diff options
Diffstat (limited to 'src/zpow.c')
| -rw-r--r-- | src/zpow.c | 18 |
1 files changed, 13 insertions, 5 deletions
@@ -5,6 +5,9 @@ #define tc libzahl_tmp_pow_c +extern void zmul_impl(z_t a, z_t b, z_t c); +extern void zsqr_impl(z_t a, z_t b); + void zpow(z_t a, z_t b, z_t c) { @@ -16,6 +19,7 @@ zpow(z_t a, z_t b, z_t c) size_t i, j, n, bits; zahl_char_t x; + int neg; if (unlikely(zsignum(c) <= 0)) { if (zzero(c)) { @@ -36,7 +40,8 @@ zpow(z_t a, z_t b, z_t c) bits = zbits(c); n = FLOOR_BITS_TO_CHARS(bits); - zset(tb, b); + neg = znegative(b) && zodd(c); + zabs(tb, b); zset(tc, c); zsetu(a, 1); @@ -44,14 +49,17 @@ zpow(z_t a, z_t b, z_t c) x = tc->chars[i]; for (j = BITS_PER_CHAR; j--; x >>= 1) { if (x & 1) - zmul(a, a, tb); - zsqr(tb, tb); + zmul_impl(a, a, tb); + zsqr_impl(tb, tb); } } x = tc->chars[i]; for (; x; x >>= 1) { if (x & 1) - zmul(a, a, tb); - zsqr(tb, tb); + zmul_impl(a, a, tb); + zsqr_impl(tb, tb); } + + if (neg) + zneg(a, a); } |