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/* See LICENSE file for copyright and license details. */
#include "internals.h"
static inline void
zsub_impl(z_t a, z_t b, size_t n)
{
zahl_char_t carry = 0, tcarry;
size_t i;
for (i = 0; i < n; i++) {
tcarry = carry ? (a->chars[i] <= b->chars[i]) : (a->chars[i] < b->chars[i]);
a->chars[i] -= b->chars[i];
a->chars[i] -= carry;
carry = tcarry;
}
if (carry) {
while (!a->chars[i])
a->chars[i++] = ZAHL_CHAR_MAX;
if (a->chars[i] == 1)
a->used--;
else
a->chars[i] -= 1;
}
}
static inline void
libzahl_zsub_unsigned(z_t a, z_t b, z_t c)
{
int magcmp;
size_t n;
if (unlikely(zzero(b))) {
zabs(a, c);
zneg(a, a);
return;
} else if (unlikely(zzero(c))) {
zabs(a, b);
return;
}
magcmp = zcmpmag(b, c);
if (unlikely(magcmp <= 0)) {
if (unlikely(magcmp == 0)) {
SET_SIGNUM(a, 0);
return;
}
n = b->used;
if (a == b) {
zset(libzahl_tmp_sub, b);
SET(a, c);
zsub_impl(a, libzahl_tmp_sub, n);
} else {
SET(a, c);
zsub_impl(a, b, n);
}
} else {
n = c->used;
if (unlikely(a == c)) {
zset(libzahl_tmp_sub, c);
SET(a, b);
zsub_impl(a, libzahl_tmp_sub, n);
} else {
SET(a, b);
zsub_impl(a, c, n);
}
}
SET_SIGNUM(a, magcmp);
}
void
zsub_unsigned(z_t a, z_t b, z_t c)
{
libzahl_zsub_unsigned(a, b, c);
}
void
zsub_nonnegative_assign(z_t a, z_t b)
{
if (unlikely(zzero(b)))
zabs(a, a);
else if (unlikely(!zcmpmag(a, b)))
SET_SIGNUM(a, 0);
else
zsub_impl(a, b, b->used);
}
void
zsub_positive_assign(z_t a, z_t b)
{
zsub_impl(a, b, b->used);
}
void
zsub(z_t a, z_t b, z_t c)
{
if (unlikely(zzero(b))) {
zneg(a, c);
} else if (unlikely(zzero(c))) {
SET(a, b);
} else if (unlikely(znegative(b))) {
if (znegative(c)) {
libzahl_zsub_unsigned(a, c, b);
} else {
zadd_unsigned(a, b, c);
SET_SIGNUM(a, -zsignum(a));
}
} else if (znegative(c)) {
zadd_unsigned(a, b, c);
} else {
libzahl_zsub_unsigned(a, b, c);
}
}
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