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    1   /**
    2    * Copyright (c) 2008-2011, http://www.snakeyaml.org
    3    *
    4    * Licensed under the Apache License, Version 2.0 (the "License");
    5    * you may not use this file except in compliance with the License.
    6    * You may obtain a copy of the License at
    7    *
    8    *     http://www.apache.org/licenses/LICENSE-2.0
    9    *
    10   * Unless required by applicable law or agreed to in writing, software
    11   * distributed under the License is distributed on an "AS IS" BASIS,
    12   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    13   * See the License for the specific language governing permissions and
    14   * limitations under the License.
    15   */
    16
    17  package org.yaml.snakeyaml.reader;
    18
    19  /**
    20   version: 1.1 / 2007-01-25
    21   - changed BOM recognition ordering (longer boms first)
    22
    23   Original pseudocode   : Thomas Weidenfeller
    24   Implementation tweaked: Aki Nieminen
    25   Implementation changed: Andrey Somov
    26   * UTF-32 removed because it is not supported by YAML
    27   * no default encoding
    28
    29   http://www.unicode.org/unicode/faq/utf_bom.html
    30   BOMs:
    31   00 00 FE FF    = UTF-32, big-endian
    32   FF FE 00 00    = UTF-32, little-endian
    33   EF BB BF       = UTF-8,
    34   FE FF          = UTF-16, big-endian
    35   FF FE          = UTF-16, little-endian
    36
    37   Win2k Notepad:
    38   Unicode format = UTF-16LE
    39   ***/
    40
    41  import java.io.IOException;
    42  import java.io.InputStream;
    43  import java.io.InputStreamReader;
    44  import java.io.PushbackInputStream;
    45  import java.io.Reader;
    46
    47  /**
    48   * Generic unicode textreader, which will use BOM mark to identify the encoding
    49   * to be used. If BOM is not found then use a given default or system encoding.
    50   */
    51  public class UnicodeReader extends Reader {
    52      PushbackInputStream internalIn;
    53      InputStreamReader internalIn2 = null;
    54
    55      private static final int BOM_SIZE = 3;
    56
    57      /**
    58       * @param in
    59       *            InputStream to be read
    60       */
    61      public UnicodeReader(InputStream in) {
    62          internalIn = new PushbackInputStream(in, BOM_SIZE);
    63      }
    64
    65      /**
    66       * Get stream encoding or NULL if stream is uninitialized. Call init() or
    67       * read() method to initialize it.
    68       */
    69      public String getEncoding() {
    70          return internalIn2.getEncoding();
    71      }
    72
    73      /**
    74       * Read-ahead four bytes and check for BOM marks. Extra bytes are unread
    75       * back to the stream, only BOM bytes are skipped.
    76       */
    77      protected void init() throws IOException {
    78          if (internalIn2 != null)
    79              return;
    80
    81          String encoding;
    82          byte bom[] = new byte[BOM_SIZE];
    83          int n, unread;
    84          n = internalIn.read(bom, 0, bom.length);
    85
    86          if ((bom[0] == (byte) 0xEF) && (bom[1] == (byte) 0xBB) && (bom[2] == (byte) 0xBF)) {
    87              encoding = "UTF-8";
    88              unread = n - 3;
    89          } else if ((bom[0] == (byte) 0xFE) && (bom[1] == (byte) 0xFF)) {
    90              encoding = "UTF-16BE";
    91              unread = n - 2;
    92          } else if ((bom[0] == (byte) 0xFF) && (bom[1] == (byte) 0xFE)) {
    93              encoding = "UTF-16LE";
    94              unread = n - 2;
    95          } else {
    96              // Unicode BOM mark not found, unread all bytes
    97              encoding = "UTF-8";
    98              unread = n;
    99          }
    100
    101         if (unread > 0)
    102             internalIn.unread(bom, (n - unread), unread);
    103
    104         // Use given encoding
    105         internalIn2 = new InputStreamReader(internalIn, encoding);
    106     }
    107
    108     public void close() throws IOException {
    109         init();
    110         internalIn2.close();
    111     }
    112
    113     public int read(char[] cbuf, int off, int len) throws IOException {
    114         init();
    115         return internalIn2.read(cbuf, off, len);
    116     }
    117 }