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 "llvm/ADT/identity.h"
26 #include <cassert>
27 
28 namespace llvm {
29 
30 template <typename T, typename ToIndexT = identity<unsigned>>
31   class IndexedMap {
32     using IndexT = typename ToIndexT::argument_type;
33     // Prefer SmallVector with zero inline storage over std::vector. IndexedMaps
34     // can grow very large and SmallVector grows more efficiently as long as T
35     // is trivially copyable.
36     using StorageT = SmallVector<T, 0>;
37 
38     StorageT storage_;
39     T nullVal_;
40     ToIndexT toIndex_;
41 
42   public:
43     IndexedMap() : nullVal_(T()) {}
44 
45     explicit IndexedMap(const T& val) : nullVal_(val) {}
46 
47     typename StorageT::reference operator[](IndexT n) {
48       assert(toIndex_(n) < storage_.size() && "index out of bounds!");
49       return storage_[toIndex_(n)];
50     }
51 
52     typename StorageT::const_reference operator[](IndexT n) const {
53       assert(toIndex_(n) < storage_.size() && "index out of bounds!");
54       return storage_[toIndex_(n)];
55     }
56 
57     void reserve(typename StorageT::size_type s) {
58       storage_.reserve(s);
59     }
60 
61     void resize(typename StorageT::size_type s) {
62       storage_.resize(s, nullVal_);
63     }
64 
65     void clear() {
66       storage_.clear();
67     }
68 
69     void grow(IndexT n) {
70       unsigned NewSize = toIndex_(n) + 1;
71       if (NewSize > storage_.size())
72         resize(NewSize);
73     }
74 
75     bool inBounds(IndexT n) const {
76       return toIndex_(n) < storage_.size();
77     }
78 
79     typename StorageT::size_type size() const {
80       return storage_.size();
81     }
82   };
83 
84 } // end namespace llvm
85 
86 #endif // LLVM_ADT_INDEXEDMAP_H
87