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byteswap.h: Add a glibc/linux compatible byteswap.h

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For endian.h to work instead of sys/endian.h, some software needs
byteswap.h available. It must define {__,}byteswap_{16,32,64}.
Included sys/_endian.h to get an appropriate __byteswap16, etc
and defines the new macros in terms of them. Enhance _endian.h
to allow it to be included from here too.

Sponsored by:		Netflix
Reviewed by:		markj
Differential Revision:	https://reviews.freebsd.org/D32051
This commit is contained in:
Warner Losh 2023-01-20 16:33:37 -07:00
parent 30e0d2a510
commit 1761b09bf4
3 changed files with 44 additions and 2 deletions
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3
include/Makefile
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@ -12,7 +12,8 @@ SUBDIR= arpa protocols rpcsvc rpc xlocale
SUBDIR+= i386
.endif
SUBDIR_PARALLEL=
INCS= a.out.h ar.h assert.h bitstring.h complex.h cpio.h _ctype.h ctype.h \
INCS= a.out.h ar.h assert.h bitstring.h byteswap.h \
complex.h cpio.h _ctype.h ctype.h \
db.h \
dirent.h dlfcn.h elf.h elf-hints.h endian.h err.h fmtmsg.h fnmatch.h \
fstab.h fts.h ftw.h getopt.h glob.h grp.h \

41
include/byteswap.h Normal file
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@ -0,0 +1,41 @@
/*-
* Copyright (c) 2021 M. Warner Losh <imp@FreeBSD.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
/*
* A mostly Linux/glibc-compatible byteswap.h
*/
#ifndef _BYTESWAP_H_
#define _BYTESWAP_H_
/*
* sys/_endian.h brings in the shared interfaces between BSD's sys/endian.h, and
* glibc's endian.h. However, we need to include it here to get the
* __bswap{16,32,64} definitions that we use. sys/_endian.h has been consturcted to
* be compatible with including <endian.h>, <byteswap.h> or both in either order,
* as well as providing the BSD the bulk of sys/endian.h functionality.
*/
#include <sys/_endian.h>
/*
* glibc's <byteswap.h> defines the bswap_* and __bswap_* macros below. Most
* software uses either just <sys/endian.h>, or both <endian.h> and
* <byteswap.h>. However, one can't define bswap16, etc in <endian.h> because
* several software packages will define them only when they detect <endian.h>
* is included (but not when sys/endian.h is included). Defining bswap16, etc
* here causes compilation errors for those packages. <endian.h> and
* <byteswap.h> need to be paired together, with the below defines here, for
* the highest level of glibc compatibility.
*/
#define __bswap_16(x) __bswap16(x)
#define __bswap_32(x) __bswap32(x)
#define __bswap_64(x) __bswap64(x)
#define bswap_16(x) __bswap16(x)
#define bswap_32(x) __bswap32(x)
#define bswap_64(x) __bswap64(x)
#endif /* _BYTESWAP_H_ */

2
sys/sys/_endian.h
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@ -32,7 +32,7 @@
#ifndef _SYS__ENDIAN_H_
#define _SYS__ENDIAN_H_
#if !defined(_MACHINE_ENDIAN_H_) && !defined(_ENDIAN_H_)
#if !defined(_MACHINE_ENDIAN_H_) && !defined(_BYTESWAP_H_) && !defined(_ENDIAN_H_)
#error "sys/_endian.h should not be included directly"
#endif