0c038fc65a
In 1af265f0 (compat/bswap.h: simplify MSVC endianness
detection, 2020-11-08) we attempted to simplify code by assuming MSVC
builds will be for little-endian machines, since only unusably old
versions of MSVC supported big-endian MIPS and m68k architectures.
However, it's possible that MSVC could be ported to build for a
big-endian architecture again, so the simplification wasn't as
future-proof as hoped.
So let's go back to the old way of detecting MSVC, and then checking
architecture from a list of little-endian architecture macros.
Note that MSVC does not treat ARM64 as bi-endian, so we can safely treat
it as little-endian.
Helped-by: brian m. carlson <sandals@crustytoothpaste.net>
Helped-by: Jeff King <peff@peff.net>
Helped-by: Johannes Schindelin <Johannes.Schindelin@gmx.de>
Helped-by: Junio C Hamano <gitster@pobox.com>
Signed-off-by: Daniel Gurney <dgurney99@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
194 lines
4.4 KiB
C
194 lines
4.4 KiB
C
#ifndef COMPAT_BSWAP_H
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#define COMPAT_BSWAP_H
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/*
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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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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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#undef bswap32
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#undef bswap64
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#if defined(__GNUC__) && (defined(__i386__) || defined(__x86_64__))
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#define bswap32 git_bswap32
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static inline uint32_t git_bswap32(uint32_t x)
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{
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uint32_t result;
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if (__builtin_constant_p(x))
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result = default_swab32(x);
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else
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__asm__("bswap %0" : "=r" (result) : "0" (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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#elif defined(_MSC_VER) && (defined(_M_IX86) || defined(_M_X64) || defined(_M_ARM64))
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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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#if defined(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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#if defined(bswap64)
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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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#else
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#undef ntohll
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#undef htonll
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#if defined(__BYTE_ORDER) && defined(__LITTLE_ENDIAN) && defined(__BIG_ENDIAN)
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# define GIT_BYTE_ORDER __BYTE_ORDER
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# define GIT_LITTLE_ENDIAN __LITTLE_ENDIAN
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# define GIT_BIG_ENDIAN __BIG_ENDIAN
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#elif defined(BYTE_ORDER) && defined(LITTLE_ENDIAN) && defined(BIG_ENDIAN)
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# define GIT_BYTE_ORDER BYTE_ORDER
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# define GIT_LITTLE_ENDIAN LITTLE_ENDIAN
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# define GIT_BIG_ENDIAN BIG_ENDIAN
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#else
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# define GIT_BIG_ENDIAN 4321
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# define GIT_LITTLE_ENDIAN 1234
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# if defined(_BIG_ENDIAN) && !defined(_LITTLE_ENDIAN)
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# define GIT_BYTE_ORDER GIT_BIG_ENDIAN
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# elif defined(_LITTLE_ENDIAN) && !defined(_BIG_ENDIAN)
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# define GIT_BYTE_ORDER GIT_LITTLE_ENDIAN
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# elif defined(__THW_BIG_ENDIAN__) && !defined(__THW_LITTLE_ENDIAN__)
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# define GIT_BYTE_ORDER GIT_BIG_ENDIAN
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# elif defined(__THW_LITTLE_ENDIAN__) && !defined(__THW_BIG_ENDIAN__)
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# define GIT_BYTE_ORDER GIT_LITTLE_ENDIAN
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# else
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# error "Cannot determine endianness"
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# endif
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#endif
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#if GIT_BYTE_ORDER == GIT_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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#endif
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static inline uint16_t get_be16(const void *ptr)
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{
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const unsigned char *p = ptr;
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return (uint16_t)p[0] << 8 |
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(uint16_t)p[1] << 0;
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}
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static inline uint32_t get_be32(const void *ptr)
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{
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const unsigned char *p = ptr;
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return (uint32_t)p[0] << 24 |
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(uint32_t)p[1] << 16 |
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(uint32_t)p[2] << 8 |
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(uint32_t)p[3] << 0;
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}
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static inline uint64_t get_be64(const void *ptr)
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{
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const unsigned char *p = ptr;
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return (uint64_t)get_be32(&p[0]) << 32 |
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(uint64_t)get_be32(&p[4]) << 0;
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}
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static inline void put_be32(void *ptr, uint32_t value)
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{
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unsigned char *p = ptr;
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p[0] = value >> 24;
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p[1] = value >> 16;
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p[2] = value >> 8;
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p[3] = value >> 0;
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}
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static inline void put_be64(void *ptr, uint64_t value)
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{
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unsigned char *p = ptr;
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p[0] = value >> 56;
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p[1] = value >> 48;
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p[2] = value >> 40;
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p[3] = value >> 32;
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p[4] = value >> 24;
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p[5] = value >> 16;
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p[6] = value >> 8;
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p[7] = value >> 0;
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}
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#endif /* COMPAT_BSWAP_H */
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