50 lines
1.2 KiB
C++
50 lines
1.2 KiB
C++
/*
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Copyright (C) 2013 Tim Mayberry
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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*/
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#include "pbd/ffs.h"
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#ifndef COMPILER_MSVC
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#include <strings.h>
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#endif
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namespace PBD {
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int
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ffs (int x)
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{
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#if defined (COMPILER_MINGW)
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return __builtin_ffs(x);
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#elif defined (COMPILER_MSVC)
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unsigned long index;
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#ifdef WIN64
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if (0 != _BitScanForward64(&index, (__int64)x))
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#else
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if (0 != _BitScanForward(&index, (unsigned long)x))
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#endif
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index++; // Make the result 1-based
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else
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index = 0; // All bits were zero
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return (int)index;
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#else
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return ::ffs(x);
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#endif
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}
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}
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