The odds of even one name-collision are extremely small;

Do you consider a 1 in 30 chance as "extremely small"? 

>perl -E"$h{rand()}++ for 1..1e6; printf qq[prob: %.3f%%\n], (keys(%h)
+/1e4)"
prob: 3.277%

>perl -E"$h{rand()}++ for 1..1e6; printf qq[prob: %.3f%%\n], (keys(%h)
+/1e4)"
prob: 3.277%

>perl -E"$h{rand()}++ for 1..1e6; printf qq[prob: %.3f%%\n], (keys(%h)
+/1e4)"
prob: 3.277%

>perl -E"$h{rand()}++ for 1..1e6; printf qq[prob: %.3f%%\n], (keys(%h)
+/1e4)"
prob: 3.277%

[download]

What I've implemented is this (the code is to be part of an XS module): 

void makeDir( void ) {
    in t i = 10;
    do {
     sprintf( dir, "c:/tmp/MYAPP04x%04X/", 
            GetCurrentProcessId(), GetTickCount64() & 0xffff );
            --i || expire( -99999 );
    } while( _mkdir( dir ) == ERROR_FILE_EXISTS );

    GetLastError() && expire( - GetLastError() );

    return;
}

[download]

GetTickCount64() returns the uptime in milliseconds. By truncating it to 16-bits it proves to be a better rand() than MS' CRT rand() :).

The error codes are provisional!

Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
"Science is about questioning the status quo. Questioning authority".
In the absence of evidence, opinion is indistinguishable from prejudice.
RIP an inspiration; A true Folk's Guy

In reply to Re^6: Generate a unique ID by BrowserUk
in thread Generate a unique ID by BrowserUk

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