Improve FileTransfer.writeToStream()

let's use the standard idiom for Input- to OutputStream transfers. This
also avoids an initial no-op on the first write, when the count is '0'.

Also fixes a bug when the size of file/stream transferred is '0' (which
is perfectly fine and possible).

smack-extensions/src/main/java/org/jivesoftware/smackx/filetransfer/FileTransfer.java

@@ -206,15 +206,10 @@ protected void writeToStream(final InputStream in, final OutputStream out)
 		int count = 0;
 		amountWritten = 0;
 
-        do {
-			// write to the output stream
-			out.write(b, 0, count);
-
-			amountWritten += count;
-
-			// read more bytes from the input stream
-			count = in.read(b);
-		} while (count != -1 && !getStatus().equals(Status.cancelled));
+        while ((count = in.read(b)) > 0 && !getStatus().equals(Status.cancelled)) {
+            out.write(b, 0, count);
+            amountWritten += count;
+        }
 
 		// the connection was likely terminated abruptly if these are not equal
 		if (!getStatus().equals(Status.cancelled) && getError() == Error.none