xref: /external/astl/include/limits

/* -*- c++ -*- */
/*
 * Copyright (C) 2010 The Android Open Source Project
 * All rights reserved.
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#ifndef ANDROID_ASTL_LIMITS__
#define ANDROID_ASTL_LIMITS__

#include <limits.h>
// GNU C++ compiler?
#ifndef __GNUG__
#error "__GNUG__ is not defined"
#endif

#ifdef _T
#error "_T is defined"
#endif

// This is very incomplete partial implementation of the standard
// <limits>. Only partial support for float and double is provided.

namespace {
// Template to return the number of decimal digits in a number
// representation based on the number of bits and sign.
// e.g  digits10<int,64,true>::value == 19
template<typename T, T bits, bool is_signed> struct digits10 {
    static const int value = 0;
};

// Specialization that can be used to initialize static constant at
// compile time.
template<> struct digits10<int,  8, false> { static const int value = 3; };
template<> struct digits10<int,  8, true>  { static const int value = 3; };
template<> struct digits10<int, 16, false> { static const int value = 5; };
template<> struct digits10<int, 16, true>  { static const int value = 5; };
template<> struct digits10<int, 32, false> { static const int value = 10; };
template<> struct digits10<int, 32, true>  { static const int value = 10; };
template<> struct digits10<int, 64, false> { static const int value = 20; };
template<> struct digits10<int, 64, true>  { static const int value = 19; };
}

namespace std {

struct __numeric_limits_base
{
    // True for all fundamental types.
    static const bool is_specialized = false;

    // True if the type is signed.
    static const bool is_signed = false;

    // True if the type is integer.
    static const bool is_integer = false;

    // The number of radix digits that be represented without change. For
    // integer types, the number of non-sign bits in the representation; for
    // floating-point types, the number of radix digits in the mantissa.
    // Equivalent to FLT_MANT_DIG, DBL_MANT_DIG.
    static const int digits = 0;

    // The number of base 10 digits that can be represented without change.
    // Equivalent to FLT_DIG, DBL_DIG, LDBL_MANT_DIG.
    static const int digits10 = 0;
};


// Properties of fundamental types.
// Only a subset of the properties is supported.
template<typename _T>
struct numeric_limits : public __numeric_limits_base
{
    // The minimum finite value.
    static _T min() { return static_cast<_T>(0); }

    // The maximum finite value.
    static _T max() { return static_cast<_T>(0); }
};

// Specializations for some fundamental types.

// numeric_limits<float>
template<>
struct numeric_limits<float>
{
    static const bool is_specialized = true;

    static float min() { return __FLT_MIN__; }
    static float max() { return __FLT_MAX__; }

    static const bool is_signed = true;
    static const bool is_integer = false;

    static const int digits = __FLT_MANT_DIG__;
    static const int digits10 = __FLT_DIG__;
};

// numeric_limits<double>
template<>
struct numeric_limits<double>
{
    static const bool is_specialized = true;

    static double min() { return __DBL_MIN__; }
    static double max() { return __DBL_MAX__; }

    static const bool is_signed = true;
    static const bool is_integer = false;

    static const int digits = __DBL_MANT_DIG__;
    static const int digits10 = __DBL_DIG__;
};

// numeric_limits<int>
template<>
struct numeric_limits<int>
{
    static const bool is_specialized = true;

    static int min() { return INT_MIN; }
    static int max() { return INT_MAX; }

    static const bool is_signed = true;
    static const bool is_integer = true;

    static const int digits = static_cast<int>(sizeof(int) * CHAR_BIT);
    static const int digits10 = digits10<int, digits, is_signed>::value;
};

// numeric_limits<unsigned int>
template<>
struct numeric_limits<unsigned int>
{
    static const bool is_specialized = true;

    static unsigned int min() { return 0; }
    static unsigned int max() { return UINT_MAX; }

    static const bool is_signed = false;
    static const bool is_integer = true;

    static const int digits = static_cast<int>(sizeof(unsigned int) * CHAR_BIT);
    static const int digits10 = digits10<int, digits, is_signed>::value;
};

// numeric_limits<long>
template<>
struct numeric_limits<long>
{
    static const bool is_specialized = true;

    static long min() { return LONG_MIN; }
    static long max() { return LONG_MAX; }

    static const bool is_signed = true;
    static const bool is_integer = true;

    static const int digits = LONG_BIT;
    static const int digits10 = digits10<int, digits, is_signed>::value;
};

// numeric_limits<unsigned long>
template<>
struct numeric_limits<unsigned long>
{
    static const bool is_specialized = true;

    static unsigned long min() { return 0; }
    static unsigned long max() { return ULONG_MAX; }

    static const bool is_signed = true;
    static const bool is_integer = true;

    static const int digits = LONG_BIT;
    static const int digits10 = digits10<int, digits, is_signed>::value;
};

// numeric_limits<long long>
template<>
struct numeric_limits<long long>
{
    static const bool is_specialized = true;

    static long long min() { return LLONG_MIN; }
    static long long max() { return LLONG_MAX; }

    static const bool is_signed = true;
    static const bool is_integer = true;

    static const int digits = static_cast<int>(sizeof(long long) * CHAR_BIT);
    static const int digits10 = digits10<int, digits, is_signed>::value;
};

// numeric_limits<unsigned long long>
template<>
struct numeric_limits<unsigned long long>
{
    static const bool is_specialized = true;

    static unsigned long long min() { return 0; }
    static unsigned long long max() { return ULLONG_MAX; }

    static const bool is_signed = true;
    static const bool is_integer = true;

    static const int digits = static_cast<int>(sizeof(unsigned long long) * CHAR_BIT);
    static const int digits10 = digits10<int, digits, is_signed>::value;
};

}  // namespace std


#endif