Mathieu,
My main concern with this UID generation algorithm is that
it takes up 15 characters (16 with the trailing dot) to
add the encoding of "gdcm" into the uid. This seems like
a lot of characters and all it does is ensure that gdcm
uids are REALLY REALLY unique from the other uids that
may be generated from that root. But the ip address and
datestamp/timestamp should make the uid's unique enough.
You also want to transform the ip address somehow so that
the UID cannot be easily tracked back to a particular
machine. Having an IP address in the UID could be
an issue with ensuring anonymonization of data.
Jim
-----Original Message-----
From: Mathieu Malaterre [mailto:***@kitware.com]
Sent: Thursday, January 06, 2005 9:51 AM
To: ***@dclunie.com
Cc: Insight-developers (E-mail)
Subject: Re: [Insight-developers] DICOM UID generation
Post by David ClunieHi Jim
Sending money to ANSI is a complete waste of money, since there are
free UID roots available, and nobody cares where your root comes from
as long as it is unique.
"http://www.dclunie.com/medical-image-faq/html/part8.html#UIDRegistration"
Your biggest problem though is not getting a root, it is making sure
that every file generated by ITK anywhere no matter where and by whom
it is installed is globally unique.
Typically this is done with something unique to the device on which it
is installed, e.g. serial number, hostid, MAC address or similar, as
well as any process or thread running on that device (e.g. process
number). It is very hard to get this right in a multi-platform toolkit.
The MAC address, process number, a date time stamp with high precision
and a random number might be necessary. If it won't all fit into 64
bytes, considering feeding everything (after the root) into some sort
of cryptographic hash function.
David,
Could you please comment on the code bellow. This is extracted from
GDCM CVS tree.
The code works as follow:
echo "gdcm" | od -b
0000000 147 144 143 155 012
Then we build the UID with:
radical (if passed in) + 147.144.143.155 + IP + time()
Therefore even organization without radical can create unique DICOM
images internal within their organization.
Mathieu
/**
* \ingroup Util
* \brief Return the IP adress of the machine writting the DICOM image
*/
std::string Util::GetIPAddress()
{
// This is a rip from
http://www.codeguru.com/Cpp/I-N/internet/network/article.php/c3445/
#ifndef HOST_NAME_MAX
// SUSv2 guarantees that `Host names are limited to 255 bytes'.
// POSIX 1003.1-2001 guarantees that `Host names (not including the
// terminating NUL) are limited to HOST_NAME_MAX bytes'.
# define HOST_NAME_MAX 255
// In this case we should maybe check the string was not truncated.
// But I don't known how to check that...
#if defined(_MSC_VER) || defined(__BORLANDC__)
// with WinSock DLL we need to initialise the WinSock before using
gethostname
WORD wVersionRequested = MAKEWORD(1,0);
WSADATA WSAData;
int err = WSAStartup(wVersionRequested,&WSAData);
if (err != 0) {
/* Tell the user that we could not find a usable */
/* WinSock DLL. */
WSACleanup();
return "127.0.0.1";
}
#endif
#endif //HOST_NAME_MAX
std::string str;
char szHostName[HOST_NAME_MAX+1];
int r = gethostname(szHostName, HOST_NAME_MAX);
if( r == 0 )
{
// Get host adresses
struct hostent * pHost = gethostbyname(szHostName);
for( int i = 0; pHost!= NULL && pHost->h_addr_list[i]!= NULL; i++ )
{
for( int j = 0; j<pHost->h_length; j++ )
{
if( j > 0 ) str += ".";
str += Util::Format("%u",
(unsigned int)((unsigned char*)pHost->h_addr_list[i])[j]);
}
// str now contains one local IP address
#if defined(_MSC_VER) || defined(__BORLANDC__)
WSACleanup();
#endif
}
}
// If an error occur r == -1
// Most of the time it will return 127.0.0.1...
return str;
}
/**
* \ingroup Util
* \brief Creates a new UID. As stipulate in the DICOM ref
* each time a DICOM image is create it should have
* a unique identifier (URI)
*/
std::string Util::CreateUniqueUID(const std::string& root)
{
// The code works as follow:
// echo "gdcm" | od -b
// 0000000 147 144 143 155 012
// Therefore we return
// radical + 147.144.143.155 + IP + time()
std::string radical = root;
if( !root.size() ) //anything better ?
{
radical = "0.0."; // Is this really usefull ?
}
// else
// A root was specified use it to forge our new UID:
radical += "147.144.143.155"; // gdcm
radical += ".";
radical += Util::GetIPAddress();
radical += ".";
radical += Util::GetCurrentDate();
radical += ".";
radical += Util::GetCurrentTime();
return radical;
}
