From ec9bb1417e5d76e4be4c735962ddea087e39bed3 Mon Sep 17 00:00:00 2001 From: Michael Gartsbein Date: Thu, 28 Apr 2016 12:02:29 +0300 Subject: [PATCH] compile time endianess check, faster on little endian cpus --- lib/capnp_c.h | 60 ++++++++++++++++++++++++++++++++++----------------- 1 file changed, 40 insertions(+), 20 deletions(-) diff --git a/lib/capnp_c.h b/lib/capnp_c.h index 900bfc3..58d1051 100644 --- a/lib/capnp_c.h +++ b/lib/capnp_c.h @@ -24,6 +24,8 @@ extern "C" { #define CAPN_INLINE static #endif +#define IS_BIG_ENDIAN (*(uint16_t *)"\0\xff" < 0x100) + #define CAPN_VERSION 1 /* struct capn is a common structure shared between segments in the same @@ -299,30 +301,48 @@ CAPN_INLINE uint8_t capn_flip8(uint8_t v) { return v; } CAPN_INLINE uint16_t capn_flip16(uint16_t v) { - union { uint16_t u; uint8_t v[2]; } s; - s.v[0] = (uint8_t)v; - s.v[1] = (uint8_t)(v>>8); - return s.u; +#if __BYTE_ORDER == __BIG_ENDIAN + union { uint16_t u; uint8_t v[2]; } s; + s.v[0] = (uint8_t)v; + s.v[1] = (uint8_t)(v>>8); + return s.u; +#elif __BYTE_ORDER == __LITTLE_ENDIAN + return v; +#else +#error "Unable to determine endianess "; +#endif } CAPN_INLINE uint32_t capn_flip32(uint32_t v) { - union { uint32_t u; uint8_t v[4]; } s; - s.v[0] = (uint8_t)v; - s.v[1] = (uint8_t)(v>>8); - s.v[2] = (uint8_t)(v>>16); - s.v[3] = (uint8_t)(v>>24); - return s.u; +#if __BYTE_ORDER == __BIG_ENDIAN + union { uint32_t u; uint8_t v[4]; } s; + s.v[0] = (uint8_t)v; + s.v[1] = (uint8_t)(v>>8); + s.v[2] = (uint8_t)(v>>16); + s.v[3] = (uint8_t)(v>>24); + return s.u; +#elif __BYTE_ORDER == __LITTLE_ENDIAN + return v; +#else +#error "Unable to determine endianess "; +#endif } CAPN_INLINE uint64_t capn_flip64(uint64_t v) { - union { uint64_t u; uint8_t v[8]; } s; - s.v[0] = (uint8_t)v; - s.v[1] = (uint8_t)(v>>8); - s.v[2] = (uint8_t)(v>>16); - s.v[3] = (uint8_t)(v>>24); - s.v[4] = (uint8_t)(v>>32); - s.v[5] = (uint8_t)(v>>40); - s.v[6] = (uint8_t)(v>>48); - s.v[7] = (uint8_t)(v>>56); - return s.u; +#if __BYTE_ORDER == __BIG_ENDIAN + union { uint64_t u; uint8_t v[8]; } s; + s.v[0] = (uint8_t)v; + s.v[1] = (uint8_t)(v>>8); + s.v[2] = (uint8_t)(v>>16); + s.v[3] = (uint8_t)(v>>24); + s.v[4] = (uint8_t)(v>>32); + s.v[5] = (uint8_t)(v>>40); + s.v[6] = (uint8_t)(v>>48); + s.v[7] = (uint8_t)(v>>56); + return s.u; +#elif __BYTE_ORDER == __LITTLE_ENDIAN + return v; +#else +#error "Unable to determine endianess "; +#endif } CAPN_INLINE int capn_write1(capn_ptr p, int off, int val) {