Subversion Repositories planix.SVN

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

mpint*
mprand(int bits, void (*gen)(uchar*, int), mpint *b)
{
        int n, m;
        mpdigit mask;
        uchar *p;

        n = DIGITS(bits);
        if(b == nil)
                b = mpnew(bits);
        else
                mpbits(b, bits);

        p = malloc(n*Dbytes);
        if(p == nil)
                return nil;
        (*gen)(p, n*Dbytes);
        betomp(p, n*Dbytes, b);
        free(p);

        // make sure we don't give too many bits
        m = bits%Dbits;
        n--;
        if(m > 0){
                mask = 1;
                mask <<= m;
                mask--;
                b->p[n] &= mask;
        }

        for(; n >= 0; n--)
                if(b->p[n] != 0)
                        break;
        b->top = n+1;
        b->sign = 1;
        return b;
}