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>
Vicent Marti committed
Nov 14, 2013 at 07:43 UTC
7e3dae494370b5596a6ea76af1191829ce11bce2
1 file changed
+75
-1
compat/bswap.h
+75
-1
@@ -17,7 +17,20 @@ static inline uint32_t default_swab32(uint32_t val)
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((val & 0x000000ff) << 24));
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}
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+static inline uint64_t default_bswap64(uint64_t val)
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+{
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+ return (((val & (uint64_t)0x00000000000000ffULL) << 56) |
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+ ((val & (uint64_t)0x000000000000ff00ULL) << 40) |
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+ ((val & (uint64_t)0x0000000000ff0000ULL) << 24) |
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+ ((val & (uint64_t)0x00000000ff000000ULL) << 8) |
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+ ((val & (uint64_t)0x000000ff00000000ULL) >> 8) |
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+ ((val & (uint64_t)0x0000ff0000000000ULL) >> 24) |
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+ ((val & (uint64_t)0x00ff000000000000ULL) >> 40) |
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+ ((val & (uint64_t)0xff00000000000000ULL) >> 56));
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+}
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+
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#undef bswap32
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+#undef bswap64
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#if defined(__GNUC__) && (defined(__i386__) || defined(__x86_64__))
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@@ -32,15 +45,42 @@ static inline uint32_t git_bswap32(uint32_t x)
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return result;
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}
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+#define bswap64 git_bswap64
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+#if defined(__x86_64__)
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+static inline uint64_t git_bswap64(uint64_t x)
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+{
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+ uint64_t result;
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+ if (__builtin_constant_p(x))
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+ result = default_bswap64(x);
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+ else
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+ __asm__("bswap %q0" : "=r" (result) : "0" (x));
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+ return result;
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+}
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+#else
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+static inline uint64_t git_bswap64(uint64_t x)
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+{
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+ union { uint64_t i64; uint32_t i32[2]; } tmp, result;
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+ if (__builtin_constant_p(x))
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+ result.i64 = default_bswap64(x);
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+ else {
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+ tmp.i64 = x;
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+ result.i32[0] = git_bswap32(tmp.i32[1]);
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+ result.i32[1] = git_bswap32(tmp.i32[0]);
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+ }
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+ return result.i64;
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+}
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+#endif
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+
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#elif defined(_MSC_VER) && (defined(_M_IX86) || defined(_M_X64))
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#include <stdlib.h>
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#define bswap32(x) _byteswap_ulong(x)
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+#define bswap64(x) _byteswap_uint64(x)
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#endif
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-#ifdef bswap32
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+#if defined(bswap32)
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#undef ntohl
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#undef htonl
@@ -48,3 +88,37 @@ static inline uint32_t git_bswap32(uint32_t x)
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#define htonl(x) bswap32(x)
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#endif
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+
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+#if defined(bswap64)
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+
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+#undef ntohll
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+#undef htonll
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+#define ntohll(x) bswap64(x)
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+#define htonll(x) bswap64(x)
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+
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+#else
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+
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+#undef ntohll
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+#undef htonll
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+
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+#if !defined(__BYTE_ORDER)
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+# if defined(BYTE_ORDER) && defined(LITTLE_ENDIAN) && defined(BIG_ENDIAN)
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+# define __BYTE_ORDER BYTE_ORDER
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+# define __LITTLE_ENDIAN LITTLE_ENDIAN
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+# define __BIG_ENDIAN BIG_ENDIAN
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+# endif
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+#endif
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+
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+#if !defined(__BYTE_ORDER)
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+# error "Cannot determine endianness"
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+#endif
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+
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+#if __BYTE_ORDER == __BIG_ENDIAN
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+# define ntohll(n) (n)
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+# define htonll(n) (n)
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+#else
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+# define ntohll(n) default_bswap64(n)
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+# define htonll(n) default_bswap64(n)
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+#endif
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+
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+#endif