Subversion Repositories planix.SVN

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

// convert a big-endian byte array (most significant byte first) to an mpint
mpint*
betomp(uchar *p, uint n, mpint *b)
{
        int m, s;
        mpdigit x;

        if(b == nil){
                b = mpnew(0);
                setmalloctag(b, getcallerpc(&p));
        }

        // dump leading zeros
        while(*p == 0 && n > 1){
                p++;
                n--;
        }

        // get the space
        mpbits(b, n*8);
        b->top = DIGITS(n*8);
        m = b->top-1;

        // first digit might not be Dbytes long
        s = ((n-1)*8)%Dbits;
        x = 0;
        for(; n > 0; n--){
                x |= ((mpdigit)(*p++)) << s;
                s -= 8;
                if(s < 0){
                        b->p[m--] = x;
                        s = Dbits-8;
                        x = 0;
                }
        }

        return b;
}