summaryrefslogtreecommitdiffstats log msg author committer range
path: root/apps/codecs/libatrac/fixp_math.c
 ```1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 ``` ``````#include "fixp_math.h" inline int32_t fixmul31(int32_t x, int32_t y) { int64_t temp; temp = x; temp *= y; temp >>= 31; //16+31-16 = 31 bits return (int32_t)temp; } /* * Fast integer square root adapted from algorithm, * Martin Guy @ UKC, June 1985. * Originally from a book on programming abaci by Mr C. Woo. * This is taken from : * http://wiki.forum.nokia.com/index.php/How_to_use_fixed_point_maths#How_to_get_square_root_for_integers * with a added shift up of the result by 8 bits to return result in 16.16 fixed-point representation. */ inline int32_t fastSqrt(int32_t n) { /* * Logically, these are unsigned. * We need the sign bit to test * whether (op - res - one) underflowed. */ int32_t op, res, one; op = n; res = 0; /* "one" starts at the highest power of four <= than the argument. */ one = 1 << 30; /* second-to-top bit set */ while (one > op) one >>= 2; while (one != 0) { if (op >= res + one) { op = op - (res + one); res = res + (one<<1); } res >>= 1; one >>= 2; } return(res << 8); } inline int32_t fixmul16(int32_t x, int32_t y) { int64_t temp; temp = x; temp *= y; temp >>= 16; return (int32_t)temp; } inline int32_t fixdiv16(int32_t x, int32_t y) { int64_t temp; temp = x << 16; temp /= y; return (int32_t)temp; } ``````