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//===--- Utility.h ----------------------------------------------*- C++ -*-===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//
// This file contains several utility classes used by the demangle library.
//===----------------------------------------------------------------------===//

#ifndef LLVM_DEMANGLE_UTILITY_H
#define LLVM_DEMANGLE_UTILITY_H

#include <cstring>

// Stream that AST nodes write their string representation into after the AST
// has been parsed.
class OutputStream {
  char *Buffer;
  size_t CurrentPosition;
  size_t BufferCapacity;

  // Ensure there is at least n more positions in buffer.
  void grow(size_t N) {
    if (N + CurrentPosition >= BufferCapacity) {
      BufferCapacity *= 2;
      if (BufferCapacity < N + CurrentPosition)
        BufferCapacity = N + CurrentPosition;
      Buffer = static_cast<char *>(std::realloc(Buffer, BufferCapacity));
    }
  }

public:
  OutputStream(char *StartBuf, size_t Size)
      : Buffer(StartBuf), CurrentPosition(0), BufferCapacity(Size) {}
  OutputStream() = default;
  void reset(char *Buffer_, size_t BufferCapacity_) {
    CurrentPosition = 0;
    Buffer = Buffer_;
    BufferCapacity = BufferCapacity_;
  }

  /// If a ParameterPackExpansion (or similar type) is encountered, the offset
  /// into the pack that we're currently printing.
  unsigned CurrentPackIndex = std::numeric_limits<unsigned>::max();
  unsigned CurrentPackMax = std::numeric_limits<unsigned>::max();

  OutputStream &operator+=(StringView R) {
    size_t Size = R.size();
    if (Size == 0)
      return *this;
    grow(Size);
    std::memmove(Buffer + CurrentPosition, R.begin(), Size);
    CurrentPosition += Size;
    return *this;
  }

  OutputStream &operator+=(char C) {
    grow(1);
    Buffer[CurrentPosition++] = C;
    return *this;
  }

  size_t getCurrentPosition() const { return CurrentPosition; }
  void setCurrentPosition(size_t NewPos) { CurrentPosition = NewPos; }

  char back() const {
    return CurrentPosition ? Buffer[CurrentPosition - 1] : '\0';
  }

  bool empty() const { return CurrentPosition == 0; }

  char *getBuffer() { return Buffer; }
  char *getBufferEnd() { return Buffer + CurrentPosition - 1; }
  size_t getBufferCapacity() { return BufferCapacity; }
};

template <class T> class SwapAndRestore {
  T &Restore;
  T OriginalValue;

public:
  SwapAndRestore(T &Restore_, T NewVal)
      : Restore(Restore_), OriginalValue(Restore) {
    Restore = std::move(NewVal);
  }
  ~SwapAndRestore() { Restore = std::move(OriginalValue); }

  SwapAndRestore(const SwapAndRestore &) = delete;
  SwapAndRestore &operator=(const SwapAndRestore &) = delete;
};

#endif
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