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 //===- ASTVector.h - Vector that uses ASTContext for allocation ---*- C++ -*-=//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 //
 //  This file provides ASTVector, a vector  ADT whose contents are
 //  allocated using the allocator associated with an ASTContext..
 //
 //===----------------------------------------------------------------------===//
 
 // FIXME: Most of this is copy-and-paste from BumpVector.h and SmallVector.h.
 // We can refactor this core logic into something common.
 
 #ifndef LLVM_CLANG_AST_ASTVECTOR_H
 #define LLVM_CLANG_AST_ASTVECTOR_H
 
 #include "clang/AST/ASTContextAllocate.h"
 #include "llvm/ADT/PointerIntPair.h"
 #include <algorithm>
 #include <cassert>
 #include <cstddef>
 #include <cstring>
 #include <iterator>
 #include <memory>
 #include <type_traits>
 #include <utility>
 
 namespace clang {
 
 class ASTContext;
 
 template<typename T>
 class ASTVector {
 private:
   T *Begin = nullptr;
   T *End = nullptr;
   llvm::PointerIntPair<T *, 1, bool> Capacity;
 
   void setEnd(T *P) { this->End = P; }
 
 protected:
   // Make a tag bit available to users of this class.
   // FIXME: This is a horrible hack.
   bool getTag() const { return Capacity.getInt(); }
   void setTag(bool B) { Capacity.setInt(B); }
 
 public:
   // Default ctor - Initialize to empty.
   ASTVector() : Capacity(nullptr, false) {}
 
   ASTVector(ASTVector &&O) : Begin(O.Begin), End(O.End), Capacity(O.Capacity) {
     O.Begin = O.End = nullptr;
     O.Capacity.setPointer(nullptr);
     O.Capacity.setInt(false);
   }
 
   ASTVector(const ASTContext &C, unsigned N) : Capacity(nullptr, false) {
     reserve(C, N);
   }
 
   ASTVector &operator=(ASTVector &&RHS) {
     ASTVector O(std::move(RHS));
 
     using std::swap;
 
     swap(Begin, O.Begin);
     swap(End, O.End);
     swap(Capacity, O.Capacity);
     return *this;
   }
 
   ~ASTVector() {
     if (std::is_class<T>::value) {
       // Destroy the constructed elements in the vector.
       destroy_range(Begin, End);
     }
   }
 
   using size_type = size_t;
   using difference_type = ptrdiff_t;
   using value_type = T;
   using iterator = T *;
   using const_iterator = const T *;
 
   using const_reverse_iterator = std::reverse_iterator<const_iterator>;
   using reverse_iterator = std::reverse_iterator<iterator>;
 
   using reference = T &;
   using const_reference = const T &;
   using pointer = T *;
   using const_pointer = const T *;
 
   // forward iterator creation methods.
   iterator begin() { return Begin; }
   const_iterator begin() const { return Begin; }
   iterator end() { return End; }
   const_iterator end() const { return End; }
 
   // reverse iterator creation methods.
   reverse_iterator rbegin()            { return reverse_iterator(end()); }
   const_reverse_iterator rbegin() const{ return const_reverse_iterator(end()); }
   reverse_iterator rend()              { return reverse_iterator(begin()); }
   const_reverse_iterator rend() const { return const_reverse_iterator(begin());}
 
   bool empty() const { return Begin == End; }
   size_type size() const { return End-Begin; }
 
   reference operator[](unsigned idx) {
     assert(Begin + idx < End);
     return Begin[idx];
   }
   const_reference operator[](unsigned idx) const {
     assert(Begin + idx < End);
     return Begin[idx];
   }
 
   reference front() {
     return begin()[0];
   }
   const_reference front() const {
     return begin()[0];
   }
 
   reference back() {
     return end()[-1];
   }
   const_reference back() const {
     return end()[-1];
   }
 
   void pop_back() {
     --End;
     End->~T();
   }
 
   T pop_back_val() {
     T Result = back();
     pop_back();
     return Result;
   }
 
   void clear() {
     if (std::is_class<T>::value) {
       destroy_range(Begin, End);
     }
     End = Begin;
   }
 
   /// data - Return a pointer to the vector's buffer, even if empty().
   pointer data() {
     return pointer(Begin);
   }
 
   /// data - Return a pointer to the vector's buffer, even if empty().
   const_pointer data() const {
     return const_pointer(Begin);
   }
 
   void push_back(const_reference Elt, const ASTContext &C) {
     if (End < this->capacity_ptr()) {
     Retry:
       new (End) T(Elt);
       ++End;
       return;
     }
     grow(C);
     goto Retry;
   }
 
   void reserve(const ASTContext &C, unsigned N) {
     if (unsigned(this->capacity_ptr()-Begin) < N)
       grow(C, N);
   }
 
   /// capacity - Return the total number of elements in the currently allocated
   /// buffer.
   size_t capacity() const { return this->capacity_ptr() - Begin; }
 
   /// append - Add the specified range to the end of the SmallVector.
   template<typename in_iter>
   void append(const ASTContext &C, in_iter in_start, in_iter in_end) {
     size_type NumInputs = std::distance(in_start, in_end);
 
     if (NumInputs == 0)
       return;
 
     // Grow allocated space if needed.
     if (NumInputs > size_type(this->capacity_ptr()-this->end()))
       this->grow(C, this->size()+NumInputs);
 
     // Copy the new elements over.
     // TODO: NEED To compile time dispatch on whether in_iter is a random access
     // iterator to use the fast uninitialized_copy.
     std::uninitialized_copy(in_start, in_end, this->end());
     this->setEnd(this->end() + NumInputs);
   }
 
   /// append - Add the specified range to the end of the SmallVector.
   void append(const ASTContext &C, size_type NumInputs, const T &Elt) {
     // Grow allocated space if needed.
     if (NumInputs > size_type(this->capacity_ptr()-this->end()))
       this->grow(C, this->size()+NumInputs);
 
     // Copy the new elements over.
     std::uninitialized_fill_n(this->end(), NumInputs, Elt);
     this->setEnd(this->end() + NumInputs);
   }
 
   /// uninitialized_copy - Copy the range [I, E) onto the uninitialized memory
   /// starting with "Dest", constructing elements into it as needed.
   template<typename It1, typename It2>
   static void uninitialized_copy(It1 I, It1 E, It2 Dest) {
     std::uninitialized_copy(I, E, Dest);
   }
 
   iterator insert(const ASTContext &C, iterator I, const T &Elt) {
     if (I == this->end()) {  // Important special case for empty vector.
       push_back(Elt, C);
       return this->end()-1;
     }
 
     if (this->End < this->capacity_ptr()) {
     Retry:
       new (this->end()) T(this->back());
       this->setEnd(this->end()+1);
       // Push everything else over.
       std::copy_backward(I, this->end()-1, this->end());
       *I = Elt;
       return I;
     }
     size_t EltNo = I-this->begin();
     this->grow(C);
     I = this->begin()+EltNo;
     goto Retry;
   }
 
   iterator insert(const ASTContext &C, iterator I, size_type NumToInsert,
                   const T &Elt) {
     // Convert iterator to elt# to avoid invalidating iterator when we reserve()
     size_t InsertElt = I - this->begin();
 
     if (I == this->end()) { // Important special case for empty vector.
       append(C, NumToInsert, Elt);
       return this->begin() + InsertElt;
     }
 
     // Ensure there is enough space.
     reserve(C, static_cast<unsigned>(this->size() + NumToInsert));
 
     // Uninvalidate the iterator.
     I = this->begin()+InsertElt;
 
     // If there are more elements between the insertion point and the end of the
     // range than there are being inserted, we can use a simple approach to
     // insertion.  Since we already reserved space, we know that this won't
     // reallocate the vector.
     if (size_t(this->end()-I) >= NumToInsert) {
       T *OldEnd = this->end();
       append(C, this->end()-NumToInsert, this->end());
 
       // Copy the existing elements that get replaced.
       std::copy_backward(I, OldEnd-NumToInsert, OldEnd);
 
       std::fill_n(I, NumToInsert, Elt);
       return I;
     }
 
     // Otherwise, we're inserting more elements than exist already, and we're
     // not inserting at the end.
 
     // Copy over the elements that we're about to overwrite.
     T *OldEnd = this->end();
     this->setEnd(this->end() + NumToInsert);
     size_t NumOverwritten = OldEnd-I;
     this->uninitialized_copy(I, OldEnd, this->end()-NumOverwritten);
 
     // Replace the overwritten part.
     std::fill_n(I, NumOverwritten, Elt);
 
     // Insert the non-overwritten middle part.
     std::uninitialized_fill_n(OldEnd, NumToInsert-NumOverwritten, Elt);
     return I;
   }
 
   template<typename ItTy>
   iterator insert(const ASTContext &C, iterator I, ItTy From, ItTy To) {
     // Convert iterator to elt# to avoid invalidating iterator when we reserve()
     size_t InsertElt = I - this->begin();
 
     if (I == this->end()) { // Important special case for empty vector.
       append(C, From, To);
       return this->begin() + InsertElt;
     }
 
     size_t NumToInsert = std::distance(From, To);
 
     // Ensure there is enough space.
     reserve(C, static_cast<unsigned>(this->size() + NumToInsert));
 
     // Uninvalidate the iterator.
     I = this->begin()+InsertElt;
 
     // If there are more elements between the insertion point and the end of the
     // range than there are being inserted, we can use a simple approach to
     // insertion.  Since we already reserved space, we know that this won't
     // reallocate the vector.
     if (size_t(this->end()-I) >= NumToInsert) {
       T *OldEnd = this->end();
       append(C, this->end()-NumToInsert, this->end());
 
       // Copy the existing elements that get replaced.
       std::copy_backward(I, OldEnd-NumToInsert, OldEnd);
 
       std::copy(From, To, I);
       return I;
     }
 
     // Otherwise, we're inserting more elements than exist already, and we're
     // not inserting at the end.
 
     // Copy over the elements that we're about to overwrite.
     T *OldEnd = this->end();
     this->setEnd(this->end() + NumToInsert);
     size_t NumOverwritten = OldEnd-I;
     this->uninitialized_copy(I, OldEnd, this->end()-NumOverwritten);
 
     // Replace the overwritten part.
     for (; NumOverwritten > 0; --NumOverwritten) {
       *I = *From;
       ++I; ++From;
     }
 
     // Insert the non-overwritten middle part.
     this->uninitialized_copy(From, To, OldEnd);
     return I;
   }
 
   void resize(const ASTContext &C, unsigned N, const T &NV) {
     if (N < this->size()) {
       this->destroy_range(this->begin()+N, this->end());
       this->setEnd(this->begin()+N);
     } else if (N > this->size()) {
       if (this->capacity() < N)
         this->grow(C, N);
       construct_range(this->end(), this->begin()+N, NV);
       this->setEnd(this->begin()+N);
     }
   }
 
 private:
   /// grow - double the size of the allocated memory, guaranteeing space for at
   /// least one more element or MinSize if specified.
   void grow(const ASTContext &C, size_type MinSize = 1);
 
   void construct_range(T *S, T *E, const T &Elt) {
     for (; S != E; ++S)
       new (S) T(Elt);
   }
 
   void destroy_range(T *S, T *E) {
     while (S != E) {
       --E;
       E->~T();
     }
   }
 
 protected:
   const_iterator capacity_ptr() const {
     return (iterator) Capacity.getPointer();
   }
 
   iterator capacity_ptr() { return (iterator)Capacity.getPointer(); }
 };
 
 // Define this out-of-line to dissuade the C++ compiler from inlining it.
 template <typename T>
 void ASTVector<T>::grow(const ASTContext &C, size_t MinSize) {
   size_t CurCapacity = this->capacity();
   size_t CurSize = size();
   size_t NewCapacity = 2*CurCapacity;
   if (NewCapacity < MinSize)
     NewCapacity = MinSize;
 
   // Allocate the memory from the ASTContext.
   T *NewElts = new (C, alignof(T)) T[NewCapacity];
 
   // Copy the elements over.
   if (Begin != End) {
     if (std::is_class<T>::value) {
       std::uninitialized_copy(Begin, End, NewElts);
       // Destroy the original elements.
       destroy_range(Begin, End);
     } else {
       // Use memcpy for PODs (std::uninitialized_copy optimizes to memmove).
       memcpy(NewElts, Begin, CurSize * sizeof(T));
     }
   }
 
   // ASTContext never frees any memory.
   Begin = NewElts;
   End = NewElts+CurSize;
   Capacity.setPointer(Begin+NewCapacity);
 }
 
 } // namespace clang
 
 #endif // LLVM_CLANG_AST_ASTVECTOR_H

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