47 lines
838 B
C
47 lines
838 B
C
#include "os.h"
|
|
#include <mp.h>
|
|
#include "dat.h"
|
|
|
|
// res = b << shift
|
|
void
|
|
mpleft(mpint *b, int shift, mpint *res)
|
|
{
|
|
int d, l, r, i, otop;
|
|
mpdigit this, last;
|
|
|
|
// a negative left shift is a right shift
|
|
if(shift < 0){
|
|
mpright(b, -shift, res);
|
|
return;
|
|
}
|
|
|
|
// b and res may be the same so remember the old top
|
|
otop = b->top;
|
|
|
|
// shift
|
|
mpbits(res, otop*Dbits + shift); // overkill
|
|
res->top = DIGITS(otop*Dbits + shift);
|
|
d = shift/Dbits;
|
|
l = shift - d*Dbits;
|
|
r = Dbits - l;
|
|
|
|
if(l == 0){
|
|
for(i = otop-1; i >= 0; i--)
|
|
res->p[i+d] = b->p[i];
|
|
} else {
|
|
last = 0;
|
|
for(i = otop-1; i >= 0; i--) {
|
|
this = b->p[i];
|
|
res->p[i+d+1] = (last<<l) | (this>>r);
|
|
last = this;
|
|
}
|
|
res->p[d] = last<<l;
|
|
}
|
|
for(i = 0; i < d; i++)
|
|
res->p[i] = 0;
|
|
|
|
// normalize
|
|
while(res->top > 0 && res->p[res->top-1] == 0)
|
|
res->top--;
|
|
}
|