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21e403a7b9
Since commit 0fcabdeb52, compat/bswap.h
redefined htonl and ntohl to bswap32 not only if bswap32 has been
defined earlier in compat/bswap.h (which is done only on selected
platforms), but also if bswap32 has been defined anywhere else. This
broke Git at least for NetBSD systems running on big-endian machines
(where ntohl and htonl should, of course, be NOOPs), since NetBSD
defines a bswap32 macro in the system headers.
So, we now undefine any previously defined bswap32 in compat/bswap.h
before defining our own.
Signed-off-by: Holger Weiß <holger@zedat.fu-berlin.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
48 lines
1 KiB
C
48 lines
1 KiB
C
/*
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* Let's make sure we always have a sane definition for ntohl()/htonl().
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* Some libraries define those as a function call, just to perform byte
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* shifting, bringing significant overhead to what should be a simple
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* operation.
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*/
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/*
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* Default version that the compiler ought to optimize properly with
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* constant values.
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*/
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static inline uint32_t default_swab32(uint32_t val)
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{
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return (((val & 0xff000000) >> 24) |
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((val & 0x00ff0000) >> 8) |
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((val & 0x0000ff00) << 8) |
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((val & 0x000000ff) << 24));
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}
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#undef bswap32
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#if defined(__GNUC__) && (defined(__i386__) || defined(__x86_64__))
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#define bswap32(x) ({ \
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uint32_t __res; \
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if (__builtin_constant_p(x)) { \
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__res = default_swab32(x); \
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} else { \
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__asm__("bswap %0" : "=r" (__res) : "0" ((uint32_t)(x))); \
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} \
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__res; })
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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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#endif
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#ifdef bswap32
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#undef ntohl
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#undef htonl
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#define ntohl(x) bswap32(x)
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#define htonl(x) bswap32(x)
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#endif
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