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