mem_cast.h

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/******************************************************************************
The MIT License(MIT)
 
Embedded Template Library.
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https://www.etlcpp.com
 
Copyright(c) 2021 John Wellbelove
 
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#ifndef ETL_MEM_CAST_INCLUDED
#define ETL_MEM_CAST_INCLUDED
 
#include "platform.h"
#include "memory.h"
#include "static_assert.h"
#include "largest.h"
#include "utility.h"
#include "placement_new.h"
#include "exception.h"
#include "error_handler.h"
#include "file_error_numbers.h"
#include "binary.h"
 
#include <stdint.h>
#include <string.h>
 
namespace etl
{
  //***************************************************************************
  //***************************************************************************
  class mem_cast_exception : public etl::exception
  {
  public:
 
    mem_cast_exception(string_type reason_, string_type file_name_, numeric_type line_number_)
      : exception(reason_, file_name_, line_number_)
    {
    }
  };
 
  //***************************************************************************
  //***************************************************************************
  class mem_cast_size_exception : public etl::mem_cast_exception
  {
  public:
 
    mem_cast_size_exception(string_type file_name_, numeric_type line_number_)
      : mem_cast_exception(ETL_ERROR_TEXT("mem_cast:size", ETL_MEM_CAST_FILE_ID"A"), file_name_, line_number_)
    {
    }
  };
 
  //***************************************************************************
  //***************************************************************************
  class mem_cast_nullptr_exception : public etl::mem_cast_exception
  {
  public:
 
    mem_cast_nullptr_exception(string_type file_name_, numeric_type line_number_)
      : mem_cast_exception(ETL_ERROR_TEXT("mem_cast:null pointer", ETL_MEM_CAST_FILE_ID"B"), file_name_, line_number_)
    {
    }
  };
 
  //*****************************************************************************
  //*****************************************************************************
  template <size_t Size_, size_t Alignment_>
  class mem_cast
  {
  public:
 
    static ETL_CONSTANT size_t Size      = Size_;
    static ETL_CONSTANT size_t Alignment = Alignment_;
 
    ETL_STATIC_ASSERT((Alignment == 1) || etl::is_power_of_2<Alignment>::value, "Alignment must be a power of 2");
 
    //***********************************
    //***********************************
    mem_cast()
      : buffer()
    {
    }
 
    //***********************************
    //***********************************
    template <size_t Other_Size, size_t Other_Alignment>
    mem_cast(const mem_cast<Other_Size, Other_Alignment>& other)
    {
      ETL_STATIC_ASSERT(Size >= Other_Size, "Other size is too large");
 
      memcpy(buffer, other.buffer, Size_);
    }
   
    //***********************************
    //***********************************
    template <size_t Other_Size, size_t Other_Alignment>
    mem_cast& operator =(const mem_cast<Other_Size, Other_Alignment>& rhs)
    {
      ETL_STATIC_ASSERT(Size >= Other_Size, "RHS size is too large");
 
      memcpy(buffer, rhs.buffer, Size_);
 
      return *this;
    }
 
    //***********************************
    //***********************************
    template <typename T>
    void assign(const T& value)
    {
      ETL_STATIC_ASSERT(Size >= sizeof(T), "Type size is too large");
 
      ::new (static_cast<void*>(buffer.raw)) T(value);
    }
 
    //***********************************
    //***********************************
    template <typename T>
    void assign_at_offset(size_t offset, const T& value)
    {
      char* p = static_cast<char*>(buffer.raw) + offset;
      ETL_ASSERT(sizeof(T) <= (Size - offset), ETL_ERROR(etl::mem_cast_size_exception));
 
      ::new (p) T(value);
    }
 
    //***********************************
    //***********************************
    template <typename T, size_t Offset>
    void assign_at_offset(const T& value)
    {
      char* p = static_cast<char*>(buffer.raw) + Offset;
      ETL_STATIC_ASSERT(sizeof(T) <= (Size - Offset), "Type size is too large");
 
      ::new (p) T(value);
    }
 
#if ETL_USING_CPP11
    //***********************************
    //***********************************
    template <typename T, typename... TArgs>
    T& emplace(TArgs... args)
    {
      ETL_STATIC_ASSERT(Size >= sizeof(T), "Type size is too large");
 
      ::new (static_cast<void*>(buffer.raw)) T(etl::forward<TArgs>(args)...);
 
      return ref<T>();
    }
 
    //***********************************
    //***********************************
    template <typename T, typename... TArgs>
    T& emplace_at_offset(size_t offset, TArgs... args)
    {
      char* p = static_cast<char*>(buffer.raw) + offset;
      ETL_ASSERT(sizeof(T) <= (Size - offset), ETL_ERROR(etl::mem_cast_size_exception));
 
      ::new (p) T(etl::forward<TArgs>(args)...);
 
      return ref_at_offset<T>(offset);
    }
 
    //***********************************
    //***********************************
    template <typename T, size_t Offset, typename... TArgs>
    T& emplace_at_offset(TArgs... args)
    {
      char* p = static_cast<char*>(buffer.raw) + Offset;
      ETL_STATIC_ASSERT(sizeof(T) <= (Size - Offset), "Type size is too large");
 
      ::new (p) T(etl::forward<TArgs>(args)...);
 
      return ref_at_offset<T, Offset>();
    }
#endif
 
    //***********************************
    //***********************************
    template <typename T>
    ETL_NODISCARD T& ref()
    {
      ETL_STATIC_ASSERT(sizeof(T) <= Size, "Size of type too large for storage");
 
      return *reinterpret_cast<T*>(buffer.raw);
    }
 
    //***********************************
    //***********************************
    template <typename T>
    ETL_NODISCARD const T& ref() const
    {
      ETL_STATIC_ASSERT(sizeof(T) <= Size, "Size of type too large for storage");
 
      return *reinterpret_cast<const T*>(buffer.raw);
    }
 
    //***********************************
    //***********************************
    template <typename T>
    ETL_NODISCARD T& ref_at_offset(size_t offset)
    {
      ETL_ASSERT(sizeof(T) <= (Size - offset), ETL_ERROR(etl::mem_cast_size_exception));
 
      return *reinterpret_cast<T*>(buffer.raw + offset);
    }
 
    //***********************************
    //***********************************
    template <typename T>
    ETL_NODISCARD const T& ref_at_offset(size_t offset) const
    {
      ETL_ASSERT(sizeof(T) <= (Size - offset), ETL_ERROR(etl::mem_cast_size_exception));
 
      return *reinterpret_cast<const T*>(buffer.raw + offset);
    }
 
    //***********************************
    //***********************************
    template <typename T, size_t Offset>
    ETL_NODISCARD T& ref_at_offset()
    {
      ETL_STATIC_ASSERT(sizeof(T) <= (Size - Offset), "Size of type too large for storage");
 
      return *reinterpret_cast<T*>(buffer.raw + Offset);
    }
 
    //***********************************
    //***********************************
    template <typename T, size_t Offset>
    ETL_NODISCARD const T& ref_at_offset() const
    {
      ETL_STATIC_ASSERT(sizeof(T) <= (Size - Offset), "Size of type too large for storage");
 
      return *reinterpret_cast<const T*>(buffer.raw + Offset);
    }
 
    //***********************************
    //***********************************
    ETL_NODISCARD static ETL_CONSTEXPR size_t size()
    {
      return Size;
    }
 
    //***********************************
    //***********************************
    ETL_NODISCARD static ETL_CONSTEXPR size_t alignment()
    {
      return Alignment;
    }
 
    //***********************************
    //***********************************
    ETL_NODISCARD char* data()
    {
      return buffer;
    }
 
    //***********************************
    //***********************************
    ETL_NODISCARD const char* data() const 
    {
      return buffer;
    }
 
  private:

    etl::uninitialized_buffer<Size, 1U, Alignment> buffer;
  };
 
  template <size_t Size_, size_t Alignment_>
  ETL_CONSTANT size_t mem_cast<Size_, Alignment_>::Size;
 
  template <size_t Size_, size_t Alignment_>
  ETL_CONSTANT size_t mem_cast<Size_, Alignment_>::Alignment;
 
  //*****************************************************************************
  //*****************************************************************************
  class mem_cast_ptr
  {
  public:
 
    static ETL_CONSTANT size_t Undefined_Size = etl::integral_limits<size_t>::max;
 
    //***********************************
    //***********************************
    mem_cast_ptr()
      : pbuffer(ETL_NULLPTR)
      , buffer_size(Undefined_Size)
    {
    }
 
    //***********************************
    //***********************************
    mem_cast_ptr(char* pbuffer_, size_t buffer_size_ = Undefined_Size)
      : pbuffer(pbuffer_)
      , buffer_size(buffer_size_)
    {
    }
 
    //***********************************
    //***********************************
    mem_cast_ptr(const mem_cast_ptr& other)
      : pbuffer(other.pbuffer)
      , buffer_size(other.buffer_size)
    {
    }
 
    //***********************************
    //***********************************
    mem_cast_ptr& operator =(const mem_cast_ptr& rhs)
    {
      pbuffer     = rhs.pbuffer;
      buffer_size = rhs.buffer_size;
 
      return *this;
    }
 
    //***********************************
    //***********************************
    template <typename T>
    void assign(const T& value)
    {
      ETL_ASSERT((pbuffer != ETL_NULLPTR), ETL_ERROR(etl::mem_cast_nullptr_exception));
      ETL_ASSERT(sizeof(T) <= buffer_size, ETL_ERROR(etl::mem_cast_size_exception));
 
      ::new (pbuffer) T(value);
    }
 
    //***********************************
    //***********************************
    template <typename T>
    void assign_at_offset(size_t offset, const T& value)
    {
      ETL_ASSERT((pbuffer != ETL_NULLPTR), ETL_ERROR(etl::mem_cast_nullptr_exception));
      char* p = pbuffer + offset;
      ETL_ASSERT(sizeof(T) <= (buffer_size - offset), ETL_ERROR(etl::mem_cast_size_exception));
 
      ::new (p) T(value);
    }
 
    //***********************************
    //***********************************
    template <typename T, size_t Offset>
    void assign_at_offset(const T& value)
    {
      ETL_ASSERT((pbuffer != ETL_NULLPTR), ETL_ERROR(etl::mem_cast_nullptr_exception));
      char* p = pbuffer + Offset;
      ETL_ASSERT(sizeof(T) <= (buffer_size - Offset), ETL_ERROR(etl::mem_cast_size_exception));
 
      ::new (p) T(value);
    }
 
#if ETL_USING_CPP11
    //***********************************
    //***********************************
    template <typename T, typename... TArgs>
    T& emplace(TArgs... args)
    {
      ETL_ASSERT((pbuffer != ETL_NULLPTR), ETL_ERROR(etl::mem_cast_nullptr_exception));
      ETL_ASSERT(sizeof(T) <= buffer_size, ETL_ERROR(etl::mem_cast_size_exception));
 
      ::new (pbuffer) T(etl::forward<TArgs>(args)...);
 
      return ref<T>();
    }
 
    //***********************************
    //***********************************
    template <typename T, typename... TArgs>
    T& emplace_at_offset(size_t offset, TArgs... args)
    {
      ETL_ASSERT((pbuffer != ETL_NULLPTR), ETL_ERROR(etl::mem_cast_nullptr_exception));
      char* p = pbuffer + offset;
      ETL_ASSERT(sizeof(T) <= (buffer_size - offset), ETL_ERROR(etl::mem_cast_size_exception));
 
      ::new (p) T(etl::forward<TArgs>(args)...);
 
      return ref_at_offset<T>(offset);
    }
 
    //***********************************
    //***********************************
    template <typename T, size_t Offset, typename... TArgs>
    T& emplace_at_offset(TArgs... args)
    {
      ETL_ASSERT((pbuffer != ETL_NULLPTR), ETL_ERROR(etl::mem_cast_nullptr_exception));
      char* p = pbuffer + Offset;
      ETL_ASSERT(sizeof(T) <= (buffer_size - Offset), ETL_ERROR(etl::mem_cast_size_exception));
 
      ::new (p) T(etl::forward<TArgs>(args)...);
 
      return ref_at_offset<T, Offset>();
    }
#endif
 
    //***********************************
    //***********************************
    template <typename T>
    ETL_NODISCARD T& ref()
    {
      ETL_ASSERT((pbuffer != ETL_NULLPTR), ETL_ERROR(etl::mem_cast_nullptr_exception));
      ETL_ASSERT(sizeof(T) <= buffer_size, ETL_ERROR(etl::mem_cast_size_exception));
 
      T* p = reinterpret_cast<T*>(pbuffer);
 
      return *p;
    }
 
    //***********************************
    //***********************************
    template <typename T>
    ETL_NODISCARD const T& ref() const
    {
      ETL_ASSERT((pbuffer != ETL_NULLPTR), ETL_ERROR(etl::mem_cast_nullptr_exception));
      ETL_ASSERT(sizeof(T) <= buffer_size, ETL_ERROR(etl::mem_cast_size_exception));
 
      const T* p = reinterpret_cast<const T*>(pbuffer);
 
      return *p;
    }
 
    //***********************************
    //***********************************
    template <typename T>
    ETL_NODISCARD T& ref_at_offset(size_t offset)
    {
      ETL_ASSERT((pbuffer != ETL_NULLPTR), ETL_ERROR(etl::mem_cast_nullptr_exception));
      ETL_ASSERT(sizeof(T) <= (buffer_size - offset), ETL_ERROR(etl::mem_cast_size_exception));
 
      T* p = reinterpret_cast<T*>(pbuffer + offset);
 
      return *p;
    }
 
    //***********************************
    //***********************************
    template <typename T>
    ETL_NODISCARD const T& ref_at_offset(size_t offset) const
    {
      ETL_ASSERT((pbuffer != ETL_NULLPTR), ETL_ERROR(etl::mem_cast_nullptr_exception));
      ETL_ASSERT(sizeof(T) <= (buffer_size - offset), ETL_ERROR(etl::mem_cast_size_exception));
 
      const T* p = reinterpret_cast<const T*>(pbuffer + offset);
 
      return *p;
    }
 
    //***********************************
    //***********************************
    template <typename T, size_t Offset>
    ETL_NODISCARD T& ref_at_offset()
    {
      ETL_ASSERT((pbuffer != ETL_NULLPTR), ETL_ERROR(etl::mem_cast_nullptr_exception));
      ETL_ASSERT(sizeof(T) <= (buffer_size - Offset), ETL_ERROR(etl::mem_cast_size_exception));
 
      T* p = reinterpret_cast<T*>(pbuffer + Offset);
 
      return *p;
    }
 
    //***********************************
    //***********************************
    template <typename T, size_t Offset>
    ETL_NODISCARD const T& ref_at_offset() const
    {
      ETL_ASSERT((pbuffer != ETL_NULLPTR), ETL_ERROR(etl::mem_cast_nullptr_exception));
      ETL_ASSERT(sizeof(T) <= (buffer_size - Offset), ETL_ERROR(etl::mem_cast_size_exception));
 
      const T* p = reinterpret_cast<const T*>(pbuffer + Offset);
 
      return *p;
    }
 
    //***********************************
    //***********************************
    ETL_NODISCARD size_t size() const
    {
      return buffer_size;
    }
 
    //***********************************
    //***********************************
    ETL_NODISCARD size_t alignment() const
    {
      typedef typename etl::smallest_uint_for_bits<sizeof(uintptr_t)* CHAR_BIT>::type type;
 
      const type p = reinterpret_cast<type>(pbuffer);    
 
      return size_t(1U) << etl::count_trailing_zeros(p);
    }
 
    //***********************************
    //***********************************
    void data(char* pbuffer_, size_t buffer_size_ = Undefined_Size)
    {
      pbuffer     = pbuffer_;
      buffer_size = buffer_size_;
    }
 
    //***********************************
    //***********************************
    ETL_NODISCARD char* data()
    {
      return pbuffer;
    }
 
    //***********************************
    //***********************************
    ETL_NODISCARD const char* data() const
    {
      return pbuffer;
    }
 
  private:

    char*  pbuffer;
    size_t buffer_size;
  };
 
  //*****************************************************************************
  //*****************************************************************************
#if ETL_USING_CPP11 && !defined(ETL_MEM_CAST_FORCE_CPP03_IMPLEMENTATION)
  template <typename... TTypes>
  using mem_cast_types = etl::mem_cast<etl::largest<TTypes...>::size, etl::largest<TTypes...>::alignment>;
#else
  template <typename T1,         typename T2  = char, typename T3  = char, typename T4  = char,
            typename T5 = char,  typename T6  = char, typename T7  = char, typename T8  = char,
            typename T9 = char,  typename T10 = char, typename T11 = char, typename T12 = char,
            typename T13 = char, typename T14 = char, typename T15 = char, typename T16 = char>
  struct mem_cast_types : public etl::mem_cast<etl::largest<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16>::size,
                                               etl::largest<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16>::alignment>
  {
  };
#endif
}
 
#endif