X-Git-Url: https://codewiz.org/gitweb?a=blobdiff_plain;f=bertos%2Fcfg%2Fmacros.h;h=073ad55fc84a30ad3ea952d4aa4f15a04414e27a;hb=d513d5362c8572a5721e7628ead88329f9773e37;hp=0a721ac5a060f703d00a594ed9ab7cad25ae926e;hpb=1c11ac0ab0636d07db3899b02c5d89e2d0b020bc;p=bertos.git

diff --git a/bertos/cfg/macros.h b/bertos/cfg/macros.h
index 0a721ac5..073ad55f 100644
--- a/bertos/cfg/macros.h
+++ b/bertos/cfg/macros.h
@@ -192,11 +192,46 @@
 
 /**
  * Perform an integer division rounding the result to the upper int value.
- * \note \a divisor should preferibly be a costant, otherwise this macro generates
- * 2 division. Also divisor is evaluated twice.
+ * \note \a divisor is evaluated twice.
  */
 #define DIV_ROUNDUP(dividend, divisor)  (((dividend) + (divisor) - 1) / (divisor))
 
+
+/**
+ * Perform a multiply between the integer \a a and the float constant \a f.
+ *
+ * This macro can be used in order to avoid floating point arithmetics
+ * in expressions like this:
+ * \code
+ * int a, b;
+ * a = b * 0.5579652750;
+ * \endcode
+ *
+ * This macro rounds the floating point constant to a fraction,
+ * usign (2 ^ prec) as the denominator.
+ * For instance, with prec = 8, the constant 0.5579652750 will be rounded to:
+ * (143 / 256) = 0.55859375
+ * So, the former code will be transformed to:
+ * \code
+ * a = b * 143 / 256;
+ * \endcode
+ *
+ * Since the denominator is a power of 2, we rely on the compiler to optimize
+ * this to a right shift.
+ * So, when you have to multiply an integer by a float constant, this macro
+ * will not use the floating point arithmentics.
+ * The operation will be converted to a mul + shift, with a huge performance boost.
+ *
+ * \note \a f MUST be a constant in order gain performance benefits.
+ *
+ * \param a integer you want to multiply
+ * \param f floating point constant which you want to multply with \a a
+ * \param prec conversion precision, ranges from 1 to the number of bits in a long.
+ *             The higher, the better the approximation of the float constant will be.
+ */
+#define INT_MULT(a, f, prec) (((a) * (long)((f) * (1 << (prec)) + 0.5)) >> (prec))
+
+
 /** Round up \a x to an even multiple of the 2's power \a pad. */
 #define ROUND_UP2(x, pad) (((x) + ((pad) - 1)) & ~((pad) - 1))
 
@@ -363,6 +398,14 @@
  */
 typedef uint32_t id_t;
 
+/**
+ * Check if a pointer is aligned to a certain power-of-2 size
+ */
+INLINE bool is_aligned(const void *addr, size_t size)
+{
+	return ((size_t)addr & (size - 1)) == 0;
+}
+
 /** \} */ //defgroup macros
 
 #endif /* MACROS_H */