SetVector.h

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//===- llvm/ADT/SetVector.h - Set with insert order iteration ---*- C++ -*-===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements a set that has insertion order iteration
// characteristics. This is useful for keeping a set of things that need to be
// visited later but in a deterministic order (insertion order). The interface
// is purposefully minimal.
//
// This file defines SetVector and SmallSetVector, which performs no allocations
// if the SetVector has less than a certain number of elements.
//
//===----------------------------------------------------------------------===//

#ifndef LLVM_ADT_SETVECTOR_H
#define LLVM_ADT_SETVECTOR_H

#include "llvm/ADT/SmallSet.h"
#include <algorithm>
#include <cassert>
#include <vector>

namespace llvm {

/// \brief A vector that has set insertion semantics.
///
/// This adapter class provides a way to keep a set of things that also has the
/// property of a deterministic iteration order. The order of iteration is the
/// order of insertion.
template <typename T, typename Vector = std::vector<T>,
                      typename Set = SmallSet<T, 16> >
class SetVector {
public:
  typedef T value_type;
  typedef T key_type;
  typedef T& reference;
  typedef const T& const_reference;
  typedef Set set_type;
  typedef Vector vector_type;
  typedef typename vector_type::const_iterator iterator;
  typedef typename vector_type::const_iterator const_iterator;
  typedef typename vector_type::size_type size_type;

  /// \brief Construct an empty SetVector
  SetVector() {}

  /// \brief Initialize a SetVector with a range of elements
  template<typename It>
  SetVector(It Start, It End) {
    insert(Start, End);
  }

  /// \brief Determine if the SetVector is empty or not.
  bool empty() const {
    return vector_.empty();
  }

  /// \brief Determine the number of elements in the SetVector.
  size_type size() const {
    return vector_.size();
  }

  /// \brief Get an iterator to the beginning of the SetVector.
  iterator begin() {
    return vector_.begin();
  }

  /// \brief Get a const_iterator to the beginning of the SetVector.
  const_iterator begin() const {
    return vector_.begin();
  }

  /// \brief Get an iterator to the end of the SetVector.
  iterator end() {
    return vector_.end();
  }

  /// \brief Get a const_iterator to the end of the SetVector.
  const_iterator end() const {
    return vector_.end();
  }

  /// \brief Return the last element of the SetVector.
  const T &back() const {
    assert(!empty() && "Cannot call back() on empty SetVector!");
    return vector_.back();
  }

  /// \brief Index into the SetVector.
  const_reference operator[](size_type n) const {
    assert(n < vector_.size() && "SetVector access out of range!");
    return vector_[n];
  }

  /// \brief Insert a new element into the SetVector.
  /// \returns true iff the element was inserted into the SetVector.
  bool insert(const value_type &X) {
    bool result = set_.insert(X);
    if (result)
      vector_.push_back(X);
    return result;
  }

  /// \brief Insert a range of elements into the SetVector.
  template<typename It>
  void insert(It Start, It End) {
    for (; Start != End; ++Start)
      if (set_.insert(*Start))
        vector_.push_back(*Start);
  }

  /// \brief Remove an item from the set vector.
  bool remove(const value_type& X) {
    if (set_.erase(X)) {
      typename vector_type::iterator I =
        std::find(vector_.begin(), vector_.end(), X);
      assert(I != vector_.end() && "Corrupted SetVector instances!");
      vector_.erase(I);
      return true;
    }
    return false;
  }

  /// \brief Remove items from the set vector based on a predicate function.
  ///
  /// This is intended to be equivalent to the following code, if we could
  /// write it:
  ///
  /// \code
  ///   V.erase(std::remove_if(V.begin(), V.end(), P), V.end());
  /// \endcode
  ///
  /// However, SetVector doesn't expose non-const iterators, making any
  /// algorithm like remove_if impossible to use.
  ///
  /// \returns true if any element is removed.
  template <typename UnaryPredicate>
  bool remove_if(UnaryPredicate P) {
    typename vector_type::iterator I
      = std::remove_if(vector_.begin(), vector_.end(),
                       TestAndEraseFromSet<UnaryPredicate>(P, set_));
    if (I == vector_.end())
      return false;
    vector_.erase(I, vector_.end());
    return true;
  }


  /// \brief Count the number of elements of a given key in the SetVector.
  /// \returns 0 if the element is not in the SetVector, 1 if it is.
  size_type count(const key_type &key) const {
    return set_.count(key);
  }

  /// \brief Completely clear the SetVector
  void clear() {
    set_.clear();
    vector_.clear();
  }

  /// \brief Remove the last element of the SetVector.
  void pop_back() {
    assert(!empty() && "Cannot remove an element from an empty SetVector!");
    set_.erase(back());
    vector_.pop_back();
  }
  
  T LLVM_ATTRIBUTE_UNUSED_RESULT pop_back_val() {
    T Ret = back();
    pop_back();
    return Ret;
  }

  bool operator==(const SetVector &that) const {
    return vector_ == that.vector_;
  }

  bool operator!=(const SetVector &that) const {
    return vector_ != that.vector_;
  }

private:
  /// \brief A wrapper predicate designed for use with std::remove_if.
  ///
  /// This predicate wraps a predicate suitable for use with std::remove_if to
  /// call set_.erase(x) on each element which is slated for removal.
  template <typename UnaryPredicate>
  class TestAndEraseFromSet {
    UnaryPredicate P;
    set_type &set_;

  public:
    TestAndEraseFromSet(UnaryPredicate P, set_type &set_) : P(P), set_(set_) {}

    template <typename ArgumentT>
    bool operator()(const ArgumentT &Arg) {
      if (P(Arg)) {
        set_.erase(Arg);
        return true;
      }
      return false;
    }
  };

  set_type set_;         ///< The set.
  vector_type vector_;   ///< The vector.
};

/// \brief A SetVector that performs no allocations if smaller than
/// a certain size.
template <typename T, unsigned N>
class SmallSetVector : public SetVector<T, SmallVector<T, N>, SmallSet<T, N> > {
public:
  SmallSetVector() {}

  /// \brief Initialize a SmallSetVector with a range of elements
  template<typename It>
  SmallSetVector(It Start, It End) {
    this->insert(Start, End);
  }
};

} // End llvm namespace

// vim: sw=2 ai
#endif