Subversion Repositories planix.SVN

#include "os.h"
#include <mp.h>
#include "dat.h"

// convert an mpint into a big endian byte array (most significant byte first)
//   return number of bytes converted
//   if p == nil, allocate and result array
int
mptobe(mpint *b, uchar *p, uint n, uchar **pp)
{
        int i, j, suppress;
        mpdigit x;
        uchar *e, *s, c;

        if(p == nil){
                n = (b->top+1)*Dbytes;
                p = malloc(n);
                setmalloctag(p, getcallerpc(&b));
        }
        if(p == nil)
                return -1;
        if(pp != nil)
                *pp = p;
        memset(p, 0, n);

        // special case 0
        if(b->top == 0){
                if(n < 1)
                        return -1;
                else
                        return 1;
        }
                
        s = p;
        e = s+n;
        suppress = 1;
        for(i = b->top-1; i >= 0; i--){
                x = b->p[i];
                for(j = Dbits-8; j >= 0; j -= 8){
                        c = x>>j;
                        if(c == 0 && suppress)
                                continue;
                        if(p >= e)
                                return -1;
                        *p++ = c;
                        suppress = 0;
                }
        }

        // guarantee at least one byte
        if(s == p){
                if(p >= e)
                        return -1;
                *p++ = 0;
        }

        return p - s;
}