66 lines
1.3 KiB
C
66 lines
1.3 KiB
C
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#include "tommath_private.h"
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#ifdef S_MP_LOG_D_C
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/* LibTomMath, multiple-precision integer library -- Tom St Denis */
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/* SPDX-License-Identifier: Unlicense */
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static mp_word s_pow(mp_word base, mp_word exponent)
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{
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mp_word result = 1u;
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while (exponent != 0u) {
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if ((exponent & 1u) == 1u) {
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result *= base;
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}
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exponent >>= 1;
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base *= base;
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}
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return result;
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}
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int s_mp_log_d(mp_digit base, mp_digit n)
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{
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mp_word bracket_low = 1uLL, bracket_high = base, N = n;
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int ret, high = 1, low = 0;
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if (n < base) {
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return 0;
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}
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if (n == base) {
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return 1;
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}
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while (bracket_high < N) {
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low = high;
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bracket_low = bracket_high;
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high <<= 1;
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bracket_high *= bracket_high;
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}
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while (((mp_digit)(high - low)) > 1uL) {
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int mid = (low + high) >> 1;
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mp_word bracket_mid = bracket_low * s_pow(base, (mp_word)(mid - low));
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if (N < bracket_mid) {
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high = mid ;
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bracket_high = bracket_mid ;
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}
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if (N > bracket_mid) {
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low = mid ;
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bracket_low = bracket_mid ;
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}
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if (N == bracket_mid) {
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return mid;
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}
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}
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if (bracket_high == N) {
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ret = high;
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} else {
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ret = low;
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}
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return ret;
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}
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#endif
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