util: Group functions for bitwise tests.

[openvswitch] / lib / util.h

diff --git a/lib/util.h b/lib/util.h
index 60ec737e2ad9580c9214a4b94aec303571682ceb..c087b53f4f3cf7a6bca6345e9014904e8b245055 100644 (file)
--- a/lib/util.h
+++ b/lib/util.h
@@ -17,6 +17,7 @@
 #ifndef UTIL_H
 #define UTIL_H 1
 
+#include <limits.h>
 #include <stdarg.h>
 #include <stdbool.h>
 #include <stddef.h>
@@ -61,6 +62,16 @@
 #define BUILD_ASSERT_DECL_GCCONLY(EXPR) ((void) 0)
 #endif
 
+/* Casts 'pointer' to 'type' and issues a compiler warning if the cast changes
+ * anything other than an outermost "const" or "volatile" qualifier.
+ *
+ * The cast to int is present only to suppress an "expression using sizeof
+ * bool" warning from "sparse" (see
+ * http://permalink.gmane.org/gmane.comp.parsers.sparse/2967). */
+#define CONST_CAST(TYPE, POINTER)                               \
+    ((void) sizeof ((int) ((POINTER) == (TYPE) (POINTER))),     \
+     (TYPE) (POINTER))
+
 extern const char *program_name;
 extern const char *subprogram_name;
 
@@ -85,14 +96,6 @@ is_pow2(uintmax_t x)
     return IS_POW2(x);
 }
 
-/* Returns the rightmost 1-bit in 'x' (e.g. 01011000 => 00001000), or 0 if 'x'
- * is 0. */
-static inline uintmax_t
-rightmost_1bit(uintmax_t x)
-{
-    return x & -x;
-}
-
 #ifndef MIN
 #define MIN(X, Y) ((X) < (Y) ? (X) : (Y))
 #endif
@@ -223,10 +226,52 @@ char *xreadlink(const char *filename);
 char *follow_symlinks(const char *filename);
 
 void ignore(bool x OVS_UNUSED);
+\f
+/* Bitwise tests. */
+
+/* Returns the number of trailing 0-bits in 'n'.  Undefined if 'n' == 0.
+ *
+ * This compiles to a single machine instruction ("bsf") with GCC on x86. */
+#if !defined(UINT_MAX) || !defined(UINT32_MAX)
+#error "Someone screwed up the #includes."
+#elif __GNUC__ >= 4 && UINT_MAX == UINT32_MAX
+static inline int
+raw_ctz(uint32_t n)
+{
+    return __builtin_ctz(n);
+}
+#else
+/* Defined in util.c. */
+int raw_ctz(uint32_t n);
+#endif
+
+/* Returns the number of trailing 0-bits in 'n', or 32 if 'n' is 0. */
+static inline int
+ctz(uint32_t n)
+{
+    return n ? raw_ctz(n) : 32;
+}
+
 int log_2_floor(uint32_t);
 int log_2_ceil(uint32_t);
-int ctz(uint32_t);
+int popcount(uint32_t);
 
+/* Returns the rightmost 1-bit in 'x' (e.g. 01011000 => 00001000), or 0 if 'x'
+ * is 0. */
+static inline uintmax_t
+rightmost_1bit(uintmax_t x)
+{
+    return x & -x;
+}
+
+/* Returns 'x' with its rightmost 1-bit changed to a zero (e.g. 01011000 =>
+ * 01010000), or 0 if 'x' is 0. */
+static inline uintmax_t
+zero_rightmost_1bit(uintmax_t x)
+{
+    return x & (x - 1);
+}
+\f
 bool is_all_zeros(const uint8_t *, size_t);
 bool is_all_ones(const uint8_t *, size_t);
 void bitwise_copy(const void *src, unsigned int src_len, unsigned int src_ofs,