[RESOLVED] Reading binary file

[redback]

Hey everybody,

Firstly, thanks for reading this thread. I'm c++ n00b so don't be too harsh on me . Anyway I'm struggling to solve my first cpp project. Before I worked for a few month with .NET. So I reckon I have some basics, hopefully . Now to my problem.

So, I have a file from gps receiver. I can't specify exactly what type it is, but I suppose it's binary file. Definitely it's not a text and there many unreadable characters. Some of them are actually readable e.g. pair of identifiers for certain messages (µb=0xB5 0x62). After these identifiers there is a body with the message that has to be converted to whatever(int,long,double....).
I want to read sequentially the whole file from the start to the end (say it's around 150MB). Find these pair identifiers. Read the body of each identifier (with defined length ) to unique struct. I don't worry about the output for now. I would be glad if you can help me with the main loop. I have this for now:

void FileManager::openFile(){
	//variables are located in FileManager.h
	ifstream fp;
	unsigned long len;
	char *buf;
	streambuf * pbuf;

	char bufferA;
	char bufferB;
	fp.open("raw.ubx", ifstream::binary | ios::in);
	fp.seekg(0, ios::end);
	len = fp.tellg();
	fp.seekg(0, ios::beg);
	pbuf = fp.rdbuf();
	while (pbuf->sgetc()!=EOF){
		bufferB = pbuf->sbumpc();
		if ((bufferB == 'µ') && (bufferA == 'b')){
			/*function call of this identifier*/
		}
		bufferA = bufferB;
	}
}

In my file on the first position there is µ character. But I get "-75" instead. All advices and tips from you are more than appreciated.
Also I would be glad if you know where to get offline ISO c++ documentation.

Thank you in advance

[treuss]

1. You are checking the content of bufferA before you ever assign anything to it.

2. For non-Ascii characters, use the numeric value that the character has according to the encoding your file is in.

3. The logic in your code will find bµ and not µb

4. Why do you access the streambuf. Why not just

char bufferB;
while (fp>>bufferB) {
  // ...
}

[redback]

Thank you for quick response, mate .
1) I reckon I should assign at least 0 at first, right ? Will do.
2)should I use atoi to get the numeric value? I don't think it's possible to do something like this int (bufferB). Can you give me an example, pls ?
3)Oooo yeaahh, you're right. silly me
4)Not sure, I suppose I found some examples and tried to use them in my way

[treuss]

2)should I use atoi to get the numeric value?

No, just compare char to number:

if (bufferA == 0xB5)

If that gives a warning, cast bufferA to unsigned char.

[redback]

it works, great. Thanks a lot. I need to study much more