/*

  * Licensed to the Apache Software Foundation (ASF) under one or more

  * contributor license agreements.  See the NOTICE file distributed with

  * this work for additional information regarding copyright ownership.

  * The ASF licenses this file to You under the Apache License, Version 2.0

  * (the "License"); you may not use this file except in compliance with

  * the License.  You may obtain a copy of the License at

  *

  *  http://www.apache.org/licenses/LICENSE-2.0

  *

  * Unless required by applicable law or agreed to in writing, software

  * distributed under the License is distributed on an "AS IS" BASIS,

  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

  * See the License for the specific language governing permissions and

  * limitations under the License.

  */

 package org.apache.any23.mime.purifier;

 import java.io.IOException;

 import java.io.InputStream;

 /**

  * Implementation of {@link Purifier} that removes all the eventual blank

  * characters at the header of a file that might prevents its <i>MIME Type</i> detection.

  *

  * @author Davide Palmisano ( dpalmisano@gmail.com )

  */

 public class WhiteSpacesPurifier implements Purifier {

     /**

      * {@inheritDoc}

      */

     public void purify(InputStream inputStream) throws IOException {

         if(!inputStream.markSupported())

             throw new IllegalArgumentException("Provided InputStream does not support marks");

         // mark the current position

         inputStream.mark(Integer.MAX_VALUE);

         int byteRead = inputStream.read();

         char charRead = (char) byteRead;

         while(isBlank(charRead) && (byteRead != -1)) {

             // if here means that the previos character must be removed, so mark.

             inputStream.mark(Integer.MAX_VALUE);            

             byteRead = inputStream.read();

             charRead = (char) byteRead;

         }

         // if exit go back to the last valid mark.

         inputStream.reset();

     }

     private boolean isBlank(char c) {

         return c == '\t' || c == '\n' || c == ' ' || c == '\r' || c == '\b' || c == '\f';

     }

 }