Question

i have a big text file (like 1gb) and i need to insert line breaks every 40 characters.

how to do so using streamReader?

i tried using ReadBLock, but cant seem to make it work. Heres the code so far:

int index = 0;
try
{
    using (StreamReader sr = new StreamReader(@"C:\bigfile.txt"))
    {
        char [] buf = new char [1024];
        //sr.ReadBlock (buf, 0, 40);
        while (sr.ReadBlock (buf, index, 40) != 0)
        {
            using (StreamWriter sw = new StreamWriter(@"C:\bigfilelinebreak.txt"))
            {
                //Console.WriteLine(buf);
                sw.Write (buf);
                sw.WriteLine(Environment.NewLine);
            }
            index += 40;
        }

    }
}

Answer 1

There are a few issues:

1. You don’t need to increment your index – always just write to index zero.
2. You are recreating your StreamWriter for each block.
3. You may be writing out the wrong number of characters (you’re not checking how many you read, which, at the end of the file, could be less than 40)

Try the following:

    try
    {
        using (StreamReader sr = new StreamReader(@"C:\bigfile.txt"))
        {
            using (StreamWriter sw = new StreamWriter(@"C:\bigfilelinebreak.txt"))
            {
                char [] buf = new char[40];
                int read = sr.ReadBlock (buf, 0, 40);
                while (read != 0)
                {
                    sw.Write(buf, 0, read);
                    sw.WriteLine();
                    read = sr.ReadBlock (buf, 0, 40);
                }
            }
        }
    }