kopia lustrzana https://github.com/xaelsouth/rtl-wmbus
413 wiersze
12 KiB
C
413 wiersze
12 KiB
C
#ifndef _FIXEDPTC_H_
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#define _FIXEDPTC_H_
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/*
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* fixedptc.h is a 32-bit or 64-bit fixed point numeric library.
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*
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* The symbol FIXEDPT_BITS, if defined before this library header file
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* is included, determines the number of bits in the data type (its "width").
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* The default width is 32-bit (FIXEDPT_BITS=32) and it can be used
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* on any recent C99 compiler. The 64-bit precision (FIXEDPT_BITS=64) is
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* available on compilers which implement 128-bit "long long" types. This
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* precision has been tested on GCC 4.2+.
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*
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* The FIXEDPT_WBITS symbols governs how many bits are dedicated to the
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* "whole" part of the number (to the left of the decimal point). The larger
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* this width is, the larger the numbers which can be stored in the fixedpt
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* number. The rest of the bits (available in the FIXEDPT_FBITS symbol) are
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* dedicated to the fraction part of the number (to the right of the decimal
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* point).
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*
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* Since the number of bits in both cases is relatively low, many complex
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* functions (more complex than div & mul) take a large hit on the precision
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* of the end result because errors in precision accumulate.
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* This loss of precision can be lessened by increasing the number of
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* bits dedicated to the fraction part, but at the loss of range.
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*
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* Adventurous users might utilize this library to build two data types:
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* one which has the range, and one which has the precision, and carefully
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* convert between them (including adding two number of each type to produce
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* a simulated type with a larger range and precision).
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*
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* The ideas and algorithms have been cherry-picked from a large number
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* of previous implementations available on the Internet.
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* Tim Hartrick has contributed cleanup and 64-bit support patches.
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*
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* == Special notes for the 32-bit precision ==
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* Signed 32-bit fixed point numeric library for the 24.8 format.
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* The specific limits are -8388608.999... to 8388607.999... and the
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* most precise number is 0.00390625. In practice, you should not count
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* on working with numbers larger than a million or to the precision
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* of more than 2 decimal places. Make peace with the fact that PI
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* is 3.14 here. :)
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*/
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/*-
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* Copyright (c) 2010-2012 Ivan Voras <ivoras@freebsd.org>
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* Copyright (c) 2012 Tim Hartrick <tim@edgecast.com>
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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#ifndef FIXEDPT_BITS
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#define FIXEDPT_BITS 32
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#endif
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#include <stdint.h>
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#if FIXEDPT_BITS == 32
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typedef int32_t fixedpt;
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typedef int64_t fixedptd;
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typedef uint32_t fixedptu;
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typedef uint64_t fixedptud;
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#elif FIXEDPT_BITS == 64
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typedef int64_t fixedpt;
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typedef __int128_t fixedptd;
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typedef uint64_t fixedptu;
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typedef __uint128_t fixedptud;
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#else
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#error "FIXEDPT_BITS must be equal to 32 or 64"
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#endif
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#ifndef FIXEDPT_WBITS
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#define FIXEDPT_WBITS 24
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#endif
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#if FIXEDPT_WBITS >= FIXEDPT_BITS
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#error "FIXEDPT_WBITS must be less than or equal to FIXEDPT_BITS"
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#endif
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#define FIXEDPT_VCSID "$Id$"
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#define FIXEDPT_FBITS (FIXEDPT_BITS - FIXEDPT_WBITS)
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#define FIXEDPT_FMASK (((fixedpt)1 << FIXEDPT_FBITS) - 1)
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#define fixedpt_rconst(R) ((fixedpt)((R) * FIXEDPT_ONE + ((R) >= 0 ? 0.5 : -0.5)))
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#define fixedpt_fromint(I) ((fixedptd)(I) << FIXEDPT_FBITS)
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#define fixedpt_toint(F) ((F) >> FIXEDPT_FBITS)
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#define fixedpt_add(A,B) ((A) + (B))
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#define fixedpt_sub(A,B) ((A) - (B))
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#define fixedpt_xmul(A,B) \
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((fixedpt)(((fixedptd)(A) * (fixedptd)(B)) >> FIXEDPT_FBITS))
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#define fixedpt_xdiv(A,B) \
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((fixedpt)(((fixedptd)(A) << FIXEDPT_FBITS) / (fixedptd)(B)))
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#define fixedpt_fracpart(A) ((fixedpt)(A) & FIXEDPT_FMASK)
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#define FIXEDPT_ONE ((fixedpt)((fixedpt)1 << FIXEDPT_FBITS))
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#define FIXEDPT_ONE_HALF (FIXEDPT_ONE >> 1)
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#define FIXEDPT_TWO (FIXEDPT_ONE + FIXEDPT_ONE)
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#define FIXEDPT_PI fixedpt_rconst(3.14159265358979323846)
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#define FIXEDPT_TWO_PI fixedpt_rconst(2 * 3.14159265358979323846)
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#define FIXEDPT_HALF_PI fixedpt_rconst(3.14159265358979323846 / 2)
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#define FIXEDPT_E fixedpt_rconst(2.7182818284590452354)
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#define fixedpt_abs(A) ((A) < 0 ? -(A) : (A))
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/* fixedpt is meant to be usable in environments without floating point support
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* (e.g. microcontrollers, kernels), so we can't use floating point types directly.
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* Putting them only in macros will effectively make them optional. */
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#define fixedpt_tofloat(T) ((float) ((T)*((float)(1)/(float)(1 << FIXEDPT_FBITS))))
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/* Multiplies two fixedpt numbers, returns the result. */
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static inline fixedpt
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fixedpt_mul(fixedpt A, fixedpt B)
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{
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return (((fixedptd)A * (fixedptd)B) >> FIXEDPT_FBITS);
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}
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/* Divides two fixedpt numbers, returns the result. */
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static inline fixedpt
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fixedpt_div(fixedpt A, fixedpt B)
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{
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return (((fixedptd)A << FIXEDPT_FBITS) / (fixedptd)B);
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}
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/*
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* Note: adding and substracting fixedpt numbers can be done by using
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* the regular integer operators + and -.
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*/
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/**
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* Convert the given fixedpt number to a decimal string.
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* The max_dec argument specifies how many decimal digits to the right
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* of the decimal point to generate. If set to -1, the "default" number
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* of decimal digits will be used (2 for 32-bit fixedpt width, 10 for
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* 64-bit fixedpt width); If set to -2, "all" of the digits will
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* be returned, meaning there will be invalid, bogus digits outside the
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* specified precisions.
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*/
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static inline void
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fixedpt_str(fixedpt A, char *str, int max_dec)
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{
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int ndec = 0, slen = 0;
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char tmp[12] = {0};
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fixedptud fr, ip;
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const fixedptud one = (fixedptud)1 << FIXEDPT_BITS;
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const fixedptud mask = one - 1;
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if (max_dec == -1)
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#if FIXEDPT_BITS == 32
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#if FIXEDPT_WBITS > 16
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max_dec = 2;
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#else
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max_dec = 4;
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#endif
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#elif FIXEDPT_BITS == 64
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max_dec = 10;
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#else
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#error Invalid width
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#endif
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else if (max_dec == -2)
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max_dec = 15;
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if (A < 0) {
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str[slen++] = '-';
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A *= -1;
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}
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ip = fixedpt_toint(A);
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do {
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tmp[ndec++] = '0' + ip % 10;
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ip /= 10;
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} while (ip != 0);
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while (ndec > 0)
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str[slen++] = tmp[--ndec];
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str[slen++] = '.';
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fr = (fixedpt_fracpart(A) << FIXEDPT_WBITS) & mask;
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do {
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fr = (fr & mask) * 10;
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str[slen++] = '0' + (fr >> FIXEDPT_BITS) % 10;
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ndec++;
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} while (fr != 0 && ndec < max_dec);
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if (ndec > 1 && str[slen-1] == '0')
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str[slen-1] = '\0'; /* cut off trailing 0 */
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else
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str[slen] = '\0';
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}
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/* Converts the given fixedpt number into a string, using a static
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* (non-threadsafe) string buffer */
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static inline char*
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fixedpt_cstr(const fixedpt A, const int max_dec)
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{
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static char str[25];
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fixedpt_str(A, str, max_dec);
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return (str);
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}
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/* Returns the square root of the given number, or -1 in case of error */
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static inline fixedpt
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fixedpt_sqrt(fixedpt A)
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{
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int invert = 0;
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int iter = FIXEDPT_FBITS;
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int l, i;
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if (A < 0)
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return (-1);
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if (A == 0 || A == FIXEDPT_ONE)
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return (A);
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if (A < FIXEDPT_ONE && A > 6) {
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invert = 1;
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A = fixedpt_div(FIXEDPT_ONE, A);
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}
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if (A > FIXEDPT_ONE) {
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int s = A;
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iter = 0;
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while (s > 0) {
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s >>= 2;
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iter++;
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}
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}
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/* Newton's iterations */
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l = (A >> 1) + 1;
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for (i = 0; i < iter; i++)
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l = (l + fixedpt_div(A, l)) >> 1;
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if (invert)
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return (fixedpt_div(FIXEDPT_ONE, l));
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return (l);
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}
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/* Returns the sine of the given fixedpt number.
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* Note: the loss of precision is extraordinary! */
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static inline fixedpt
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fixedpt_sin(fixedpt fp)
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{
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int sign = 1;
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fixedpt sqr, result;
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const fixedpt SK[2] = {
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fixedpt_rconst(7.61e-03),
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fixedpt_rconst(1.6605e-01)
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};
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fp %= 2 * FIXEDPT_PI;
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if (fp < 0)
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fp = FIXEDPT_PI * 2 + fp;
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if ((fp > FIXEDPT_HALF_PI) && (fp <= FIXEDPT_PI))
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fp = FIXEDPT_PI - fp;
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else if ((fp > FIXEDPT_PI) && (fp <= (FIXEDPT_PI + FIXEDPT_HALF_PI))) {
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fp = fp - FIXEDPT_PI;
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sign = -1;
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} else if (fp > (FIXEDPT_PI + FIXEDPT_HALF_PI)) {
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fp = (FIXEDPT_PI << 1) - fp;
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sign = -1;
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}
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sqr = fixedpt_mul(fp, fp);
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result = SK[0];
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result = fixedpt_mul(result, sqr);
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result -= SK[1];
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result = fixedpt_mul(result, sqr);
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result += FIXEDPT_ONE;
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result = fixedpt_mul(result, fp);
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return sign * result;
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}
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/* Returns the cosine of the given fixedpt number */
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static inline fixedpt
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fixedpt_cos(fixedpt A)
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{
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return (fixedpt_sin(FIXEDPT_HALF_PI - A));
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}
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/* Returns the tangens of the given fixedpt number */
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static inline fixedpt
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fixedpt_tan(fixedpt A)
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{
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return fixedpt_div(fixedpt_sin(A), fixedpt_cos(A));
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}
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/* Returns the value exp(x), i.e. e^x of the given fixedpt number. */
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static inline fixedpt
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fixedpt_exp(fixedpt fp)
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{
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fixedpt xabs, k, z, R, xp;
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const fixedpt LN2 = fixedpt_rconst(0.69314718055994530942);
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const fixedpt LN2_INV = fixedpt_rconst(1.4426950408889634074);
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const fixedpt EXP_P[5] = {
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fixedpt_rconst(1.66666666666666019037e-01),
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fixedpt_rconst(-2.77777777770155933842e-03),
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fixedpt_rconst(6.61375632143793436117e-05),
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fixedpt_rconst(-1.65339022054652515390e-06),
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fixedpt_rconst(4.13813679705723846039e-08),
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};
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if (fp == 0)
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return (FIXEDPT_ONE);
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xabs = fixedpt_abs(fp);
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k = fixedpt_mul(xabs, LN2_INV);
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k += FIXEDPT_ONE_HALF;
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k &= ~FIXEDPT_FMASK;
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if (fp < 0)
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k = -k;
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fp -= fixedpt_mul(k, LN2);
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z = fixedpt_mul(fp, fp);
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/* Taylor */
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R = FIXEDPT_TWO +
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fixedpt_mul(z, EXP_P[0] + fixedpt_mul(z, EXP_P[1] +
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fixedpt_mul(z, EXP_P[2] + fixedpt_mul(z, EXP_P[3] +
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fixedpt_mul(z, EXP_P[4])))));
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xp = FIXEDPT_ONE + fixedpt_div(fixedpt_mul(fp, FIXEDPT_TWO), R - fp);
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if (k < 0)
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k = FIXEDPT_ONE >> (-k >> FIXEDPT_FBITS);
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else
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k = FIXEDPT_ONE << (k >> FIXEDPT_FBITS);
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return (fixedpt_mul(k, xp));
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}
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/* Returns the natural logarithm of the given fixedpt number. */
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static inline fixedpt
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fixedpt_ln(fixedpt x)
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{
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fixedpt log2, xi;
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fixedpt f, s, z, w, R;
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const fixedpt LN2 = fixedpt_rconst(0.69314718055994530942);
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const fixedpt LG[7] = {
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fixedpt_rconst(6.666666666666735130e-01),
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fixedpt_rconst(3.999999999940941908e-01),
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fixedpt_rconst(2.857142874366239149e-01),
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fixedpt_rconst(2.222219843214978396e-01),
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fixedpt_rconst(1.818357216161805012e-01),
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fixedpt_rconst(1.531383769920937332e-01),
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fixedpt_rconst(1.479819860511658591e-01)
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};
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if (x < 0)
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return (0);
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if (x == 0)
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return 0xffffffff;
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log2 = 0;
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xi = x;
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while (xi > FIXEDPT_TWO) {
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xi >>= 1;
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log2++;
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}
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f = xi - FIXEDPT_ONE;
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s = fixedpt_div(f, FIXEDPT_TWO + f);
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z = fixedpt_mul(s, s);
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w = fixedpt_mul(z, z);
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R = fixedpt_mul(w, LG[1] + fixedpt_mul(w, LG[3]
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+ fixedpt_mul(w, LG[5]))) + fixedpt_mul(z, LG[0]
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+ fixedpt_mul(w, LG[2] + fixedpt_mul(w, LG[4]
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+ fixedpt_mul(w, LG[6]))));
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return (fixedpt_mul(LN2, (log2 << FIXEDPT_FBITS)) + f
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- fixedpt_mul(s, f - R));
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}
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/* Returns the logarithm of the given base of the given fixedpt number */
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static inline fixedpt
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fixedpt_log(fixedpt x, fixedpt base)
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{
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return (fixedpt_div(fixedpt_ln(x), fixedpt_ln(base)));
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}
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/* Return the power value (n^exp) of the given fixedpt numbers */
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static inline fixedpt
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fixedpt_pow(fixedpt n, fixedpt exp)
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{
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if (exp == 0)
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return (FIXEDPT_ONE);
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if (n < 0)
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return 0;
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return (fixedpt_exp(fixedpt_mul(fixedpt_ln(n), exp)));
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}
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#endif
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