content: /*
   * 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 mf.org.apache.xerces.impl.io;
  
  import java.io.IOException;
  import java.io.InputStream;
  import java.io.Reader;
  import java.util.Locale;
  
  import mf.org.apache.xerces.impl.msg.XMLMessageFormatter;
  import mf.org.apache.xerces.util.MessageFormatter;
  
  
  /**
   * <p>A UTF-16 reader. Can also be used for UCS-2 (i.e. ISO-10646-UCS-2).</p>
   *
   * @author Michael Glavassevich, IBM
   * @version $Id: UTF16Reader.java 718095 2008-11-16 20:00:14Z mrglavas $
   * @xerces.internal
   */
  public final class UTF16Reader
          extends Reader {
  
      //
      // Constants
      //
  
      /**
       * Default byte buffer size (4096).
       */
      public static final int DEFAULT_BUFFER_SIZE = 4096;
  
      //
      // Data
      //
  
      /**
       * Input stream.
       */
      protected final InputStream fInputStream;
  
      /**
       * Byte buffer.
       */
      protected final byte[] fBuffer;
  
      /**
       * Endianness.
       */
      protected final boolean fIsBigEndian;
  
      // message formatter; used to produce localized exception messages
      private final MessageFormatter fFormatter;
  
      // Locale to use for messages
      private final Locale fLocale;
  
      //
      // Constructors
      //
  
      /**
       * Constructs a UTF-16 reader from the specified input stream
       * using the default buffer size. Primarily for testing.
       *
       * @param inputStream The input stream.
       * @param isBigEndian The byte order.
       */
      public UTF16Reader(InputStream inputStream, boolean isBigEndian) {
          this(inputStream, DEFAULT_BUFFER_SIZE, isBigEndian,
                  new XMLMessageFormatter(), Locale.getDefault());
      } // <init>(InputStream, boolean)
  
      /**
       * Constructs a UTF-16 reader from the specified input stream
       * using the default buffer size and the given MessageFormatter.
       *
       * @param inputStream The input stream.
       * @param isBigEndian The byte order.
       */
      public UTF16Reader(InputStream inputStream, boolean isBigEndian,
                         MessageFormatter messageFormatter, Locale locale) {
          this(inputStream, DEFAULT_BUFFER_SIZE, isBigEndian, messageFormatter, locale);
      } // <init>(InputStream, boolean, MessageFormatter, Locale)
  
      /**
       * Constructs a UTF-16 reader from the specified input stream
       * and buffer size and given MessageFormatter.
       *
       * @param inputStream      The input stream.
       * @param size             The initial buffer size.
       * @param isBigEndian      The byte order.
       * @param messageFormatter Given MessageFormatter
       * @param locale           Locale to use for messages
       */
      public UTF16Reader(InputStream inputStream, int size, boolean isBigEndian,
                         MessageFormatter messageFormatter, Locale locale) {
          this(inputStream, new byte[size], isBigEndian, messageFormatter, locale);
      } // <init>(InputStream, int, boolean, MessageFormatter, Locale)
  
      /**
       * Constructs a UTF-16 reader from the specified input stream,
       * buffer and MessageFormatter.
       *
       * @param inputStream      The input stream.
       * @param buffer           The byte buffer.
       * @param isBigEndian      The byte order.
       * @param messageFormatter Given MessageFormatter
       * @param locale           Locale to use for messages
       */
      public UTF16Reader(InputStream inputStream, byte[] buffer, boolean isBigEndian,
                         MessageFormatter messageFormatter, Locale locale) {
          fInputStream = inputStream;
          fBuffer = buffer;
          fIsBigEndian = isBigEndian;
          fFormatter = messageFormatter;
          fLocale = locale;
      } // <init>(InputStream, byte[], boolean, MessageFormatter, Locale)
  
      //
      // Reader methods
      //
  
      /**
       * Read a single character.  This method will block until a character is
       * available, an I/O error occurs, or the end of the stream is reached.
       * <p/>
       * <p> Subclasses that intend to support efficient single-character input
       * should override this method.
       *
       * @return The character read, as an integer in the range 0 to 65535
       * (<tt>0x00-0xffff</tt>), or -1 if the end of the stream has
       * been reached
       * @throws IOException If an I/O error occurs
       */
      @Override
      public int read() throws IOException {
          final int b0 = fInputStream.read();
          if (b0 == -1) {
              return -1;
          }
          final int b1 = fInputStream.read();
          if (b1 == -1) {
              expectedTwoBytes();
          }
          // UTF-16BE
          if (fIsBigEndian) {
              return (b0 << 8) | b1;
          }
          // UTF-16LE
          return (b1 << 8) | b0;
      } // read():int
  
      /**
       * Read characters into a portion of an array.  This method will block
       * until some input is available, an I/O error occurs, or the end of the
       * stream is reached.
       *
       * @param ch     Destination buffer
       * @param offset Offset at which to start storing characters
       * @param length Maximum number of characters to read
       * @return The number of characters read, or -1 if the end of the
       * stream has been reached
       * @throws IOException If an I/O error occurs
       */
      @Override
      public int read(char ch[], int offset, int length) throws IOException {
          int byteLength = length << 1;
          if (byteLength > fBuffer.length) {
              byteLength = fBuffer.length;
          }
          int byteCount = fInputStream.read(fBuffer, 0, byteLength);
          if (byteCount == -1) {
              return -1;
          }
          // If an odd number of bytes were read, we still need to read one more.
          if ((byteCount & 1) != 0) {
              int b = fInputStream.read();
              if (b == -1) {
                  expectedTwoBytes();
              }
              fBuffer[byteCount++] = (byte) b;
          }
          final int charCount = byteCount >> 1;
          if (fIsBigEndian) {
              processBE(ch, offset, charCount);
          } else {
              processLE(ch, offset, charCount);
          }
          return charCount;
      } // read(char[],int,int)
  
      /**
       * Skip characters.  This method will block until some characters are
       * available, an I/O error occurs, or the end of the stream is reached.
       *
       * @param n The number of characters to skip
       * @return The number of characters actually skipped
       * @throws IOException If an I/O error occurs
       */
      @Override
      public long skip(long n) throws IOException {
          long bytesSkipped = fInputStream.skip(n << 1);
          if ((bytesSkipped & 1) != 0) {
              int b = fInputStream.read();
              if (b == -1) {
                  expectedTwoBytes();
              }
              ++bytesSkipped;
          }
          return bytesSkipped >> 1;
      } // skip(long):long
  
      /**
       * Tell whether this stream is ready to be read.
       *
       * @return True if the next read() is guaranteed not to block for input,
       * false otherwise.  Note that returning false does not guarantee that the
       * next read will block.
       * @throws IOException If an I/O error occurs
       */
      @Override
      public boolean ready() throws IOException {
          return false;
      } // ready()
  
      /**
       * Tell whether this stream supports the mark() operation.
       */
      @Override
      public boolean markSupported() {
          return false;
      } // markSupported()
  
      /**
       * Mark the present position in the stream.  Subsequent calls to reset()
       * will attempt to reposition the stream to this point.  Not all
       * character-input streams support the mark() operation.
       *
       * @param readAheadLimit Limit on the number of characters that may be
       *                       read while still preserving the mark.  After
       *                       reading this many characters, attempting to
       *                       reset the stream may fail.
       * @throws IOException If the stream does not support mark(),
       *                     or if some other I/O error occurs
       */
      @Override
      public void mark(int readAheadLimit) throws IOException {
          throw new IOException(fFormatter.formatMessage(fLocale, "OperationNotSupported", new Object[]{"mark()", "UTF-16"}));
      } // mark(int)
  
      /**
       * Reset the stream.  If the stream has been marked, then attempt to
       * reposition it at the mark.  If the stream has not been marked, then
       * attempt to reset it in some way appropriate to the particular stream,
       * for example by repositioning it to its starting point.  Not all
       * character-input streams support the reset() operation, and some support
       * reset() without supporting mark().
       *
       * @throws IOException If the stream has not been marked,
       *                     or if the mark has been invalidated,
       *                     or if the stream does not support reset(),
       *                     or if some other I/O error occurs
       */
      @Override
      public void reset() throws IOException {
      } // reset()
  
      /**
       * Close the stream.  Once a stream has been closed, further read(),
       * ready(), mark(), or reset() invocations will throw an IOException.
       * Closing a previously-closed stream, however, has no effect.
       *
       * @throws IOException If an I/O error occurs
       */
      @Override
      public void close() throws IOException {
          fInputStream.close();
      } // close()
  
      //
      // Private methods
      //
  
      /**
       * Decodes UTF-16BE
       **/
      private void processBE(final char ch[], int offset, final int count) {
          int curPos = 0;
          for (int i = 0; i < count; ++i) {
              final int b0 = fBuffer[curPos++] & 0xff;
              final int b1 = fBuffer[curPos++] & 0xff;
              ch[offset++] = (char) ((b0 << 8) | b1);
          }
      } // processBE(char[],int,int)
  
      /**
       * Decodes UTF-16LE
       **/
      private void processLE(final char ch[], int offset, final int count) {
          int curPos = 0;
          for (int i = 0; i < count; ++i) {
              final int b0 = fBuffer[curPos++] & 0xff;
              final int b1 = fBuffer[curPos++] & 0xff;
              ch[offset++] = (char) ((b1 << 8) | b0);
          }
      } // processLE(char[],int,int)
  
      /**
       * Throws an exception for expected byte.
       */
      private void expectedTwoBytes()
              throws MalformedByteSequenceException {
          throw new MalformedByteSequenceException(fFormatter,
                  fLocale,
                  XMLMessageFormatter.XML_DOMAIN,
                  "ExpectedByte",
                  new Object[]{"2", "2"});
      } // expectedTwoBytes()
  
  } // class UTF16Reader
  