//===- ThreadSafetyUtil.h --------------------------------------*- C++ --*-===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file defines some basic utility classes for use by ThreadSafetyTIL.h
//
//===----------------------------------------------------------------------===//

#ifndef LLVM_CLANG_THREAD_SAFETY_UTIL_H
#define LLVM_CLANG_THREAD_SAFETY_UTIL_H

#include "llvm/ADT/StringRef.h"
#include "llvm/Support/AlignOf.h"
#include "llvm/Support/Allocator.h"
#include "llvm/Support/Compiler.h"
#include "clang/AST/ExprCXX.h"

#include <cassert>
#include <cstddef>
#include <vector>
#include <utility>

namespace clang {
namespace threadSafety {
namespace til {

// Simple wrapper class to abstract away from the details of memory management.
// SExprs are allocated in pools, and deallocated all at once.
class MemRegionRef {
private:
  union AlignmentType {
    double d;
    void *p;
    long double dd;
    long long ii;
  };

public:
  MemRegionRef() : Allocator(nullptr) {}
  MemRegionRef(llvm::BumpPtrAllocator *A) : Allocator(A) {}

  void *allocate(size_t Sz) {
    return Allocator->Allocate(Sz, llvm::AlignOf<AlignmentType>::Alignment);
  }

  template <typename T> T *allocateT() { return Allocator->Allocate<T>(); }

  template <typename T> T *allocateT(size_t NumElems) {
    return Allocator->Allocate<T>(NumElems);
  }

private:
  llvm::BumpPtrAllocator *Allocator;
};


} // end namespace til
} // end namespace threadSafety
} // end namespace clang


inline void *operator new(size_t Sz,
                          clang::threadSafety::til::MemRegionRef &R) {
  return R.allocate(Sz);
}


namespace clang {
namespace threadSafety {

std::string getSourceLiteralString(const clang::Expr *CE);

using llvm::StringRef;
using clang::SourceLocation;

namespace til {


// A simple fixed size array class that does not manage its own memory,
// suitable for use with bump pointer allocation.
template <class T> class SimpleArray {
public:
  SimpleArray() : Data(nullptr), Size(0), Capacity(0) {}
  SimpleArray(T *Dat, size_t Cp, size_t Sz = 0)
      : Data(Dat), Size(Sz), Capacity(Cp) {}
  SimpleArray(MemRegionRef A, size_t Cp)
      : Data(Cp == 0 ? nullptr : A.allocateT<T>(Cp)), Size(0), Capacity(Cp) {}
  SimpleArray(SimpleArray<T> &&A)
      : Data(A.Data), Size(A.Size), Capacity(A.Capacity) {
    A.Data = nullptr;
    A.Size = 0;
    A.Capacity = 0;
  }

  SimpleArray &operator=(SimpleArray &&RHS) {
    if (this != &RHS) {
      Data = RHS.Data;
      Size = RHS.Size;
      Capacity = RHS.Capacity;

      RHS.Data = nullptr;
      RHS.Size = RHS.Capacity = 0;
    }
    return *this;
  }

  // Reserve space for at least Ncp items, reallocating if necessary.
  void reserve(size_t Ncp, MemRegionRef A) {
    if (Ncp <= Capacity)
      return;
    T *Odata = Data;
    Data = A.allocateT<T>(Ncp);
    Capacity = Ncp;
    memcpy(Data, Odata, sizeof(T) * Size);
    return;
  }

  // Reserve space for at least N more items.
  void reserveCheck(size_t N, MemRegionRef A) {
    if (Capacity == 0)
      reserve(u_max(InitialCapacity, N), A);
    else if (Size + N < Capacity)
      reserve(u_max(Size + N, Capacity * 2), A);
  }

  typedef T *iterator;
  typedef const T *const_iterator;

  size_t size() const { return Size; }
  size_t capacity() const { return Capacity; }

  T &operator[](unsigned i) {
    assert(i < Size && "Array index out of bounds.");
    return Data[i];
  }
  const T &operator[](unsigned i) const {
    assert(i < Size && "Array index out of bounds.");
    return Data[i];
  }

  iterator begin() { return Data; }
  iterator end() { return Data + Size; }

  const_iterator cbegin() const { return Data; }
  const_iterator cend() const { return Data + Size; }

  void push_back(const T &Elem) {
    assert(Size < Capacity);
    Data[Size++] = Elem;
  }

  void setValues(unsigned Sz, const T& C) {
    assert(Sz <= Capacity);
    Size = Sz;
    for (unsigned i = 0; i < Sz; ++i) {
      Data[i] = C;
    }
  }

  template <class Iter> unsigned append(Iter I, Iter E) {
    size_t Osz = Size;
    size_t J = Osz;
    for (; J < Capacity && I != E; ++J, ++I)
      Data[J] = *I;
    Size = J;
    return J - Osz;
  }

private:
  // std::max is annoying here, because it requires a reference,
  // thus forcing InitialCapacity to be initialized outside the .h file.
  size_t u_max(size_t i, size_t j) { return (i < j) ? j : i; }

  static const size_t InitialCapacity = 4;

  SimpleArray(const SimpleArray<T> &A) LLVM_DELETED_FUNCTION;

  T *Data;
  size_t Size;
  size_t Capacity;
};

}  // end namespace til


// A copy on write vector.
// The vector can be in one of three states:
// * invalid -- no operations are permitted.
// * read-only -- read operations are permitted.
// * writable -- read and write operations are permitted.
// The init(), destroy(), and makeWritable() methods will change state.
template<typename T>
class CopyOnWriteVector {
  class VectorData {
  public:
    VectorData() : NumRefs(1) { }
    VectorData(const VectorData &VD) : NumRefs(1), Vect(VD.Vect) { }

    unsigned NumRefs;
    std::vector<T> Vect;
  };

  // No copy constructor or copy assignment.  Use clone() with move assignment.
  CopyOnWriteVector(const CopyOnWriteVector &V) LLVM_DELETED_FUNCTION;
  void operator=(const CopyOnWriteVector &V) LLVM_DELETED_FUNCTION;

public:
  CopyOnWriteVector() : Data(nullptr) {}
  CopyOnWriteVector(CopyOnWriteVector &&V) : Data(V.Data) { V.Data = nullptr; }
  ~CopyOnWriteVector() { destroy(); }

  // Returns true if this holds a valid vector.
  bool valid() const  { return Data; }

  // Returns true if this vector is writable.
  bool writable() const { return Data && Data->NumRefs == 1; }

  // If this vector is not valid, initialize it to a valid vector.
  void init() {
    if (!Data) {
      Data = new VectorData();
    }
  }

  // Destroy this vector; thus making it invalid.
  void destroy() {
    if (!Data)
      return;
    if (Data->NumRefs <= 1)
      delete Data;
    else
      --Data->NumRefs;
    Data = nullptr;
  }

  // Make this vector writable, creating a copy if needed.
  void makeWritable() {
    if (!Data) {
      Data = new VectorData();
      return;
    }
    if (Data->NumRefs == 1)
      return;   // already writeable.
    --Data->NumRefs;
    Data = new VectorData(*Data);
  }

  // Create a lazy copy of this vector.
  CopyOnWriteVector clone() { return CopyOnWriteVector(Data); }

  CopyOnWriteVector &operator=(CopyOnWriteVector &&V) {
    destroy();
    Data = V.Data;
    V.Data = nullptr;
    return *this;
  }

  typedef typename std::vector<T>::const_iterator const_iterator;

  const std::vector<T> &elements() const { return Data->Vect; }

  const_iterator begin() const { return elements().cbegin(); }
  const_iterator end() const { return elements().cend(); }

  const T& operator[](unsigned i) const { return elements()[i]; }

  unsigned size() const { return Data ? elements().size() : 0; }

  // Return true if V and this vector refer to the same data.
  bool sameAs(const CopyOnWriteVector &V) const { return Data == V.Data; }

  // Clear vector.  The vector must be writable.
  void clear() {
    assert(writable() && "Vector is not writable!");
    Data->Vect.clear();
  }

  // Push a new element onto the end.  The vector must be writable.
  void push_back(const T &Elem) {
    assert(writable() && "Vector is not writable!");
    Data->Vect.push_back(Elem);
  }

  // Gets a mutable reference to the element at index(i).
  // The vector must be writable.
  T& elem(unsigned i) {
    assert(writable() && "Vector is not writable!");
    return Data->Vect[i];
  }

  // Drops elements from the back until the vector has size i.
  void downsize(unsigned i) {
    assert(writable() && "Vector is not writable!");
    Data->Vect.erase(Data->Vect.begin() + i, Data->Vect.end());
  }

private:
  CopyOnWriteVector(VectorData *D) : Data(D) {
    if (!Data)
      return;
    ++Data->NumRefs;
  }

  VectorData *Data;
};


} // end namespace threadSafety
} // end namespace clang

#endif  // LLVM_CLANG_THREAD_SAFETY_UTIL_H