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UCSReader.javaAPI DocApache Xerces 3.0.112025Fri Sep 14 20:33:52 BST 2007org.apache.xerces.impl.io

UCSReader

public class UCSReader extends 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 449317 2006-09-23 22:12:30Z mrglavas $

Fields Summary
public static final int
DEFAULT_BUFFER_SIZE
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 short
UCS2LE
public static final short
UCS2BE
public static final short
UCS4LE
public static final short
UCS4BE
protected final InputStream
fInputStream
Input stream.
protected final byte[]
fBuffer
Byte buffer.
protected final short
fEncoding
Constructors Summary
public UCSReader(InputStream inputStream, short encoding)
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.


    //
    // Constructors
    //

                                                        
         
        this(inputStream, DEFAULT_BUFFER_SIZE, encoding);
    
public UCSReader(InputStream inputStream, int size, short encoding)
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.

        this(inputStream, new byte[size], encoding);
    
public UCSReader(InputStream inputStream, byte[] buffer, short encoding)
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.

        fInputStream = inputStream;
        fBuffer = buffer;
        fEncoding = encoding;
    
Methods Summary
public voidclose()
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

         fInputStream.close();
     
public voidmark(int readAheadLimit)
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

	    fInputStream.mark(readAheadLimit);
    
public booleanmarkSupported()
Tell whether this stream supports the mark() operation.

	    return fInputStream.markSupported();
    
public intread()
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

 
        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;
    
public intread(char[] ch, int offset, int length)
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

        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;
    
public booleanready()
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

	    return false;
    
public voidreset()
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

        fInputStream.reset();
    
public longskip(long n)
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

        // 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;