CODEWITHSUNDEEP
c#optimizationstreambuffer
Anatolii Gabuza
Anatolii Gabuza

Reputation: 6260

Difference between buffer size when streams copying

I saw a lot of examples of CopyStream implementation but I have question about buffer size when we copy streams.
Sample of one of CopyStreams implementation:

private void ReadWriteStream(Stream readStream, Stream writeStream)
{
    int Length = 256;
    Byte[] buffer = new Byte[Length];
    int bytesRead = readStream.Read(buffer, 0, Length);
    // write the required bytes
    while (bytesRead > 0)
    {
        writeStream.Write(buffer, 0, bytesRead);
        bytesRead = readStream.Read(buffer, 0, Length);
    }
    readStream.Close();
    writeStream.Close();
}

Questions are:

Related questions:
File IO with Streams - Best Memory Buffer Size - nice File IO answer. But what about in memory copying?

My case:
There is MemotyStream which I create using ClosedXML workbook.SaveAs(memoryStream); and it allocates huge amount of memory in managed heap. I've looked into sources and found that there is CopyStream method that uses 8 * 1024 buffer size. Could changing this size somehow decrease memory usage?
Note: Stream takes almost 1Gb of memory.

Upvotes: 2

Views: 5381

Answers (1)

Maciej
Maciej

Reputation: 7961

If you are using .NET 4 you can do it simpler:

srcStream.CopyTo(dstStream);

But if you want/need to implement it yourself I would suggest smaller buffer (256B - 1KB) for memory streams and medium size buffer (10KB) for file streams. You can also make it dependent on size of the source stream for example 10% with some size limit of 1MB or so.

For files, the bigger the buffer the faster copy operation (to a degree) but less safe. For memory streams small buffer is pretty much just as effective as big one but easier on memory (if you copy a lot).

Upvotes: 6

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