.. _program_listing_file__tmp_ws_src_lms1xx_include_LMS1xx_lms_buffer.h:

Program Listing for File lms_buffer.h
=====================================

|exhale_lsh| :ref:`Return to documentation for file <file__tmp_ws_src_lms1xx_include_LMS1xx_lms_buffer.h>` (``/tmp/ws/src/lms1xx/include/LMS1xx/lms_buffer.h``)

.. |exhale_lsh| unicode:: U+021B0 .. UPWARDS ARROW WITH TIP LEFTWARDS

.. code-block:: cpp

   /*
    * lms_buffer.h
    *
    *  Author: Mike Purvis <mpurvis@clearpathrobotics.com>
    *  Author: Shravan S Rai <shravansomashekara.rai@gmail.com>
    ***************************************************************************
    *   This library is free software; you can redistribute it and/or         *
    *   modify it under the terms of the GNU Lesser General Public            *
    *   License as published by the Free Software Foundation; either          *
    *   version 2.1 of the License, or (at your option) any later version.    *
    *                                                                         *
    *   This library is distributed in the hope that it will be useful,       *
    *   but WITHOUT ANY WARRANTY; without even the implied warranty of        *
    *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU     *
    *   Lesser General Public License for more details.                       *
    *                                                                         *
    *   You should have received a copy of the GNU Lesser General Public      *
    *   License along with this library; if not, write to the Free Software   *
    *   Foundation, Inc., 59 Temple Place,                                    *
    *   Suite 330, Boston, MA  02111-1307  USA                                *
    *                                                                         *
    ***************************************************************************/
   
   #ifndef LMS1XX_LMS_BUFFER_H_
   #define LMS1XX_LMS_BUFFER_H_
   
   #include <stdint.h>
   #include <string.h>
   #include <unistd.h>
   
   
   #define LMS_BUFFER_SIZE 50000
   #define LMS_STX 0x02
   #define LMS_ETX 0x03
   
   
   class LMSBuffer
   {
   public:
     LMSBuffer() : total_length_(0), end_of_first_message_(0)
     {
     }
   
     void readFrom(int fd)
     {
       int ret = read(fd, buffer_ + total_length_, sizeof(buffer_) - total_length_);
   
       if (ret > 0)
       {
         total_length_ += ret;
         //printf("Read %d bytes from fd, total length is %d.", ret, total_length_);
       }
       else
       {
         //printf("Buffer read() returned error.");
       }
     }
   
     char* getNextBuffer()
     {
       if (total_length_ == 0)
       {
         // Buffer is empty, no scan data present.
         //printf("Empty buffer, nothing to return.");
         return NULL;
       }
   
       // The objective is to have a message starting at the start of the buffer, so if that's not
       // the case, then we look for a start-of-message character and shift the buffer back, discarding
       // any characters in the middle.
       char* start_of_message = (char*)memchr(buffer_, LMS_STX, total_length_);
       if (start_of_message == NULL)
       {
         // None found, buffer reset.
         //printf("No STX found, dropping %d bytes from buffer.", total_length_);
         total_length_ = 0;
       }
       else if (buffer_ != start_of_message)
       {
         // Start of message found, ahead of the start of buffer. Therefore shift the buffer back.
         //printf("Shifting buffer, dropping %ld bytes, %ld bytes remain.",
         //        (start_of_message - buffer_), total_length_ - (start_of_message - buffer_));
         shiftBuffer(start_of_message);
       }
   
       // Now look for the end of message character.
       end_of_first_message_ = (char*)memchr(buffer_, LMS_ETX, total_length_);
       if (end_of_first_message_ == NULL)
       {
         // No end of message found, therefore no message to parse and return.
         //printf("No ETX found, nothing to return.");
         return NULL;
       }
   
       // Null-terminate buffer.
       *end_of_first_message_ = 0;
       return buffer_;
     }
   
     void popLastBuffer()
     {
       if (end_of_first_message_)
       {
         shiftBuffer(end_of_first_message_ + 1);
         end_of_first_message_ = NULL;
       }
     }
   
   private:
     void shiftBuffer(char* new_start)
     {
       // Shift back anything remaining in the buffer.
       uint16_t remaining_length = total_length_ - (new_start - buffer_);
   
       if (remaining_length > 0)
       {
         memmove(buffer_, new_start, remaining_length);
       }
       total_length_ = remaining_length;
     }
   
     char buffer_[LMS_BUFFER_SIZE];
     uint16_t total_length_;
   
     char* end_of_first_message_;
   };
   
   #endif  // LMS1XX_LMS_BUFFER_H_