106 lines
2.7 KiB
C++
106 lines
2.7 KiB
C++
/**
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* Copyright - See the COPYRIGHT that is included with this distribution.
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* pvxs is distributed subject to a Software License Agreement found
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* in file LICENSE that is included with this distribution.
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*/
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#include <algorithm>
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#include <pvxs/bitmask.h>
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namespace pvxs {
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BitMask::BitMask(BitMask&& o) noexcept
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:_words(std::move(o._words))
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,_size(o._size)
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{
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o._size = 0u;
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}
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BitMask& BitMask::operator=(BitMask&& o) noexcept
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{
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_words = std::move(o._words);
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_size = o._size;
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o._size = 0u;
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return *this;
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}
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BitMask::BitMask(std::initializer_list<size_t> bits, size_t nbits)
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{
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if(bits.size()>0u) {
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auto it_max = std::max_element(bits.begin(), bits.end());
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resize(std::max(nbits, 1u+*it_max));
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for(auto bit : bits) {
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(*this)[bit] = true;
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}
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} else {
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resize(nbits);
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}
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}
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void BitMask::resize(size_t bits) {
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// round up to multiple of 64
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size_t storebits = ((bits-1u)|0x3f)+1u;
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_words.resize(storebits/64u, 0u);
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_size = bits;
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}
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size_t BitMask::findSet(size_t start) const
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{
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while(start < _size) {
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size_t word = start/64u,
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bit = start%64u;
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// first see if we can skip to next word
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uint64_t mask = ~((1ull<<bit)-1); // mask of bit and higher
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uint64_t masked = _words[word]&mask;
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if(masked==0u) {
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start = (word+1u)*64u;
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continue;
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}
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// the answer is in range [bit, 64)
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// count consecutive "trailing" zeros.
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// http://graphics.stanford.edu/~seander/bithacks.html#ZerosOnRightParallel
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masked &= -masked; // and with two's complement. neat. clears all except the bit we care about
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// now a binary search
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// we know masked is non-zero, and can start from 63
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//bit = 64u;
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//if(masked) bit--;
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bit = 63u;
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if(masked&0x00000000ffffffffull) bit -= 32u;
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if(masked&0x0000ffff0000ffffull) bit -= 16u;
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if(masked&0x00ff00ff00ff00ffull) bit -= 8u;
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if(masked&0x0f0f0f0f0f0f0f0full) bit -= 4u;
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if(masked&0x3333333333333333ull) bit -= 2u; // 0xb0011 repeated
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if(masked&0x5555555555555555ull) bit -= 1u; // 0xb0101 repeated
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return (word*64u) | bit;
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}
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return _size;
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}
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//BitMask& BitMask::operator&=(const BitMask& o) {}
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//BitMask& BitMask::operator|=(const BitMask& o) {}
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//BitMask& BitMask::operator^=(const BitMask& o) {}
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std::ostream& operator<<(std::ostream& strm, const BitMask& mask)
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{
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strm.put('{');
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bool first = true;
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for(auto bit : mask.onlySet()) {
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if(first) first = false;
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else strm<<", ";
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strm<<bit;
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}
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strm.put('}');
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return strm;
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}
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} // namespace pvxs
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