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Diffstat (limited to 'nuttx/lib/math/lib_fixedmath.c')
| -rw-r--r-- | nuttx/lib/math/lib_fixedmath.c | 272 |
1 files changed, 272 insertions, 0 deletions
diff --git a/nuttx/lib/math/lib_fixedmath.c b/nuttx/lib/math/lib_fixedmath.c new file mode 100644 index 000000000..b20158dc8 --- /dev/null +++ b/nuttx/lib/math/lib_fixedmath.c @@ -0,0 +1,272 @@ +/**************************************************************************** + * lib/math/lib_fixedmath.c + * + * Copyright (C) 2008-2009, 2011 Gregory Nutt. All rights reserved. + * Author: Gregory Nutt <spudmonkey@racsa.co.cr> + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * + * 1. Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * 2. Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in + * the documentation and/or other materials provided with the + * distribution. + * 3. Neither the name NuttX nor the names of its contributors may be + * used to endorse or promote products derived from this software + * without specific prior written permission. + * + * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS + * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT + * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS + * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE + * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, + * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, + * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS + * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED + * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT + * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN + * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE + * POSSIBILITY OF SUCH DAMAGE. + * + ****************************************************************************/ + +/**************************************************************************** + * Included Files + ****************************************************************************/ + +#include <nuttx/config.h> + +#include <stdint.h> +#include <stdbool.h> +#include <fixedmath.h> + +#ifndef CONFIG_HAVE_LONG_LONG + +/**************************************************************************** + * Pre-processor Definitions + ****************************************************************************/ + +/**************************************************************************** + * Private Type Declarations + ****************************************************************************/ + +/**************************************************************************** + * Private Function Prototypes + ****************************************************************************/ + +/**************************************************************************** + * Public Data + ****************************************************************************/ + +/**************************************************************************** + * Private Data + ****************************************************************************/ + +/**************************************************************************** + * Name: fixsign + ****************************************************************************/ + +static void fixsign(b16_t *parg1, b16_t *parg2, bool *pnegate) +{ + bool negate = false; + b16_t arg; + + arg = *parg1; + if (arg < 0) + { + *parg1 = -arg; + negate = true; + } + + arg = *parg2; + if (arg < 0) + { + *parg2 = -arg; + negate ^= true; + } + + *pnegate = negate; +} + +/**************************************************************************** + * Name: adjustsign + ****************************************************************************/ + +static b16_t adjustsign(b16_t result, bool negate) +{ + /* If the product is negative, then we overflowed */ + + if (result < 0) + { + if (result) + { + return b16MIN; + } + else + { + return b16MAX; + } + } + + /* correct the sign of the result */ + + if (negate) + { + return -result; + } + return result; +} + +/**************************************************************************** + * Public Functions + ****************************************************************************/ + +/**************************************************************************** + * Name: b16mulb16 + ****************************************************************************/ + +b16_t b16mulb16(b16_t m1, b16_t m2) +{ + bool negate; + b16_t product; + + fixsign(&m1, &m2, &negate); + product = (b16_t)ub16mulub16((ub16_t)m1, (ub16_t)m2); + return adjustsign(product, negate); +} + +/**************************************************************************** + * Name: ub16mulub16 + **************************************************************************/ + +ub16_t ub16mulub16(ub16_t m1, ub16_t m2) +{ + /* Let: + * + * m1 = m1i*2**16 + m1f (b16) + * m2 = m2i*2**16 + m2f (b16) + * + * Then: + * + * m1*m2 = (m1i*m2i)*2**32 + (m1i*m2f + m2i*m1f)*2**16 + m1f*m2f (b32) + * = (m1i*m2i)*2**16 + (m1i*m2f + m2i*m1f) + m1f*m2f*2**-16 (b16) + * = a*2**16 + b + c*2**-16 + */ + + uint32_t m1i = ((uint32_t)m1 >> 16); + uint32_t m2i = ((uint32_t)m1 >> 16); + uint32_t m1f = ((uint32_t)m1 & 0x0000ffff); + uint32_t m2f = ((uint32_t)m2 & 0x0000ffff); + + return (m1i*m2i << 16) + m1i*m2f + m2i*m1f + (((m1f*m2f) + b16HALF) >> 16); +} + +/**************************************************************************** + * Name: b16divb16 + **************************************************************************/ + +b16_t b16sqr(b16_t a) +{ + b16_t sq; + + /* The result is always positive. Just take the absolute value */ + + if (a < 0) + { + a = -a; + } + + /* Overflow occurred if the result is negative */ + + sq = (b16_t)ub16sqr(a); + if (sq < 0) + { + sq = b16MAX; + } + return sq; +} + +/**************************************************************************** + * Name: b16divb16 + **************************************************************************/ + +ub16_t ub16sqr(ub16_t a) +{ + /* Let: + * + * m = mi*2**16 + mf (b16) + * + * Then: + * + * m*m = (mi*mi)*2**32 + 2*(m1*m2)*2**16 + mf*mf (b32) + * = (mi*mi)*2**16 + 2*(mi*mf) + mf*mf*2**-16 (b16) + */ + + uint32_t mi = ((uint32_t)a >> 16); + uint32_t mf = ((uint32_t)a & 0x0000ffff); + + return (mi*mi << 16) + (mi*mf << 1) + ((mf*mf + b16HALF) >> 16); +} + +/**************************************************************************** + * Name: b16divb16 + **************************************************************************/ + +b16_t b16divb16(b16_t num, b16_t denom) +{ + bool negate; + b16_t quotient; + + fixsign(&num, &denom, &negate); + quotient = (b16_t)ub16divub16((ub16_t)num, (ub16_t)denom); + return adjustsign(quotient, negate); +} + +/**************************************************************************** + * Name: ub16divub16 + **************************************************************************/ + +ub16_t ub16divub16(ub16_t num, ub16_t denom) +{ + uint32_t term1; + uint32_t numf; + uint32_t product; + + /* Let: + * + * num = numi*2**16 + numf (b16) + * den = deni*2**16 + denf (b16) + * + * Then: + * + * num/den = numi*2**16 / den + numf / den (b0) + * = numi*2**32 / den + numf*2**16 /den (b16) + */ + + /* Check for overflow in the first part of the quotient */ + + term1 = ((uint32_t)num & 0xffff0000) / denom; + if (term1 >= 0x00010000) + { + return ub16MAX; /* Will overflow */ + } + + /* Finish the division */ + + numf = num - term1 * denom; + term1 <<= 16; + product = term1 + (numf + (denom >> 1)) / denom; + + /* Check for overflow */ + + if (product < term1) + { + return ub16MAX; /* Overflowed */ + } + return product; +} + +#endif |