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#include <prng.h>
#include <thread.h>
#define EPOOLSIZE 2048
static uint32_t x = 211;
static int n = 0;
static char entropy[EPOOLSIZE];
static int entropy_count = 0;
static const uint32_t a = 16807;
static const uint32_t m = 0x7FFFFFFF;
uint16_t prng_word() {
int st = enter_critical(CL_NOINT);
if (++n >= 100) {
n = 0;
if (entropy_count) {
x += entropy[--entropy_count];
}
}
x = (x * a) % m;
uint16_t ret = x & 0xFFFF;
exit_critical(st);
return ret;
}
void prng_bytes(uint8_t* out, size_t nbytes) {
uint16_t *d = (uint16_t*)out;
for (size_t i = 0; i < nbytes / 2; i++) {
d[i] = prng_word();
}
if (nbytes & 1) out[nbytes-1] = prng_word() & 0xFF;
}
void prng_add_entropy(const uint8_t* ptr, size_t nbytes) {
int st = enter_critical(CL_NOINT);
while (nbytes-- && entropy_count < EPOOLSIZE - 1) {
entropy[entropy_count++] = *(ptr++);
}
exit_critical(st);
}
/* vim: set ts=4 sw=4 tw=0 noet :*/
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