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/*
 * 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.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)).
 * 
 * @xerces.internal
 *
 * @author Neil Graham, IBM
 *
 * @version $Id: UCSReader.java 718095 2008-11-16 20:00:14Z mrglavas $
 */
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);
    } // (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);
    } // (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;
    } // (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.
     *
     * 

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 * (0x00-0x7f), or -1 if the end of the stream has * been reached * * @exception IOException If an I/O error occurs */ 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 * * @exception IOException If an I/O error occurs */ 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 * * @exception IOException If an I/O error occurs */ 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; 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. * * @exception IOException If an I/O error occurs */ public boolean ready() throws IOException { return false; } // ready() /** * Tell whether this stream supports the mark() operation. */ 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. * * @exception IOException If the stream does not support mark(), * or if some other I/O error occurs */ 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(). * * @exception 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 */ 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. * * @exception IOException If an I/O error occurs */ public void close() throws IOException { fInputStream.close(); } // close() } // class UCSReader





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