[RESOLVED] Editing ASCII files

[Buzzyous]

Good day to all.

I'm accessing an ASCII file, a large one, and my application needs to insert a character in a certain position to update data. The question is related to physical memory handling in moving the part of file that follows the newly inserted character... It is the only way to create a new file in which copy the part that precedes the inserted new char, then append the char and finally paste the subsequent original second part of the file? Because of the size of the file, this is not very fast...
If it is the only way, does anybody have some hint on how to perform it faster?

Thanks in advances, and nice holidays to all!

[TheCPUWizard]

What do you mean byt "LARGE"???

A quick test on my machine did this for a 100MB vector in under 100mS....

[Buzzyous]

What about 12 GB?

[Paul McKenzie]

What about 12 GB?

Isn't this something you should be trying yourself before assuming it's slow? If it is slow, then show us the code you're using to do this operation.

Regards,

Paul McKenzie

[marceln]

I cannot think now of a classical IO approach that will make this acceptably fast (from an end user's point of view).

Have you thought of using MMF's? (Memory Mapped Files). They would make altering such a large file relatively easy, considering the alternative.
Here's an article to get you started: http://msdn.microsoft.com/en-us/library/ms810613.aspx

You can post here if you have any more questions about this technique.

[TheCPUWizard]

IHave you thought of using MMF's? (Memory Mapped Files). They would make altering such a large file relatively easy, considering the alternative.
Here's an article to get you started: http://msdn.microsoft.com/en-us/library/ms810613.aspx

As a 64 bit application on a machine with ALOT of memory, that might be feasible.....Unfortunately most "affordable" machines will only support 12GB total RAM....

But to be honest, I have NEVER seen a 12GB text file.

If that was printed as a set of books, it would take over 120 meters of shelf space...More than a football (American or European) field is long.

[Buzzyous]

It is not text file, just ASCII file. I can access data as characters, but data is not necessarily to be interpreted in that form. They can be anything, like imagines, audio, video, etc.
The solution in the link seems nice, but in any case I found an error in the program; it now works in the times presented by CPUWizard, that are more acceptable than before.

Thanks to all for the very fructuous help, it really fastened things up for me. As usual, Codeguru is OK.

Bye to all, until next time!

[marceln]

You managed to do this:

create a new file in which copy the part that precedes the inserted new char, then append the char and finally paste the subsequent original second part of the file

with a 12 gb file in under 100 ms?

[TheCPUWizard]

I

Bye to all, until next time!

Dont forget to mark threads as resolved, and to rate those who helped....

[Buzzyous]

You managed to do this:

with a 12 gb file in under 100 ms?

Ahaha! No of course not... in 100 ms for 100Mb of course!