1 #include "os.h"
2 #include <mp.h>
3 #include "dat.h"
4 
5 mpint*
6 mprand(int bits, void (*gen)(uchar*, int), mpint *b)
7 {
8 	int n, m;
9 	mpdigit mask;
10 	uchar *p;
11 
12 	n = DIGITS(bits);
13 	if(b == nil)
14 		b = mpnew(bits);
15 	else
16 		mpbits(b, bits);
17 
18 	p = malloc(n*Dbytes);
19 	if(p == nil)
20 		return nil;
21 	(*gen)(p, n*Dbytes);
22 	betomp(p, n*Dbytes, b);
23 	free(p);
24 
25 	/* make sure we don't give too many bits */
26 	m = bits%Dbits;
27 	n--;
28 	if(m > 0){
29 		mask = 1;
30 		mask <<= m;
31 		mask--;
32 		b->p[n] &= mask;
33 	}
34 
35 	for(; n >= 0; n--)
36 		if(b->p[n] != 0)
37 			break;
38 	b->top = n+1;
39 	b->sign = 1;
40 	return b;
41 }