From: Rusty Russell Date: Mon, 8 Apr 2013 07:08:24 +0000 (+0930) Subject: endian: add constant versions. X-Git-Url: https://git.ozlabs.org/?p=ccan;a=commitdiff_plain;h=6abc867fce8c3eba40eb26092d31e34b47dd9165 endian: add constant versions. Sometimes you really need a compile-time constant, but there's no generic way to create a macro which does this and only evaluates its argument once. Thus we need specific const macros. Signed-off-by: Rusty Russell --- diff --git a/ccan/endian/endian.h b/ccan/endian/endian.h index 59500496..5b408786 100644 --- a/ccan/endian/endian.h +++ b/ccan/endian/endian.h @@ -4,6 +4,59 @@ #include #include "config.h" +/** + * BSWAP_16_CONST - reverse bytes in a constant uint16_t value. + * @val: constant value whose bytes to swap. + * + * Designed to be usable in constant-requiring initializers. + * + * Example: + * struct mystruct { + * char buf[BSWAP_16_CONST(0x1234)]; + * }; + */ +#define BSWAP_16_CONST(val) \ + ((((uint16_t)val & 0x00ff) << 8) \ + | (((uint16_t)val & 0xff00) >> 8)) + +/** + * BSWAP_32_CONST - reverse bytes in a constant uint32_t value. + * @val: constant value whose bytes to swap. + * + * Designed to be usable in constant-requiring initializers. + * + * Example: + * struct mystruct { + * char buf[BSWAP_32_CONST(0xff000000)]; + * }; + */ +#define BSWAP_32_CONST(val) \ + ((((uint32_t)val & 0x000000ff) << 24) \ + | (((uint32_t)val & 0x0000ff00) << 8) \ + | (((uint32_t)val & 0x00ff0000) >> 8) \ + | (((uint32_t)val & 0xff000000) >> 24)) + +/** + * BSWAP_64_CONST - reverse bytes in a constant uint64_t value. + * @val: constantvalue whose bytes to swap. + * + * Designed to be usable in constant-requiring initializers. + * + * Example: + * struct mystruct { + * char buf[BSWAP_64_CONST(0xff00000000000000ULL)]; + * }; + */ +#define BSWAP_64_CONST(val) \ + ((((uint64_t)val & 0x00000000000000ffULL) << 56) \ + | (((uint64_t)val & 0x000000000000ff00ULL) << 40) \ + | (((uint64_t)val & 0x0000000000ff0000ULL) << 24) \ + | (((uint64_t)val & 0x00000000ff000000ULL) << 8) \ + | (((uint64_t)val & 0x000000ff00000000ULL) >> 8) \ + | (((uint64_t)val & 0x0000ff0000000000ULL) >> 24) \ + | (((uint64_t)val & 0x00ff000000000000ULL) >> 40) \ + | (((uint64_t)val & 0xff00000000000000ULL) >> 56)) + #if HAVE_BYTESWAP_H #include #else @@ -17,8 +70,7 @@ */ static inline uint16_t bswap_16(uint16_t val) { - return ((val & (uint16_t)0x00ffU) << 8) - | ((val & (uint16_t)0xff00U) >> 8); + return BSWAP_16_CONST(val); } /** @@ -31,10 +83,7 @@ static inline uint16_t bswap_16(uint16_t val) */ static inline uint32_t bswap_32(uint32_t val) { - return ((val & (uint32_t)0x000000ffUL) << 24) - | ((val & (uint32_t)0x0000ff00UL) << 8) - | ((val & (uint32_t)0x00ff0000UL) >> 8) - | ((val & (uint32_t)0xff000000UL) >> 24); + return BSWAP_32_CONST(val); } #endif /* !HAVE_BYTESWAP_H */ @@ -50,14 +99,7 @@ static inline uint32_t bswap_32(uint32_t val) */ static inline uint64_t bswap_64(uint64_t val) { - return ((val & (uint64_t)0x00000000000000ffULL) << 56) - | ((val & (uint64_t)0x000000000000ff00ULL) << 40) - | ((val & (uint64_t)0x0000000000ff0000ULL) << 24) - | ((val & (uint64_t)0x00000000ff000000ULL) << 8) - | ((val & (uint64_t)0x000000ff00000000ULL) >> 8) - | ((val & (uint64_t)0x0000ff0000000000ULL) >> 24) - | ((val & (uint64_t)0x00ff000000000000ULL) >> 40) - | ((val & (uint64_t)0xff00000000000000ULL) >> 56); + return BSWAP_64_CONST(val); } #endif @@ -68,17 +110,106 @@ static inline uint64_t bswap_64(uint64_t val) #error "Can't compile for both big and little endian." #endif +#if HAVE_LITTLE_ENDIAN +/** + * CPU_TO_LE64_CONST - convert a constant uint64_t value to little-endian + * @native: constant to convert + */ +#define CPU_TO_LE64_CONST(native) (native) + +/** + * CPU_TO_LE32_CONST - convert a constant uint32_t value to little-endian + * @native: constant to convert + */ +#define CPU_TO_LE32_CONST(native) (native) + +/** + * CPU_TO_LE16_CONST - convert a constant uint16_t value to little-endian + * @native: constant to convert + */ +#define CPU_TO_LE16_CONST(native) (native) + +/** + * LE64_TO_CPU_CONST - convert a little-endian uint64_t constant + * @le_val: little-endian constant to convert + */ +#define LE64_TO_CPU_CONST(le_val) (le_val) + +/** + * LE32_TO_CPU_CONST - convert a little-endian uint32_t constant + * @le_val: little-endian constant to convert + */ +#define LE32_TO_CPU_CONST(le_val) (le_val) + +/** + * LE16_TO_CPU_CONST - convert a little-endian uint16_t constant + * @le_val: little-endian constant to convert + */ +#define LE16_TO_CPU_CONST(le_val) (le_val) + +#else /* ... HAVE_BIG_ENDIAN */ +#define CPU_TO_LE64_CONST(native) BSWAP_64_CONST(native) +#define CPU_TO_LE32_CONST(native) BSWAP_32_CONST(native) +#define CPU_TO_LE16_CONST(native) BSWAP_16_CONST(native) +#define LE64_TO_CPU_CONST(le_val) BSWAP_64_CONST(le_val) +#define LE32_TO_CPU_CONST(le_val) BSWAP_32_CONST(le_val) +#define LE16_TO_CPU_CONST(le_val) BSWAP_16_CONST(le_val) +#endif /* HAVE_BIG_ENDIAN */ + +#if HAVE_BIG_ENDIAN +/** + * CPU_TO_BE64_CONST - convert a constant uint64_t value to big-endian + * @native: constant to convert + */ +#define CPU_TO_BE64_CONST(native) (native) + +/** + * CPU_TO_BE32_CONST - convert a constant uint32_t value to big-endian + * @native: constant to convert + */ +#define CPU_TO_BE32_CONST(native) (native) + +/** + * CPU_TO_BE16_CONST - convert a constant uint16_t value to big-endian + * @native: constant to convert + */ +#define CPU_TO_BE16_CONST(native) (native) + +/** + * BE64_TO_CPU_CONST - convert a big-endian uint64_t constant + * @le_val: big-endian constant to convert + */ +#define BE64_TO_CPU_CONST(le_val) (le_val) + +/** + * BE32_TO_CPU_CONST - convert a big-endian uint32_t constant + * @le_val: big-endian constant to convert + */ +#define BE32_TO_CPU_CONST(le_val) (le_val) + +/** + * BE16_TO_CPU_CONST - convert a big-endian uint16_t constant + * @le_val: big-endian constant to convert + */ +#define BE16_TO_CPU_CONST(le_val) (le_val) + +#else /* ... HAVE_LITTLE_ENDIAN */ +#define CPU_TO_BE64_CONST(native) BSWAP_64_CONST(native) +#define CPU_TO_BE32_CONST(native) BSWAP_32_CONST(native) +#define CPU_TO_BE16_CONST(native) BSWAP_16_CONST(native) +#define BE64_TO_CPU_CONST(le_val) BSWAP_64_CONST(le_val) +#define BE32_TO_CPU_CONST(le_val) BSWAP_32_CONST(le_val) +#define BE16_TO_CPU_CONST(le_val) BSWAP_16_CONST(le_val) +#endif /* HAVE_LITTE_ENDIAN */ + + /** * cpu_to_le64 - convert a uint64_t value to little-endian * @native: value to convert */ static inline uint64_t cpu_to_le64(uint64_t native) { -#if HAVE_LITTLE_ENDIAN - return native; -#else - return bswap_64(native); -#endif + return CPU_TO_LE64_CONST(native); } /** @@ -87,11 +218,7 @@ static inline uint64_t cpu_to_le64(uint64_t native) */ static inline uint32_t cpu_to_le32(uint32_t native) { -#if HAVE_LITTLE_ENDIAN - return native; -#else - return bswap_32(native); -#endif + return CPU_TO_LE32_CONST(native); } /** @@ -100,11 +227,7 @@ static inline uint32_t cpu_to_le32(uint32_t native) */ static inline uint16_t cpu_to_le16(uint16_t native) { -#if HAVE_LITTLE_ENDIAN - return native; -#else - return bswap_16(native); -#endif + return CPU_TO_LE16_CONST(native); } /** @@ -113,11 +236,7 @@ static inline uint16_t cpu_to_le16(uint16_t native) */ static inline uint64_t le64_to_cpu(uint64_t le_val) { -#if HAVE_LITTLE_ENDIAN - return le_val; -#else - return bswap_64(le_val); -#endif + return LE64_TO_CPU_CONST(le_val); } /** @@ -126,11 +245,7 @@ static inline uint64_t le64_to_cpu(uint64_t le_val) */ static inline uint32_t le32_to_cpu(uint32_t le_val) { -#if HAVE_LITTLE_ENDIAN - return le_val; -#else - return bswap_32(le_val); -#endif + return LE32_TO_CPU_CONST(le_val); } /** @@ -139,11 +254,7 @@ static inline uint32_t le32_to_cpu(uint32_t le_val) */ static inline uint16_t le16_to_cpu(uint16_t le_val) { -#if HAVE_LITTLE_ENDIAN - return le_val; -#else - return bswap_16(le_val); -#endif + return LE16_TO_CPU_CONST(le_val); } /** @@ -152,11 +263,7 @@ static inline uint16_t le16_to_cpu(uint16_t le_val) */ static inline uint64_t cpu_to_be64(uint64_t native) { -#if HAVE_LITTLE_ENDIAN - return bswap_64(native); -#else - return native; -#endif + return CPU_TO_BE64_CONST(native); } /** @@ -165,11 +272,7 @@ static inline uint64_t cpu_to_be64(uint64_t native) */ static inline uint32_t cpu_to_be32(uint32_t native) { -#if HAVE_LITTLE_ENDIAN - return bswap_32(native); -#else - return native; -#endif + return CPU_TO_BE32_CONST(native); } /** @@ -178,11 +281,7 @@ static inline uint32_t cpu_to_be32(uint32_t native) */ static inline uint16_t cpu_to_be16(uint16_t native) { -#if HAVE_LITTLE_ENDIAN - return bswap_16(native); -#else - return native; -#endif + return CPU_TO_BE16_CONST(native); } /** @@ -191,11 +290,7 @@ static inline uint16_t cpu_to_be16(uint16_t native) */ static inline uint64_t be64_to_cpu(uint64_t be_val) { -#if HAVE_LITTLE_ENDIAN - return bswap_64(be_val); -#else - return be_val; -#endif + return BE64_TO_CPU_CONST(be_val); } /** @@ -204,11 +299,7 @@ static inline uint64_t be64_to_cpu(uint64_t be_val) */ static inline uint32_t be32_to_cpu(uint32_t be_val) { -#if HAVE_LITTLE_ENDIAN - return bswap_32(be_val); -#else - return be_val; -#endif + return BE32_TO_CPU_CONST(be_val); } /** @@ -217,11 +308,7 @@ static inline uint32_t be32_to_cpu(uint32_t be_val) */ static inline uint16_t be16_to_cpu(uint16_t be_val) { -#if HAVE_LITTLE_ENDIAN - return bswap_16(be_val); -#else - return be_val; -#endif + return BE16_TO_CPU_CONST(be_val); } #endif /* CCAN_ENDIAN_H */ diff --git a/ccan/endian/test/compile_ok-constant.c b/ccan/endian/test/compile_ok-constant.c new file mode 100644 index 00000000..5f172f78 --- /dev/null +++ b/ccan/endian/test/compile_ok-constant.c @@ -0,0 +1,12 @@ +#include + +struct foo { + char one[BSWAP_16_CONST(0xFF00)]; + char two[BSWAP_32_CONST(0xFF000000)]; + char three[BSWAP_64_CONST(0xFF00000000000000ULL)]; +}; + +int main(void) +{ + return 0; +}