How to read/write to a file which is over the size barrier of 2 GB?

Question

So, i don\'t have a single idea to get through this situation i have a function that patches a file by replacing the values i want but he file i am trying to patch is about 4.5G

Answer 1

Your problem is that File.ReadAllBytes will not open files with lengths longer than Int.MaxValue. Loading an entire file into memory just to scan it for a pattern is a bad design no matter how big the file is. You should open the file as a stream and use the Scanner pattern to step through the file, replacing bytes that match your pattern. A rather simplistic implementation using BinaryReader:

static void PatchStream(Stream source, Stream target
    , IList<byte> searchPattern, IList<byte> replacementPattern)
{
    using (var input = new BinaryReader(source))
    using (var output = new BinaryWriter(target))
    {
        var buffer = new Queue<byte>();
        while (true)
        {
            if (buffer.Count < searchPattern.Count)
            {
                if (input.BaseStream.Position < input.BaseStream.Length)
                    buffer.Enqueue(input.ReadByte());
                else
                    break;
            }
            else if (buffer.Zip(searchPattern, (b, s) => b == s).All(c => c))
            {
                foreach (var b in replacementPattern)
                    output.Write(b);
                buffer.Clear();
            }
            else
            {
                output.Write(buffer.Dequeue());
            }
        }

        foreach (var b in buffer)
            output.Write(b);
    }
}

You can call it on files with code like:

PatchStream(new FileInfo(...).OpenRead(),
    new FileInfo(...).OpenWrite(),
    new[] { (byte)'a', (byte)'b', (byte)'c' },
    new[] { (byte)'A', (byte)'B', (byte)'C' });