utils: add const_* byteswapping functions

[project/libubox.git] / utils.h

diff --git a/utils.h b/utils.h
index 6a53b3f5d42595fe1714fc352cc8c85aab5419c4..27f81e568bf5aa2d5c1bfe8cec883215e29593f1 100644 (file)
--- a/utils.h
+++ b/utils.h
@@ -125,14 +125,39 @@ int clock_gettime(int type, struct timespec *tv);
        (sizeof(int) == sizeof(*(1 ? ((void*)((long)(x) * 0l)) : (int*)1)))
 
 #define __eval_once(func, x)                                           \
-       ({ typeof(x) __x = x; func(__x); })
+       ({ __typeof__(x) __x = x; func(__x); })
 
+#ifdef __cplusplus
+/*
+ * g++ does not support __builtin_choose_expr, so always use __eval_once.
+ * Unfortunately this means that the byte order functions can't be used
+ * as a constant expression anymore
+ */
+#define __eval_safe(func, x) __eval_once(func, x)
+#else
 #define __eval_safe(func, x)                                           \
        __builtin_choose_expr(__is_constant(x),                         \
                              func(x), __eval_once(func, x))
+#endif
 
 #if __BYTE_ORDER == __LITTLE_ENDIAN
 
+#define const_cpu_to_be64(x) __constant_swap64(x)
+#define const_cpu_to_be32(x) __constant_swap32(x)
+#define const_cpu_to_be16(x) __constant_swap16(x)
+
+#define const_be64_to_cpu(x) __constant_swap64(x)
+#define const_be32_to_cpu(x) __constant_swap32(x)
+#define const_be16_to_cpu(x) __constant_swap16(x)
+
+#define const_cpu_to_le64(x) (x)
+#define const_cpu_to_le32(x) (x)
+#define const_cpu_to_le16(x) (x)
+
+#define const_le64_to_cpu(x) (x)
+#define const_le32_to_cpu(x) (x)
+#define const_le16_to_cpu(x) (x)
+
 #define cpu_to_be64(x) __eval_safe(__constant_swap64, x)
 #define cpu_to_be32(x) __eval_safe(__constant_swap32, x)
 #define cpu_to_be16(x) __eval_safe(__constant_swap16, x)
@@ -151,6 +176,22 @@ int clock_gettime(int type, struct timespec *tv);
 
 #else /* __BYTE_ORDER == __LITTLE_ENDIAN */
 
+#define const_cpu_to_le64(x) __constant_swap64(x)
+#define const_cpu_to_le32(x) __constant_swap32(x)
+#define const_cpu_to_le16(x) __constant_swap16(x)
+
+#define const_le64_to_cpu(x) __constant_swap64(x)
+#define const_le32_to_cpu(x) __constant_swap32(x)
+#define const_le16_to_cpu(x) __constant_swap16(x)
+
+#define const_cpu_to_be64(x) (x)
+#define const_cpu_to_be32(x) (x)
+#define const_cpu_to_be16(x) (x)
+
+#define const_be64_to_cpu(x) (x)
+#define const_be32_to_cpu(x) (x)
+#define const_be16_to_cpu(x) (x)
+
 #define cpu_to_le64(x) __eval_safe(__constant_swap64, x)
 #define cpu_to_le32(x) __eval_safe(__constant_swap32, x)
 #define cpu_to_le16(x) __eval_safe(__constant_swap16, x)