libUFN/inc-c/ufn/ufn_round.h

// ufn_round.h: More feature-rich rounding functions.
// Under MIT-License. Copyright by Eric-Paul Ickhorn (epickh).

#ifndef UFN_ROUND_H
#define UFN_ROUND_H

#include <stdint.h>

/// @brief Rounds a value down to the last multiple of a stepping.
/// @param value Value to round down (floor).
/// @param stepping Stepping to round the value to.
/// @return Rounded value
int64_t ufn_floor_i64(int64_t value, int64_t stepping);

/// @brief Rounds a value up to the next multiple of a stepping.
/// @param value Value to round up (ceil).
/// @param stepping Stepping to round the value to.
/// @return Rounded value
int64_t ufn_ceil_i64(int64_t value, int64_t stepping);

/// @brief Rounds down (Floors) a value to the last power of 2.
/// @param value Value to find the nearest lower power of 2 of.
/// @return Power of 2 which is nearest lower one to 'value'.
uint64_t ufn_floor_pow2(uint64_t value);

/// @brief Rounds up (Ceils) a value to the next power of 2.
/// @note Internally, this uses the 'ufn_floor_pow2'-function but multiplies
///       its result by two to get the next higher power.
/// @param value Value to round up to the next power of 2.
/// @return Power of 2 which is the nearest higher one from 'value'.
uint64_t ufn_ceil_pow2(uint64_t value);

#ifdef UFN_IMPLEMENTATION

int64_t ufn_floor_i64(int64_t value, int64_t stepping)
{
    return value - (value % stepping);
}

int64_t ufn_ceil_i64(int64_t value, int64_t stepping)
{
    return ufn_floor_i64(value, stepping) + stepping;
}

uint64_t ufn_floor_pow2(uint64_t value)
{
    // Find highest-priority bit which is 1

    int8_t bit_index = 63;
    while(bit_index >= 0)
    {
        if(value & (1 << bit_index))
        {
            break;
        }
        --bit_index;
    }
    return 1 << bit_index;
}

uint64_t ufn_ceil_pow2(uint64_t value)
{
    uint64_t floored = ufn_floor_pow2(value);
    if(value == floored)
    {
        return value;
    }
    return floored * 2;
}

#endif // UFN_IMPLEMENTATION

#endif // UFN_ROUND_H