// Copyright 2023 Alejandro Colomar <alx@kernel.org>
// SPDX-License-Identifier:  LGPL-3.0-or-later WITH LGPL-3.0-linking-exception


#ifndef INCLUDE_C_RAND_CSRAND_CSRAND_UNIFORM_H_
#define INCLUDE_C_RAND_CSRAND_CSRAND_UNIFORM_H_


#include <stdint.h>

#include <c/bit/ceil.h>
#include <c/rand/csrand/csrand.h>


#pragma clang assume_nonnull begin
inline uint64_t c_csrand64_uniform(uint64_t n);
inline uint64_t c_csrand64_interval(uint64_t min, uint64_t max);


inline uint64_t
c_csrand64_uniform(uint64_t n)
{
	uint64_t  r, max, mask;

	max = n - 1;
	mask = c_bit_ceil_wrap_64(n) - 1;

	do {
		r = c_csrand64();
		r &= mask;
	} while (r > max);

	return r;
}


inline uint64_t
c_csrand64_interval(uint64_t min, uint64_t max)
{
	return c_csrand64_uniform(max - min + 1) + min;
}
#pragma clang assume_nonnull end


#endif  // Header guard