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f4ac32c03a
The compiler is in general able to recognize the endian shift and
replace it with an optimized opcode if possible. On certain
architectures such as RiscV or MIPS the situation can get complicated.
They don't provide an optimized opcode and masking the "higher" bits may
required loading a constant which needs shifting. This causes the
compiler to emit a lot of instructions for the operation.
The provided builtin directive on these architecture calls a function
which does the operation instead of emitting the code for operation.
Bring back the change from commit 6547d1c9 (bswap.h: add support for
built-in bswap functions, 2025-04-23). The bswap32/64 macro can now be
defined unconditionally so it won't regress on big endian architectures.
Signed-off-by: Sebastian Andrzej Siewior <sebastian@breakpoint.cc>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
176 lines
4.4 KiB
C
176 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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/*
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* __has_builtin is available since Clang 10 and GCC 10.
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* Below is a fallback for older compilers.
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*/
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#ifndef __has_builtin
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# define __has_builtin(x) 0
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#endif
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#undef bswap32
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#undef bswap64
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#if 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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#define GIT_LITTLE_ENDIAN 1234
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#define GIT_BIG_ENDIAN 4321
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#define GIT_BYTE_ORDER GIT_LITTLE_ENDIAN
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#elif __has_builtin(__builtin_bswap32) && __has_builtin(__builtin_bswap64)
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#define bswap32(x) __builtin_bswap32((x))
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#define bswap64(x) __builtin_bswap64((x))
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#endif
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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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#elif defined(__BYTE_ORDER__) && defined(__ORDER_LITTLE_ENDIAN__) && defined(__ORDER_BIG_ENDIAN__)
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# define GIT_BYTE_ORDER __BYTE_ORDER__
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# define GIT_LITTLE_ENDIAN __ORDER_LITTLE_ENDIAN__
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# define GIT_BIG_ENDIAN __ORDER_BIG_ENDIAN__
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#elif !defined(GIT_BYTE_ORDER)
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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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#undef ntohl
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#undef htonl
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#undef ntohll
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#undef htonll
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#if GIT_BYTE_ORDER == GIT_BIG_ENDIAN
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# define ntohl(x) (x)
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# define htonl(x) (x)
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# define ntohll(x) (x)
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# define htonll(x) (x)
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#else
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# if defined(bswap32)
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# define ntohl(x) bswap32(x)
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# define htonl(x) bswap32(x)
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# else
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# define ntohl(x) default_swab32(x)
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# define htonl(x) default_swab32(x)
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# endif
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# if defined(bswap64)
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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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# define ntohll(x) default_bswap64(x)
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# define htonll(x) default_bswap64(x)
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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) & 0xff;
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p[1] = (value >> 16) & 0xff;
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p[2] = (value >> 8) & 0xff;
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p[3] = (value >> 0) & 0xff;
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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) & 0xff;
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p[1] = (value >> 48) & 0xff;
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p[2] = (value >> 40) & 0xff;
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p[3] = (value >> 32) & 0xff;
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p[4] = (value >> 24) & 0xff;
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p[5] = (value >> 16) & 0xff;
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p[6] = (value >> 8) & 0xff;
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p[7] = (value >> 0) & 0xff;
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}
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#endif /* COMPAT_BSWAP_H */
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