1 //===- llvm/ADT/IndexedMap.h - An index map implementation ------*- C++ -*-===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 ///
9 /// \file
10 /// This file implements an indexed map. The index map template takes two
11 /// types. The first is the mapped type and the second is a functor
12 /// that maps its argument to a size_t. On instantiation a "null" value
13 /// can be provided to be used as a "does not exist" indicator in the
14 /// map. A member function grow() is provided that given the value of
15 /// the maximally indexed key (the argument of the functor) makes sure
16 /// the map has enough space for it.
17 ///
18 //===----------------------------------------------------------------------===//
19 
20 #ifndef LLVM_ADT_INDEXEDMAP_H
21 #define LLVM_ADT_INDEXEDMAP_H
22 
23 #include "llvm/ADT/SmallVector.h"
24 #include "llvm/ADT/STLExtras.h"
25 #include <cassert>
26 
27 namespace llvm {
28 
29 template <typename T, typename ToIndexT = identity<unsigned>>
30   class IndexedMap {
31     using IndexT = typename ToIndexT::argument_type;
32     // Prefer SmallVector with zero inline storage over std::vector. IndexedMaps
33     // can grow very large and SmallVector grows more efficiently as long as T
34     // is trivially copyable.
35     using StorageT = SmallVector<T, 0>;
36 
37     StorageT storage_;
38     T nullVal_;
39     ToIndexT toIndex_;
40 
41   public:
42     IndexedMap() : nullVal_(T()) {}
43 
44     explicit IndexedMap(const T& val) : nullVal_(val) {}
45 
46     typename StorageT::reference operator[](IndexT n) {
47       assert(toIndex_(n) < storage_.size() && "index out of bounds!");
48       return storage_[toIndex_(n)];
49     }
50 
51     typename StorageT::const_reference operator[](IndexT n) const {
52       assert(toIndex_(n) < storage_.size() && "index out of bounds!");
53       return storage_[toIndex_(n)];
54     }
55 
56     void reserve(typename StorageT::size_type s) {
57       storage_.reserve(s);
58     }
59 
60     void resize(typename StorageT::size_type s) {
61       storage_.resize(s, nullVal_);
62     }
63 
64     void clear() {
65       storage_.clear();
66     }
67 
68     void grow(IndexT n) {
69       unsigned NewSize = toIndex_(n) + 1;
70       if (NewSize > storage_.size())
71         resize(NewSize);
72     }
73 
74     bool inBounds(IndexT n) const {
75       return toIndex_(n) < storage_.size();
76     }
77 
78     typename StorageT::size_type size() const {
79       return storage_.size();
80     }
81   };
82 
83 } // end namespace llvm
84 
85 #endif // LLVM_ADT_INDEXEDMAP_H
86