IndexOutOfRangeException when a stream is a multiple of the buffer size
- by dnord
I don't have a lot of experience with streams and buffers, but I'm having to do it for a project, and I'm stuck on an exception being thrown when the stream I'm reading is a multiple of the buffer size I've chosen. Let me show you:
My code starts by reading bufferSize (100, let's say) bytes from the stream:
numberOfBytesRead = DataReader.GetBytes(0, index, output, 0, bufferSize);
Then, I loop through a while loop:
while (numberOfBytesRead == bufferSize)
{
BufferWriter.Write(output);
BufferWriter.Flush();
index += bufferSize;
numberOfBytesRead = DataReader.GetBytes(0, index, output, 0, bufferSize);
}
... and, once we get to a non-bufferSize read, we know we've hit the end of the stream and can move on.
But if the bufferSize is 100, and the stream is 200, we'll read positions 0-99, 100-199, and then the attempt to read 200-299 errors out. I'd like it if it returned 0, but it throws an error. What I'm doing to handle that is, well, a try-catch:
catch (System.IndexOutOfRangeException)
numberOfBytesRead = 0;
...which ends the loop, and successfully finishes the thing, but we all know I don't want to control code flow with error handling.
Is there a better (more standard?) way to handle stream reading when the stream length is unknown? This seems like a small wrinkle in a fairly reasonable strategy for reading streams, but I just don't know if I've got it wrong or what.
The specifics of this (which I've cleaned up a little bit for posting) are a MySqlDataReader hitting a LARGEBLOB column. It's working whenever the buffer is larger than the number of returned bytes, or when the number of returned bytes is not a multiple of bufferSize. Because we don't, in that case, throw an IndexOutOfRangeException.
