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-rw-r--r--apps/codecs/libatrac/fixp_math.h69
1 files changed, 65 insertions, 4 deletions
diff --git a/apps/codecs/libatrac/fixp_math.h b/apps/codecs/libatrac/fixp_math.h
index b6621b6f1a..8a734f6b68 100644
--- a/apps/codecs/libatrac/fixp_math.h
+++ b/apps/codecs/libatrac/fixp_math.h
@@ -9,7 +9,68 @@
#define fix31tof64(x) (float)((float)(x) / (float)(1 << 31))
/* Fixed point math routines for use in atrac3.c */
-inline int32_t fixmul16(int32_t x, int32_t y);
-inline int32_t fixmul31(int32_t x, int32_t y);
-inline int32_t fixdiv16(int32_t x, int32_t y);
-inline int32_t fastSqrt(int32_t n);
+
+static inline int32_t fixmul16(int32_t x, int32_t y)
+{
+ int64_t temp;
+ temp = x;
+ temp *= y;
+
+ temp >>= 16;
+
+ return (int32_t)temp;
+}
+
+static 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;
+}
+
+static inline int32_t fixdiv16(int32_t x, int32_t y)
+{
+ int64_t temp;
+ temp = x << 16;
+ temp /= y;
+
+ 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.
+ */
+static 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);
+}