helpers.c

This code is used to TCP/IP connection It is developed by PIC18F452 and all this code is successfull

#include "compiler.h"
#include "tcptask.h"


WORD swaps(WORD v)
{
    WORD_VAL t;
    BYTE b;

    t.Val   = v;
    b       = t.v[1];
    t.v[1]  = t.v[0];
    t.v[0]  = b;

    return t.Val;
}


DWORD swapl(DWORD v)
{
    BYTE b;
    DWORD myV;
    DWORD_VAL *myP;

    myV     = v;
    myP     = (DWORD_VAL*)&myV;

    b       = myP->v[3];
    myP->v[3] = myP->v[0];
    myP->v[0] = b;

    b       = myP->v[2];
    myP->v[2] = myP->v[1];
    myP->v[1] = b;

    return myV;

}

WORD CalcIPChecksum(BYTE* buffer, WORD count)
{
    WORD i;
    WORD *val;

    union
    {
        DWORD Val;
        struct
        {
            WORD_VAL LSB;
            WORD_VAL MSB;
        } words;
    } tempSum, sum;

    sum.Val = 0;

    i = count >> 1;
    val = (WORD *)buffer;

    while( i-- )
        sum.Val += *val++;

    if ( count & 1 )
        sum.Val += *(BYTE *)val;

    tempSum.Val = sum.Val;

    while( (i = tempSum.words.MSB.Val) != 0 )
    {
        sum.words.MSB.Val = 0;
        sum.Val = (DWORD)sum.words.LSB.Val + (DWORD)i;
        tempSum.Val = sum.Val;
    }

    return (~sum.words.LSB.Val);
}