C# FileStream and BinaryReader Issue

[Drayshak]

Hi,

I'm currently making an application which reads a file and extracts information from it. Whole files are embedded in this single file, and information about each file that is embedded is stored at a specific location within this file.

fs = new FileStream(@"File Location", FileMode.Open);
br = new BinaryReader(fs);
rtbOutput.AppendText("English Title: " + getLanguage(br));

public string getLanguage(BinaryReader reader)
        {
            byte[] data = ReadSection(reader, 1296, 256); // reader variable, offset, length
            return GetString(data);
        }

public static byte[] ReadSection(BinaryReader reader, int offset, int length)
        {
            reader.BaseStream.Seek(offset, SeekOrigin.Begin);
            return reader.ReadBytes(length);
        }

That is the code that I am using to attempt to read the language from the file, however, I cannot seek past (what seems) 256 bytes; nothing else seems to be available in the stream. The file itself is around 3.1mb, so I know that there is more that should be available to seek to, and I don't want to load the whole file in to a buffer (that would take ages, VB uses FileGet and doesnt need to load the whole thing in to a buffer).

I would basically like to know how I seek past 256 bytes in a large file, without resorting to cycling through all the data and sticking it in a buffer. I've spent ages trying to think of a way to do this, and searching online to attempt to find a solution. I suppose what I'm looking for is somthing that lets me randomly access anywhere in a large file.

Apologies for in-efficient code and such, I'm reasonably new to C# :P

[Drayshak]

Sorry, I forgot to add that I am using Visual Studio 2005, on Windows XP SP2 (im not sure if that makes much difference, but I thought I'd post it anyway :)

[kenobewan]

Have you tried calling reader.DiscardBufferedData() after you perform the Seek() operation? This is so the stream reader does not get stale data from its buffer.

[Drayshak]

Have you tried calling reader.DiscardBufferedData() after you perform the Seek() operation? This is so the stream reader does not get stale data from its buffer.

Thanks for the swift reply, I'll try this as soon as I get home :)

[Drayshak]

Have you tried calling reader.DiscardBufferedData() after you perform the Seek() operation? This is so the stream reader does not get stale data from its buffer.

There doesn't seem to be a function called that, and I've tried the Flush() function as well, still no luck. I am still only getting the first 256 bytes of the file, and I cannot seek past that point.

[kenobewan]

Does it have anything to do with the reader length in:

byte[] data = ReadSection(reader, 1296, 256);

[Drayshak]

I thought the offset (1296 or something like that) would move the reader position forwards before reading the 256 bytes?

The 256 bytes is just a null padded 'universal title' for the file.

[kenobewan]

If it is not the reader length, then I don't know. Anyone else?

[Drayshak]

I've sorted the problem out. I have chosen to use the SetFilePointer function in C++ to do this instead.

[kenobewan]

Good work! Thanks for sharing the solution :).