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#include "aescpp.h"
#include <iostream>
#include <cstring>
#include <sys/types.h>
#include <unistd.h>
#include <sys/time.h>
#include <limits>
#include "dns_random.hh"
using namespace std;
static aes_encrypt_ctx g_cx;
static unsigned char g_counter[16];
static uint32_t g_in;
void dns_random_init(const char data[16])
{
aes_init();
aes_encrypt_key128((const unsigned char*)data, &g_cx);
struct timeval now;
gettimeofday(&now, 0);
memcpy(g_counter, &now.tv_usec, sizeof(now.tv_usec));
memcpy(g_counter+sizeof(now.tv_usec), &now.tv_sec, sizeof(now.tv_sec));
g_in = getpid() | (getppid()<<16);
srandom(dns_random(numeric_limits<uint32_t>::max()));
}
static void counterIncrement(unsigned char* counter)
{
if(!++counter[0])
if(!++counter[1])
if(!++counter[2])
if(!++counter[3])
if(!++counter[4])
if(!++counter[5])
if(!++counter[6])
if(!++counter[7])
if(!++counter[8])
if(!++counter[9])
if(!++counter[10])
if(!++counter[11])
if(!++counter[12])
if(!++counter[13])
if(!++counter[14])
++counter[15];
}
unsigned int dns_random(unsigned int n)
{
uint32_t out;
aes_ctr_encrypt((unsigned char*) &g_in, (unsigned char*)& out, sizeof(g_in), g_counter, counterIncrement, &g_cx);
return out % n;
}
#if 0
int main()
{
dns_random_init("0123456789abcdef");
for(int n = 0; n < 16; n++)
cerr<<dns_random(16384)<<endl;
}
#endif
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