glusterfs

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/* bit search implementation
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 *
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 * Copyright (C) 2004 Red Hat, Inc. All Rights Reserved.
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 * Written by David Howells (dhowells@redhat.com)
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 *
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 * Copyright (C) 2008 IBM Corporation
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 * 'find_last_bit' is written by Rusty Russell <rusty@rustcorp.com.au>
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 * (Inspired by David Howell's find_next_bit implementation)
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 *
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 * Rewritten by Yury Norov <yury.norov@gmail.com> to decrease
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 * size and improve performance, 2015.
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 *
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 * This program is free software; you can redistribute it and/or
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 * modify it under the terms of the GNU General Public License
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 * as published by the Free Software Foundation; either version
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 * 2 of the License, or (at your option) any later version.
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 */
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/**
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 * @find_last_bit
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 * optimized implementation of find last bit in
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 */
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#ifndef BITS_PER_LONG
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#ifdef __LP64__
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#define BITS_PER_LONG 64
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#else
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#define BITS_PER_LONG 32
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#endif
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#endif
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unsigned long gw_tw_fls (unsigned long word)
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{
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        int num = BITS_PER_LONG;
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#if BITS_PER_LONG == 64
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        if (!(word & (~0ul << 32))) {
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                num -= 32;
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                word <<= 32;
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        }
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#endif
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        if (!(word & (~0ul << (BITS_PER_LONG-16)))) {
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                num -= 16;
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                word <<= 16;
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        }
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        if (!(word & (~0ul << (BITS_PER_LONG-8)))) {
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                num -= 8;
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                word <<= 8;
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        }
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        if (!(word & (~0ul << (BITS_PER_LONG-4)))) {
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                num -= 4;
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                word <<= 4;
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        }
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        if (!(word & (~0ul << (BITS_PER_LONG-2)))) {
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                num -= 2;
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                word <<= 2;
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        }
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        if (!(word & (~0ul << (BITS_PER_LONG-1))))
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                num -= 1;
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        return num;
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}
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