/**

  * Copyright (c) 2008-2012, http://www.snakeyaml.org

  *

  * Licensed 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.yaml.snakeyaml.reader;

 /**

  version: 1.1 / 2007-01-25

  - changed BOM recognition ordering (longer boms first)

  Original pseudocode   : Thomas Weidenfeller

  Implementation tweaked: Aki Nieminen

  Implementation changed: Andrey Somov 

  * UTF-32 removed because it is not supported by YAML

  * no default encoding

  http://www.unicode.org/unicode/faq/utf_bom.html

  BOMs:

  00 00 FE FF    = UTF-32, big-endian

  FF FE 00 00    = UTF-32, little-endian

  EF BB BF       = UTF-8,

  FE FF          = UTF-16, big-endian

  FF FE          = UTF-16, little-endian

  Win2k Notepad:

  Unicode format = UTF-16LE

  ***/

 import java.io.IOException;

 import java.io.InputStream;

 import java.io.InputStreamReader;

 import java.io.PushbackInputStream;

 import java.io.Reader;

 import java.nio.charset.Charset;

 import java.nio.charset.CharsetDecoder;

 import java.nio.charset.CodingErrorAction;

 /**

  * Generic unicode textreader, which will use BOM mark to identify the encoding

  * to be used. If BOM is not found then use a given default or system encoding.

  */

 public class UnicodeReader extends Reader {

     private static final Charset UTF8 = Charset.forName("UTF-8");

     private static final Charset UTF16BE = Charset.forName("UTF-16BE");

     private static final Charset UTF16LE = Charset.forName("UTF-16LE");

     PushbackInputStream internalIn;

     InputStreamReader internalIn2 = null;

     private static final int BOM_SIZE = 3;

     /**

      * @param in

      *            InputStream to be read

      */

     public UnicodeReader(InputStream in) {

         internalIn = new PushbackInputStream(in, BOM_SIZE);

     }

     /**

      * Get stream encoding or NULL if stream is uninitialized. Call init() or

      * read() method to initialize it.

      */

     public String getEncoding() {

         return internalIn2.getEncoding();

     }

     /**

      * Read-ahead four bytes and check for BOM marks. Extra bytes are unread

      * back to the stream, only BOM bytes are skipped.

      */

     protected void init() throws IOException {

         if (internalIn2 != null)

             return;

         Charset encoding;

         byte bom[] = new byte[BOM_SIZE];

         int n, unread;

         n = internalIn.read(bom, 0, bom.length);

         if ((bom[0] == (byte) 0xEF) && (bom[1] == (byte) 0xBB) && (bom[2] == (byte) 0xBF)) {

             encoding = UTF8;

             unread = n - 3;

         } else if ((bom[0] == (byte) 0xFE) && (bom[1] == (byte) 0xFF)) {

             encoding = UTF16BE;

             unread = n - 2;

         } else if ((bom[0] == (byte) 0xFF) && (bom[1] == (byte) 0xFE)) {

             encoding = UTF16LE;

             unread = n - 2;

         } else {

             // Unicode BOM mark not found, unread all bytes

             encoding = UTF8;

             unread = n;

         }

         if (unread > 0)

             internalIn.unread(bom, (n - unread), unread);

         // Use given encoding

         CharsetDecoder decoder = encoding.newDecoder().onUnmappableCharacter(

                 CodingErrorAction.REPORT);

         internalIn2 = new InputStreamReader(internalIn, decoder);

     }

     public void close() throws IOException {

         init();

         internalIn2.close();

     }

     public int read(char[] cbuf, int off, int len) throws IOException {

         init();

         return internalIn2.read(cbuf, off, len);

     }

 }