📄 math.htm
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<BODY><PRE>/*
Copyright (c) 2006 Michael P. Thompson <mpthompson@gmail.com>
Permission is hereby granted, free of charge, to any person
obtaining a copy of this software and associated documentation
files (the "Software"), to deal in the Software without
restriction, including without limitation the rights to use, copy,
modify, merge, publish, distribute, sublicense, and/or sell copies
of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be
included in all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
DEALINGS IN THE SOFTWARE.
$Id: math.h,v 1.2 2006/02/13 18:21:15 mpthompson Exp $
*/
#ifndef _OS_MATH_H_
#define _OS_MATH_H_ 1
static inline int16_t shift_right16(int16_t val, uint8_t cnt)
// Arithmetic right shift of the signed 16-bit value.
{
asm volatile (
"L_asr1%=:" "\n\t"
"cp %1,__zero_reg__" "\n\t"
"breq L_asr2%=" "\n\t"
"dec %1" "\n\t"
"asr %B0" "\n\t"
"ror %A0" "\n\t"
"rjmp L_asr1%=" "\n\t"
"L_asr2%=:" "\n\t"
: "=&r" (val)
: "r" (cnt), "0" (val)
);
return val;
}
static inline int32_t shift_right32(int32_t val, uint8_t cnt)
// Arithmetic right shift of the signed 32-bit value.
{
asm volatile (
"L_asr1%=:" "\n\t"
"cp %1,__zero_reg__" "\n\t"
"breq L_asr2%=" "\n\t"
"dec %1" "\n\t"
"asr %D0" "\n\t"
"ror %C0" "\n\t"
"ror %B0" "\n\t"
"ror %A0" "\n\t"
"rjmp L_asr1%=" "\n\t"
"L_asr2%=:" "\n\t"
: "=&r" (val)
: "r" (cnt), "0" (val)
);
return val;
}
#if FIXED_MATH_ENABLED
// Multiplies the two 16-bit values num1 and num2 into a 32-bit
// product. The product is then right shifted by the specified
// amount and the lower 16-bits of the value returned. The purpose
// of this function is to facilitate fixed point arithmetic. When
// multiplying two fixed point numbers with fixed points at bit
// fp_1 and fp_2 (counted from the least significant bit), the
// result will have the fixed point bit at:
//
// fp_result = fp_1 + fp_2
//
// To fit to a desired fixed point precision fp_3 the result must
// be shifted to the right by:
//
// shift = fp_result - fp_3
//
int16_t fixed_multiply(int16_t num1, int16_t num2, int8_t shift);
#endif
#endif // _OS_MATH_H_
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