Question

I have a class in a dll which parses a file and returns a Stream which represents an FAT image (or any other)

My problem is when there is any other image the class creates about 3702 (on average) null bytes at the beginning of the stream.

So I have to edit the stream first and then save it to a file.

I have a code already but it works slow.

[Note : fts is the returned FileStream.]

BufferedStream bfs = new BufferedStream(fts);
BinaryReader bbr = new BinaryReader(bfs);
byte[] all_bytes = bbr.ReadBytes((int)fts.Length);

List<byte> nls = new List<byte>();
int index = 0;

foreach (byte bbrs in all_bytes)
{
    if (bbrs == 0x00)
    {
        index++;
        nls.Add(bbrs);
    }
    else
    {
        break;
    }
}

byte[] nulls = new byte[nls.Count];
nulls = nls.ToArray();

//File.WriteAllBytes(outputDir + "Nulls.bin", nulls);
long siz = fts.Length - index;
byte[] file = new byte[siz];

bbr.BaseStream.Position = index;
file = bbr.ReadBytes((int)siz);

bbr.Close();
bfs.Close();
fts.Close();

bfs = null;
fts = null;

fts = new FileStream(outputDir + "Image.bin", FileMode.Create, FileAccess.Write);
bfs = new BufferedStream(fts);

bfs.Write(file, 0, (int)siz);

bfs.Close();
fts.Close();

Now, my question is :

How can I remove the nulls more efficiently and faster than the above code?

Answer 1

Instead of pushing bytes onto a List you could simply loop through your stream until you find the first non-null byte and then just copy the array from there using Array.Copy.

I would think about something like this (untested code):

int index = 0;
int currByte = 0;

while ((currByte = bbrs.ReadByte()) == 0x00)
{
    index++;
}

// now currByte and everything to the end of the stream are the bytes you want.