checksum.h

00001 /**
00002  * @file    checksum.h
00003  * @brief   Utility Function - Data integrity helpers
00004  * @author  sam grove
00005  * @version 1.0
00006  *
00007  * Copyright (c) 2013
00008  *
00009  * Licensed under the Apache License, Version 2.0 (the "License");
00010  * you may not use this file except in compliance with the License.
00011  * You may obtain a copy of the License at
00012  *
00013  *     http://www.apache.org/licenses/LICENSE-2.0
00014  *
00015  * Unless required by applicable law or agreed to in writing, software
00016  * distributed under the License is distributed on an "AS IS" BASIS,
00017  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
00018  * See the License for the specific language governing permissions and
00019  * limitations under the License.
00020  */
00021  
00022 #ifndef CHECKSUM_H
00023 #define CHECKSUM_H
00024 
00025 #include <stdint.h>
00026  
00027 /** Helpers for working data streams
00028  *
00029  * Example:
00030  * @code
00031  *  #include "mbed.h"
00032  *  #include "checksum.h"
00033  *
00034  *  DigitalOut myled(LED1);
00035  *  
00036  *  template <int T>
00037  *  struct data{
00038  *      uint8_t buf[T];
00039  *      uint8_t checksum;
00040  *  };
00041  *  data<12> all_ones = {{1,1,1,1,1,1,1,1,1,1,1,1}};
00042  *
00043  *  int main() 
00044  *  {
00045  *      calculateChecksum( all_ones.buf, sizeof(all_ones) );
00046  *      
00047  *      for(int i=0; i<sizeof(all_ones); i++)
00048  *      {
00049  *          printf("%02d: %d\n", i, *(all_ones.buf+i));
00050  *      }
00051  *
00052  *      printf("checksum test: %s\n", (result)?"passed":"failed");
00053  *
00054  *      while(1) 
00055  *      {
00056  *          myled = 1;
00057  *          wait(0.2);
00058  *          myled = 0;
00059  *          wait(0.2);
00060  *      }
00061  *  }
00062  * @endcode
00063  */
00064 
00065 /** Calculate the checksum of a data stream
00066  *  Assumes the checksum is in the last position, 8-bits and 0 - the sum of data 
00067  *  @param pkt - A pointer to the data
00068  *  @param length - The amount of data that the checksum calculates
00069  *  @returns true if the checksum is correct and false otherwise
00070  */
00071 bool validateChecksum( uint8_t const *pkt, uint32_t const length );
00072 
00073 /** Calculate and store the checksum into the last position of a data stream
00074  *
00075  *  @param pkt - A pointer to the data
00076  *  @param length - The amount of data that the checksum calculates
00077  */
00078 void calculateChecksum( uint8_t *pkt, uint32_t const length );
00079 
00080 #endif