etl/src/queue.h

///\file

/******************************************************************************
The MIT License(MIT)

Embedded Template Library.
https://github.com/ETLCPP/etl
http://www.etlcpp.com

Copyright(c) 2014 jwellbelove

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
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.
******************************************************************************/

#ifndef __ETL_QUEUE__
#define __ETL_QUEUE__

#include <stddef.h>
#include <stdint.h>

#include "container.h"
#include "alignment.h"
#include "array.h"
#include "exception.h"
#include "error_handler.h"
#include "debug_count.h"
#include "type_traits.h"
#include "parameter_type.h"

#undef ETL_FILE
#define ETL_FILE "13"

//*****************************************************************************
///\defgroup queue queue
/// A First-in / first-out queue with the capacity defined at compile time,
/// written in the STL style.
///\ingroup containers
//*****************************************************************************

namespace etl
{
  //***************************************************************************
  /// The base class for queue exceptions.
  ///\ingroup queue
  //***************************************************************************
  class queue_exception : public exception
  {
  public:

    queue_exception(string_type what, string_type file_name, numeric_type line_number)
      : exception(what, file_name, line_number)
    {
    }
  };

  //***************************************************************************
  /// The exception thrown when the queue is full.
  ///\ingroup queue
  //***************************************************************************
  class queue_full : public queue_exception
  {
  public:

    queue_full(string_type file_name, numeric_type line_number)
      : queue_exception(ETL_ERROR_TEXT("queue:full", ETL_FILE"A"), file_name, line_number)
    {
    }
  };

  //***************************************************************************
  /// The exception thrown when the queue is empty.
  ///\ingroup queue
  //***************************************************************************
  class queue_empty : public queue_exception
  {
  public:

    queue_empty(string_type file_name, numeric_type line_number)
      : queue_exception(ETL_ERROR_TEXT("queue:empty", ETL_FILE"B"), file_name, line_number)
    {
    }
  };

  //***************************************************************************
  /// The base class for all queues.
  ///\ingroup queue
  //***************************************************************************
  class queue_base
  {
  public:

    typedef size_t size_type; ///< The type used for determining the size of queue.

    //*************************************************************************
    /// Returns the current number of items in the queue.
    //*************************************************************************
    size_type size() const
    {
      return current_size;
    }

    //*************************************************************************
    /// Returns the maximum number of items that can be queued.
    //*************************************************************************
    size_type max_size() const
    {
      return CAPACITY;
    }

    //*************************************************************************
    /// Checks to see if the queue is empty.
    /// \return <b>true</b> if the queue is empty, otherwise <b>false</b>
    //*************************************************************************
    bool empty() const
    {
      return current_size == 0;
    }

    //*************************************************************************
    /// Checks to see if the queue is full.
    /// \return <b>true</b> if the queue is full, otherwise <b>false</b>
    //*************************************************************************
    bool full() const
    {
      return current_size == CAPACITY;
    }

    //*************************************************************************
    /// Returns the remaining capacity.
    ///\return The remaining capacity.
    //*************************************************************************
    size_t available() const
    {
      return max_size() - size();
    }

  protected:

    //*************************************************************************
    /// The constructor that is called from derived classes.
    //*************************************************************************
    queue_base(size_type max_size)
      : in(0),
      out(0),
      current_size(0),
      CAPACITY(max_size)
    {
    }

    size_type in;                     ///< Where to input new data.
    size_type out;                    ///< Where to get the oldest data.
    size_type current_size;           ///< The number of items in the queue.
    const size_type CAPACITY;         ///< The maximum number of items in the queue.
    etl::debug_count construct_count; ///< For internal debugging purposes.
  };

  //***************************************************************************
  ///\ingroup queue
  ///\brief This is the base for all queues that contain a particular type.
  ///\details Normally a reference to this type will be taken from a derived queue.
  ///\code
  /// etl::queue<int, 10> myQueue;
  /// etl::iqueue<int>& iQueue = myQueue;
  ///\endcode
  /// \warning This queue cannot be used for concurrent access from multiple threads.
  /// \tparam T The type of value that the queue holds.
  //***************************************************************************
  template <typename T>
  class iqueue : public etl::queue_base
  {
  public:

    typedef T                     value_type;      ///< The type stored in the queue.
    typedef T&                    reference;       ///< A reference to the type used in the queue.
    typedef const T&              const_reference; ///< A const reference to the type used in the queue.
    typedef T*                    pointer;         ///< A pointer to the type used in the queue.
    typedef const T*              const_pointer;   ///< A const pointer to the type used in the queue.
    typedef queue_base::size_type size_type;       ///< The type used for determining the size of the queue.

  private:

    typedef typename etl::parameter_type<T>::type parameter_t;

  public:

    //*************************************************************************
    /// Gets a reference to the value at the front of the queue.<br>
    /// \return A reference to the value at the front of the queue.
    //*************************************************************************
    reference front()
    {
      return p_buffer[out];
    }

    //*************************************************************************
    /// Gets a const reference to the value at the front of the queue.<br>
    /// \return A const reference to the value at the front of the queue.
    //*************************************************************************
    const_reference front() const
    {
      return p_buffer[out];
    }

    //*************************************************************************
    /// Gets a reference to the value at the back of the queue.<br>
    /// \return A reference to the value at the back of the queue.
    //*************************************************************************
    reference back()
    {
      return p_buffer[in == 0 ? CAPACITY - 1 : in - 1];
    }

    //*************************************************************************
    /// Gets a const reference to the value at the back of the queue.<br>
    /// \return A const reference to the value at the back of the queue.
    //*************************************************************************
    const_reference back() const
    {
      return p_buffer[in == 0 ? CAPACITY - 1 : in - 1];
    }

    //*************************************************************************
    /// Adds a value to the queue.
    /// If asserts or exceptions are enabled, throws an etl::queue_full if the queue if already full,
    /// otherwise does nothing if full.
    ///\param value The value to push to the queue.
    //*************************************************************************
    void push(parameter_t value)
    {
#if defined(ETL_CHECK_PUSH_POP)
      ETL_ASSERT(!full(), ETL_ERROR(queue_full));
#endif
      ::new (&p_buffer[in]) T(value);
      in = (in == (CAPACITY - 1)) ? 0 : in + 1;
      ++current_size;
      ++construct_count;
    }

    //*************************************************************************
    /// Allows a possibly more efficient 'push' by moving to the next input value
    /// and returning a reference to it.
    /// This may eliminate a copy by allowing direct construction in-place.<br>
    /// If asserts or exceptions are enabled, throws an etl::queue_full is the queue is already full,
    /// otherwise does nothing if full.
    /// \return A reference to the position to 'push' to.
    //*************************************************************************
    reference push()
    {
      const size_type next = in;

#if defined(ETL_CHECK_PUSH_POP)
      ETL_ASSERT(!full(), ETL_ERROR(queue_full));
#endif
      ::new (&p_buffer[in]) T();
      in = (in == (CAPACITY - 1)) ? 0 : in + 1;
      ++current_size;
      ++construct_count;

      return p_buffer[next];
    }

    //*************************************************************************
    /// Clears the queue to the empty state.
    //*************************************************************************
    void clear()
    {
      while (current_size > 0)
      {
        p_buffer[out].~T();
        out = (out == (CAPACITY - 1)) ? 0 : out + 1;
        --current_size;
        --construct_count;
      }

      in = 0;
      out = 0;
    }

    //*************************************************************************
    /// Removes the oldest value from the back of the queue.
    /// Does nothing if the queue is already empty.
    //*************************************************************************
    void pop()
    {
#if defined(ETL_CHECK_PUSH_POP)
      ETL_ASSERT(!empty(), ETL_ERROR(queue_empty));
#endif
      p_buffer[out].~T();
      out = (out == (CAPACITY - 1)) ? 0 : out + 1;
      --current_size;
      --construct_count;
    }

    //*************************************************************************
    /// Assignment operator.
    //*************************************************************************
    iqueue& operator = (const iqueue& rhs)
    {
      if (&rhs != this)
      {
        clone(rhs);
      }

      return *this;
    }

  protected:

    //*************************************************************************
    /// Make this a clone of the supplied queue
    //*************************************************************************
    void clone(const iqueue& other)
    {
      size_t index = other.out;

      for (size_t i = 0; i < other.size(); ++i)
      {
        push(other.p_buffer[index]);
        index = (index == (CAPACITY - 1)) ? 0 : index + 1;
      }
    }

    //*************************************************************************
    /// The constructor that is called from derived classes.
    //*************************************************************************
    iqueue(T* p_buffer, size_type max_size)
      : queue_base(max_size),
      p_buffer(p_buffer)
    {
    }

  private:

    // Disable copy construction.
    iqueue(const iqueue&);

    T* p_buffer; ///< The internal buffer.
  };

  //***************************************************************************
  ///\ingroup queue
  /// A fixed capacity queue.
  /// This queue does not support concurrent access by different threads.
  /// \tparam T    The type this queue should support.
  /// \tparam SIZE The maximum capacity of the queue.
  //***************************************************************************
  template <typename T, const size_t SIZE>
  class queue : public etl::iqueue<T>
  {
  public:

    static const size_t MAX_SIZE = SIZE;

    //*************************************************************************
    /// Default constructor.
    //*************************************************************************
    queue()
      : etl::iqueue<T>(reinterpret_cast<T*>(&buffer[0]), SIZE)
    {
    }

    //*************************************************************************
    /// Copy constructor
    //*************************************************************************
    queue(const queue& rhs)
      : etl::iqueue<T>(reinterpret_cast<T*>(&buffer[0]), SIZE)
    {
      etl::iqueue<T>::clone(rhs);
    }

    //*************************************************************************
    /// Destructor.
    //*************************************************************************
    ~queue()
    {
      etl::iqueue<T>::clear();
    }

    //*************************************************************************
    /// Assignment operator.
    //*************************************************************************
    queue& operator = (const queue& rhs)
    {
      if (&rhs != this)
      {
        etl::iqueue<T>::clone(rhs);
      }

      return *this;
    }

  private:

    /// The uninitialised buffer of T used in the stack.
    typename etl::aligned_storage<sizeof(T), etl::alignment_of<T>::value>::type buffer[SIZE];
  };
}

#undef ETL_FILE

#endif