How to write and read from binary files

[Momergil]

Hello!

I'm planning a software that will plot a graph using Qwt or OpenGL (yet not decided) and the data of the graph would be catch by reading a .bin file, but this is the first time I deal with binary files so I'm a "little" bit ignorant on how do I proceed.

Before writing the actual software, I'm developing a second one to help me in my process of learning how to deal with binary files. This software has two QTextEdit side-by-side and have a "instant connection" between them (i.e. if one of them is edited, the other immediately should change base on what is written in the changed QTextEdit). But one of the QTextEdit is supposed to be connected with a .bin file and originally show what is written in the file in binary code (so one of the QTextEdit will show only a set of 0000 and 1111 and so on), while the other should be its translator, i.e. should show the binary code of the first QTextEdit in ASCII characters.

Now I already noticed that to work in this project I will use QDataStream and QFile. But the problem is that I'm not familiar with QDataStream::readBytes() and readRayData(), and nether with the write functions. So for example in the beginning, when the QFile is opened and should show in on of the QTextEdit the bin data contained in the .bin file, I don't know which function to use in the place of QTextStream::readAll().

Could somebody help me in this project? Which function do I use to read a binary code and show them in ASCII (e.g. 01000001 shows 65), how can I give a readAll() and how can I write an ASCII character and the software translate it to binary? And how can I make sure that the user will only write "0"s or "1"s in the QTextEdit for binary data, calling a warning if the user attempts to write a non-binary caracter? (i.e. try to put an ASCII char)


Thanks!!


Momergil



Note: It's something like this I want to do: http://www.roubaixinteractive.com/Pl...ry_To_Text.asp

[mvuori]

Even though people talk about "binary files", nobody in his/her right mind would ever think of their contents as being ones and zeros, but what ever expression some data structure or number format might require. Do yourself a favor and stop thinking in ones and zeros and think like a programmer should -- at the highest abstraction level that your tool supports.
Saving the files in some textual format would make them something like thousand times easier to debug when you change your code, data structures and file contents.

[marcvanriet]

Hi,

Don't do the qtextedit thing, it's just over-complicated and irrelevant.

How do you know what is in your .bin file ? Is it generated by some datalogger or so, and do you have documentation about that ?

First you should know how to interpret the .bin file, and then read it byte for byte and manipulate the bytes to turn them into usefull information.

Regards,
Marc

[ChrisW67]

If the files you are using as input are just being treated as a sequence of bytes then you do not need QDataStream, which is more aimed at providing an object serialisation system for Qt applications, you can just use the QIODevice interface directly.

QString::number can convert a byte to its string representation in any base you like between 2 and 36.
QString::toLong can do the opposite magic.

Ultimately I am not sure how useful your experiment will be in getting to your end goal of graphing a data stream from another source.