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// Copyright 2011-2023 David Robillard <d@drobilla.net>
// SPDX-License-Identifier: ISC
#ifndef ZIX_TEST_DATA_H
#define ZIX_TEST_DATA_H
#include <stddef.h>
#include <stdint.h>
/// Linear Congruential Generator for making random 32-bit integers
static inline uint32_t
lcg32(const uint32_t i)
{
static const uint32_t a = 134775813U;
static const uint32_t c = 1U;
return (a * i) + c;
}
/// Linear Congruential Generator for making random 64-bit integers
static inline uint64_t
lcg64(const uint64_t i)
{
static const uint64_t a = 6364136223846793005ULL;
static const uint64_t c = 1ULL;
return (a * i) + c;
}
/// Linear Congruential Generator for making random pointer-sized integers
static inline uintptr_t
lcg(const uintptr_t i)
{
#if UINTPTR_MAX >= UINT64_MAX
return lcg64(i);
#else
return lcg32(i);
#endif
}
/// Return a pseudo-pseudo-pseudo-random-ish integer with no duplicates
static inline size_t
unique_rand(size_t i)
{
i ^= 0x5CA1AB1EU; // Juggle bits to avoid linear clumps
// Largest prime < 2^32 which satisfies (2^32 = 3 mod 4)
static const size_t prime = 4294967291U;
const size_t residue = (size_t)(((uint64_t)i * i) % prime);
return (i >= prime) ? i // Values >= prime are mapped to themselves
: (i <= prime / 2) ? residue
: prime - residue;
}
#endif // ZIX_TEST_DATA_H
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