Initial data pattern to buffer

[cheney]

Hi all:

$nBytes = 1024

$hBuffer = DllStructCreate("ubyte buffer[" & $nBytes & "]")

$pBuffer = DllStructGetPtr($hBuffer)

.

How to fill data pattern 0x55AA or any data pattern to $hBuffe not with "for"?

What method is fast ?? call memset ??

Thanks for your answer

Edited July 16, 2010 by cheney

[AndyG]

$nBytes = 1024
$hBuffer = DllStructCreate("ubyte buffer[" & $nBytes & "]")
$pBuffer = DllStructGetPtr($hBuffer)


$word = BinaryToString("0x55AA")

$t = TimerInit()
Do ;create string
    $word &= $word & $word ;grows fast....
Until StringLen($word) >= $nBytes
$word = StringLeft($word, $nBytes) ;strip
DllStructSetData($hBuffer, 1, $word)
$m = TimerDiff($t)

;verify
MsgBox(0, "Filled $hbuffer in " & $m & " ms", DllStructGetData($hBuffer, 1))

Edited July 16, 2010 by AndyG

[Spiff59]

After flipping the high/low order of the bytes, this seems to be blazing fast:

DllCall("ntdll.dll", "none", "RtlFillMemoryUlong", "ptr", $pBuffer, "int", 1024, "ulong", 0xAA55AA55)

Edited July 16, 2010 by Spiff59

[AndyG]

    now it is academically....i ran 10000 loops with each solution.... 

dll-call 250 ms     vs      string 165 ms

both equally fast....

But the bigger the struct, the faster the dll......i would prefer the dll 

Edited July 16, 2010 by AndyG

[Spiff59]

I just went and looked on MSDN and found that call when I read the original post in here.

But I don't think I'd regard 165 vs 250 as equally fast.

I've never liked doing benchmarks via TimerInit/Diff, you can get some crazy results run-to-run, or weird fluctuations depending on the iterations. I just tried this:

expandcollapse popup

#include <Array.au3>

$nBytes = 1024
$hBuffer = DllStructCreate("ubyte buffer[" & $nBytes & "]")
$pBuffer = DllStructGetPtr($hBuffer)

Global $loop, $Benchtable[5][4]
For $loop = 0 to 4
    $Benchtable[$loop][0] = 10 ^ ($loop + 1)
    Benchmark()
Next
_ArrayDisplay($Benchtable)
Exit

;===============================================================================
Func Benchmark()
    $t = TimerInit()
    For $x = 1 to $Benchtable[$loop][0]
        $word = BinaryToString("0x55AA") ; needs to be inside loop to be reset when doing multiple iterations for benchmark testing
        Do ;create string
            $word &= $word & $word ;grows fast....
        Until StringLen($word) >= $nBytes
        $word = StringLeft($word, $nBytes) ;strip
        ;   DllStructSetData($hBuffer, 1, $word)
    Next
    $Benchtable[$loop][1] = TimerDiff($t)

    $t = TimerInit()
    For $x = 1 to $Benchtable[$loop][0]
        $word = BinaryToString("0x55AA") ; statement here only to make the benchmark comparison fair
        DllCall( "ntdll.dll", "none", "RtlFillMemoryUlong", "ptr", $pBuffer, "int", 1024, "ulong", 0xAA55AA55)
    Next
    $Benchtable[$loop][2] = TimerDiff($t)

    $t = TimerInit()
    $dll = DllOpen("ntdll.dll") ; faster when called multiple times with this statement
    For $x = 1 to $Benchtable[$loop][0]
        DllCall($dll, "none", "RtlFillMemoryUlong", "ptr", $pBuffer, "int", 1024, "ulong", 0xAA55AA55)
    Next
    DllClose($dll)
    $Benchtable[$loop][3] = TimerDiff($t)
EndFunc

I wasn't sure how to fairly handle resetting the $Word variable... I put a reset of it in the second loop, and tuned the third loop for speed

typo

Edited July 16, 2010 by Spiff59

[cheney]

Thank you all for the answering

Edited July 17, 2010 by cheney