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       zpowu.c - libzahl - big integer library
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       ---
       zpowu.c (550B)
       ---
            1 /* See LICENSE file for copyright and license details. */
            2 #include "internals.h"
            3 
            4 #define tb  libzahl_tmp_pow_b
            5 
            6 
            7 void
            8 zpowu(z_t a, z_t b, unsigned long long int c)
            9 {
           10         int neg;
           11 
           12         if (unlikely(!c)) {
           13                 if (check(zzero(b)))
           14                         libzahl_failure(-ZERROR_0_POW_0);
           15                 zsetu(a, 1);
           16                 return;
           17         } else if (unlikely(zzero(b))) {
           18                 SET_SIGNUM(a, 0);
           19                 return;
           20         }
           21 
           22         neg = znegative(b) && (c & 1);
           23         zabs(tb, b);
           24 
           25         if (c & 1)
           26                 zset(a, tb);
           27         else
           28                 zsetu(a, 1);
           29         while (c >>= 1) {
           30                 zsqr_ll(tb, tb);
           31                 if (c & 1)
           32                         zmul_ll(a, a, tb);
           33         }
           34 
           35         if (neg)
           36                 zneg(a, a);
           37 }