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utils: add nm_utils_is_power_of_two() macro

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Thomas Haller
2015-05-12 09:24:05 +02:00
parent 56b07b1a3f
commit 0a3c1f5774
2 changed files with 115 additions and 0 deletions
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17
include/nm-macros-internal.h
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@@ -181,6 +181,23 @@ nm_clear_g_source (guint *id)
/*****************************************************************************/
/* Determine whether @x is a power of two (@x being an integer type).
* For the special cases @x equals zero or one, it also returns true.
* For negative @x, always returns FALSE. That only applies, is the data
* type of @x is signed. */
#define nm_utils_is_power_of_two(x) ({ \
const typeof(x) __x = (x); \
\
((__x & (__x - 1)) == 0) && \
/* Check if the value is negative. In that case, return FALSE.
* The first expression is a compile time constant, depending on whether
* the type is signed. The second expression is a clumsy way for (__x >= 0),
* which causes a compiler warning for unsigned types. */ \
( ( ((typeof(__x)) -1) > ((typeof(__x)) 0) ) || (__x > 0) || (__x == 0) ); \
})
/*****************************************************************************/
/* check if @flags has exactly one flag (@check) set. You should call this
* only with @check being a compile time constant and a power of two. */
#define NM_FLAGS_HAS(flags, check) \