113 lines
2.2 KiB
C
113 lines
2.2 KiB
C
#include <stdint.h>
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#include <math.h>
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#include <unistd.h>
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#include <time.h>
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#ifdef LINUX
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#include <sys/time.h>
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#include <fcntl.h>
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#endif
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#include <SDL.h>
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#include "rng.h"
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#include "log.h"
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// Mersenne twister state.
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static uint32_t MT[624];
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static uint32_t mt_y;
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static int mt_pos = 0; // Current number.
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static uint32_t rng_timeEntropy(void);
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// Mersenne twister.
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static void mt_initArray(uint32_t seed);
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static void mt_genArray(void);
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static uint32_t mt_getInt(void);
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void rng_init(void) {
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uint32_t i;
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#ifdef LINUX
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int fd; char buf[4];
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fd = open("/dev/random", O_RDONLY);
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if(fd != -1) {
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if(read(fd, buf, 4) < 4)
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memcpy(&i, buf, 4);
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else
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i = rng_timeEntropy();
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close(fd);
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} else
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i = rng_timeEntropy();
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#else
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i = rng_timeEntropy();
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#endif
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mt_initArray(i);
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for(i = 0; i < 10; i++)
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// Generate numbers to get away from poor initial values.
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mt_genArray();
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}
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// Use the time as source of entropy.
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static uint32_t rng_timeEntropy(void) {
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int i;
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#ifdef WIN32
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struct _timeb tb;
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_ftime(&tb);
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i = tb.time * 1000 + tb.millitm;
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#else
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struct timeval tv;
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gettimeofday(&tv, NULL);
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i = tv.tv_sec * 1000000 + tv.tv_usec;
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#endif
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return i;
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}
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// Generates the initial mersenne twister based on seed.
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static void mt_initArray(uint32_t seed) {
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int i;
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MT[0] = seed;
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for(i = 1; i < 624; i++)
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MT[i] = 1812433253 * (MT[i-1] ^ (((MT[i-1])) + i) >> 30);
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mt_pos = 0;
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}
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// Generate an array of numbers.
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static void mt_genArray(void) {
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int i;
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for(i = 0; i < 624; i++) {
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mt_y = (MT[i] & 0x80000000) + ((MT[i] % 624) & 0x7FFFFFFF);
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if(mt_y % 2)
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// Odd.
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MT[i] = (MT[(i+397) % 624] ^ (mt_y >> 1)) ^ 2567483615;
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else
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// Even.
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MT[i] = MT[(i+397) % 624] ^ (mt_y >> 1);
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}
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mt_pos = 0;
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}
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// Get the next int.
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static uint32_t mt_getInt(void) {
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if(mt_pos >= 624) mt_genArray();
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mt_y = MT[mt_pos++];
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mt_y ^= mt_y >> 11;
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mt_y ^= (mt_y << 7) & 2636928640;
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mt_y ^= (mt_y << 15) & 4022730752;
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mt_y ^= (mt_y >> 18);
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return mt_y;
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}
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// Return a random int.
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unsigned int randint(void) {
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return mt_getInt();
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}
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// Return a random double.
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static double m_div = (double)(0xFFFFFFFF) + 1.;
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double randfp(void) {
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double m = (double)mt_getInt();
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return m / m_div;
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}
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