PIC C code for the 32bit math functions.

////////////////////////////////////////////////////////////////////////////
//                                                                        //
// This code is based on code by Vadim Gerasimov (vadim@media.mit.edu),   //
// and extended skillfully by Mark Newman (newman@media.mit.edu) for the  //
// Robotic F.A.C.E. project                                               //
//                                                                        //
// Copyright (C) 2001-2004 MIT Media Laboratory                           //
//                                                                        //
////////////////////////////////////////////////////////////////////////////


// 32-bit arithmetic
#define move32(to,from) {to[0]=from[0];to[1]=from[1];to[2]=from[2];to[3]=from[3];}
#define zero32(n) {n[0]=0;n[1]=0;n[2]=0;n[3]=0;}
#define is_zero32(n) ((n[0]|n[1]|n[2]|n[3])==0)
#define inc32(n) {if(++n[0]==0)if(++n[1]==0)if(++n[2]==0)++n[3];}

void dec32 (char* n) {
  if (n[0]--==0) if(n[1]--==0) if (n[2]--==0) --n[3];
}

void add32 (char* a, char* b)
{
   byte r[4];

   r[0] = *(b);
   r[1] = *(b + 1);
   r[2] = *(b + 2);
   r[3] = *(b + 3);

#asm
   movf    a,w
   movwf   4
   movf    r[0],w
   addwf   0,f
   movf    r[1],w
   incf    4,f
   btfsc   3,0
   incfsz  r[1],w
   addwf   0,f
   movf    r[2],w
   incf    4,f
   btfsc   3,0
   incfsz  r[2],w
   addwf   0,f
   movf    r[3],w
   incf    4,f
   btfsc   3,0
   incfsz  r[3],w
   addwf   0,f
#endasm
}

void sub32(char* a, char* b) { // a = a - b
   byte r[4];
   r[0] = *(b);
   r[1] = *(b + 1);
   r[2] = *(b + 2);
   r[3] = *(b + 3);
#asm
   movf    a,w
   movwf   4
   movf    r[0],w
   subwf   0,f
   movf    r[1],w
   incf    4,f
   btfss   3,0
   incfsz  r[1],w
   subwf   0,f
   movf    r[2],w
   incf    4,f
   btfss   3,0
   incfsz  r[2],w
   subwf   0,f
   movf    r[3],w
   incf    4,f
   btfss   3,0
   incfsz  r[3],w
   subwf   0,f
#endasm
}

int lt32(char *a, char *b) {
	int i;
	for (i = 3; i >= 0; i--) {
		if (a[i] > b[i])
			return 0;
		if (a[i] < b[i])
			return 1;
	}
	return 0;
}
int le32(char *a, char *b) {
	int i;
	for (i = 3; i >= 0; i--) {
		if (a[i] < b[i])
			return 1;
		if (a[i] > b[i])
			return 0;
	}
	return 1;
}
int gt32(char *a, char *b) {
	int i;
	for (i = 3; i >= 0; i--) {
		if (a[i] < b[i])
			return 0;
		if (a[i] > b[i])
			return 1;
	}
	return 0;
}
int ge32(char *a, char *b) {
	int i;
	for (i = 3; i >= 0; i--) {
		if (a[i] > b[i])
			return 1;
		if (a[i] < b[i])
			return 0;
	}
	return 1;
}

void shift32(char *n) {
	char i, in, out;
	in = 0;
	for (i = 0; i < 4; i++) {
		out = n[i] >> 7;
		n[i] = in + (n[i] << 1);
		in = out;
	}
}

void mult32byte(char *a, char b) {
	char i;
	char r[4];
	move32(r, a);
	zero32(a);

	for (i = 0; i < 8; i++) {
		if (b & 1)
			add32(a, r);
		b = b >> 1;
		shift32(r);
	}
	a[0] = a[1];
	a[1] = a[2];
	a[2] = a[3];
	a[3] = 0;
}