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Hi,
I have an application that performs some processing on files dropped into a 'watch folder'. The problem I'm having is detecting when the file copy to the folder is complete.
The application needs to run on both Windows and OSX, so ideally I'd like a cross-platform solution, although there is no reason (other than future maintainability) for using the same algorithm on both platforms.
The way I'm doing this at the moment is to wait until I can get a read lock on the file (by just trying to open it), then periodically checking the size of the file to make sure it's not getting any bigger.
Once both of those criteria have been met, I process the file.
The problem I'm seeing is that once in a blue moon, the two criteria will be met when the file is still being copied. My gut feeling is that it's caused by momentary network congestion, but I've been unable to reproduce the issue whilst debugging.
I can probably make it more stable by just throwing a few more checks at the problem and tweaking the time-out values, but the software engineer in me would like a more definitive solution.
Does anyone have any suggestions?
Cheers,
Charles
Charles Blessing
Software Engineer
NUGEN Audio
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Charles Blessing wrote:
The way I'm doing this at the moment is to wait until I can get a read lock on the file (by just trying to open it)...
What about an exclusive read lock, or maybe a write lock?
"One man's wage rise is another man's price increase." - Harold Wilson
"Fireproof doesn't mean the fire will never come. It means when the fire comes that you will be able to withstand it." - Michael Simmons
"Show me a community that obeys the Ten Commandments and I'll show you a less crowded prison system." - Anonymous
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One solution I've used is to write the new file to one directory (on the same system) and, when done, moving it to the target directory (on the same system) using the Win32 API, which is an atomic operation.
For one variation, we wrote the file to the same directory, but with an extra extension like ".~tmp" and then did the rename/move operation.
modified 12-Apr-13 14:51pm.
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Exactly. That is how browser file downloads work and most other file copy programs that I know of work. The destination filename does not appear until the file is complete.
I'd change your file copy program to copy to a temp file with 'guid-like' name or at least a .~nonsense extension and rename it after the transfer is complete. There are ways to do this, keeping such things as the file timestamp intact.
--
Harvey
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Hello All,
I have a MFC app being developed in VS 6.0
This app has a main dialog and from there user can open multiple dialogs. There's a possibility that at any given point there could be 2 or more dialogs open.
Now under a certain condition, i want to make all open dialogs invisible and just show up a LogIn dialog.
I think in order for this to done i need to get the handle of all open dialogs and call ShowWindow(FALSE);
How to get all dialog/window handle?
Thanks in advance.
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Donguy1976 wrote:
Now under a certain condition, i want to make all open dialogs invisible and just show up a LogIn dialog.
Or make the login dialog modal so that interfacing with the other dialogs would not be possible (until the login dialog was properly dismissed).
"One man's wage rise is another man's price increase." - Harold Wilson
"Fireproof doesn't mean the fire will never come. It means when the fire comes that you will be able to withstand it." - Michael Simmons
"Show me a community that obeys the Ten Commandments and I'll show you a less crowded prison system." - Anonymous
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Is it possible to get all dialog handles in a app? Or the number of dialogs that are open at a given time?
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the function EnumWindows may help you.This function can enum all the window in the window manager .Or you can use the relationship between the dialog and the apps to meet your point.
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Hello everyone,
Today when i was reviewing a part of C++ i noticed continue in some cycles (to be exact i managed to see atleast one example of each cycle with continue)
I remember beeing told that go to and continue shouldn't be used. You can easily do whatever you need with some other tool in c++ semantics.
What do you think? Is using continue a good practice?
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yes
==============================
Nothing to say.
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I think continue is quite okay while goto is evil.
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goto is ok. You can write bad code without it and good code with it, just depends on the code.
==============================
Nothing to say.
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In C there are a very few cases where using it is reasonable, in C++ I wouldn't hire someone who works with goto.
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pasztorpisti wrote: In C there are a very few cases where using it is reasonable
Bollocks.
pasztorpisti wrote: , in C++ I wouldn't hire someone who works with goto.
Dogmatist.
==============================
Nothing to say.
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I have no doubt a good programmer can write good programs with any syntax element of any language, but that doesn't mean that everyone should! Even the best program deterioates over time. Of all elements of the C/C++ language, goto is the one with the biggest potential for abuse, and the biggest potential for misinterpreting its intended use when maintaining the code. Therefore, even if you're the worlds best programmer, you should never deliberately use goto without a very good reason, and only if the existing alternatives would present a bigger potential for maintenance problems in the future.
You might argue that for throwaway code that you know is going to be ditched within a couple of months there is really no risk, but some of the most long-lived tools were originally designed as throwaway code. Even if the program as a whole gets thrown away, parts of it may be reused elsewhere. We are in an age of VCSs and code reuse; you can't take back code: once you've written it it can not be unwritten!
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Is there, use it.
(I know the same argument might used for the goto statement).
Veni, vidi, vici.
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Which I use, as well as the = ? : thingummyjob.
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Nothing to say.
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Me too.
Is there anybody against ternary operator usage, really?
Veni, vidi, vici.
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I am against ternary operator because my ancient VC++ stopped cooperating when I want to watch the variable in debug mode. It just won't paste it correctly.
I know this is not a good reason and I need to upgrade to whatever MS is pushing today.(LOL)
But if you use continue or ternary operator it NEEDS to be commented so one can remain sane when in debug mode!
I sometime use goto and label to have a common point for generic error code, but I would be curious if optimizer would do the same in release code anyway.
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I even use nested ternary operators, sometimes a few deep. That really messes with your head! 
==============================
Nothing to say.
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Erudite_Eric wrote: That really messes with your head!
Or rather, the poor sod who has the job of maintaining/debugging your code. 
Use the best guess
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If you cant stand the heat.....
Actually a lot of programmers cant handle casting and pointrs. I wrote some C code that couldnt be maintained by another team, so they took my product, f***ed it up, made it slower and then released it to the customer.
Oh, they also couldmt understand why doing heavy work in the GUI thread was a bad idea. Dumbfucks. I had it in a seperate thread, but they didnt know why, and probably never did even after I pointed out to them that their app didnt paint or respond to button clicks.
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Nothing to say.
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I worked on a project like that. In the end I stopped tryint to tell people why I thought it important to do something in a particular way; not that it mattered when management canned it.
Use the best guess
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Is it confusing? If it's not stop stressing.
Steve
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Argonia wrote: Today when i was reviewing a part of C++ i noticed continue in some cycles...
Use of 'continue' within a loop to request branch back to the next loop iteration is the main reason for its existence and accepted practice.
Use of 'continue' with a label as a subject of a 'goto' is probably some code that was translated from FORTRAN where 'continue' also exists but means something quite different. This combination of 'goto' and 'continue' should not be used anywhere in C or C++ and should be exterminated wherever found.
In C/C++, use of 'goto' (without continue) is disparaged and at best, controversial. It can be justified in some languages but I never use it in C/C++ and would question such code and require justification for every instance, in every code review.
[I came from an age where 'goto' was prolific.]
--
Harvey
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