GUID (Globally Unique Identifier)

2023-02-24

GUID/UUID

Globally uniqueIdentifierGUID (Globally Unique Identifier) ​​is an algorithmically generatedBinaryA 128-bit numeric identifier. GUIDs are mainly used in networks or systems with multiple nodes or computers. Ideally, any computer andComputer clusterNo two identical GUIDs will be generated. The total number of GUIDs is 2^128 (3.4×10^38), so the probability of randomly generating two identical GUIDs is very small, but not zero. Therefore, the algorithms used to generate GUIDs usually add non-random parameters (such as time) to ensure that such duplication does not occur.

The term GUID is sometimes also used to refer toMicrosoftImplementation of the UUID standard.
On the Windows platform, GUID is widely used in Microsoft products to identifyRegistry Key, class and interface identifiers, databases,System CatalogAnd other objects.


Format

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The format of the GUID is "xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx", where each x is a number in the range 0-9 or af.hexadecimalFor example: 6F9619FF-8B86-D011-B42D-00C04FC964FF is a valid GUID value.

Features

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1. When a GUID is needed, it can be automatically generated by an algorithm without the need for an authoritative organization to manage it.

2. GUID can theoretically generate a unique value in the entire universe, which is very convenient for future data import.

dispute

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The potential drawbacks of GUID values ​​have been raisedConfidentialityAdvocateIn March 1999, the Federal Trade Commission of the United States was asked toMicrosoftThe controversy mainly concernsOffice 97andOffice 2000Documents use GUID values. Office documents, such as Word files orExcelelectronicData Sheet, the GUID values ​​used are invisible to the user. However, there are many reports that the author of a document can be tracked by tracing the GUID value, and even if the author has adopted special methods, they can still be tracked. In response to the above problems, Microsoft has released a patch version of Office 97 SR2, which disables the use of the GUID function and can also remove the GUID of existing documents.

The potential misuse of Intel processor serial numbers is essentially the same as the issue with GUID values ​​described above.

program

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VB
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Option Explicit
Private Type GUID
Data1As Long
Data2 As Integer
Data3As Integer
Data4(8) As Byte
End Type
Private Declare Function CoCreateGuid Lib "ole32.dll" (pguid As GUID) As Long
Private Declare Function StringFromGUID2 Lib "ole32.dll" (rguid As Any, ByVal lpstrClsId As Long, ByVal cbMax As Long) As Long
Private Function GUIDGen() As String 'Generate GUID
Dim uGUID As GUID
Dim sGUID As String
Dim bGUID() As Byte
Dim lLenAs Long
Dim RetVal As Long
lLen = 40
bGUID = String(lLen, 0)
CoCreateGuid uGUID 'Convert the structure into a displayable string
RetVal = StringFromGUID2(uGUID, VarPtr(bGUID(0)), lLen)
sGUID = bGUID
If (Asc(Mid$(sGUID, RetVal, 1)) = 0) Then RetVal = RetVal - 1
GUIDGen = Left$(sGUID, RetVal)
End Function
C++
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#include 
#include 
//--Generate GUID
const char* newGUID()
{
static char buf[64] = {0};
GUID guid;
if (S_OK == ::CoCreateGuid(&guid))
{
_snprintf(buf, sizeof(buf)
, "{%08X-%04X-%04x-%02X%02X-%02X%02X%02X%02X%02X%02X}"
, guid.Data1
, guid.Data2
, guid.Data3
, guid.Data4[0], guid.Data4[1]
, guid.Data4[2], guid.Data4[3], guid.Data4[4], guid.Data4[5]
, guid.Data4[6], guid.Data4[7]
);
}
return (const char*)buf;
}
int main(int argc, char* argv[])
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