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git.proxmox.com Git - ceph.git/blob - ceph/src/common/reverse.c
1 // -*- mode:C++; tab-width:8; c-basic-offset:2; indent-tabs-mode:t -*-
2 // vim: ts=8 sw=2 smarttab
4 * Ceph - scalable distributed file system
6 * Copyright (C) 2004-2006 Sage Weil <sage@newdream.net>
8 * This is free software; you can redistribute it and/or
9 * modify it under the terms of the GNU Lesser General Public
10 * License version 2.1, as published by the Free Software
11 * Foundation. See file COPYING.
17 uint32_t reverse_bits(uint32_t v
) {
22 * swap odd and even bits
24 v
= ((v
>> 1) & 0x55555555) | ((v
& 0x55555555) << 1);
25 /* swap consecutive pairs */
26 v
= ((v
>> 2) & 0x33333333) | ((v
& 0x33333333) << 2);
27 /* swap nibbles ... */
28 v
= ((v
>> 4) & 0x0F0F0F0F) | ((v
& 0x0F0F0F0F) << 4);
30 v
= ((v
>> 8) & 0x00FF00FF) | ((v
& 0x00FF00FF) << 8);
31 /* swap 2-byte long pairs */
32 v
= ( v
>> 16 ) | ( v
<< 16);
36 uint32_t reverse_nibbles(uint32_t retval
) {
38 retval
= ((retval
& 0x0f0f0f0f) << 4) | ((retval
& 0xf0f0f0f0) >> 4);
39 retval
= ((retval
& 0x00ff00ff) << 8) | ((retval
& 0xff00ff00) >> 8);
40 retval
= ((retval
& 0x0000ffff) << 16) | ((retval
& 0xffff0000) >> 16);