libcruft-util/maths.cpp

/*
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 * Copyright 2010-2014 Danny Robson <danny@nerdcruft.net>
 */

#include "maths.hpp"

#include "debug.hpp"

#include "float.hpp"

#include <cmath>
#include <type_traits>


///////////////////////////////////////////////////////////////////////////////
template <typename T>
T
util::log2up (T v)
{
    return log2 ((v << 1) - 1);
}

template uint32_t util::log2up (uint32_t);
template uint64_t util::log2up (uint64_t);


///////////////////////////////////////////////////////////////////////////////
template <typename T>
T
util::log2 (T v)
{
    static_assert (std::is_integral<T>::value,
                   "log2 is only implemented for integers");

    T l = 0;
    while (v >>= 1)
        ++l;

    return l;
}

template uint8_t  util::log2 (uint8_t);
template uint16_t util::log2 (uint16_t);
template uint32_t util::log2 (uint32_t);
template uint64_t util::log2 (uint64_t);


///////////////////////////////////////////////////////////////////////////////
namespace util {
    template <>
    unsigned
    digits (const uint32_t &v)
    {
        return (v >= 1000000000) ? 10 :
               (v >=  100000000) ?  9 :
               (v >=   10000000) ?  8 :
               (v >=    1000000) ?  7 :
               (v >=     100000) ?  6 :
               (v >=      10000) ?  5 :
               (v >=       1000) ?  4 :
               (v >=        100) ?  3 :
               (v >=         10) ?  2 :
                                    1;
    }
}


///////////////////////////////////////////////////////////////////////////////
template <typename T>
std::enable_if_t<
    std::is_integral<T>::value, T
>
util::round_pow2 (T value)
{
    using return_type = std::enable_if_t<std::is_integral<T>::value, T>;

    --value;

    for (unsigned i = 1; i < sizeof (T) * 8; i <<= 1) {
        value |= value >> i;
    }

    ++value;
    return (return_type)value;
}


//-----------------------------------------------------------------------------
template uint8_t  util::round_pow2 (uint8_t);
template uint16_t util::round_pow2 (uint16_t);
template uint32_t util::round_pow2 (uint32_t);
template uint64_t util::round_pow2 (uint64_t);


///////////////////////////////////////////////////////////////////////////////
template const float  util::PI<float>;
template const double util::PI<double>;


///////////////////////////////////////////////////////////////////////////////
// Simple instantiations. Some functions aren't used internally to the library
// so it's easier to instantiate early and check for broken code at library
// build time.

template float util::limit (float, float, float);

template float  util::smoothstep (float,  float,  float);
template double util::smoothstep (double, double, double);