Sam Grove / checksum

Utility functions for working with data streams

Example usage:

http://andy.dynamicbits.com/hdradio/

#include "mbed.h"
#include "checksum.h"

DigitalOut myled(LED1);

template <int T>
struct data{
    uint8_t buf[T];
    uint8_t checksum;
};

data<12> all_ones = {{1,1,1,1,1,1,1,1,1,1,1,1}};

int main() 
{
    calculateChecksum( all_ones.buf, sizeof(all_ones) );
      
    for(int i=0; i<sizeof(all_ones); i++)
    {
        printf("%02d: %d\n", i, *(all_ones.buf+i));
    }

    printf("checksum test: %s\n", (result)?"passed":"failed");

    while(1) 
    {
        myled = 1;
        wait(0.2);
        myled = 0;
        wait(0.2);
    }
}

checksum.cpp@1:ace4b3aef52b, 2013-03-07 (annotated)

Committer:
sam_grove
Date:
Thu Mar 07 20:59:49 2013 +0000
Revision:
1:ace4b3aef52b
Parent:
0:39b5762958a4 
More documentation updates

Who changed what in which revision?

UserRevisionLine numberNew contents of line
sam_grove 0:39b5762958a4 1 /**
sam_grove 0:39b5762958a4 2 * @file checksum.cpp
sam_grove 0:39b5762958a4 3 * @brief Utility Function - Data integrity helpers
sam_grove 0:39b5762958a4 4 * @author sam grove
sam_grove 0:39b5762958a4 5 * @version 1.0
sam_grove 0:39b5762958a4 6 *
sam_grove 0:39b5762958a4 7 * Copyright (c) 2013
sam_grove 0:39b5762958a4 8 *
sam_grove 0:39b5762958a4 9 * Licensed under the Apache License, Version 2.0 (the "License");
sam_grove 0:39b5762958a4 10 * you may not use this file except in compliance with the License.
sam_grove 0:39b5762958a4 11 * You may obtain a copy of the License at
sam_grove 0:39b5762958a4 12 *
sam_grove 0:39b5762958a4 13 * http://www.apache.org/licenses/LICENSE-2.0
sam_grove 0:39b5762958a4 14 *
sam_grove 0:39b5762958a4 15 * Unless required by applicable law or agreed to in writing, software
sam_grove 0:39b5762958a4 16 * distributed under the License is distributed on an "AS IS" BASIS,
sam_grove 0:39b5762958a4 17 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
sam_grove 0:39b5762958a4 18 * See the License for the specific language governing permissions and
sam_grove 0:39b5762958a4 19 * limitations under the License.
sam_grove 0:39b5762958a4 20 */
sam_grove 0:39b5762958a4 21
sam_grove 0:39b5762958a4 22 #include "checksum.h"
sam_grove 0:39b5762958a4 23
sam_grove 0:39b5762958a4 24 bool validateChecksum( uint8_t const *pkt, uint32_t const length )
sam_grove 0:39b5762958a4 25 {
sam_grove 0:39b5762958a4 26 uint32_t pos = 0;
sam_grove 0:39b5762958a4 27 uint8_t sum = 0;
sam_grove 0:39b5762958a4 28 while ( pos < (length-1) )
sam_grove 0:39b5762958a4 29 {
sam_grove 0:39b5762958a4 30 sum += *(pkt+pos++);
sam_grove 0:39b5762958a4 31 }
sam_grove 0:39b5762958a4 32 sum = 0x0 - sum;
sam_grove 0:39b5762958a4 33 // return 0 or 1 based on the checksum test
sam_grove 0:39b5762958a4 34 return (sum == *(pkt+pos)) ? 1 : 0;
sam_grove 0:39b5762958a4 35 }
sam_grove 0:39b5762958a4 36
sam_grove 0:39b5762958a4 37 void calculateChecksum( uint8_t *pkt, uint32_t const length )
sam_grove 0:39b5762958a4 38 {
sam_grove 0:39b5762958a4 39 uint32_t pos = 0;
sam_grove 0:39b5762958a4 40 uint8_t sum = 0;
sam_grove 0:39b5762958a4 41 while ( pos < (length-1) )
sam_grove 0:39b5762958a4 42 {
sam_grove 0:39b5762958a4 43 sum += *(pkt+pos++);
sam_grove 0:39b5762958a4 44 }
sam_grove 0:39b5762958a4 45 // put the checksum into the data stream
sam_grove 0:39b5762958a4 46 *(pkt+pos) = 0x0 - sum;
sam_grove 0:39b5762958a4 47
sam_grove 0:39b5762958a4 48 return;
sam_grove 0:39b5762958a4 49 }
sam_grove 0:39b5762958a4 50