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