API - CopyMemory

[Dennis]

I am trying to use CopyMemory to copy arrays as follows:

Private Declare Sub CopyMemory Lib "kernel32" Alias "RtlMoveMem ory" (ByVal
pDst As Long, ByVal pSrc As Long, ByVal ByteLen As Integer)

dim kin(11) as Integer
dim kout(11) as Integer

kin(1)= 1 'set values for two elements to see if Kout is the same
kin(5) = 5

CopyMemory(kout (0), kin(0), 48)

It compiles and runs but all I get in Kout is "0" for all elements.

--
Dennis in Houston

[Al Reid]

Re: API - CopyMemory

"Dennis" <Dennis@discuss ions.microsoft. com> wrote in message
news:56EB7C46-010F-4B0C-A70E-55F9BB89321F@mi crosoft.com...[color=blue]
>I am trying to use CopyMemory to copy arrays as follows:
>
> Private Declare Sub CopyMemory Lib "kernel32" Alias "RtlMoveMem ory" (ByVal
> pDst As Long, ByVal pSrc As Long, ByVal ByteLen As Integer)
>
> dim kin(11) as Integer
> dim kout(11) as Integer
>
> kin(1)= 1 'set values for two elements to see if Kout is the same
> kin(5) = 5
>
> CopyMemory(kout (0), kin(0), 48)
>
> It compiles and runs but all I get in Kout is "0" for all elements.
>
> --
> Dennis in Houston[/color]

Try changing Long to Integer in the API declare. Looks like a VB6
declaration. VB6 Long = VB.Net Integer

--
Al Reid

[Dennis]

Re: API - CopyMemory

Tried that, no change. I found an example on the web that timed the various
methods of copying arrays, i.e., for loop, assignment, and CopyMemory written
for vb.net. It doesn't work either as it only copies zeros. The author
apparently didn't test it by actually putting values in the source array.
--
Dennis in Houston


"Al Reid" wrote:
[color=blue]
> "Dennis" <Dennis@discuss ions.microsoft. com> wrote in message
> news:56EB7C46-010F-4B0C-A70E-55F9BB89321F@mi crosoft.com...[color=green]
> >I am trying to use CopyMemory to copy arrays as follows:
> >
> > Private Declare Sub CopyMemory Lib "kernel32" Alias "RtlMoveMem ory" (ByVal
> > pDst As Long, ByVal pSrc As Long, ByVal ByteLen As Integer)
> >
> > dim kin(11) as Integer
> > dim kout(11) as Integer
> >
> > kin(1)= 1 'set values for two elements to see if Kout is the same
> > kin(5) = 5
> >
> > CopyMemory(kout (0), kin(0), 48)
> >
> > It compiles and runs but all I get in Kout is "0" for all elements.
> >
> > --
> > Dennis in Houston[/color]
>
> Try changing Long to Integer in the API declare. Looks like a VB6
> declaration. VB6 Long = VB.Net Integer
>
> --
> Al Reid
>
>
>[/color]

[Jack Russell]

Re: API - CopyMemory

Dennis wrote:
[color=blue]
> Tried that, no change. I found an example on the web that timed the various
> methods of copying arrays, i.e., for loop, assignment, and CopyMemory written
> for vb.net. It doesn't work either as it only copies zeros. The author
> apparently didn't test it by actually putting values in the source array.[/color]
I would have the that you should be passing by ref not by val but ....

[Herfried K. Wagner [MVP]]

Re: API - CopyMemory

"Dennis" <Dennis@discuss ions.microsoft. com> schrieb:[color=blue]
> CopyMemory(kout (0), kin(0), 48)
>
> It compiles and runs but all I get in Kout is "0" for all elements.[/color]

I am curious why you would want to use 'CopyMemory'. You may want to use
'Buffer.BlockCo py' instead, which is pretty fast.

--
M S Herfried K. Wagner
M V P <URL:http://dotnet.mvps.org/>
V B <URL:http://classicvb.org/petition/>

[Dragon]

Re: API - CopyMemory

Dennis,

First, pDst and pSrc should be declared as ByRef. They are pointers, and
passing pointers ByVal doesn't make much sense.
Second, their type must match the type of an array.

So, your declatation should look like:

~
Declare Sub CopyMemory Lib "kernel32.d ll" Alias "RtlMoveMem ory" ( _
ByRef Destination As Integer, _
ByRef Source As Integer, _
ByVal Length As Integer _
)
~

Third, you can declare them as arrays, so it will be:

~
Declare Sub CopyMemory Lib "kernel32.d ll" Alias "RtlMoveMem ory" ( _
<MarshalAs(Unma nagedType.LPArr ay)> ByVal Destination() As
Integer, _
<MarshalAs(Unma nagedType.LPArr ay)> ByVal Source() As Integer, _
ByVal Length As Integer _
)
~

Fourth, why don't you use the Array.Copy method?

Roman

"Dennis" <Dennis@discuss ions.microsoft. com> ÓÏÏÂÝÉÌ/ÓÏÏÂÝÉÌÁ × ÎÏ×ÏÓÔÑÈ
ÓÌÅÄÕÀÝÅÅ: news:56EB7C46-010F-4B0C-A70E-55F9BB89321F@mi crosoft.com...[color=blue]
> I am trying to use CopyMemory to copy arrays as follows:
>
> Private Declare Sub CopyMemory Lib "kernel32" Alias "RtlMoveMem ory"[/color]
(ByVal[color=blue]
> pDst As Long, ByVal pSrc As Long, ByVal ByteLen As Integer)
>
> dim kin(11) as Integer
> dim kout(11) as Integer
>
> kin(1)= 1 'set values for two elements to see if Kout is the same
> kin(5) = 5
>
> CopyMemory(kout (0), kin(0), 48)
>
> It compiles and runs but all I get in Kout is "0" for all elements.
>
> --
> Dennis in Houston[/color]

[Dennis]

Re: API - CopyMemory

Thanks for the corrections to my code. You are absolutely correct in that I
need byRef. However, on the type in the declaration of CopyMemory, when
passed by reference, isn't an integer or long passed to the Com routine as
the address? For example, if my array is of type byte and I pass the array
by reference, what is actually passed...isn't it a 4 byte address?

As for using Array.CopyTo, in the end, I actually will be using CopyMemory
to copy a structure into an array for use with another com object.
--
Dennis in Houston


"Dragon" wrote:
[color=blue]
> Dennis,
>
> First, pDst and pSrc should be declared as ByRef. They are pointers, and
> passing pointers ByVal doesn't make much sense.
> Second, their type must match the type of an array.
>
> So, your declatation should look like:
>
> ~
> Declare Sub CopyMemory Lib "kernel32.d ll" Alias "RtlMoveMem ory" ( _
> ByRef Destination As Integer, _
> ByRef Source As Integer, _
> ByVal Length As Integer _
> )
> ~
>
> Third, you can declare them as arrays, so it will be:
>
> ~
> Declare Sub CopyMemory Lib "kernel32.d ll" Alias "RtlMoveMem ory" ( _
> <MarshalAs(Unma nagedType.LPArr ay)> ByVal Destination() As
> Integer, _
> <MarshalAs(Unma nagedType.LPArr ay)> ByVal Source() As Integer, _
> ByVal Length As Integer _
> )
> ~
>
> Fourth, why don't you use the Array.Copy method?
>
> Roman
>
> "Dennis" <Dennis@discuss ions.microsoft. com> ÓÏÏÂÝÉÌ/ÓÏÏÂÝÉÌà  × ÎÏ×ÏÓÔÑà ˆ
> ÓÌÅÄÕÀÝà …Ã…: news:56EB7C46-010F-4B0C-A70E-55F9BB89321F@mi crosoft.com...[color=green]
> > I am trying to use CopyMemory to copy arrays as follows:
> >
> > Private Declare Sub CopyMemory Lib "kernel32" Alias "RtlMoveMem ory"[/color]
> (ByVal[color=green]
> > pDst As Long, ByVal pSrc As Long, ByVal ByteLen As Integer)
> >
> > dim kin(11) as Integer
> > dim kout(11) as Integer
> >
> > kin(1)= 1 'set values for two elements to see if Kout is the same
> > kin(5) = 5
> >
> > CopyMemory(kout (0), kin(0), 48)
> >
> > It compiles and runs but all I get in Kout is "0" for all elements.
> >
> > --
> > Dennis in Houston[/color]
>
>
>[/color]

[Dennis]

Re: API - CopyMemory

Thanks, you are correct in that I should be using byref. I was trying code
from an example I got from the net (it didn't work either) and that's why.
--
Dennis in Houston


"Jack Russell" wrote:
[color=blue]
> Dennis wrote:
>[color=green]
> > Tried that, no change. I found an example on the web that timed the various
> > methods of copying arrays, i.e., for loop, assignment, and CopyMemory written
> > for vb.net. It doesn't work either as it only copies zeros. The author
> > apparently didn't test it by actually putting values in the source array.[/color]
> I would have the that you should be passing by ref not by val but ....
>[/color]

[Dennis]

Re: API - CopyMemory

Thanks Herfried but in the end, I want to copy a structure into an array
contained in another array for passing to another com object. That's why I
didn't use Buffer class.
--
Dennis in Houston


"Herfried K. Wagner [MVP]" wrote:
[color=blue]
> "Dennis" <Dennis@discuss ions.microsoft. com> schrieb:[color=green]
> > CopyMemory(kout (0), kin(0), 48)
> >
> > It compiles and runs but all I get in Kout is "0" for all elements.[/color]
>
> I am curious why you would want to use 'CopyMemory'. You may want to use
> 'Buffer.BlockCo py' instead, which is pretty fast.
>
> --
> M S Herfried K. Wagner
> M V P <URL:http://dotnet.mvps.org/>
> V B <URL:http://classicvb.org/petition/>
>
>[/color]

[Dragon]

Re: API - CopyMemory

"Dennis" <Dennis@discuss ions.microsoft. com> ñîîáùèë/ñîîáùèëà â íîâîñòÿõ
ñëåäóþùåå: news:3280A299-60AD-41B2-ABB4-D3C25007256F@mi crosoft.com...[color=blue]
> Thanks for the corrections to my code. You are absolutely correct in[/color]
that I[color=blue]
> need byRef. However, on the type in the declaration of CopyMemory,[/color]
when[color=blue]
> passed by reference, isn't an integer or long passed to the Com[/color]
routine as[color=blue]
> the address? For example, if my array is of type byte and I pass the[/color]
array[color=blue]
> by reference, what is actually passed...isn't it a 4 byte address?[/color]

First, CopyMemory isn't a COM routine. 8=]

Yes, passing ByRef means passing IntPtr (platform-dependent integer)
value which represents address of a variable, so if you wanted to
specify an address (ByVal), you should declare it as IntPtr. But when
you declare parameter ByRef you specify a type of variable itself, not
type of pointer to it, don't you?

If you pass an array by reference you get garbage 8=]. You can either
pass its first element by reference, or pass the whole array by value.
You will get the same result though.
[color=blue]
>
> As for using Array.CopyTo, in the end, I actually will be using[/color]
CopyMemory[color=blue]
> to copy a structure into an array for use with another com object.[/color]

You can use Marshal.Structu reToPtr() method for this, for example:

~
Dim a(Marshal.SizeO f(GetType(Decim al)) - 1) As Byte
Marshal.Structu reToPtr(23568.2 3573D,
Marshal.UnsafeA ddrOfPinnedArra yElement(a, 0), False)
Stop
~
[color=blue]
> --
> Dennis in Houston
>[/color]

Roman

[Jay B. Harlow [MVP - Outlook]]

Re: API - CopyMemory

Dennis,
Rather then risk memory, or at least to minimize, memory corruption.

I would recommend using Buffer.BlockCop y to copy arrays (as you initially
asked).

Alternatively I would use Marshal.Copy, Marshal.PtrToSt ructure,
Marshal.Structu reToPtr and possible other methods on the
System.Runtime. InteropServices .Marshal class to marshal from the Managed to
Unmanaged world.

I would not attempt to implement my own marshaller with CopyMemory as the
..NET Framework team has already done the work for me...

--
Hope this helps
Jay
T.S. Bradley - http://www.tsbradley.net


"Dennis" <Dennis@discuss ions.microsoft. com> wrote in message
news:56EB7C46-010F-4B0C-A70E-55F9BB89321F@mi crosoft.com...
|I am trying to use CopyMemory to copy arrays as follows:
|
| Private Declare Sub CopyMemory Lib "kernel32" Alias "RtlMoveMem ory" (ByVal
| pDst As Long, ByVal pSrc As Long, ByVal ByteLen As Integer)
|
| dim kin(11) as Integer
| dim kout(11) as Integer
|
| kin(1)= 1 'set values for two elements to see if Kout is the same
| kin(5) = 5
|
| CopyMemory(kout (0), kin(0), 48)
|
| It compiles and runs but all I get in Kout is "0" for all elements.
|
| --
| Dennis in Houston