How can I generate UUID in C

Question

I am creating an  idl file programmatically   How do I create UUIDs for the interfaces and Methods Programmatically   Can I generate the UUID programmatically

User · Accepted Answer

You are probably looking for System Guid NewGuid

User · Answer

I have a GitHub Gist with a Java like UUID implementation in C   https   gist github com rickbeerendonk 13655dd24ec574954366  The UUID can be created from the least and most significant bits  just like in Java  It also exposes them  The implementation has an explicit conversion to a GUID and an implicit conversion from a GUID

User · Answer

I don t know about methods  however  the type to GUID can be done via   Guid iid   System Runtime InteropServices Marshal GenerateGuidForType typeof IFoo      http   msdn microsoft com en-us library system runtime interopservices marshal generateguidfortype aspx

User · Answer

Be careful  while the string representations for  NET Guid and  RFC4122  UUID are identical  the storage format is not   NET trades in little-endian bytes for the first three Guid parts   If you are transmitting the bytes  for example  as base64   you can t just use Guid ToByteArray   and encode it  You ll need to Array Reverse the first three parts  Data1-3    I do it this way   var rfc4122bytes   Convert FromBase64String  aguidthatIgotonthewire      Array Reverse rfc4122bytes 0 4   Array Reverse rfc4122bytes 4 2   Array Reverse rfc4122bytes 6 2   var guid   new Guid rfc4122bytes     See this answer for the specific  NET implementation details   Edit  Thanks to Jeff Walker  Code Ranger  for pointing out that the internals are not relevant to the format of the byte array that goes in and out of the byte-array constructor and ToByteArray

User · Answer

Here is a client side  sequential guid  solution   http   www pinvoke net default aspx rpcrt4 uuidcreate  using System  using System Runtime InteropServices    namespace MyCompany MyTechnology Framework CrossDomain GuidExtend       public static class Guid                            Original Reference for Code          http   www pinvoke net default aspx rpcrt4 UuidCreateSequential html                        DllImport  rpcrt4 dll   SetLastError   true           static extern int UuidCreateSequential out System Guid guid            public static System Guid NewGuid                         return CreateSequentialUuid                        public static System Guid CreateSequentialUuid                         const int RPC S OK   0              System Guid g              int hr   UuidCreateSequential out g               if  hr    RPC S OK                  throw new ApplicationException  UuidCreateSequential failed      hr               return g                                  Text From URL above           UuidCreateSequential  rpcrt4           Type a page name and press Enter  You ll jump to the page if it exists  or you can create it if it doesn t          To create a page in a module other than rpcrt4  prefix the name with the module name and a period            Summary         Creates a new UUID          C  Signature           DllImport  rpcrt4 dll   SetLastError true           static extern int UuidCreateSequential out Guid guid             VB Signature          Declare Function UuidCreateSequential Lib  rpcrt4 dll   ByRef id As Guid  As Integer           User-Defined Types          None           Notes          Microsoft changed the UuidCreate function so it no longer uses the machine s MAC address as part of the UUID  Since CoCreateGuid calls UuidCreate to get its GUID  its output also changed  If you still like the GUIDs to be generated in sequential order  helpful for keeping a related group of GUIDs together in the system registry   you can use the UuidCreateSequential function           CoCreateGuid generates random-looking GUIDs like these           92E60A8A-2A99-4F53-9A71-AC69BD7E4D75         BB88FD63-DAC2-4B15-8ADF-1D502E64B92F         28F8800C-C804-4F0F-B6F1-24BFC4D4EE80         EBD133A6-6CF3-4ADA-B723-A8177B70D268         B10A35C0-F012-4EC1-9D24-3CC91D2B7122            UuidCreateSequential generates sequential GUIDs like these           19F287B4-8830-11D9-8BFC-000CF1ADC5B7         19F287B5-8830-11D9-8BFC-000CF1ADC5B7         19F287B6-8830-11D9-8BFC-000CF1ADC5B7         19F287B7-8830-11D9-8BFC-000CF1ADC5B7         19F287B8-8830-11D9-8BFC-000CF1ADC5B7            Here is a summary of the differences in the output of UuidCreateSequential           The last six bytes reveal your MAC address          Several GUIDs generated in a row are sequential          Tips  amp  Tricks          Please add some           Sample Code in C           static Guid UuidCreateSequential                        const int RPC S OK   0             Guid g             int hr   UuidCreateSequential out g              if  hr    RPC S OK               throw new ApplicationException                  UuidCreateSequential failed      hr              return g                       Sample Code in VB          Sub Main              Dim myId As Guid            Dim code As Integer            code   UuidCreateSequential myId             If code  lt  gt  0 Then              Console WriteLine  UuidCreateSequential failed   0    code             Else              Console WriteLine myId             End If         End Sub                                  Keywords  CreateSequentialUUID SequentialUUID

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