kc3-lang/angle/src/common/BitSetIterator.h

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• Author : Jamie Madill
  Date : 2016-10-31 12:17:19
  Hash : 60e6edfa
  Message : Make ASSERT reference the conditional expression. This should prevent further unexpected bot breakage due to unreferenced variables in the ASSERT expression. Also remove the no longer needed variable referencing macro. BUG=angleproject:1586 Change-Id: I127695165bdfe39c51fe8d17e00daf6bf2fa8252 Reviewed-on: https://chromium-review.googlesource.com/404948 Reviewed-by: Jamie Madill <jmadill@chromium.org> Commit-Queue: Jamie Madill <jmadill@chromium.org>

• src/common/BitSetIterator.h

• //
  // Copyright 2015 The ANGLE Project Authors. All rights reserved.
  // Use of this source code is governed by a BSD-style license that can be
  // found in the LICENSE file.
  //
  // BitSetIterator:
  //   A helper class to quickly bitscan bitsets for set bits.
  //
  
  #ifndef COMMON_BITSETITERATOR_H_
  #define COMMON_BITSETITERATOR_H_
  
  #include <stdint.h>
  
  #include <bitset>
  
  #include "common/angleutils.h"
  #include "common/debug.h"
  #include "common/mathutil.h"
  #include "common/platform.h"
  
  namespace angle
  {
  template <size_t N>
  class BitSetIterator final
  {
    public:
      BitSetIterator(const std::bitset<N> &bitset);
      BitSetIterator(const BitSetIterator &other);
      BitSetIterator &operator=(const BitSetIterator &other);
  
      class Iterator final
      {
        public:
          Iterator(const std::bitset<N> &bits);
          Iterator &operator++();
  
          bool operator==(const Iterator &other) const;
          bool operator!=(const Iterator &other) const;
          unsigned long operator*() const { return mCurrentBit; }
  
        private:
          unsigned long getNextBit();
  
          static const size_t BitsPerWord = sizeof(unsigned long) * 8;
          std::bitset<N> mBits;
          unsigned long mCurrentBit;
          unsigned long mOffset;
      };
  
      Iterator begin() const { return Iterator(mBits); }
      Iterator end() const { return Iterator(std::bitset<N>(0)); }
  
    private:
      const std::bitset<N> mBits;
  };
  
  template <size_t N>
  BitSetIterator<N>::BitSetIterator(const std::bitset<N> &bitset)
      : mBits(bitset)
  {
  }
  
  template <size_t N>
  BitSetIterator<N>::BitSetIterator(const BitSetIterator &other)
      : mBits(other.mBits)
  {
  }
  
  template <size_t N>
  BitSetIterator<N> &BitSetIterator<N>::operator=(const BitSetIterator &other)
  {
      mBits = other.mBits;
      return *this;
  }
  
  template <size_t N>
  BitSetIterator<N>::Iterator::Iterator(const std::bitset<N> &bits)
      : mBits(bits), mCurrentBit(0), mOffset(0)
  {
      if (bits.any())
      {
          mCurrentBit = getNextBit();
      }
      else
      {
          mOffset = static_cast<unsigned long>(rx::roundUp(N, BitsPerWord));
      }
  }
  
  template <size_t N>
  typename BitSetIterator<N>::Iterator &BitSetIterator<N>::Iterator::operator++()
  {
      ASSERT(mBits.any());
      mBits.set(mCurrentBit - mOffset, 0);
      mCurrentBit = getNextBit();
      return *this;
  }
  
  inline unsigned long ScanForward(unsigned long bits)
  {
      ASSERT(bits != 0);
  #if defined(ANGLE_PLATFORM_WINDOWS)
      unsigned long firstBitIndex = 0ul;
      unsigned char ret = _BitScanForward(&firstBitIndex, bits);
      ASSERT(ret != 0);
      return firstBitIndex;
  #elif defined(ANGLE_PLATFORM_POSIX)
      return static_cast<unsigned long>(__builtin_ctzl(bits));
  #else
  #error Please implement bit-scan-forward for your platform!
  #endif
  }
  
  template <size_t N>
  bool BitSetIterator<N>::Iterator::operator==(const Iterator &other) const
  {
      return mOffset == other.mOffset && mBits == other.mBits;
  }
  
  template <size_t N>
  bool BitSetIterator<N>::Iterator::operator!=(const Iterator &other) const
  {
      return !(*this == other);
  }
  
  template <size_t N>
  unsigned long BitSetIterator<N>::Iterator::getNextBit()
  {
      static std::bitset<N> wordMask(std::numeric_limits<unsigned long>::max());
  
      while (mOffset < N)
      {
          unsigned long wordBits = (mBits & wordMask).to_ulong();
          if (wordBits != 0ul)
          {
              return ScanForward(wordBits) + mOffset;
          }
  
          mBits >>= BitsPerWord;
          mOffset += BitsPerWord;
      }
      return 0;
  }
  
  // Helper to avoid needing to specify the template parameter size
  template <size_t N>
  BitSetIterator<N> IterateBitSet(const std::bitset<N> &bitset)
  {
      return BitSetIterator<N>(bitset);
  }
  
  }  // angle
  
  #endif  // COMMON_BITSETITERATOR_H_