How can I prevent CPU Usage increasing to 100 percent when copying files from CD?

[J French]

Re: How can I prevent CPU Usage increasing to 100 percent when copying files from CD?

On 9 Jan 2004 15:53:14 -0800, bwr@unicon.com (Bryan Rickard) wrote:
[color=blue]
>Steve, thank you very much! That took care of the problem.
>
>I wonder, though, why VB doesn't reallocate the same memory when you
>redefine a fixed-length string. You would think it would.[/color]

I agree, but even so it would still be quite a lot of unnecessary work
for the App.

Also, did you get my point about using Byte Arrays
- when VB reads data into a String it converts single bytes into 2
byte Unicode
- and when it writes it, it converts 2 byte Unicode to single bytes

[Raoul Watson]

Re: How can I prevent CPU Usage increasing to 100 percent when copying files from CD?


"Bryan Rickard" <bwr@unicon.com > wrote in message
news:2b02b188.0 401071806.1337d 16d@posting.goo gle.com...[color=blue]
> I wrote a simple program in VB6 to copy all the files from a directory
> on a CD-ROM to my hard disk. There are about 10 files, each about
> 30MB.
>
> The program uses Get and Put to get data from the CD into a buffer and
> then put it into the disk. See code below. It works, but it slows
> down drastically before it copies all the files. Windows Task Manager
> shows the CPU usage gradually increasing as the files are copied,
> until it reaches 100 percent after about 6 files. That's when it
> starts to get slow.
>
> How can I prevent the CPU usage increasing? Here's the guts of the
> code. All this is within another loop that goes through all the files
> in sCDPath with Dir$. I've tried buffer sizes from 50000 to 2
> million, makes no difference.
>
> iCDFN = FreeFile
> Open sCDPath & sFileName For Binary Access Read As #iCDFN
> iDiskFN = FreeFile
> Open sDiskPath & sFileName For Binary Access Write As #iDiskFN
> Do
> If lStartPos + lIncrement > lFileLen Then _
> lIncrement = lFileLen - lStartPos + 1
> sBuffer = String(lIncreme nt, " ")
> Get #iCDFN, , sBuffer
> Put #iDiskFN, , sBuffer
> lStartPos = lStartPos + lIncrement
> If lStartPos > lFileLen Then Exit Do
> Loop
> Close iCDFN
> Close iDiskFN
>
> TIA - Bryan Rickard[/color]

Bryan..

I know this doesn't address your question but just out of curiosity why
don't you just shell out? The operating system has optimized file copying
functions that I think we should make use of instead of bloating our code /
re-inventing the wheel.

You can either shell out, use API, or the file system object.

[Charles Kincaid]

Re: How can I prevent CPU Usage increasing to 100 percent when copying files from CD?

bwr@unicon.com (Bryan Rickard) wrote in
news:2b02b188.0 401091552.ecec8 35@posting.goog le.com:
[color=blue]
> Steve, thank you very much! That took care of the problem.
>
> I wonder, though, why VB doesn't reallocate the same memory when you
> redefine a fixed-length string. You would think it would.
>
> - Bryan[/color]

Because it is not a fixed-length string. String returns a variant
containing a variable length string of the length specified containing
the specified byte. Please read that carfully. String returns a variant
while String$ returns a string. Variant type conversions can be very
slow in VB. So if sBuffer is declared a string (you do use Option
Explicit and correctly type all of your variables, right?) then sBuffer =
String(lIncreme nt," ") where lIncrement=3 million creates a 3 million
byte string in a variant and then copies that to a 3 million byte string.

Steve Gerrard is also right when he says build the string buffer only
when the buffer size changes. As far as writing the little piece first I
gave that up some years back as I realized that by doing so I avoid any
benefits of trying to help the OS by picking the right size buffer.

A far as lIncrement size: Pick an exact multiple of the destination
volume cluster size. Do keep it reasonably small. If there are not 3
miilon free bytes in the pool then a 3 meg string is going to get
virtualized. Less likely to happen with lengths of 64 K or so.

--
ATB

Charles Kincaid

[Bryan Rickard]

Re: How can I prevent CPU Usage increasing to 100 percent when copying files from CD?

"Raoul Watson" <WatsonR@Intell igenCIA.com> wrote in message news:<n1gMb.555 5$Qq.4640@nwrdn y01.gnilink.net >...[color=blue]
>
> Bryan..
>
> I know this doesn't address your question but just out of curiosity why
> don't you just shell out? The operating system has optimized file copying
> functions that I think we should make use of instead of bloating our code /
> re-inventing the wheel.
>
> You can either shell out, use API, or the file system object.[/color]

Raoul - do you mean something like RetVal = Shell("explorer .exe", 1)?
If so, I need something more customized for this application, at the
very least it would need to open with the CD drive contents showing,
but a new Explorer window always opens at My Documents (annoyingly).
Thanks for the input anyway, I might find a need for that one day, and
I hadn't thought of it.

- Bryan

[Raoul Watson]

Re: How can I prevent CPU Usage increasing to 100 percent when copying files from CD?


"Bryan Rickard" <bwr@unicon.com > wrote in message
news:2b02b188.0 401131659.653d9 999@posting.goo gle.com...[color=blue]
> "Raoul Watson" <WatsonR@Intell igenCIA.com> wrote in message[/color]
news:<n1gMb.555 5$Qq.4640@nwrdn y01.gnilink.net >...[color=blue][color=green]
> >
> > Bryan..
> >
> > I know this doesn't address your question but just out of curiosity why
> > don't you just shell out? The operating system has optimized file[/color][/color]
copying[color=blue][color=green]
> > functions that I think we should make use of instead of bloating our[/color][/color]
code /[color=blue][color=green]
> > re-inventing the wheel.
> >
> > You can either shell out, use API, or the file system object.[/color]
>
> Raoul - do you mean something like RetVal = Shell("explorer .exe", 1)?
> If so, I need something more customized for this application, at the
> very least it would need to open with the CD drive contents showing,
> but a new Explorer window always opens at My Documents (annoyingly).
> Thanks for the input anyway, I might find a need for that one day, and
> I hadn't thought of it.
>
> - Bryan[/color]

Not really. What I mean is have a file selection dialog and once the source
file is identified use Windows API or the file system object to copy it or
simple shell out to a batch file like Shell "copy.bat" where copy.bat would
have copy d:\whateverdir\ whateverfile c:\whereever

If you need it, give me a holler, I'll e-mail you.

[Raoul Watson]

Re: How can I prevent CPU Usage increasing to 100 percent when copying files from CD?


"Bryan Rickard" <bwr@unicon.com > wrote in message
news:2b02b188.0 401131659.653d9 999@posting.goo gle.com...[color=blue]
> "Raoul Watson" <WatsonR@Intell igenCIA.com> wrote in message[/color]
news:<n1gMb.555 5$Qq.4640@nwrdn y01.gnilink.net >...[color=blue][color=green]
> >
> > Bryan..
> >
> > I know this doesn't address your question but just out of curiosity why
> > don't you just shell out? The operating system has optimized file[/color][/color]
copying[color=blue][color=green]
> > functions that I think we should make use of instead of bloating our[/color][/color]
code /[color=blue][color=green]
> > re-inventing the wheel.
> >
> > You can either shell out, use API, or the file system object.[/color]
>
> Raoul - do you mean something like RetVal = Shell("explorer .exe", 1)?
> If so, I need something more customized for this application, at the
> very least it would need to open with the CD drive contents showing,
> but a new Explorer window always opens at My Documents (annoyingly).
> Thanks for the input anyway, I might find a need for that one day, and
> I hadn't thought of it.
>
> - Bryan[/color]

Here is one quick way..
Dim SourceF, DestF
SourceF = "D:\WHATEVERDIR \MYFILE.DAT" ' Define source file name.
DestF = "C:\WHEREVER\MY FILE.DAT" ' Define target file name.
FileCopy SourceF, DestF ' Copy source to target.

[Bryan Rickard]

Re: How can I prevent CPU Usage increasing to 100 percent when copying files from CD?

erewhon@nowhere .com (J French) wrote in message news:<3fffcecf. 169051856@news. btclick.com>...[color=blue]
> Also, did you get my point about using Byte Arrays
> - when VB reads data into a String it converts single bytes into 2
> byte Unicode
> - and when it writes it, it converts 2 byte Unicode to single bytes[/color]

I tried using Byte Arrays, they work fine with fixed length arrays but
for the left-over bytes I had to use a dynamic array, and the Put
statement added an extra string of hundreds of nulls (hex 0) onto the
end of the left-over bytes. Here's the code I used:

Dim bBytes(65536) As Byte
Dim bLeftOverBytes( ) As Byte
...
Do
If lStartPos + lIncrement > lFileLen Then
lLeftOver = lFileLen - lStartPos + 1
ReDim bLeftOverBytes( lLeftOver)
Get #iCDFN, , bLeftOverBytes
Put #iDiskFN, , bLeftOverBytes 'writes too many bytes
Exit Do
Else 'this is the normal loop, it works fine
lStartPos = lStartPos + lIncrement
Get #iCDFN, , bBytes
Put #iDiskFN, , bBytes
End If
Loop

Any ideas?

[Bryan Rickard]

Re: How can I prevent CPU Usage increasing to 100 percent when copying files from CD?

Charles Kincaid <kincaic@swbell .net> wrote in message news:<Xns946F6D 78DA5D7kincaics wbellnet@38.144 .126.67>...[color=blue]
>
> Because it is not a fixed-length string. String returns a variant
> containing a variable length string of the length specified containing
> the specified byte. Please read that carfully. String returns a variant
> while String$ returns a string. Variant type conversions can be very
> slow in VB. So if sBuffer is declared a string (you do use Option
> Explicit and correctly type all of your variables, right?) then sBuffer =
> String(lIncreme nt," ") where lIncrement=3 million creates a 3 million
> byte string in a variant and then copies that to a 3 million byte string.
>
> Steve Gerrard is also right when he says build the string buffer only
> when the buffer size changes. As far as writing the little piece first I
> gave that up some years back as I realized that by doing so I avoid any
> benefits of trying to help the OS by picking the right size buffer.
>
> A far as lIncrement size: Pick an exact multiple of the destination
> volume cluster size. Do keep it reasonably small. If there are not 3
> miilon free bytes in the pool then a 3 meg string is going to get
> virtualized. Less likely to happen with lengths of 64 K or so.[/color]

Thank you, Charles, good inputs.