text: // 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 command parser class.
  
  #ifndef GPU_COMMAND_BUFFER_SERVICE_CMD_PARSER_H_
  #define GPU_COMMAND_BUFFER_SERVICE_CMD_PARSER_H_
  
  #include <stddef.h>
  #include <stdint.h>
  
  #include "gpu/command_buffer/common/cmd_buffer_common.h"
  #include "gpu/command_buffer/common/constants.h"
  #include "gpu/gpu_export.h"
  
  namespace gpu {
  
  class AsyncAPIInterface;
  
  // Command parser class. This class parses commands from a shared memory
  // buffer, to implement some asynchronous RPC mechanism.
  class GPU_EXPORT CommandParser {
   public:
    static const int kParseCommandsSlice = 20;
  
    explicit CommandParser(AsyncAPIInterface* handler);
  
    // Sets the buffer to read commands from.
    void SetBuffer(
        void* shm_address,
        size_t shm_size,
        ptrdiff_t offset,
        size_t size);
  
    // Gets the "get" pointer. The get pointer is an index into the command
    // buffer considered as an array of CommandBufferEntry.
    CommandBufferOffset get() const { return get_; }
  
    // Sets the "get" pointer. The get pointer is an index into the command buffer
    // considered as an array of CommandBufferEntry.
    bool set_get(CommandBufferOffset get) {
      if (get >= 0 && get < entry_count_) {
        get_ = get;
        return true;
      }
      return false;
    }
  
    // Sets the "put" pointer. The put pointer is an index into the command
    // buffer considered as an array of CommandBufferEntry.
    void set_put(CommandBufferOffset put) { put_ = put; }
  
    // Gets the "put" pointer. The put pointer is an index into the command
    // buffer considered as an array of CommandBufferEntry.
    CommandBufferOffset put() const { return put_; }
  
    // Checks whether there are commands to process.
    bool IsEmpty() const { return put_ == get_; }
  
    // Processes one command, updating the get pointer. This will return an error
    // if there are no commands in the buffer.
    error::Error ProcessCommands(int num_commands);
  
    // Processes all commands until get == put.
    error::Error ProcessAllCommands();
  
   private:
    CommandBufferOffset get_;
    CommandBufferOffset put_;
    CommandBufferEntry* buffer_;
    int32_t entry_count_;
    AsyncAPIInterface* handler_;
  };
  
  // This class defines the interface for an asynchronous API handler, that
  // is responsible for de-multiplexing commands and their arguments.
  class GPU_EXPORT AsyncAPIInterface {
   public:
    AsyncAPIInterface() {}
    virtual ~AsyncAPIInterface() {}
  
    // Executes a single 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.
    virtual error::Error DoCommand(
        unsigned int command,
        unsigned int arg_count,
        const void* cmd_data) = 0;
  
    // Executes multiple commands.
    // Parameters:
    //    num_commands: maximum number of commands to execute from buffer.
    //    buffer: pointer to first command entry to process.
    //    num_entries: number of sequential command buffer entries in buffer.
    //    entries_processed: if not 0, is set to the number of entries processed.
    virtual error::Error DoCommands(unsigned int num_commands,
                                    const void* buffer,
                                    int num_entries,
                                    int* entries_processed);
  
    // Returns a name for a command. Useful for logging / debuging.
    virtual const char* GetCommandName(unsigned int command_id) const = 0;
  };
  
  }  // namespace gpu
  
  #endif  // GPU_COMMAND_BUFFER_SERVICE_CMD_PARSER_H_
  