ifstream

[NeoGeoEch13]

Hello, everyone, thanks for the site and the support.
I need to read an ansi encoded .txt file.
(http://www.cplusplus.com/reference/iostream/istream/read/)

I'am creating a class that has char* fileData that is initialized to null on constructor and delete[] if not null in destructor.

I use fileData as follows:

char* FileLogger::read(const std::string& fileName)
{
	std::ifstream myInputFileStream;
	try
	{
		long fileLength;
	
		myInputFileStream.open( fileName.c_str());
		if(!myInputFileStream)
		{
			throw std::exception("Error opening the requested file.");
		}
		
		myInputFileStream.seekg (0, ios::end);
		fileLength = myInputFileStream.tellg();

		fileData = new char[fileLength];

		myInputFileStream.seekg (0, ios::beg);

		myInputFileStream.read(fileData, fileLength);
		
		myInputFileStream.close();

		return fileData;
		

	}
	catch(std::exception& myExc)
	{
		if(myInputFileStream.is_open())
		{
			myInputFileStream.close();
		}

		std::cout << myExc.what() << endl;
	}

}

then on my main:

printf("%s", myFL.read("C:\\Documents and Settings\\Neo_Geo\\Desktop\\blues.txt"));

but it adds some extra weird chars at the end.
Could someone help me out please?
Thank you in advance.

[moorecm]

The printf call expects the string to be null-terminated.

Try:

fileData = new char[fileLength + 1];
//...
fileData[fileLength] = 0;

[NeoGeoEch13]

I tried what you said and

fileData[fileLength] = '\0';

but still the same :(

[moorecm]

I'm stumped then. Could it be something with the seekg/tellg to get the length?

[NeoGeoEch13]

In the console I get:

chord movement of F7-Bb7-F7-C7.
You'll hear similar eight-bar chord progressions on songs like
"Someday After a While" by Freddie King,
"It Hurts Me Too" by Elmore James and
"Sitting on Top of the World" by Howlin' Wolf.════

The .txt ends at "...Wolf."
I don't have any trailing cr/lf or white spaces and it is saved in Ansi encoding.
Anyways, I'll check back tomorrow, goodnight everyone.

[guestgulkan]

To be sure - what you can do is set the buffer array to 0 to begin with.
fileData = new char[fileLength+1](); //the () at the end means initialise to zero

[NeoGeoEch13]

This works guestgulkan, thank you! (I will mark as solved in the night...)

What is the cost of initializing this way all reserved memory address to 0 pointed to by fileData?

Why can't I just initialize the last element?

Oh and should I init to length+1? for the extra null?
Because it works for both

fileData = new char[fileLength + 1]();
fileData = new char[fileLength]();

Am I waisting a byte in the 1st one?

[NeoGeoEch13]

I really don't get it...even

fileData = new char[fileLength -3]();

works just fine. What's happening?

[firedraco]

Instead of using C-strings and stuff, why can't you just use an std::string?

[NeoGeoEch13]

firedraco...,but ifstream member method .read() takes char* to write to, what can I do?

By the way if I do something like

string s1;
string s2="contents of 100mb txt file";
s1.assign(s2);
s2.clear();
s1.clear();

Is the memory reclaimed?
If I don't do .clear(), does it happen when s1, s2 go out of scope or not?

[blackcoder41]

you should open the file in binary mode myInputFileStream.open( fileName.c_str(), ios::binary);

remember that newline in windows is CR+LF (that's 2 bytes), if you are not reading the file in binary mode fstream is interpreting the CR+LF as only one character (2bytes read as one)..

hope that helps

[NeoGeoEch13]

Opening in ios::binary

with

fileData = new char[fileLength+1];
fileData[fileLength] = '\0';

works fine.
So just to make sure I understand,
everytime I need to reserve the size of the file in bytes + 1 to store the null terminator.

Thank you very much guys, blackcoder41 that makes sense about Cr\Lf thank you for pointing that out!