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#include <stdlib.h>
#include <stdio.h>
#include <stdint.h>
#include <stdbool.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
struct rngstate{
uint64_t state[16];
int idx;
};
static struct rngstate global_rng_state;
void init_rng(){
memset( (void*)&global_rng_state, 0, sizeof(struct rngstate) );
uint64_t seed_val = (uint64_t)SEED_VAL;
size_t c_idx = 0;
for ( ; c_idx < 16; c_idx++ ){
seed_val = seed_val * 0x13371337;
seed_val = seed_val ^ (seed_val >> 16);
global_rng_state.state[c_idx] = seed_val;
}
global_rng_state.idx = 0;
return;
}
uint64_t get_rng_output(){
int c_idx = global_rng_state.idx;
const uint64_t next_state = global_rng_state.state[c_idx++];
uint64_t use_state = global_rng_state.state[c_idx &= 15];
use_state ^= use_state << 31;
use_state ^= use_state >> 16;
use_state ^= next_state ^ (next_state >> 31);
global_rng_state.state[c_idx] = use_state;
global_rng_state.idx = c_idx;
return use_state * 0x1337;
}
unsigned int get_random_int( unsigned int min, unsigned int max ){
if ( min >= max )
return min;
uint64_t nmax = 0xffffffffffffffff;
uint64_t ncount = (max - min) + 1;
uint64_t upper_limit = nmax - (nmax % ncount);
uint64_t rand_int = get_rng_output();
if ( rand_int > upper_limit ){
while ( rand_int > upper_limit )
rand_int = get_rng_output();
}
return (unsigned int)(rand_int % max) + min;
}
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