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;
  
  /**
   * Reader for UCS-2 and UCS-4 encodings.
   * (i.e., encodings from ISO-10646-UCS-(2|4)).
   *
   * @author Neil Graham, IBM
   * @version $Id: UCSReader.java 718095 2008-11-16 20:00:14Z mrglavas $
   * @xerces.internal
   */
  public final class UCSReader extends Reader {
  
      //
      // Constants
      //
  
      /**
       * Default byte buffer size (8192, larger than that of ASCIIReader
       * since it's reasonable to surmise that the average UCS-4-encoded
       * file should be 4 times as large as the average ASCII-encoded file).
       */
      public static final int DEFAULT_BUFFER_SIZE = 8192;
  
      public static final short UCS2LE = 1;
      public static final short UCS2BE = 2;
      public static final short UCS4LE = 4;
      public static final short UCS4BE = 8;
  
      //
      // Data
      //
  
      /**
       * Input stream.
       */
      protected final InputStream fInputStream;
  
      /**
       * Byte buffer.
       */
      protected final byte[] fBuffer;
  
      // what kind of data we're dealing with
      protected final short fEncoding;
  
      //
      // Constructors
      //
  
      /**
       * Constructs a UCS reader from the specified input stream
       * using the default buffer size.  The Endian-ness and whether this is
       * UCS-2 or UCS-4 needs also to be known in advance.
       *
       * @param inputStream The input stream.
       * @param encoding    One of UCS2LE, UCS2BE, UCS4LE or UCS4BE.
       */
      public UCSReader(InputStream inputStream, short encoding) {
          this(inputStream, DEFAULT_BUFFER_SIZE, encoding);
      } // <init>(InputStream, short)
  
      /**
       * Constructs a UCS reader from the specified input stream
       * and buffer size.  The Endian-ness and whether this is
       * UCS-2 or UCS-4 needs also to be known in advance.
       *
       * @param inputStream The input stream.
       * @param size        The initial buffer size.
       * @param encoding    One of UCS2LE, UCS2BE, UCS4LE or UCS4BE.
       */
      public UCSReader(InputStream inputStream, int size, short encoding) {
          this(inputStream, new byte[size], encoding);
      } // <init>(InputStream,int,short)
  
      /**
       * Constructs a UCS reader from the specified input stream
       * and buffer.  The Endian-ness and whether this is
       * UCS-2 or UCS-4 needs also to be known in advance.
       *
       * @param inputStream The input stream.
       * @param buffer      The byte buffer.
       * @param encoding    One of UCS2LE, UCS2BE, UCS4LE or UCS4BE.
       */
      public UCSReader(InputStream inputStream, byte[] buffer, short encoding) {
          fInputStream = inputStream;
          fBuffer = buffer;
          fEncoding = encoding;
      } // <init>(InputStream,int,short)
  
      //
      // 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 127
       * (<tt>0x00-0x7f</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 {
          int b0 = fInputStream.read() & 0xff;
          if (b0 == 0xff) {
              return -1;
          }
          int b1 = fInputStream.read() & 0xff;
          if (b1 == 0xff) {
              return -1;
          }
          // UCS-4
          if (fEncoding >= 4) {
              int b2 = fInputStream.read() & 0xff;
              if (b2 == 0xff) {
                  return -1;
              }
              int b3 = fInputStream.read() & 0xff;
              if (b3 == 0xff) {
                  return -1;
              }
              if (fEncoding == UCS4BE) {
                  return (b0 << 24) + (b1 << 16) + (b2 << 8) + b3;
              }
              return (b3 << 24) + (b2 << 16) + (b1 << 8) + b0;
          }
          // UCS-2
          if (fEncoding == UCS2BE) {
              return (b0 << 8) + b1;
          }
          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 << ((fEncoding >= 4) ? 2 : 1);
          if (byteLength > fBuffer.length) {
              byteLength = fBuffer.length;
          }
          int count = fInputStream.read(fBuffer, 0, byteLength);
          if (count == -1) return -1;
          // try and make count be a multiple of the number of bytes we're looking for
          if (fEncoding >= 4) { // BigEndian
              // this looks ugly, but it avoids an if at any rate...
              int numToRead = (4 - (count & 3) & 3);
              for (int i = 0; i < numToRead; i++) {
                  int charRead = fInputStream.read();
                  if (charRead == -1) { // end of input; something likely went wrong!A  Pad buffer with nulls.
                      for (int j = i; j < numToRead; j++) {
                          fBuffer[count + j] = 0;
                      }
                      break;
                  }
                  fBuffer[count + i] = (byte) charRead;
              }
              count += numToRead;
          } else {
              int numToRead = count & 1;
              if (numToRead != 0) {
                  count++;
                  int charRead = fInputStream.read();
                  if (charRead == -1) { // end of input; something likely went wrong!A  Pad buffer with nulls.
                      fBuffer[count] = 0;
                  } else {
                      fBuffer[count] = (byte) charRead;
                  }
              }
          }
  
          // now count is a multiple of the right number of bytes
          int numChars = count >> ((fEncoding >= 4) ? 2 : 1);
          int curPos = 0;
          for (int i = 0; i < numChars; i++) {
              int b0 = fBuffer[curPos++] & 0xff;
              int b1 = fBuffer[curPos++] & 0xff;
              // UCS-4
              if (fEncoding >= 4) {
                  int b2 = fBuffer[curPos++] & 0xff;
                  int b3 = fBuffer[curPos++] & 0xff;
                  if (fEncoding == UCS4BE) {
                      ch[offset + i] = (char) ((b0 << 24) + (b1 << 16) + (b2 << 8) + b3);
                  } else {
                      ch[offset + i] = (char) ((b3 << 24) + (b2 << 16) + (b1 << 8) + b0);
                  }
              } else { // UCS-2
                  if (fEncoding == UCS2BE) {
                      ch[offset + i] = (char) ((b0 << 8) + b1);
                  } else {
                      ch[offset + i] = (char) ((b1 << 8) + b0);
                  }
              }
          }
          return numChars;
      } // 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 {
          // charWidth will represent the number of bits to move
          // n leftward to get num of bytes to skip, and then move the result rightward
          // to get num of chars effectively skipped.
          // The trick with &'ing, as with elsewhere in this dcode, is
          // intended to avoid an expensive use of / that might not be optimized
          // away.
          int charWidth = (fEncoding >= 4) ? 2 : 1;
          long bytesSkipped = fInputStream.skip(n << charWidth);
          if ((bytesSkipped & (charWidth | 1)) == 0) return bytesSkipped >> charWidth;
          return (bytesSkipped >> charWidth) + 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 fInputStream.markSupported();
      } // 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 {
          fInputStream.mark(readAheadLimit);
      } // 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 {
          fInputStream.reset();
      } // 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()
  
  } // class UCSReader
  