tpl_memArray.H

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/*
                          Aleph_w
 
  Data structures & Algorithms
  version 2.0.0b
  https://github.com/lrleon/Aleph-w
 
  This file is part of Aleph-w library
 
  Copyright (c) 2002-2026 Leandro Rabindranath Leon
 
  Permission is hereby granted, free of charge, to any person obtaining a copy
  of this software and associated documentation files (the "Software"), to deal
  in the Software without restriction, including without limitation the rights
  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  copies of the Software, and to permit persons to whom the Software is
  furnished to do so, subject to the following conditions:
 
  The above copyright notice and this permission notice shall be included in all
  copies or substantial portions of the Software.
 
  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  SOFTWARE.
*/
 
#ifndef TPL_MEMARRAY_H
#define TPL_MEMARRAY_H
 
#include <utility>
#include <cstdlib>
#include <cmath>
#include <limits>
#include <stdexcept>
 
#include <ah-errors.H>
#include <ahUtils.H>
#include <ahDry.H>
#include <ahIterator.H>
#include <array_it.H>
#include <array_utils.H>
 
namespace Aleph {
template <typename T>
class MemArray
{
public:
  static constexpr size_t Min_Dim = 4;
 
protected:
  T *ptr = nullptr;
  size_t dim = Min_Dim;
  size_t n = 0;
 
public:
  mutable size_t contract_threshold;
 
  T *get_ptr() const noexcept
  {
    return ptr;
  }
 
  const size_t &get_dim() const noexcept
  {
    return dim;
  }
 
protected:
  static size_t next_power_of_two(const size_t requested)
  {
    size_t ret = 1;
    while (ret < requested)
      {
        ah_overflow_error_if(ret > (std::numeric_limits<size_t>::max() >> 1))
          << "MemArray capacity overflow";
        ret <<= 1;
      }
    return ret;
  }
 
  void allocate()
  {
    assert(is_power_of_2(dim));
    ptr = new T[dim];
    contract_threshold = dim / 4;
  }
 
  bool expand(const size_t first = 0)
  {
    assert(ptr);
    assert(is_power_of_2(dim));
    if (n < dim)
      return false;
 
    ah_overflow_error_if(dim > (std::numeric_limits<size_t>::max() >> 1))
      << "MemArray::expand(): capacity overflow";
    const size_t newsz = dim << 1;  // 2*dim
    const size_t mask = dim - 1;
    // Value-initialize (not just default-initialize): for scalar T,
    // `new T[newsz]` alone leaves every slot indeterminate, and the
    // std::swap() below reads new_ptr[i] before this loop ever writes a
    // real value into it -- an uninitialized-read even though the stale
    // bits end up discarded a few lines later (Coverity CID 412651).
    T *new_ptr = new T[newsz]();
    for (size_t i = 0; i < dim; ++i)
      {
        assert(((i + first) & mask) == ((i + first) % dim));
        std::swap(ptr[(i + first) & mask], new_ptr[i]);
      }
    delete[] ptr;
    ptr = new_ptr;
    dim = newsz;
    contract_threshold = dim / 4;
 
    return true;
  }
 
  bool contract(const size_t first = 0)
  {
    assert(ptr);
    if (n > contract_threshold)
      return false;
 
    const size_t newsz = dim >> 1;  // dim/2
 
    if (newsz <= Min_Dim)
      return false;
 
    // Same rationale as expand(): value-initialize so the std::swap()
    // below never reads an indeterminate scalar out of new_ptr[i].
    T *new_ptr = new T[newsz]();
 
    const size_t mask = dim - 1;
    for (size_t i = 0; i < newsz; ++i)
      {
        assert(((first + i) & mask) == ((first + i) % dim));
        std::swap(ptr[(first + i) & mask], new_ptr[i]);
      }
 
    delete[] ptr;
    ptr = new_ptr;
    dim = newsz;
    contract_threshold = dim / 4;
 
    return true;
  }
 
  void init_dim(size_t d)
  {
    if (d == 0)
      d = Min_Dim;
 
    dim = is_power_of_2(d) ? d : next_power_of_two(d);
 
    assert(dim >= d);
    assert(is_power_of_2(dim));
  }
 
public:
  using Item_Type = T;  
 
  [[nodiscard]] constexpr size_t capacity() const noexcept
  {
    return dim;
  }
 
  size_t size() const noexcept
  {
    return n;
  }
 
  bool is_empty() const noexcept
  {
    return n == 0;
  }
 
  MemArray(size_t _dim = Min_Dim) : ptr(nullptr), n(0)
  {
    static_assert(std::is_move_constructible_v<T>, "T must be move constructible");
    static_assert(std::is_move_assignable_v<T>, "T must be move assignable");
    init_dim(_dim);
    allocate();
  }
 
  ~MemArray()
  {
    if (ptr != nullptr)
      {
        delete[] ptr;
        ptr = nullptr;
      }
  }
 
  void swap(MemArray &a) noexcept
  {
    std::swap(ptr, a.ptr);
    std::swap(dim, a.dim);
    std::swap(n, a.n);
    std::swap(contract_threshold, a.contract_threshold);
  }
 
  MemArray(const MemArray &a)
    requires(std::is_copy_constructible_v<T> && std::is_copy_assignable_v<T>)
    : ptr(nullptr), dim(a.dim), n(a.n)
  {
    allocate();
    for (size_t i = 0; i < n; ++i)
      ptr[i] = a.ptr[i];
  }
 
  MemArray(MemArray &&a) noexcept : ptr(nullptr), dim(0), n(0), contract_threshold(0)
  {
    assert(a.ptr);
    swap(a);
  }
 
  MemArray &operator=(const MemArray &a)
    requires(std::is_copy_constructible_v<T> && std::is_copy_assignable_v<T>)
  {
    if (this == &a)
      return *this;
 
    assert(a.ptr);
 
    T *newptr = new T[a.dim];         // allocate a new array
    for (size_t i = 0; i < a.n; ++i)  // copy items to a new array
      newptr[i] = a.ptr[i];
 
    if (ptr != nullptr)
      delete[] ptr;
    ptr = newptr;
    dim = a.dim;
    n = a.n;
    contract_threshold = dim / 4;
 
    return *this;
  }
 
  MemArray &operator=(MemArray &&a) noexcept
  {
    swap(a);
    return *this;
  }
 
  void empty() noexcept
  {
    n = 0;
  }
 
  void clear() noexcept
  {
    empty();
  }
 
  void empty_and_release()
  {
    n = 0;
    if (dim <= Min_Dim)
      return;
 
    assert(ptr);
    delete[] ptr;
    ptr = nullptr;
    dim = Min_Dim;
    allocate();
  }
 
  T &put(const T &item)
    requires std::is_copy_assignable_v<T>
  {
    assert(ptr);
    expand();
 
    ptr[n] = item;
    T &ret = ptr[n++];
    return ret;
  }
 
  T &put(T &&item)
  {
    assert(ptr);
    expand();
 
    ptr[n] = std::forward<T>(item);
    T &ret = ptr[n++];
    return ret;
  }
 
private:
  void open_gap(size_t pos = 0, size_t num_entries = 1)
  {
    putn(num_entries);
    Aleph::open_gap(ptr, n, pos, num_entries);
  }
 
  void close_gap(size_t pos, size_t num_entries = 1)
  {
    Aleph::close_gap(ptr, n, pos, num_entries);
    get(num_entries);
  }
 
public:
  T &push(const T &item)
    requires std::is_copy_assignable_v<T>
  {
    assert(ptr);
    open_gap();
 
    ptr[0] = item;
    T &ret = ptr[0];
    return ret;
  }
 
  T &push(T &&item)
  {
    assert(ptr);
    open_gap(0, 1);
 
    ptr[0] = std::forward<T>(item);
    T &ret = ptr[0];
    return ret;
  }
 
  T &top() const
  {
    ah_underflow_error_if(n == 0) << "top(): MemArray is empty";
 
    return ptr[0];
  }
 
  T remove_first()
  {
    ah_underflow_error_if(n == 0) << "remove_first(): MemArray is empty";
    assert(ptr);
    T ret = std::move(ptr[0]);
    this->close_gap(0, 1);
    return ret;
  }
 
  T pop()
  {
    return remove_first();
  }
 
  T &append(const T &item)
    requires std::is_copy_assignable_v<T>
  {
    assert(ptr);
    return put(item);
  }
 
  T &append(T &&item)
  {
    assert(ptr);
    return put(std::forward<T>(item));
  }
 
  T &insert(const T &item)
    requires std::is_copy_assignable_v<T>
  {
    assert(ptr);
    return push(item);
  }
 
  T &insert(T &&item)
  {
    assert(ptr);
    return push(std::forward<T>(item));
  }
 
  void putn(const size_t more)
  {
    assert(ptr);
    ah_overflow_error_if(more > std::numeric_limits<size_t>::max() - n)
      << "MemArray::putn(): size overflow";
    const size_t new_n = n + more;
    if (new_n <= dim)
      {
        n = new_n;
        return;
      }
 
    size_t new_dim = dim;
    while (new_dim < new_n)
      {
        ah_overflow_error_if(new_dim > (std::numeric_limits<size_t>::max() >> 1))
          << "MemArray::putn(): capacity overflow";
        new_dim <<= 1;  // dim = 2*dim
      }
 
    T *new_ptr = new T[new_dim];
    for (size_t i = 0; i < n; ++i)
      std::swap(ptr[i], new_ptr[i]);
 
    delete[] ptr;
    ptr = new_ptr;
    dim = new_dim;
    n = new_n;
    contract_threshold = dim / 4;
  }
 
  MemArray &append(const MemArray &a)
    requires std::is_copy_assignable_v<T>
  {
    const size_t old_n = n;
    const size_t num_entries = a.size();
    putn(num_entries);
    for (size_t i = 0; i < num_entries; ++i)
      ptr[old_n + i] = a.ptr[i];
 
    return *this;
  }
 
  void reserve(const size_t cap)
  {
    assert(ptr);
    if (cap < dim)
      return;
 
    const size_t new_dim = is_power_of_2(cap) ? cap : next_power_of_two(cap);
 
    T *new_ptr = new T[new_dim];
    for (size_t i = 0; i < n; ++i)
      std::swap(ptr[i], new_ptr[i]);
 
    delete[] ptr;
    ptr = new_ptr;
    dim = new_dim;
    contract_threshold = dim / 4;
  }
 
  T get(const size_t i = 1)
  {
    assert(ptr);
    ah_underflow_error_if(i == 0 or i > n)
      << "MemArray::get(): invalid number of entries";
 
    n -= i;
    T ret = std::move(ptr[n]);
 
    contract();
 
    return ret;
  }
 
  T get_ne(const size_t i = 1) noexcept
  {
    assert(ptr);
    assert(i > 0);
    assert(i <= n);
    n -= i;
    T ret = std::move(ptr[n]);
 
    contract();
 
    return ret;
  }
 
  T remove_last()
  {
    return get();
  }
 
  T &last() const
  {
    ah_underflow_error_if(n == 0) << "MemArray::last(): empty array";
    return ptr[n - 1];
  }
 
  T &first() const
  {
    ah_underflow_error_if(n == 0) << "MemArray::first(): empty array";
    return ptr[0];
  }
 
  T &get_first() const
  {
    return first();
  }
 
  T &get_last() const
  {
    return last();
  }
 
  MemArray &reverse()
  {
    if (n < 2)
      return *this;
 
    for (size_t i = 0, j = n - 1; i < j; ++i, --j)
      std::swap(ptr[i], ptr[j]);
    return *this;
  }
 
  T &access(const size_t i) const noexcept
  {
    assert(ptr);
    return ptr[i];
  }
 
  T &operator[](const size_t i) const
  {
    assert(ptr);
    ah_out_of_range_error_if(i >= n) << "access out of range";
 
    return ptr[i];
  }
 
  T &operator()(const size_t i) const noexcept
  {
    assert(ptr);
    assert(i < dim);
    return ptr[i];
  }
 
  template <class Operation>
  bool traverse(Operation &operation)
  {
    assert(ptr);
    for (size_t i = 0; i < n; i++)
      if (not operation(ptr[i]))
        return false;
 
    return true;
  }
 
  template <class Operation>
  bool traverse(Operation &operation) const
  {
    return const_cast<MemArray *>(this)->traverse(operation);
  }
 
  template <class Operation>
  bool traverse(Operation &&operation) const
  {
    return traverse<Operation>(operation);
  }
 
  template <class Operation>
  bool traverse(Operation &&operation)
  {
    return traverse<Operation>(operation);
  }
 
  bool is_valid() const noexcept
  {
    return ptr;
  }
 
  struct Iterator : public Array_Iterator<T>
  {
    using Base = Array_Iterator<T>;
    using Base::Base;
 
    Iterator(const MemArray<T> &a) noexcept
      : Array_Iterator<T>(no_exception_ctor, a.ptr, a.dim, a.n)
    {
      assert(a.ptr != nullptr);
    }
  };
};
}  // end namespace Aleph
 
#endif  // TPL_MEMARRAY_H