Improved checkForUtf8ByteOrderMark

Improved algorithm to check for UTF-8 Byte Order Marks. No longer expect
all three starting bytes to be read at once, but reads them as blocks.

Issue: SWS-845

Author: Arjen Poutsma

core/src/main/java/org/springframework/ws/soap/saaj/SaajSoapMessageFactory.java

@@ -251,8 +251,16 @@ private MimeHeaders parseMimeHeaders(InputStream inputStream) throws IOException
     private InputStream checkForUtf8ByteOrderMark(InputStream inputStream) throws IOException {
         PushbackInputStream pushbackInputStream = new PushbackInputStream(new BufferedInputStream(inputStream), 3);
         byte[] bytes = new byte[3];
-        int bytesRead = pushbackInputStream.read(bytes);
-        if (bytesRead != -1) {
+        int bytesRead = 0;
+	    while (bytesRead < bytes.length) {
+		    int n = pushbackInputStream.read(bytes, bytesRead, bytes.length - bytesRead);
+		    if (n > 0) {
+			    bytesRead += n;
+		    } else {
+			    break;
+		    }
+	    }
+        if (bytesRead > 0) {
             // check for the UTF-8 BOM, and remove it if there. See SWS-393
             if (!isByteOrderMark(bytes)) {
                 pushbackInputStream.unread(bytes, 0, bytesRead);