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/*
* File: private/randompatch.h
* ---------------------------
* This file patches the implementation of the random number library
* to avoid some serious bugs in standard implementations of rand,
* particularly on Mac OS X. It also includes a hack to set the
* seed from the RANDOM_SEED environment variable, which makes it
* possible to produce repeatable figures.
*/
/*
* Implementation notes: rand, srand
* ---------------------------------
* To ensure that this package works the same way on all platforms,
* this file completely reimplements the rand and srand methods. The
* algorithm is a conventional linear congruential generator with the
* parameters used in GNU's gclib. RAND_MAX for this implementation
* is 2147483647 (2^31 - 1).
*/
#define MULTIPLIER 1103515245
#define OFFSET 12345
static int _seed = 1;
#undef rand
#define rand() ((_seed = MULTIPLIER * _seed + OFFSET) & 0x7FFFFFFF)
#undef srand
#define srand(seed) (_seed = int(seed), _seed = (_seed <= 0) ? 1 : _seed)
#undef RAND_MAX
#define RAND_MAX 2147483647
/*
* Implementation notes: Windows patch
* -----------------------------------
* On some versions of Windows, the time function is too coarse to use
* as a random seed. On those versions, this definition substitutes the
* GetTickCount function.
*/
#if defined (_MSC_VER) && (_MSC_VER >= 1200)
# include <windows.h>
# define time(dummy) (GetTickCount())
#endif
#ifdef __APPLE__
# include <cstdlib>
static time_t patchedTime(time_t *) {
char *str = getenv("RANDOM_SEED");
if (str == NULL) {
return time(NULL);
} else {
return atoi(str);
}
}
# define time(dummy) patchedTime(dummy)
#endif
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