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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, getentropy
#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
{
std::string guid(16, '\0');
#ifndef __GLIBC_PREREQ
#error Where is Glibc?
#endif
#if __GLIBC_PREREQ(2, 25) //getentropy() requires Glibc 2.25 (ldd --version) PS: CentOS 7 is on 2.17
if (::getentropy(&guid[0], guid.size()) != 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\n" +
utfTo<std::string>(formatSystemError("getentropy", errno)));
#else
class RandomGeneratorPosix
{
public:
RandomGeneratorPosix()
{
if (fd_ == -1)
throw std::runtime_error(std::string(__FILE__) + '[' + numberTo<std::string>(__LINE__) + "] Failed to generate GUID." + "\n\n" +
utfTo<std::string>(formatSystemError("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\n" +
utfTo<std::string>(formatSystemError("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;
gen.getBytes(&guid[0], guid.size());
#endif
return guid;
}
}
#endif //GUID_H_80425780237502345
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