smallest.h

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/******************************************************************************
The MIT License(MIT)
 
Embedded Template Library.
https://github.com/ETLCPP/etl
https://www.etlcpp.com
 
Copyright(c) 2014 John Wellbelove
 
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#ifndef ETL_SMALLEST_INCLUDED
#define ETL_SMALLEST_INCLUDED
 
#include "platform.h"
#include "integral_limits.h"
 
#include <stdint.h>

 
namespace etl
{
#if ETL_USING_CPP11 && !defined(ETL_SMALLEST_TYPE_FORCE_CPP03_IMPLEMENTATION)
  //***************************************************************************
  //***************************************************************************
  template <typename T1, typename... TRest>
  class smallest_type
  {
  private:
 
    // Define 'smallest_other' as 'smallest_type' with all but the first
    // parameter.
    using smallest_other = typename smallest_type<TRest...>::type;
 
  public:
 
    // Set 'type' to be the smallest of the first parameter and any of the
    // others. This is recursive.
    using type = typename etl::conditional<(etl::size_of<T1>::value < etl::size_of< smallest_other>::value), // Boolean
                                           T1,                                                               // TrueType
                                           smallest_other>                                                   // FalseType
      ::type;                                                                                                // The smallest type of the two.
 
    // The size of the smallest type.
    enum
    {
      size = etl::size_of<type>::value
    };
  };
 
  //***************************************************************************
  // Specialisation for one template parameter.
  //***************************************************************************
  template <typename T1>
  class smallest_type<T1>
  {
  public:
 
    using type = T1;
 
    enum
    {
      size = etl::size_of<type>::value
    };
  };
 
  #if ETL_USING_CPP11
  template <typename... T>
  using smallest_type_t = typename smallest_type<T...>::type;
  #endif
 
  #if ETL_USING_CPP17
  template <typename... T>
  constexpr size_t smallest_type_v = smallest_type<T...>::size;
  #endif
 
#else
  #include "private/smallest_cpp03.h"
#endif
 
  namespace private_smallest
  {
    //*************************************************************************
    // Determine the type to hold the number of bits based on the index.
    //*************************************************************************
    template <int index>
    struct best_fit_uint_type;
 
    //*************************************************************************
    // Less than or equal to 8 bits.
    //*************************************************************************
    template <>
    struct best_fit_uint_type<0>
    {
      typedef uint_least8_t type;
    };
 
    //*************************************************************************
    // 9 to 16 bits.
    //*************************************************************************
    template <>
    struct best_fit_uint_type<1>
    {
      typedef uint_least16_t type;
    };
 
    //*************************************************************************
    // 17 to 31 bits.
    //*************************************************************************
    template <>
    struct best_fit_uint_type<2>
    {
      typedef uint_least32_t type;
    };
 
#if ETL_USING_64BIT_TYPES
    //*************************************************************************
    // Greater than 32 bits.
    //*************************************************************************
    template <>
    struct best_fit_uint_type<3>
    {
      typedef uint_least64_t type;
    };
#endif
 
    //*************************************************************************
    // Determine the type to hold the number of bits based on the index.
    //*************************************************************************
    template <int index>
    struct best_fit_int_type;
 
    //*************************************************************************
    // Less than or equal to 8 bits.
    //*************************************************************************
    template <>
    struct best_fit_int_type<0>
    {
      typedef int_least8_t type;
    };
 
    //*************************************************************************
    // 9 to 16 bits.
    //*************************************************************************
    template <>
    struct best_fit_int_type<1>
    {
      typedef int_least16_t type;
    };
 
    //*************************************************************************
    // 17 to 31 bits.
    //*************************************************************************
    template <>
    struct best_fit_int_type<2>
    {
      typedef int_least32_t type;
    };
 
#if ETL_USING_64BIT_TYPES
    //*************************************************************************
    // Greater than 32 bits.
    //*************************************************************************
    template <>
    struct best_fit_int_type<3>
    {
      typedef int_least64_t type;
    };
#endif
  } // namespace private_smallest
 
  //***************************************************************************
  //***************************************************************************
  template <size_t NBITS>
  struct smallest_uint_for_bits
  {
  private:
 
    // Determines the index of the best unsigned type for the required number of
    // bits.
    static ETL_CONSTANT int TYPE_INDEX = ((NBITS > 8) ? 1 : 0) + ((NBITS > 16) ? 1 : 0) + ((NBITS > 32) ? 1 : 0);
 
  public:
 
    typedef typename private_smallest::best_fit_uint_type<TYPE_INDEX>::type type;
  };
 
  template <size_t NBITS>
  ETL_CONSTANT int smallest_uint_for_bits<NBITS>::TYPE_INDEX;
 
#if ETL_USING_CPP11
  template <size_t NBITS>
  using smallest_uint_for_bits_t = typename smallest_uint_for_bits<NBITS>::type;
#endif
 
  //***************************************************************************
  //***************************************************************************
  template <size_t NBITS>
  struct smallest_int_for_bits
  {
  private:
 
    // Determines the index of the best unsigned type for the required number of
    // bits.
    static ETL_CONSTANT int TYPE_INDEX = ((NBITS > 8) ? 1 : 0) + ((NBITS > 16) ? 1 : 0) + ((NBITS > 32) ? 1 : 0);
 
  public:
 
    typedef typename private_smallest::best_fit_int_type<TYPE_INDEX>::type type;
  };
 
  template <size_t NBITS>
  ETL_CONSTANT int smallest_int_for_bits<NBITS>::TYPE_INDEX;
 
#if ETL_USING_CPP11
  template <size_t NBITS>
  using smallest_int_for_bits_t = typename smallest_int_for_bits<NBITS>::type;
#endif
 
  //***************************************************************************
  //***************************************************************************
  template <uintmax_t VALUE>
  struct smallest_uint_for_value
  {
  private:
 
    // Determines the index of the best unsigned type for the required value.
    static ETL_CONSTANT int TYPE_INDEX = ((VALUE > UINT_LEAST8_MAX) ? 1 : 0) + ((VALUE > UINT16_MAX) ? 1 : 0) + ((VALUE > UINT32_MAX) ? 1 : 0);
 
  public:
 
    typedef typename private_smallest::best_fit_uint_type<TYPE_INDEX>::type type;
  };
 
  template <uintmax_t VALUE>
  ETL_CONSTANT int smallest_uint_for_value<VALUE>::TYPE_INDEX;
 
#if ETL_USING_CPP11
  template <uintmax_t VALUE>
  using smallest_uint_for_value_t = typename smallest_uint_for_value<VALUE>::type;
#endif
 
  //***************************************************************************
  //***************************************************************************
  template <intmax_t VALUE>
  struct smallest_int_for_value
  {
  private:
 
    // Determines the index of the best signed type for the required value.
    static ETL_CONSTANT int TYPE_INDEX = (((VALUE > intmax_t(INT_LEAST8_MAX)) || (VALUE < intmax_t(INT_LEAST8_MIN))) ? 1 : 0)
                                 + (((VALUE > intmax_t(INT16_MAX)) || (VALUE < intmax_t(INT16_MIN))) ? 1 : 0)
                                 + (((VALUE > intmax_t(INT32_MAX)) || (VALUE < intmax_t(INT32_MIN))) ? 1 : 0);
 
  public:
 
    typedef typename private_smallest::best_fit_int_type<TYPE_INDEX>::type type;
  };
 
  template <intmax_t VALUE>
  ETL_CONSTANT int smallest_int_for_value<VALUE>::TYPE_INDEX;
 
#if ETL_USING_CPP11
  template <intmax_t VALUE>
  using smallest_int_for_value_t = typename smallest_int_for_value<VALUE>::type;
#endif
} // namespace etl
 
#endif