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https://github.com/dart-lang/sdk
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98 lines
2.6 KiB
C++
98 lines
2.6 KiB
C++
// Copyright (c) 2012, the Dart project authors. Please see the AUTHORS file
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// for details. All rights reserved. Use of this source code is governed by a
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// BSD-style license that can be found in the LICENSE file.
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#ifndef RUNTIME_VM_BIT_SET_H_
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#define RUNTIME_VM_BIT_SET_H_
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#include "platform/utils.h"
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#include "vm/globals.h"
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namespace dart {
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// Just like its namesake in the STL, a BitSet object contains a fixed
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// length sequence of bits.
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template <intptr_t N>
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class BitSet {
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public:
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BitSet() { Reset(); }
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void Set(intptr_t i, bool value) {
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ASSERT(i >= 0);
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ASSERT(i < N);
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uword mask = (static_cast<uword>(1) << (i & (kBitsPerWord - 1)));
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if (value) {
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data_[i >> kBitsPerWordLog2] |= mask;
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} else {
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data_[i >> kBitsPerWordLog2] &= ~mask;
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}
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}
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bool Test(intptr_t i) const {
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ASSERT(i >= 0);
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ASSERT(i < N);
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uword mask = (static_cast<uword>(1) << (i & (kBitsPerWord - 1)));
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return (data_[i >> kBitsPerWordLog2] & mask) != 0;
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}
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intptr_t Next(intptr_t i) const {
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ASSERT(i >= 0);
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ASSERT(i < N);
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intptr_t w = i >> kBitsPerWordLog2;
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uword mask = ~static_cast<uword>(0) << (i & (kBitsPerWord - 1));
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if ((data_[w] & mask) != 0) {
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uword tz = Utils::CountTrailingZeros(data_[w] & mask);
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return (w << kBitsPerWordLog2) + tz;
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}
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while (++w < kLengthInWords) {
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if (data_[w] != 0) {
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return (w << kBitsPerWordLog2) + Utils::CountTrailingZeros(data_[w]);
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}
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}
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return -1;
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}
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intptr_t Last() const {
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for (int w = kLengthInWords - 1; w >= 0; --w) {
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uword d = data_[w];
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if (d != 0) {
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return ((w + 1) << kBitsPerWordLog2) - Utils::CountLeadingZeros(d) - 1;
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}
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}
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return -1;
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}
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intptr_t ClearLastAndFindPrevious(intptr_t current_last) {
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ASSERT(Test(current_last));
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ASSERT(Last() == current_last);
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intptr_t w = current_last >> kBitsPerWordLog2;
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uword bits = data_[w];
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// Clear the current last.
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bits ^= (static_cast<uword>(1) << (current_last & (kBitsPerWord - 1)));
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data_[w] = bits;
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// Search backwards for a non-zero word.
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while (bits == 0 && w > 0) {
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bits = data_[--w];
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}
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if (bits == 0) {
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// None found.
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return -1;
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} else {
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// Bitlength incl. w, minus leading zeroes of w, minus 1 to 0-based index.
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return ((w + 1) << kBitsPerWordLog2) - Utils::CountLeadingZeros(bits) - 1;
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}
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}
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void Reset() { memset(data_, 0, sizeof(data_)); }
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intptr_t Size() const { return N; }
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private:
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static const int kLengthInWords = 1 + ((N - 1) / kBitsPerWord);
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uword data_[kLengthInWords];
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};
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} // namespace dart
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#endif // RUNTIME_VM_BIT_SET_H_
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