myvtm/Module/mod_chromium/uuid4.cpp

/**
 * 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>
#pragma comment(lib, "Advapi32.lib")
#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* template1 = "xxxxxxxxxxxx4xxxyxxxxxxxxxxxxxxx";
	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 = template1;
	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';
}

std::string uuid4_generate(int len)
{
	char buf[UUID4_LEN];

	uuid4_init();
	uuid4_generate(buf);
	std::string result = buf;
	if (len > 0 && len <= 32)
		return result.substr(0, len);
	else
		return "";
}