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authorVicent Marti <tanoku@gmail.com>2013-11-14 12:43:36 (GMT)
committerJunio C Hamano <gitster@pobox.com>2013-11-18 18:57:42 (GMT)
commit7e3dae494370b5596a6ea76af1191829ce11bce2 (patch)
tree36f658bc1630dc150ec2f51f69881fb416759b4e
parentec73f5807cd6e6f6d55e716cde80637a1019d67d (diff)
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compat: add endianness helpers
The POSIX standard doesn't currently define a `ntohll`/`htonll` function pair to perform network-to-host and host-to-network swaps of 64-bit data. These 64-bit swaps are necessary for the on-disk storage of EWAH bitmaps if they are not in native byte order. Many thanks to Ramsay Jones <ramsay@ramsay1.demon.co.uk> and Torsten Bögershausen <tboegi@web.de> for cygwin/mingw/msvc portability fixes. Signed-off-by: Vicent Marti <tanoku@gmail.com> Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
-rw-r--r--compat/bswap.h76
1 files changed, 75 insertions, 1 deletions
diff --git a/compat/bswap.h b/compat/bswap.h
index 5061214..c18a78e 100644
--- a/compat/bswap.h
+++ b/compat/bswap.h
@@ -17,7 +17,20 @@ static inline uint32_t default_swab32(uint32_t val)
((val & 0x000000ff) << 24));
}
+static inline uint64_t default_bswap64(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));
+}
+
#undef bswap32
+#undef bswap64
#if defined(__GNUC__) && (defined(__i386__) || defined(__x86_64__))
@@ -32,15 +45,42 @@ static inline uint32_t git_bswap32(uint32_t x)
return result;
}
+#define bswap64 git_bswap64
+#if defined(__x86_64__)
+static inline uint64_t git_bswap64(uint64_t x)
+{
+ uint64_t result;
+ if (__builtin_constant_p(x))
+ result = default_bswap64(x);
+ else
+ __asm__("bswap %q0" : "=r" (result) : "0" (x));
+ return result;
+}
+#else
+static inline uint64_t git_bswap64(uint64_t x)
+{
+ union { uint64_t i64; uint32_t i32[2]; } tmp, result;
+ if (__builtin_constant_p(x))
+ result.i64 = default_bswap64(x);
+ else {
+ tmp.i64 = x;
+ result.i32[0] = git_bswap32(tmp.i32[1]);
+ result.i32[1] = git_bswap32(tmp.i32[0]);
+ }
+ return result.i64;
+}
+#endif
+
#elif defined(_MSC_VER) && (defined(_M_IX86) || defined(_M_X64))
#include <stdlib.h>
#define bswap32(x) _byteswap_ulong(x)
+#define bswap64(x) _byteswap_uint64(x)
#endif
-#ifdef bswap32
+#if defined(bswap32)
#undef ntohl
#undef htonl
@@ -48,3 +88,37 @@ static inline uint32_t git_bswap32(uint32_t x)
#define htonl(x) bswap32(x)
#endif
+
+#if defined(bswap64)
+
+#undef ntohll
+#undef htonll
+#define ntohll(x) bswap64(x)
+#define htonll(x) bswap64(x)
+
+#else
+
+#undef ntohll
+#undef htonll
+
+#if !defined(__BYTE_ORDER)
+# if defined(BYTE_ORDER) && defined(LITTLE_ENDIAN) && defined(BIG_ENDIAN)
+# define __BYTE_ORDER BYTE_ORDER
+# define __LITTLE_ENDIAN LITTLE_ENDIAN
+# define __BIG_ENDIAN BIG_ENDIAN
+# endif
+#endif
+
+#if !defined(__BYTE_ORDER)
+# error "Cannot determine endianness"
+#endif
+
+#if __BYTE_ORDER == __BIG_ENDIAN
+# define ntohll(n) (n)
+# define htonll(n) (n)
+#else
+# define ntohll(n) default_bswap64(n)
+# define htonll(n) default_bswap64(n)
+#endif
+
+#endif