How to use QList to add many QFiles.

[weixj2003ld]

Thank you very much.How to design my program?Could you give me some advice?

[ChrisW67]

How to design my program?Could you give me some advice?

Only you know your requirements. Consider these things:

• How many is "many files"? 5 is easy, 5000 would need a different approach.
• What is being written? Text or binary blobs require different approaches.
• How is it being written and how often? In response to an external event, or under your control. Every 50 milliseconds or every day. Different approaches needed.
• The same thing to every file or different things? All the same... write one and duplicate it later
• How close to real-time does it need to be? If you can accept a few seconds lag then other options are available.
• Target files local or over a network? One performs better than the other.

[weixj2003ld]

Thank you for your answer very much.My requirement is :
First I read about 10-15 column dignal datum (about 50000 rows) from one text file,and then write them into 10-15 (the same as column number) binary files differently.All the operations are in a local computer.

[Lesiok]

First step : read all data to memory creating one list/vector for one column.
Second step : write data to out files one after the other. In this case, you need a list of file names and you only have one file open at a time.

[d_stranz]

First step : read all data to memory creating one list/vector for one column.
Second step : write data to out files one after the other. In this case, you need a list of file names and you only have one file open at a time.

This will work as long as the file can fit into memory, and a 15 x 50000 entry table is probably OK. If the files get to be too big to fit into memory, then there are at least two more options:

1 - Open the file using memory mapping and let the OS take care managing the memory. If the data is stored in the file in row x column order, then you might want to take your original approach of keeping 10 - 15 files open so the memory mapping will be efficient.

2 - Don't load the file into memory, but read through it 10 - 15 times, once for each column.

It really depends on how often you want to do this conversion. If it is something you do once for each batch of data, then it really doesn't matter if it takes 1 second or 10 seconds. If it is something you will do a lot (eg. you are trying to keep up with real-time data acquisition), then you want it to be as fast as possible.

[weixj2003ld]

Thank you all,I will try it.