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/*
* Copyright © 2016 Intel Corporation
*
* Permission is hereby granted, free of charge, to any person obtaining a
* copy of this software and associated documentation files (the "Software"),
* to deal in the Software without restriction, including without limitation
* the rights to use, copy, modify, merge, publish, distribute, sublicense,
* and/or sell copies of the Software, and to permit persons to whom the
* Software is furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice (including the next
* paragraph) shall be included in all copies or substantial portions of the
* Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
* IN THE SOFTWARE.
*/
#include "igt_primes.h"
#include <stdlib.h>
#include <stdbool.h>
#include <string.h>
#include <math.h>
/**
* SECTION:igt_primes
* @short_description: Prime numbers helper library
* @title: Primes
* @include: igt_primes.h
*/
#define BITS_PER_CHAR 8
#define BITS_PER_LONG (sizeof(long)*BITS_PER_CHAR)
#define BITMAP_FIRST_WORD_MASK(start) (~0UL << ((start) & (BITS_PER_LONG - 1)))
#define BITMAP_LAST_WORD_MASK(nbits) (~0UL >> (-(nbits) & (BITS_PER_LONG - 1)))
#define __round_mask(x, y) ((__typeof__(x))((y)-1))
#define round_up(x, y) ((((x)-1) | __round_mask(x, y))+1)
#define round_down(x, y) ((x) & ~__round_mask(x, y))
#define min(x, y) ({ \
typeof(x) _min1 = (x); \
typeof(y) _min2 = (y); \
(void) (&_min1 == &_min2); \
_min1 < _min2 ? _min1 : _min2; \
})
#define max(x, y) ({ \
typeof(x) _max1 = (x); \
typeof(y) _max2 = (y); \
(void) (&_max1 == &_max2); \
_max1 > _max2 ? _max1 : _max2; \
})
static inline unsigned long __bit__(unsigned long nr)
{
return 1UL << (nr % BITS_PER_LONG);
}
static inline void set_bit(unsigned long nr, unsigned long *addr)
{
addr[nr / BITS_PER_LONG] |= __bit__(nr);
}
static inline void clear_bit(unsigned long nr, unsigned long *addr)
{
addr[nr / BITS_PER_LONG] &= ~__bit__(nr);
}
static inline bool test_bit(unsigned long nr, const unsigned long *addr)
{
return addr[nr / BITS_PER_LONG] & __bit__(nr);
}
static unsigned long
__find_next_bit(const unsigned long *addr,
unsigned long nbits, unsigned long start,
unsigned long invert)
{
unsigned long tmp;
if (!nbits || start >= nbits)
return nbits;
tmp = addr[start / BITS_PER_LONG] ^ invert;
/* Handle 1st word. */
tmp &= BITMAP_FIRST_WORD_MASK(start);
start = round_down(start, BITS_PER_LONG);
while (!tmp) {
start += BITS_PER_LONG;
if (start >= nbits)
return nbits;
tmp = addr[start / BITS_PER_LONG] ^ invert;
}
return min(start + __builtin_ffsl(tmp) - 1, nbits);
}
static unsigned long find_next_bit(const unsigned long *addr,
unsigned long size,
unsigned long offset)
{
return __find_next_bit(addr, size, offset, 0UL);
}
static unsigned long slow_next_prime_number(unsigned long x)
{
for (;;) {
unsigned long y = sqrt(++x) + 1;
while (y > 1) {
if ((x % y) == 0)
break;
y--;
}
if (y == 1)
return x;
}
}
static unsigned long mark_multiples(unsigned long x,
unsigned long *primes,
unsigned long start,
unsigned long end)
{
unsigned long m;
m = 2*x;
if (m < start)
m = (start / x + 1) * x;
while (m < end) {
clear_bit(m, primes);
m += x;
}
return x;
}
unsigned long igt_next_prime_number(unsigned long x)
{
static unsigned long *primes;
static unsigned long last, last_sz;
if (x == 0)
return 1; /* a white lie for for_each_prime_number() */
if (x == 1)
return 2;
if (x >= last) {
unsigned long sz, y;
unsigned long *nprimes;
sz = x*x;
if (sz < x)
return slow_next_prime_number(x);
sz = round_up(sz, BITS_PER_LONG);
nprimes = realloc(primes, sz / sizeof(long));
if (!nprimes)
return slow_next_prime_number(x);
/* Where memory permits, track the primes using the
* Sieve of Eratosthenes.
*/
memset(nprimes + last_sz / BITS_PER_LONG,
0xff, (sz - last_sz) / sizeof(long));
for (y = 2UL; y < sz; y = find_next_bit(nprimes, sz, y + 1))
last = mark_multiples(y, nprimes, last_sz, sz);
primes = nprimes;
last_sz = sz;
}
return find_next_bit(primes, last, x + 1);
}
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