generalbase.java

来自「This is a resource based on j2me embedde」· Java 代码 · 共 433 行

/*
 * @(#)GeneralBase.java	1.12 06/10/10
 *
 * Copyright  1990-2008 Sun Microsystems, Inc. All Rights Reserved.  
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER  
 *   
 * This program is free software; you can redistribute it and/or  
 * modify it under the terms of the GNU General Public License version  
 * 2 only, as published by the Free Software Foundation.   
 *   
 * This program is distributed in the hope that it will be useful, but  
 * WITHOUT ANY WARRANTY; without even the implied warranty of  
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU  
 * General Public License version 2 for more details (a copy is  
 * included at /legal/license.txt).   
 *   
 * You should have received a copy of the GNU General Public License  
 * version 2 along with this work; if not, write to the Free Software  
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  
 * 02110-1301 USA   
 *   
 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa  
 * Clara, CA 95054 or visit www.sun.com if you need additional  
 * information or have any questions. 
 *
 */


package com.sun.cdc.io;

import java.io.*;
import javax.microedition.io.*;

/**
 * Base class for objects that implement the DataInput and DataOutput interfaces.
 * It also behaves like a DataOutputStream so it can be used for UniversalOutputStream
 *
 * @version 1.1 2/20/2000
 */
abstract public class GeneralBase extends DataOutputStream implements DataInput, DataOutput {

    public GeneralBase() {
        super(null); // No DataOutputStream redirection wanted
    }

    /**
     * Writes the specified byte (the low eight bits of the argument
     * <code>b</code>) to the underlying output stream. If no exception
     * is thrown, the counter <code>written</code> is incremented by
     * <code>1</code>.
     * <p>
     * Implements the <code>write</code> method of <code>OutputStream</code>.
     *
     * @param      b   the <code>byte</code> to be written.
     * @exception  IOException  if an I/O error occurs.
     * @see        java.io.FilterOutputStream#out
     */
    public void write(int b) throws IOException {
        throw new RuntimeException("No write()");
    }

    /**
     * Writes <code>len</code> bytes from the specified byte array
     * starting at offset <code>off</code> to the underlying output stream.
     * If no exception is thrown, the counter <code>written</code> is
     * incremented by <code>len</code>.
     *
     * @param      b     the data.
     * @param      off   the start offset in the data.
     * @param      len   the number of bytes to write.
     * @exception  IOException  if an I/O error occurs.
     * @see        java.io.FilterOutputStream#out
     */
    public void write(byte b[], int off, int len) throws IOException {
        if (b == null) {
            throw new NullPointerException();
        } else if ((off < 0) || (off > b.length) || (len < 0) ||
                   ((off + len) > b.length) || ((off + len) < 0)) {
            throw new IndexOutOfBoundsException();
        } else if (len == 0) {
            return;
        }
        for (int i = 0 ; i < len ; i++) {
            write(b[off + i]);
        }
    }

//
// DataOutput functions are inherited from DataOutputStream
//

    /**
     * Flush the stream.
     */
    public void flush() throws IOException {
    }

    /**
     * Close the stream.
     */
    public void close() throws IOException {
    }



//
// DataInput functions
//

    /**
     * Reads the next byte of data from the input stream. The value byte is
     * returned as an <code>int</code> in the range <code>0</code> to
     * <code>255</code>. If no byte is available because the end of the stream
     * has been reached, the value <code>-1</code> is returned. This method
     * blocks until input data is available, the end of the stream is detected,
     * or an exception is thrown.
     *
     * <p> A subclass must provide an implementation of this method.
     *
     * @return     the next byte of data, or <code>-1</code> if the end of the
     *             stream is reached.
     * @exception  IOException  if an I/O error occurs.
     */
    public int read() throws IOException {
        throw new RuntimeException("No read()");
    }

    /**
     * Skips over and discards <code>n</code> bytes of data from this input
     * stream. The <code>skip</code> method may, for a variety of reasons, end
     * up skipping over some smaller number of bytes, possibly <code>0</code>.
     * This may result from any of a number of conditions; reaching end of file
     * before <code>n</code> bytes have been skipped is only one possibility.
     * The actual number of bytes skipped is returned.  If <code>n</code> is
     * negative, no bytes are skipped.
     *
     * <p> The <code>skip</code> method of <code>InputStream</code> creates a
     * byte array and then repeatedly reads into it until <code>n</code> bytes
     * have been read or the end of the stream has been reached. Subclasses are
     * encouraged to provide a more efficient implementation of this method.
     *
     * @param      n   the number of bytes to be skipped.
     * @return     the actual number of bytes skipped.
     * @exception  IOException  if an I/O error occurs.
     */
    public long skip(long n) throws IOException {
        long m = n;
        while(m > 0) {
            if(read() > 0) {
                break;
            }
            --m;
        }
        return n-m;
    }

    /**
     * See the general contract of the <code>readFully</code>
     * method of <code>DataInput</code>.
     * <p>
     * Bytes
     * for this operation are read from the contained
     * input stream.
     *
     * @param      b   the buffer into which the data is read.
     * @exception  EOFException  if this input stream reaches the end before
     *               reading all the bytes.
     * @exception  IOException   if an I/O error occurs.
     */
    public void readFully(byte b[]) throws IOException {
        readFully(b, 0, b.length);
    }

    /**
     * See the general contract of the <code>readFully</code>
     * method of <code>DataInput</code>.
     * <p>
     * Bytes
     * for this operation are read from the contained
     * input stream.
     *
     * @param      b     the buffer into which the data is read.
     * @param      off   the start offset of the data.
     * @param      len   the number of bytes to read.
     * @exception  EOFException  if this input stream reaches the end before
     *               reading all the bytes.
     * @exception  IOException   if an I/O error occurs.
     */
    public void readFully(byte b[], int off, int len) throws IOException {
        if (len < 0)
            throw new IndexOutOfBoundsException();

        int n = 0;
        while (n < len) {
            int ch = read();
            if (ch < 0) {
                throw new EOFException();
            }
            b[off+(n++)] = (byte)ch;
        }
    }

    /**
     * See the general contract of the <code>skipBytes</code>
     * method of <code>DataInput</code>.
     * <p>
     * Bytes
     * for this operation are read from the contained
     * input stream.
     *
     * @param      n   the number of bytes to be skipped.
     * @return     the actual number of bytes skipped.
     * @exception  IOException   if an I/O error occurs.
     */
    public int skipBytes(int n) throws IOException {
        int total = 0;
        int cur = 0;

        while ((total<n) && ((cur = (int) skip(n-total)) > 0)) {
            total += cur;
        }

        return total;
    }

    /**
     * See the general contract of the <code>readBoolean</code>
     * method of <code>DataInput</code>.
     * <p>
     * Bytes
     * for this operation are read from the contained
     * input stream.
     *
     * @return     the <code>boolean</code> value read.
     * @exception  EOFException  if this input stream has reached the end.
     */
    public boolean readBoolean() throws IOException {
        int ch = read();
        if (ch < 0)
            throw new EOFException();
        return (ch != 0);
    }

    /**
     * See the general contract of the <code>readByte</code>
     * method of <code>DataInput</code>.
     * <p>
     * Bytes
     * for this operation are read from the contained
     * input stream.
     *
     * @return     the next byte of this input stream as a signed 8-bit
     *             <code>byte</code>.
     * @exception  EOFException  if this input stream has reached the end.
     * @exception  IOException   if an I/O error occurs.
     */
    public byte readByte() throws IOException {
        int ch = read();
        if (ch < 0)
            throw new EOFException();
        return (byte)(ch);
    }

    /**
     * See the general contract of the <code>readUnsignedByte</code>
     * method of <code>DataInput</code>.
     * <p>
     * Bytes
     * for this operation are read from the contained
     * input stream.
     *
     * @return     the next byte of this input stream, interpreted as an
     *             unsigned 8-bit number.
     * @exception  EOFException  if this input stream has reached the end.
     * @exception  IOException   if an I/O error occurs.
     */
    public int readUnsignedByte() throws IOException {
        int ch = read();
        if (ch < 0)
            throw new EOFException();
        return ch;
    }

    /**
     * See the general contract of the <code>readShort</code>
     * method of <code>DataInput</code>.
     * <p>
     * Bytes
     * for this operation are read from the contained
     * input stream.
     *
     * @return     the next two bytes of this input stream, interpreted as a
     *             signed 16-bit number.
     * @exception  EOFException  if this input stream reaches the end before
     *               reading two bytes.
     * @exception  IOException   if an I/O error occurs.
     */
    public short readShort() throws IOException {
        int ch1 = read();
        int ch2 = read();
        if ((ch1 | ch2) < 0)
             throw new EOFException();
        return (short)((ch1 << 8) + (ch2 << 0));
    }

    /**
     * See the general contract of the <code>readUnsignedShort</code>
     * method of <code>DataInput</code>.
     * <p>
     * Bytes
     * for this operation are read from the contained
     * input stream.
     *
     * @return     the next two bytes of this input stream, interpreted as an
     *             unsigned 16-bit integer.
     * @exception  EOFException  if this input stream reaches the end before
     *               reading two bytes.
     * @exception  IOException   if an I/O error occurs.
     */
    public int readUnsignedShort() throws IOException {
        int ch1 = read();
        int ch2 = read();
        if ((ch1 | ch2) < 0)
             throw new EOFException();
        return (ch1 << 8) + (ch2 << 0);
    }

    /**
     * See the general contract of the <code>readChar</code>
     * method of <code>DataInput</code>.
     * <p>
     * Bytes
     * for this operation are read from the contained
     * input stream.
     *
     * @return     the next two bytes of this input stream as a Unicode
     *             character.
     * @exception  EOFException  if this input stream reaches the end before
     *               reading two bytes.
     * @exception  IOException   if an I/O error occurs.
     */
    public char readChar() throws IOException {
        int ch1 = read();
        int ch2 = read();
        if ((ch1 | ch2) < 0)
             throw new EOFException();
        return (char)((ch1 << 8) + (ch2 << 0));
    }

    /**
     * See the general contract of the <code>readInt</code>
     * method of <code>DataInput</code>.
     * <p>
     * Bytes
     * for this operation are read from the contained
     * input stream.
     *
     * @return     the next four bytes of this input stream, interpreted as an
     *             <code>int</code>.
     * @exception  EOFException  if this input stream reaches the end before
     *               reading four bytes.
     * @exception  IOException   if an I/O error occurs.
     */
    public int readInt() throws IOException {
        int ch1 = read();
        int ch2 = read();
        int ch3 = read();
        int ch4 = read();
        if ((ch1 | ch2 | ch3 | ch4) < 0)
             throw new EOFException();
        return ((ch1 << 24) + (ch2 << 16) + (ch3 << 8) + (ch4 << 0));
    }

    /**
     * See the general contract of the <code>readLong</code>
     * method of <code>DataInput</code>.
     * <p>
     * Bytes
     * for this operation are read from the contained
     * input stream.
     *
     * @return     the next eight bytes of this input stream, interpreted as a
     *             <code>long</code>.
     * @exception  EOFException  if this input stream reaches the end before
     *               reading eight bytes.
     * @exception  IOException   if an I/O error occurs.
     */
    public long readLong() throws IOException {
        return ((long)(readInt()) << 32) + (readInt() & 0xFFFFFFFFL);
    }

    /**
     * See the general contract of the <code>readUTF</code>
     * method of <code>DataInput</code>.
     * <p>
     * Bytes
     * for this operation are read from the contained
     * input stream.
     *
     * @return     a Unicode string.
     * @exception  EOFException  if this input stream reaches the end before
     *               reading all the bytes.
     * @exception  IOException   if an I/O error occurs.
     * @see        java.io.DataInputStream#readUTF(java.io.DataInput)
     */
    public String readUTF() throws IOException {
        return DataInputStream.readUTF(this);
    }

    /**
     * Unsupported function
     */
    public float readFloat() throws IOException {
        throw new RuntimeException("Function not supported");
    }

    /**
     * Unsupported function
     */
    public double readDouble() throws IOException {
        throw new RuntimeException("Function not supported");
    }

    /**
     * Unsupported function
     */
    public String readLine() throws IOException {
        throw new RuntimeException("Function not supported");
    }


}