlags kArgFlags = cmd::kFixed;
	static const uint8_t cmd_flags = CMD_FLAG_SET_TRACE_LEVEL(3);

	void SetHeader() {
	header.SetCmd<ValueType>();
	}

	void Init(uint32_t _bucket_id, uint32_t _size) {
	SetHeader();
	bucket_id = _bucket_id;
	size = _size;
	}
	static void* Set(void* cmd, uint32_t _bucket_id, uint32_t _size) {
	static_cast<ValueType*>(cmd)->Init(_bucket_id, _size);
	return NextCmdAddress<ValueType>(cmd);
	}

	CommandHeader header;
	uint32_t bucket_id;
	uint32_t size;
	};

	static_assert(sizeof(SetBucketSize) == 12,
	"size of SetBucketSize should equal 12");
	static_assert(offsetof(SetBucketSize, header) == 0,
	"offset of SetBucketSize.header should equal 0");
	static_assert(offsetof(SetBucketSize, bucket_id) == 4,
	"offset of SetBucketSize.bucket_id should equal 4");
	static_assert(offsetof(SetBucketSize, size) == 8,
	"offset of SetBucketSize.size should equal 8");

	// Sets the contents of a portion of a bucket on the service side from data in
	// shared memory.
	// See SetBucketSize.
	struct SetBucketData {
	typedef SetBucketData ValueType;
	static const CommandId kCmdId = kSetBucketData;
	static const cmd::ArgFlags kArgFlags = cmd::kFixed;
	static const uint8_t cmd_flags = CMD_FLAG_SET_TRACE_LEVEL(3);

	void SetHeader() {
	header.SetCmd<ValueType>();
	}

	void Init(uint32_t _bucket_id,
	uint32_t _offset,
	uint32_t _size,
	uint32_t _shared_memory_id,
	uint32_t _shared_memory_offset) {
	SetHeader();
	bucket_id = _bucket_id;
	offset = _offset;
	size = _size;
	shared_memory_id = _shared_memory_id;
	shared_memory_offset = _shared_memory_offset;
	}
	static void* Set(void* cmd,
	uint32_t _bucket_id,
	uint32_t _offset,
	uint32_t _size,
	uint32_t _shared_memory_id,
	uint32_t _shared_memory_offset) {
	static_cast<ValueType*>(cmd)->Init(
	_bucket_id,
	_offset,
	_size,
	_shared_memory_id,
	_shared_memory_offset);
	return NextCmdAddress<ValueType>(cmd);
	}

	CommandHeader header;
	uint32_t bucket_id;
	uint32_t offset;
	uint32_t size;
	uint32_t shared_memory_id;
	uint32_t shared_memory_offset;
	};

	static_assert(sizeof(SetBucketData) == 24,
	"size of SetBucketData should be 24");
	static_assert(offsetof(SetBucketData, header) == 0,
	"offset of SetBucketData.header should be 0");
	static_assert(offsetof(SetBucketData, bucket_id) == 4,
	"offset of SetBucketData.bucket_id should be 4");
	static_assert(offsetof(SetBucketData, offset) == 8,
	"offset of SetBucketData.offset should be 8");
	static_assert(offsetof(SetBucketData, size) == 12,
	"offset of SetBucketData.size should be 12");
	static_assert(offsetof(SetBucketData, shared_memory_id) == 16,
	"offset of SetBucketData.shared_memory_id should be 16");
	static_assert(offsetof(SetBucketData, shared_memory_offset) == 20,
	"offset of SetBucketData.shared_memory_offset should be 20");

	// Sets the contents of a portion of a bucket on the service side from data in
	// the command buffer.
	// See SetBucketSize.
	struct SetBucketDataImmediate {
	typedef SetBucketDataImmediate ValueType;
	static const CommandId kCmdId = kSetBucketDataImmediate;
	static const cmd::ArgFlags kArgFlags = cmd::kAtLeastN;
	static const uint8_t cmd_flags = CMD_FLAG_SET_TRACE_LEVEL(3);

	void SetHeader(uint32_t size) {
	header.SetCmdBySize<ValueType>(size);
	}

	void Init(uint32_t _bucket_id,
	uint32_t _offset,
	uint32_t _size) {
	SetHeader(_size);
	bucket_id = _bucket_id;
	offset = _offset;
	size = _size;
	}
	static void* Set(void* cmd,
	uint32_t _bucket_id,
	uint32_t _offset,
	uint32_t _size) {
	static_cast<ValueType*>(cmd)->Init(
	_bucket_id,
	_offset,
	_size);
	return NextImmediateCmdAddress<ValueType>(cmd, _size);
	}

	CommandHeader header;
	uint32_t bucket_id;
	uint32_t offset;
	uint32_t size;
	};

	static_assert(sizeof(SetBucketDataImmediate) == 16,
	"size of SetBucketDataImmediate should be 16");
	static_assert(offsetof(SetBucketDataImmediate, header) == 0,
	"offset of SetBucketDataImmediate.header should be 0");
	static_assert(offsetof(SetBucketDataImmediate, bucket_id) == 4,
	"offset of SetBucketDataImmediate.bucket_id should be 4");
	static_assert(offsetof(SetBucketDataImmediate, offset) == 8,
	"offset of SetBucketDataImmediate.offset should be 8");
	static_assert(offsetof(SetBucketDataImmediate, size) == 12,
	"offset of SetBucketDataImmediate.size should be 12");

	// Gets the start of a bucket the service has available. Sending a variable size
	// result back to the client and the portion of that result that fits in the
	// supplied shared memory. If the size of the result is larger than the supplied
	// shared memory the rest of the bucket's contents can be retrieved with
	// GetBucketData.
	//
	// This is used for example for any API that returns a string. The problem is
	// the largest thing you can send back in 1 command is the size of your shared
	// memory. This command along with GetBucketData implements a way to get a
	// result a piece at a time to help solve that problem in a generic way.
	struct GetBucketStart {
	typedef GetBucketStart ValueType;
	static const CommandId kCmdId = kGetBucketStart;
	static const cmd::ArgFlags kArgFlags = cmd::kFixed;
	static const uint8_t cmd_flags = CMD_FLAG_SET_TRACE_LEVEL(3);

	typedef uint32_t Result;

	void SetHeader() {
	header.SetCmd<ValueType>();
	}

	void Init(uint32_t _bucket_id,
	uint32_t _result_memory_id,
	uint32_t _result_memory_offset,
	uint32_t _data_memory_size,
	uint32_t _data_memory_id,
	uint32_t _data_memory_offset) {
	SetHeader();
	bucket_id = _bucket_id;
	result_memory_id = _result_memory_id;
	result_memory_offset = _result_memory_offset;
	data_memory_size = _data_memory_size;
	data_memory_id = _data_memory_id;
	data_memory_offset = _data_memory_offset;
	}
	static void* Set(void* cmd,
	uint32_t _bucket_id,
	uint32_t _result_memory_id,
	uint32_t _result_memory_offset,
	uint32_t _data_memory_size,
	uint32_t _data_memory_id,
	uint32_t _data_memory_offset) {
	static_cast<ValueType*>(cmd)->Init(
	_bucket_id,
	_result_memory_id,
	_result_memory_offset,
	_data_memory_size,
	_data_memory_id,
	_data_memory_offset);
	return NextCmdAddress<ValueType>(cmd);
	}

	CommandHeader header;
	uint32_t bucket_id;
	uint32_t result_memory_id;
	uint32_t result_memory_offset;
	uint32_t data_memory_size;
	uint32_t data_memory_id;
	uint32_t data_memory_offset;
	};

	static_assert(sizeof(GetBucketStart) == 28,
	"size of GetBucketStart should be 28");
	static_assert(offsetof(GetBucketStart, header) == 0,
	"offset of GetBucketStart.header should be 0");
	static_assert(offsetof(GetBucketStart, bucket_id) == 4,
	"offset of GetBucketStart.bucket_id should be 4");
	static_assert(offsetof(GetBucketStart, result_memory_id) == 8,
	"offset of GetBucketStart.result_memory_id should be 8");
	static_assert(offsetof(GetBucketStart, result_memory_offset) == 12,
	"offset of GetBucketStart.result_memory_offset should be 12");
	static_assert(offsetof(GetBucketStart, data_memory_size) == 16,
	"offset of GetBucketStart.data_memory_size should be 16");
	static_assert(offsetof(GetBucketStart, data_memory_id) == 20,
	"offset of GetBucketStart.data_memory_id should be 20");
	static_assert(offsetof(GetBucketStart, data_memory_offset) == 24,
	"offset of GetBucketStart.data_memory_offset should be 24");

	// Gets a piece of a result the service as available.
	// See GetBucketSize.
	struct GetBucketData {
	typedef GetBucketData ValueType;
	static const CommandId kCmdId = kGetBucketData;
	static const cmd::ArgFlags kArgFlags = cmd::kFixed;
	static const uint8_t cmd_flags = CMD_FLAG_SET_TRACE_LEVEL(3);

	void SetHeader() {
	header.SetCmd<ValueType>();
	}

	void Init(uint32_t _bucket_id,
	uint32_t _offset,
	uint32_t _size,
	uint32_t _shared_memory_id,
	uint32_t _shared_memory_offset) {
	SetHeader();
	bucket_id = _bucket_id;
	offset = _offset;
	size = _size;
	shared_memory_id = _shared_memory_id;
	shared_memory_offset = _shared_memory_offset;
	}
	static void* Set(void* cmd,
	uint32_t _bucket_id,
	uint32_t _offset,
	uint32_t _size,
	uint32_t _shared_memory_id,
	uint32_t _shared_memory_offset) {
	static_cast<ValueType*>(cmd)->Init(
	_bucket_id,
	_offset,
	_size,
	_shared_memory_id,
	_shared_memory_offset);
	return NextCmdAddress<ValueType>(cmd);
	}

	CommandHeader header;
	uint32_t bucket_id;
	uint32_t offset;
	uint32_t size;
	uint32_t shared_memory_id;
	uint32_t shared_memory_offset;
	};

	static_assert(sizeof(GetBucketData) == 24,
	"size of GetBucketData should be 24");
	static_assert(offsetof(GetBucketData, header) == 0,
	"offset of GetBucketData.header should be 0");
	static_assert(offsetof(GetBucketData, bucket_id) == 4,
	"offset of GetBucketData.bucket_id should be 4");
	static_assert(offsetof(GetBucketData, offset) == 8,
	"offset of GetBucketData.offset should be 8");
	static_assert(offsetof(GetBucketData, size) == 12,
	"offset of GetBucketData.size should be 12");
	static_assert(offsetof(GetBucketData, shared_memory_id) == 16,
	"offset of GetBucketData.shared_memory_id should be 16");
	static_assert(offsetof(GetBucketData, shared_memory_offset) == 20,
	"offset of GetBucketData.shared_memory_offset should be 20");

	} // namespace cmd

	#pragma pack(pop)

	} // namespace gpu

	#endif // GPU_COMMAND_BUFFER_COMMON_CMD_BUFFER_COMMON_H_