src/ztrunc.c


1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33

/* See LICENSE file for copyright and license details. */
#include "internals"

#include <stdlib.h>
#include <string.h>


void
ztrunc(z_t a, z_t b, size_t bits)
{
	zahl_char_t mask = 1;
	size_t chars;
	if (zzero(b)) {
		SET_SIGNUM(a, 0);
	} else {
		chars = CEILING_BITS_TO_CHARS(bits);
		a->sign = b->sign;
		a->used = chars < b->used ? chars : b->used;
		if (a->used < chars)
			bits = 0;
		if (a->alloced < b->alloced) {
			a->alloced = b->alloced;
			a->chars = realloc(a->chars, b->alloced * sizeof(*(a->chars)));
		}
		memcpy(a->chars, b->chars, a->used * sizeof(*(a->chars)));
		bits = BITS_IN_LAST_CHAR(bits);
		if (bits) {
			mask <<= bits;
			mask -= 1;
			a->chars[a->used - 1] &= mask;
		}
	}
}