include/llvm/ADT/IndexedMap.h

   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