include/llvm/ADT/IndexedMap.h

//===- llvm/ADT/IndexedMap.h - An index map implementation ------*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
///
/// \file
/// This file implements an indexed map. The index map template takes two
/// types. The first is the mapped type and the second is a functor
/// that maps its argument to a size_t. On instantiation a "null" value
/// can be provided to be used as a "does not exist" indicator in the
/// map. A member function grow() is provided that given the value of
/// the maximally indexed key (the argument of the functor) makes sure
/// the map has enough space for it.
///
//===----------------------------------------------------------------------===//

#ifndef LLVM_ADT_INDEXEDMAP_H
#define LLVM_ADT_INDEXEDMAP_H

#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/STLExtras.h"
#include <cassert>

namespace llvm {

template <typename T, typename ToIndexT = identity<unsigned>>
  class IndexedMap {
    using IndexT = typename ToIndexT::argument_type;
    // Prefer SmallVector with zero inline storage over std::vector. IndexedMaps
    // can grow very large and SmallVector grows more efficiently as long as T
    // is trivially copyable.
    using StorageT = SmallVector<T, 0>;

    StorageT storage_;
    T nullVal_;
    ToIndexT toIndex_;

  public:
    IndexedMap() : nullVal_(T()) {}

    explicit IndexedMap(const T& val) : nullVal_(val) {}

    typename StorageT::reference operator[](IndexT n) {
      assert(toIndex_(n) < storage_.size() && "index out of bounds!");
      return storage_[toIndex_(n)];
    }

    typename StorageT::const_reference operator[](IndexT n) const {
      assert(toIndex_(n) < storage_.size() && "index out of bounds!");
      return storage_[toIndex_(n)];
    }

    void reserve(typename StorageT::size_type s) {
      storage_.reserve(s);
    }

    void resize(typename StorageT::size_type s) {
      storage_.resize(s, nullVal_);
    }

    void clear() {
      storage_.clear();
    }

    void grow(IndexT n) {
      unsigned NewSize = toIndex_(n) + 1;
      if (NewSize > storage_.size())
        resize(NewSize);
    }

    bool inBounds(IndexT n) const {
      return toIndex_(n) < storage_.size();
    }

    typename StorageT::size_type size() const {
      return storage_.size();
    }
  };

} // end namespace llvm

#endif // LLVM_ADT_INDEXEDMAP_H