Question

i want to read\write a binary file which has the following structure:

The file is composed by “RECORDS”. Each “RECORD” has the following structure:
I will use the first record as example

• (red)START byte: 0x5A (always 1 byte, fixed value 0x5A)
• (green) LENGTH bytes: 0x00 0x16 (always 2 bytes, value can change from
  “0x00 0x02” to “0xFF 0xFF”)
• (blue) CONTENT: Number of Bytes indicated by the decimal value of LENGTH Field minus 2. In this case LENGHT field value is 22 (0x00 0x16 converted to decimal), therefore the CONTENT will contain 20 (22 – 2) bytes.

My goal is to read each record one by one, and write it to an output file.
Actually i have a read function and write function (some pseudocode):

private void Read(BinaryReader binaryReader, BinaryWriter binaryWriter)
{
    byte START = 0x5A;
    int decimalLenght = 0;
    byte[] content = null;
    byte[] length = new byte[2];

    while (binaryReader.PeekChar() != -1)
    {
        //Check the first byte which should be equals to 0x5A
        if (binaryReader.ReadByte() != START)
        {
            throw new Exception("0x5A Expected");
        }

        //Extract the length field value
        length = binaryReader.ReadBytes(2);

        //Convert the length field to decimal
        int decimalLenght = GetLength(length);

        //Extract the content field value
        content = binaryReader.ReadBytes(decimalLenght - 2);

        //DO WORK
        //modifying the content

        //Writing the record
        Write(binaryWriter, content, length, START);
    }
}

private void Write(BinaryWriter binaryWriter, byte[] content, byte[] length, byte START)
{
    binaryWriter.Write(START);
    binaryWriter.Write(length);
    binaryWriter.Write(content);   
}

This way is actually working.
However since I am dealing with very large files i find it to be not performing at all, cause I Read and write 3 times foreach Record. Actually I would like to read bug chunks of data instead small amount of byte and maybe work in memory, but my experience in using Stream stops with BinaryReader and BinaryWriter. Thanks in advance.

Answer 1

FileStream is already buffered, so I’d expect it to work pretty well. You could always create a BufferedStream around the original stream to add extra more buffering if you really need to, but I doubt it would make a significant difference.

You say it’s “not performing at all” – how fast is it working? How sure are you that the IO is where your time is going? Have you performed any profiling of the code?