Logo ROOT  
Reference Guide
Byteswap.h
Go to the documentation of this file.
1 /* @(#)root/base:$Id$ */
2 
3 /*************************************************************************
4  * Copyright (C) 1995-2000, Rene Brun and Fons Rademakers. *
5  * All rights reserved. *
6  * *
7  * For the licensing terms see $ROOTSYS/LICENSE. *
8  * For the list of contributors see $ROOTSYS/README/CREDITS. *
9  *************************************************************************/
10 
11 #ifndef ROOT_Byteswap
12 #define ROOT_Byteswap
13 
14 /* Originally (mid-1990s), this file contained copy/pasted assembler from RH6.0's
15  * version of <bits/byteswap.h>. Hence, we keep a copy of the FSF copyright below.
16  * I believe all the original code has been excised, perhaps with exception of the
17  * R__bswap_constant_* functions. To be on the safe side, we are keeping the
18  * copyright below.
19  * -- Brian Bockelman, August 2018
20  */
21 
22 /* Copyright (C) 1997 Free Software Foundation, Inc.
23  This file is part of the GNU C Library.
24 
25  The GNU C Library is free software; you can redistribute it and/or
26  modify it under the terms of the GNU Library General Public License as
27  published by the Free Software Foundation; either version 2 of the
28  License, or (at your option) any later version.
29 
30  The GNU C Library is distributed in the hope that it will be useful,
31  but WITHOUT ANY WARRANTY; without even the implied warranty of
32  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
33  Library General Public License for more details.
34 
35  You should have received a copy of the GNU Library General Public
36  License along with the GNU C Library; see the file COPYING.LIB. If not,
37  write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
38  Boston, MA 02111-1307, USA. */
39 
40 #if (defined(__linux) || defined(__APPLE__)) && \
41  (defined(__i386__) || defined(__x86_64__)) && \
42  (defined(__GNUC__))
43 #ifndef R__USEASMSWAP
44 #define R__USEASMSWAP
45 #endif
46 #endif
47 
48 /* Swap bytes in 16 bit value. */
49 #define R__bswap_constant_16(x) \
50  ((((x) >> 8) & 0xff) | (((x) & 0xff) << 8))
51 
52 #if defined R__USEASMSWAP
53 # define R__bswap_16(x) __builtin_bswap16(x)
54 #else
55 # define R__bswap_16(x) R__bswap_constant_16 (x)
56 #endif
57 
58 
59 /* Swap bytes in 32 bit value. */
60 #define R__bswap_constant_32(x) \
61  ((((x) & 0xff000000) >> 24) | (((x) & 0x00ff0000) >> 8) | \
62  (((x) & 0x0000ff00) << 8) | (((x) & 0x000000ff) << 24))
63 
64 #if defined R__USEASMSWAP
65 # define R__bswap_32(x) __builtin_bswap32(x)
66 #else
67 # define R__bswap_32(x) R__bswap_constant_32 (x)
68 #endif
69 
70 
71 /* Return a value with all bytes in the 16 bit argument swapped. */
72 #define Rbswap_16(x) R__bswap_16 (x)
73 
74 /* Return a value with all bytes in the 32 bit argument swapped. */
75 #define Rbswap_32(x) R__bswap_32 (x)
76 
77 /* Return a value with all bytes in the 64 bit argument swapped. */
78 
79 /* For reasons that were lost to history, Rbswap_64 used to only
80  * be defined wherever GNUC was available. To simplify the macro
81  * definitions, we extend this to wherever we can use the gcc-like
82  * builtins.
83  * -- Brian Bockelman, August 2018
84  */
85 #ifdef R__USEASMSWAP
86 # define Rbswap_64(x) __builtin_bswap64(x)
87 #endif
88 
89 #endif /* Byteswap.h */