LwFEC - Lightweight Forward Error Correction library

LwFEC is a full Reed-Solomon FEC encoder and decoder C library dedicated for embedded and other RAM usage restricted systems.

Memory usage

The aim of this library is to be safe and deterministic, thus:

• No heap (malloc) is used
• No stack-allocated arrays are used

Parity byte count limit can be changed freely according to application requirements. This allows the memory usage to stay at the required minimum.
Warning! LwFEC library is not thread/interrupt safe.

Example usage

The example below shows how to initialize library, encode and decode a message:

#include <stdint.h> //standard integer types header
#include "rs.h" //RS FEC library

#define K 12 //data size
#define T 5 //parity size
#define FCR 0 //first consecutive root index

struct LwFecRS rs; //RS encoder/decoder instance

void LwFEC(void)
{
    RsInit(&rs, T, FCR);
    uint8_t data[RS_BLOCK_SIZE] = {'H', 'e', 'l', 'l', 'o', ' ', 'w', 'o', 'r', 'l', 'd', '\0'};
    RsEncode(&rs, data, N); //encode message

    //then N=RS_BLOCK_SIZE bytes of data are sent through some channel
    //or stored on some disk
    //this may introduce errors that the decoder will try to fix
    
    //alter some bytes for demonstration
    data[1] = 'h';
    data[5] = 'x';

    uint8_t bytesFixed = 0; //store number of corrected bytes here
    if(RsDecode(&rs, data, K, &bytesFixed)) //decode message
    {
        //message decoded succesfully
    }
    else
    {
        //too many errors in message
    }
}

Important notes

The block size is always equal to RS_BLOCK_SIZE (255 bytes) due to use of GF(2^8), however the library can handle any data size K provided T + K <= RS_BLOCK_SIZE. The remaining block space is padded automatically with zeros. The application just needs to provide K bytes of data.

Size limit change

Size limits used for array preallocation are stored in rs.h:

#define RS_MAX_REDUNDANCY_BYTES 64 //maximum parity bytes

License

The code is based on Reed-Solomon codes for coders. The project is licensed under the GNU GPL v3 license (see LICENSE).