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//===- llvm/ADT/MapVector.h - Map w/ deterministic value order --*- 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 a map that provides insertion order iteration. The
/// interface is purposefully minimal. The key is assumed to be cheap to copy
/// and 2 copies are kept, one for indexing in a DenseMap, one for iteration in
/// a SmallVector.
///
//===----------------------------------------------------------------------===//
#ifndef LLVM_ADT_MAPVECTOR_H
#define LLVM_ADT_MAPVECTOR_H
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/SmallVector.h"
#include <cassert>
#include <cstddef>
#include <iterator>
#include <type_traits>
#include <utility>
namespace llvm {
/// This class implements a map that also provides access to all stored values
/// in a deterministic order. The values are kept in a SmallVector<*, 0> and the
/// mapping is done with DenseMap from Keys to indexes in that vector.
template <typename KeyT, typename ValueT,
typename MapType = DenseMap<KeyT, unsigned>,
typename VectorType = SmallVector<std::pair<KeyT, ValueT>, 0>>
class MapVector {
MapType Map;
VectorType Vector;
static_assert(
std::is_integral_v<typename MapType::mapped_type>,
"The mapped_type of the specified Map must be an integral type");
public:
using key_type = KeyT;
using value_type = typename VectorType::value_type;
using size_type = typename VectorType::size_type;
using iterator = typename VectorType::iterator;
using const_iterator = typename VectorType::const_iterator;
using reverse_iterator = typename VectorType::reverse_iterator;
using const_reverse_iterator = typename VectorType::const_reverse_iterator;
/// Clear the MapVector and return the underlying vector.
VectorType takeVector() {
Map.clear();
return std::move(Vector);
}
size_type size() const { return Vector.size(); }
/// Grow the MapVector so that it can contain at least \p NumEntries items
/// before resizing again.
void reserve(size_type NumEntries) {
Map.reserve(NumEntries);
Vector.reserve(NumEntries);
}
iterator begin() { return Vector.begin(); }
const_iterator begin() const { return Vector.begin(); }
iterator end() { return Vector.end(); }
const_iterator end() const { return Vector.end(); }
reverse_iterator rbegin() { return Vector.rbegin(); }
const_reverse_iterator rbegin() const { return Vector.rbegin(); }
reverse_iterator rend() { return Vector.rend(); }
const_reverse_iterator rend() const { return Vector.rend(); }
bool empty() const {
return Vector.empty();
}
std::pair<KeyT, ValueT> &front() { return Vector.front(); }
const std::pair<KeyT, ValueT> &front() const { return Vector.front(); }
std::pair<KeyT, ValueT> &back() { return Vector.back(); }
const std::pair<KeyT, ValueT> &back() const { return Vector.back(); }
void clear() {
Map.clear();
Vector.clear();
}
void swap(MapVector &RHS) {
std::swap(Map, RHS.Map);
std::swap(Vector, RHS.Vector);
}
ValueT &operator[](const KeyT &Key) {
std::pair<KeyT, typename MapType::mapped_type> Pair = std::make_pair(Key, 0);
std::pair<typename MapType::iterator, bool> Result = Map.insert(Pair);
auto &I = Result.first->second;
if (Result.second) {
Vector.push_back(std::make_pair(Key, ValueT()));
I = Vector.size() - 1;
}
return Vector[I].second;
}
// Returns a copy of the value. Only allowed if ValueT is copyable.
ValueT lookup(const KeyT &Key) const {
static_assert(std::is_copy_constructible_v<ValueT>,
"Cannot call lookup() if ValueT is not copyable.");
typename MapType::const_iterator Pos = Map.find(Key);
return Pos == Map.end()? ValueT() : Vector[Pos->second].second;
}
template <typename... Ts>
std::pair<iterator, bool> try_emplace(const KeyT &Key, Ts &&...Args) {
auto [It, Inserted] = Map.insert(std::make_pair(Key, 0));
if (Inserted) {
It->second = Vector.size();
Vector.emplace_back(std::piecewise_construct, std::forward_as_tuple(Key),
std::forward_as_tuple(std::forward<Ts>(Args)...));
return std::make_pair(std::prev(end()), true);
}
return std::make_pair(begin() + It->second, false);
}
template <typename... Ts>
std::pair<iterator, bool> try_emplace(KeyT &&Key, Ts &&...Args) {
auto [It, Inserted] = Map.insert(std::make_pair(Key, 0));
if (Inserted) {
It->second = Vector.size();
Vector.emplace_back(std::piecewise_construct,
std::forward_as_tuple(std::move(Key)),
std::forward_as_tuple(std::forward<Ts>(Args)...));
return std::make_pair(std::prev(end()), true);
}
return std::make_pair(begin() + It->second, false);
}
std::pair<iterator, bool> insert(const std::pair<KeyT, ValueT> &KV) {
return try_emplace(KV.first, KV.second);
}
std::pair<iterator, bool> insert(std::pair<KeyT, ValueT> &&KV) {
return try_emplace(std::move(KV.first), std::move(KV.second));
}
template <typename V>
std::pair<iterator, bool> insert_or_assign(const KeyT &Key, V &&Val) {
auto Ret = try_emplace(Key, std::forward<V>(Val));
if (!Ret.second)
Ret.first->second = std::forward<V>(Val);
return Ret;
}
template <typename V>
std::pair<iterator, bool> insert_or_assign(KeyT &&Key, V &&Val) {
auto Ret = try_emplace(std::move(Key), std::forward<V>(Val));
if (!Ret.second)
Ret.first->second = std::forward<V>(Val);
return Ret;
}
bool contains(const KeyT &Key) const { return Map.find(Key) != Map.end(); }
size_type count(const KeyT &Key) const { return contains(Key) ? 1 : 0; }
iterator find(const KeyT &Key) {
typename MapType::const_iterator Pos = Map.find(Key);
return Pos == Map.end()? Vector.end() :
(Vector.begin() + Pos->second);
}
const_iterator find(const KeyT &Key) const {
typename MapType::const_iterator Pos = Map.find(Key);
return Pos == Map.end()? Vector.end() :
(Vector.begin() + Pos->second);
}
/// Remove the last element from the vector.
void pop_back() {
typename MapType::iterator Pos = Map.find(Vector.back().first);
Map.erase(Pos);
Vector.pop_back();
}
/// Remove the element given by Iterator.
///
/// Returns an iterator to the element following the one which was removed,
/// which may be end().
///
/// \note This is a deceivingly expensive operation (linear time). It's
/// usually better to use \a remove_if() if possible.
typename VectorType::iterator erase(typename VectorType::iterator Iterator) {
Map.erase(Iterator->first);
auto Next = Vector.erase(Iterator);
if (Next == Vector.end())
return Next;
// Update indices in the map.
size_t Index = Next - Vector.begin();
for (auto &I : Map) {
assert(I.second != Index && "Index was already erased!");
if (I.second > Index)
--I.second;
}
return Next;
}
/// Remove all elements with the key value Key.
///
/// Returns the number of elements removed.
size_type erase(const KeyT &Key) {
auto Iterator = find(Key);
if (Iterator == end())
return 0;
erase(Iterator);
return 1;
}
/// Remove the elements that match the predicate.
///
/// Erase all elements that match \c Pred in a single pass. Takes linear
/// time.
template <class Predicate> void remove_if(Predicate Pred);
};
template <typename KeyT, typename ValueT, typename MapType, typename VectorType>
template <class Function>
void MapVector<KeyT, ValueT, MapType, VectorType>::remove_if(Function Pred) {
auto O = Vector.begin();
for (auto I = O, E = Vector.end(); I != E; ++I) {
if (Pred(*I)) {
// Erase from the map.
Map.erase(I->first);
continue;
}
if (I != O) {
// Move the value and update the index in the map.
*O = std::move(*I);
Map[O->first] = O - Vector.begin();
}
++O;
}
// Erase trailing entries in the vector.
Vector.erase(O, Vector.end());
}
/// A MapVector that performs no allocations if smaller than a certain
/// size.
template <typename KeyT, typename ValueT, unsigned N>
struct SmallMapVector
: MapVector<KeyT, ValueT, SmallDenseMap<KeyT, unsigned, N>,
SmallVector<std::pair<KeyT, ValueT>, N>> {
};
} // end namespace llvm
#endif // LLVM_ADT_MAPVECTOR_H
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