Home | History | Annotate | Line # | Download | only in ADT 
      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