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Hi
What is the difference between a process's ID and Handle?
I see that ID is just a number assigned to the process by the system but handle is like pointer of Process.Thay said program database.
But why do we need both of them?
Why is not enough only ID or Handle?
What are the differences?
Arent both of them unique?
Thanks.
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The process ID identifies the process. The process handle is used to perform operations on the process object.
The process id is valid until the process terminates. The process handle is not (you can release
a process handle with CloseHandle() and later obtain process handles with OpenProcess() using the process ID).
The process id will be unique in the system. The process handle is not necessarily unique
(although the object it represents is).
The details of what HANDLEs represent are (thankfully) hidden from us. Otherwise we'd need
different pointer types for all the different Win32 API sets.
Tip: A common handle leak occurs when using CreateProcess() and not releasing the returned
process and thread handles if they're not needed. I see this one often, and was guilty of it
myself for a long time 
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Thanks Mark.
I was going to reply to this one, My reply was longer, but your reply should be caligraphed and framed, and put on every system programmers wall. It is Apt and To The point.
LateNightsInNewry
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Thank you Mark Salsbery
Very good explanation.
In what situation are there many handles for a process and windows mange these handles?
Where does windows hold this id and handles?
I mean is there "one" handle table and "one" id table for one sesion?
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sawerr wrote: In what situation are there many handles for a process and windows mange these handles?
Hmmm... in the case of a process handle...say you have another process and you want to terminate
it (with extreme prejudice ). You find the process through some method, obtain a handle to it,
and use that handle in a call to TerminateProcess(). The process itself may have handle(s)
representing its own process as well. Lame example, yes. In the case of process handles maybe
there's not a good example of needing more than one process handle. The point is there CAN be
so to assume handles are unique is not correct.
sawerr wrote: Where does windows hold this id and handles?
I mean is there "one" handle table and "one" id table for one sesion?
Doesn't matter (although it can be interesting, of course). By using handles, the system is free
to implement this any way it needs to, without us having to change our code if the underlying
implementation changes. A handle could be a pointer, an index into an array, a numeric ID,
whatever the implementation uses to identify the object the handle represents. Windows may or
may not have its own handles to processes, I have no idea...the implementation is hidden from
me by handles.
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I'm working on a C++ MFC project that has a connection with a MSSQL Server and also makes HTTP requests.
What I would like to do is set up the program so all of the MSSQL traffic takes place on the local network (hardwired ethernet interface) but the HTTP communication takes place on a dialup network (modem interface). Basically, I want all of the HTTP traffic go through the external dialup network, but the database traffic needs to stay inside my LAN.
I'm using the standard MFC CRecordset classes to access the MSSQL Server (using TCP/IP via ODBC) and for my HTTP functions, I am using MFC CInternetSession and CHttpFile classes.
Is there a way I can bind these classes to a specific interface? I'm sure I can enumerate the network interfaces easily enough and identify them, but I'm not sure how to route TCP/IP traffic to a specific interface depending on the task.
Any help is greatly appreciated.
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Thanks and rats.
I suppose I'll have to change the processing logic so I'm not trying to run DB and HTTP threads at the same time and reconnect dialup between DB calls.
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I'm pretty sure in the case of TCP/IP, the microsoft stack implementation, in a multihomed
situation, will choose the adapter with the shortest path to the destination when making a
connection. Maybe it will just magically work(?). If there's not a gateway to the internet on
the LAN then wouldn't the HTTP connection choose the dialup adapter?
Mark
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Hi,
Is it possible to colored days with DayState in a MonthCalendar. Now they are only bold.
I see no chance in WinApi?
MfG schirrmie
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hi all,
the problem is
there are many icons in the system tray. i want to hide or delete one of the icons all ready present, how to get what icons are there visible or under hide inactive icon arrow mark,
do you have any idea how to get the list of icons from the system tray.
P.S. i dont want my icons to be added or deleted in the tray, i want icons of other application
Thanks
Swarup
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See here for "enumeration" ideas.
"Approved Workmen Are Not Ashamed" - 2 Timothy 2:15
"Judge not by the eye but by the heart." - Native American Proverb
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thanks a lot for the idea n help
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hi guys,
i got the idea, if anyone needs help let me know i am willing to help my best.
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There is documentation on the internet talking about a version 1.1 of GDI+ which implemets the Bitmap::ApplyEffect method.
Has this been released? There seem to be a lot of confused people asking where it can be found.
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zaccheus wrote: Has this been released?
Have you checked here?
"Approved Workmen Are Not Ashamed" - 2 Timothy 2:15
"Judge not by the eye but by the heart." - Native American Proverb
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Yes, of course I checked.
Here is a link to the latest download I can find: Platform SDK Redistributable: GDI+
The DLL it contains is dated 04 May 2004 and has version 5.1.3102.1360 - this is not v1.1 as far as I can tell.
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Yes it exists, no you cannot redistribute it. To my knowledge only Office 2003 ships with it.
Anyone who thinks he has a better idea of what's good for people than people do is a swine.
- P.J. O'Rourke
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I need to decompress HTTP streams that have been compressed with "Content-Encoding: gzip".
The gzip website ( gzip.org ) says I should use the zlib library if I want to work with data in memory.
However, it just keeps giving me DATA_FORMAT errors.
Has anyone worked with this library before? If so, please lend a helping hand!
Is this the correct library to use for HTTP compression?
I am simply taking the compressed content body, and passing it to the uncompress() function, and the documentation is so sparse, I can't tell if I'm doing it correctly.
--------------------------------
"All that is necessary for the forces of evil to win in the world is for enough good men to do nothing" -- Edmund Burke
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I have not used zlip to decompress a HTTP stream. However I use zlib to compress and decompress my own stream which is based on HTTP stream. While developing my routine I had to study the HTTP documentation (RFC). So, maybe I have an idea what could be the problem you have.
It is possible that the stream you read is 'Transfer-Encoding: chunked'. If so, trying to decompress in one gulp will not work. You probably have to decompress chunk by chunk.
Hope this helps. Keep this thread posted with your findings as I am interrested.
Louis.
Louis
* google is your friend *
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ldaoust wrote: It is possible that the stream you read is 'Transfer-Encoding: chunked'. If so, trying to decompress in one gulp will not work. You probably have to decompress chunk by chunk.
Louis, That is a brilliant insight! I hadn't thought of that. I will try to implement that right away.....
--------------------------------
"All that is necessary for the forces of evil to win in the world is for enough good men to do nothing" -- Edmund Burke
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Hi Louis, I think I have it figure out.
The content gets compressed before the chunking is applied, so it does need to be decompressed as a whole, not chunk by chunk.
However, your pointing me toward the transfer-encoding turned out to be what solved it, because I realized I was mishandling the chunks themselves. I was putting together the whole content without parsing the individual chunks to extract only the data, and not the chunk size.
Now I think I'm on the right track.
Thanks again for your brain power!
--------------------------------
"All that is necessary for the forces of evil to win in the world is for enough good men to do nothing" -- Edmund Burke
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Great!
I am curious though. Should'nt it be possible to decompress chunk by chunk ?
I am assuming that chunk transfer is the right choice when sending binary data in a streaming fashion. Since the binary data can be large and dynamic it would be built as chunk then compress then sent out. Maybe thats not the way a web server does it for files. Maybe it is still possible to do it this way. Would need something in the HTTP header to identicate this behaviour.
My implementation does it chunk by chunk, but this is between propriatary server and propriatary client application. So far works very well.
Glad I could help.
Cheers.
Louis.
"Ambition without knowledge is like a boat on dry land"
-Mr. Miyagi
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