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// *****************************************************************************
// * This file is part of the FreeFileSync project. It is distributed under *
// * GNU General Public License: https://www.gnu.org/licenses/gpl-3.0 *
// * Copyright (C) Zenju (zenju AT freefilesync DOT org) - All Rights Reserved *
// *****************************************************************************
#ifndef GUID_H_80425780237502345
#define GUID_H_80425780237502345
#include <fcntl.h> //open
#include <unistd.h> //close
#include <zen/sys_error.h>
//#include <uuid/uuid.h> -> uuid_generate(), uuid_unparse(); avoid additional dependency for "sudo apt-get install uuid-dev"
namespace zen
{
inline
std::string generateGUID() //creates a 16-byte GUID
{
#if __GLIBC__ > 2 || (__GLIBC__ == 2 && __GLIBC_MINOR__ >= 25) //getentropy() requires glibc 2.25 (ldd --version) PS: Centos 7 is on 2.17
std::string guid(16, '\0');
if (::getentropy(&guid[0], 16) != 0) //"The maximum permitted value for the length argument is 256"
throw std::runtime_error(std::string(__FILE__) + "[" + numberTo<std::string>(__LINE__) + "] Failed to generate GUID." +
"\n" + utfTo<std::string>(formatSystemError(L"getentropy", errno)));
return guid;
#else
class RandomGeneratorPosix
{
public:
RandomGeneratorPosix()
{
if (fd_ == -1)
throw std::runtime_error(std::string(__FILE__) + "[" + numberTo<std::string>(__LINE__) + "] Failed to generate GUID." +
"\n" + utfTo<std::string>(formatSystemError(L"open", errno)));
}
~RandomGeneratorPosix() { ::close(fd_); }
void getBytes(void* buf, size_t size)
{
for (size_t offset = 0; offset < size; )
{
const ssize_t bytesRead = ::read(fd_, static_cast<char*>(buf) + offset, size - offset);
if (bytesRead < 1) //0 means EOF => error in this context (should check for buffer overflow, too?)
throw std::runtime_error(std::string(__FILE__) + "[" + numberTo<std::string>(__LINE__) + "] Failed to generate GUID." +
"\n" + utfTo<std::string>(formatSystemError(L"read", bytesRead < 0 ? errno : EIO)));
offset += bytesRead;
assert(offset <= size);
}
}
private:
const int fd_ = ::open("/dev/urandom", O_RDONLY | O_CLOEXEC);
};
thread_local RandomGeneratorPosix gen;
std::string guid(16, '\0');
gen.getBytes(&guid[0], 16);
return guid;
#endif
}
}
#endif //GUID_H_80425780237502345
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