32ec828835
This gives a much clearer overview of the licensing. It also shows there are some problems: - Some files are under GPLv3 only - Some files have no known license at all.
83 lines
2.1 KiB
C
83 lines
2.1 KiB
C
/* vim:expandtab:ts=2 sw=2:
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*/
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/* Grafx2 - The Ultimate 256-color bitmap paint program
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Copyright owned by various GrafX2 authors, see COPYRIGHT.txt for details.
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Grafx2 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; version 2
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of the License.
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Grafx2 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 Grafx2; if not, see <http://www.gnu.org/licenses/>
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*/
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//////////////////////////////////////////////////////////////////////////////
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///@file bitcount.h
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/// helper functions (or macros) to count bits in machine words
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//////////////////////////////////////////////////////////////////////////////
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#ifndef BITCOUNT_H__
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#define BITCOUNT_H__
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#if defined(__GNUC__) && __GNUC__ > 2
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/* use GCC built in's */
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#define count_set_bits __builtin_popcount
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#define count_trailing_zeros __builtin_ctz
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#else
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/**
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* Count the number of bit sets "Popcount"
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*
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* Based on Wikipedia article for Hamming_weight, it's optimized
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* for cases when zeroes are more frequent.
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*/
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static int count_set_bits(unsigned int value)
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{
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int count;
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for (count = 0; value != 0; count++)
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value &= value-1;
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return count;
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}
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#if defined(_MSC_VER)
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#include <intrin.h>
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// beware : the MSVC __popcnt intrinsic is not compatible with all CPU's
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// _BitScanForward() is available on all architectures.
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static int count_trailing_zeros(unsigned int value)
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{
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unsigned long count;
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if (_BitScanForward(&count, value))
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return count;
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else
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return -1;
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}
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#else
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/**
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* Count the number of low order zero's before the first bit set
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*/
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static int count_trailing_zeros(unsigned int value)
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{
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int count;
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if (value == 0)
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return -1;
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for (count = 0; (value & 1) == 0; value >>= 1)
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count++;
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return count;
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}
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#endif
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#endif
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#endif
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