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120 lines
3.3 KiB
120 lines
3.3 KiB
// Copyright (c) 2018 Google LLC
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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#ifndef SOURCE_UTIL_BIT_VECTOR_H_
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#define SOURCE_UTIL_BIT_VECTOR_H_
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#include <cstdint>
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#include <iosfwd>
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#include <vector>
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namespace spvtools {
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namespace utils {
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// Implements a bit vector class.
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//
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// All bits default to zero, and the upper bound is 2^32-1.
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class BitVector {
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private:
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using BitContainer = uint64_t;
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enum { kBitContainerSize = 64 };
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enum { kInitialNumBits = 1024 };
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public:
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// Creates a bit vector contianing 0s.
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BitVector(uint32_t reserved_size = kInitialNumBits)
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: bits_((reserved_size - 1) / kBitContainerSize + 1, 0) {}
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// Sets the |i|th bit to 1. Returns the |i|th bit before it was set.
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bool Set(uint32_t i) {
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uint32_t element_index = i / kBitContainerSize;
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uint32_t bit_in_element = i % kBitContainerSize;
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if (element_index >= bits_.size()) {
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bits_.resize(element_index + 1, 0);
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}
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BitContainer original = bits_[element_index];
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BitContainer ith_bit = static_cast<BitContainer>(1) << bit_in_element;
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if ((original & ith_bit) != 0) {
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return true;
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} else {
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bits_[element_index] = original | ith_bit;
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return false;
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}
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}
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// Sets the |i|th bit to 0. Return the |i|th bit before it was cleared.
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bool Clear(uint32_t i) {
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uint32_t element_index = i / kBitContainerSize;
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uint32_t bit_in_element = i % kBitContainerSize;
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if (element_index >= bits_.size()) {
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return false;
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}
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BitContainer original = bits_[element_index];
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BitContainer ith_bit = static_cast<BitContainer>(1) << bit_in_element;
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if ((original & ith_bit) == 0) {
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return false;
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} else {
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bits_[element_index] = original & (~ith_bit);
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return true;
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}
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}
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// Returns the |i|th bit.
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bool Get(uint32_t i) const {
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uint32_t element_index = i / kBitContainerSize;
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uint32_t bit_in_element = i % kBitContainerSize;
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if (element_index >= bits_.size()) {
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return false;
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}
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return (bits_[element_index] &
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(static_cast<BitContainer>(1) << bit_in_element)) != 0;
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}
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// Returns true if every bit is 0.
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bool Empty() const {
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for (BitContainer b : bits_) {
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if (b != 0) {
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return false;
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}
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}
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return true;
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}
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// Print a report on the densicy of the bit vector, number of 1 bits, number
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// of bytes, and average bytes for 1 bit, to |out|.
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void ReportDensity(std::ostream& out);
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friend std::ostream& operator<<(std::ostream&, const BitVector&);
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// Performs a bitwise-or operation on |this| and |that|, storing the result in
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// |this|. Return true if |this| changed.
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bool Or(const BitVector& that);
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private:
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std::vector<BitContainer> bits_;
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};
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} // namespace utils
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} // namespace spvtools
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#endif // SOURCE_UTIL_BIT_VECTOR_H_
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