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/**
* Copyright (c) 2018 rxi
*
* This library is free software; you can redistribute it and/or modify it
* under the terms of the MIT license. See LICENSE for details.
*/
#include <stdio.h>
#include <stdint.h>
#if defined(_WIN32)
#include <windows.h>
#include <wincrypt.h>
#endif
#include "uuid4.h"
static uint64_t seed[2];
static uint64_t xorshift128plus(uint64_t *s) {
/* http://xorshift.di.unimi.it/xorshift128plus.c */
uint64_t s1 = s[0];
const uint64_t s0 = s[1];
s[0] = s0;
s1 ^= s1 << 23;
s[1] = s1 ^ s0 ^ (s1 >> 18) ^ (s0 >> 5);
return s[1] + s0;
}
int uuid4_init(void) {
#if defined(__linux__) || defined(__APPLE__) || defined(__FreeBSD__)
int res;
FILE *fp = fopen("/dev/urandom", "rb");
if (!fp) {
return UUID4_EFAILURE;
}
res = fread(seed, 1, sizeof(seed), fp);
fclose(fp);
if ( res != sizeof(seed) ) {
return UUID4_EFAILURE;
}
#elif defined(_WIN32)
int res;
HCRYPTPROV hCryptProv;
res = CryptAcquireContext(
&hCryptProv, NULL, NULL, PROV_RSA_FULL, CRYPT_VERIFYCONTEXT);
if (!res) {
return UUID4_EFAILURE;
}
res = CryptGenRandom(hCryptProv, (DWORD) sizeof(seed), (PBYTE) seed);
CryptReleaseContext(hCryptProv, 0);
if (!res) {
return UUID4_EFAILURE;
}
#else
#error "unsupported platform"
#endif
return UUID4_ESUCCESS;
}
void uuid4_generate(char *dst) {
static const char *template = "xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx";
static const char *chars = "0123456789abcdef";
union { unsigned char b[16]; uint64_t word[2]; } s;
const char *p;
int i, n;
/* get random */
s.word[0] = xorshift128plus(seed);
s.word[1] = xorshift128plus(seed);
/* build string */
p = template;
i = 0;
while (*p) {
n = s.b[i >> 1];
n = (i & 1) ? (n >> 4) : (n & 0xf);
switch (*p) {
case 'x' : *dst = chars[n]; i++; break;
case 'y' : *dst = chars[(n & 0x3) + 8]; i++; break;
default : *dst = *p;
}
dst++, p++;
}
*dst = '\0';
}
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