https://openjdk.java.net/ 
/*
 * Copyright (c) 1994, 2004, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code 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.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code 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 in the LICENSE file that
 * accompanied this code).
 *
 * 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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 */

package java.io;


A data output stream lets an application write primitive Java data
types to an output stream in a portable way. An application can
then use a data input stream to read the data back in.

Author: unascribed
See Also:
Since:  1.0
/**
 * A data output stream lets an application write primitive Java data
 * types to an output stream in a portable way. An application can
 * then use a data input stream to read the data back in.
 *
 * @author  unascribed
 * @see     java.io.DataInputStream
 * @since   1.0
 */
public
class DataOutputStream extends FilterOutputStream implements DataOutput {
    
The number of bytes written to the data output stream so far.
If this counter overflows, it will be wrapped to Integer.MAX_VALUE.

/**
     * The number of bytes written to the data output stream so far.
     * If this counter overflows, it will be wrapped to Integer.MAX_VALUE.
     */
    protected int written;

    
bytearr is initialized on demand by writeUTF

/**
     * bytearr is initialized on demand by writeUTF
     */
    private byte[] bytearr = null;

    
Creates a new data output stream to write data to the specified
underlying output stream. The counter written is
set to zero.

Params:
  • out –   the underlying output stream, to be saved for later
               use.
See Also:
/**
     * Creates a new data output stream to write data to the specified
     * underlying output stream. The counter <code>written</code> is
     * set to zero.
     *
     * @param   out   the underlying output stream, to be saved for later
     *                use.
     * @see     java.io.FilterOutputStream#out
     */
    public DataOutputStream(OutputStream out) {
        super(out);
    }

    
Increases the written counter by the specified value
until it reaches Integer.MAX_VALUE.

/**
     * Increases the written counter by the specified value
     * until it reaches Integer.MAX_VALUE.
     */
    private void incCount(int value) {
        int temp = written + value;
        if (temp < 0) {
            temp = Integer.MAX_VALUE;
        }
        written = temp;
    }

    
Writes the specified byte (the low eight bits of the argument
b) to the underlying output stream. If no exception
is thrown, the counter written is incremented by
1.


Implements the write method of OutputStream.

Params:
  • b –   the byte to be written.
Throws:
See Also:
/**
     * 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 synchronized void write(int b) throws IOException {
        out.write(b);
        incCount(1);
    }

    
Writes len bytes from the specified byte array
starting at offset off to the underlying output stream.
If no exception is thrown, the counter written is
incremented by len.

Params:
  • b –     the data.
  • off –   the start offset in the data.
  • len –   the number of bytes to write.
Throws:
See Also:
/**
     * 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 synchronized void write(byte b[], int off, int len)
        throws IOException
    {
        out.write(b, off, len);
        incCount(len);
    }

    
Flushes this data output stream. This forces any buffered output
bytes to be written out to the stream.


The flush method of DataOutputStream
calls the flush method of its underlying output stream.

Throws:
  • IOException –  if an I/O error occurs.
See Also:
/**
     * Flushes this data output stream. This forces any buffered output
     * bytes to be written out to the stream.
     * <p>
     * The <code>flush</code> method of <code>DataOutputStream</code>
     * calls the <code>flush</code> method of its underlying output stream.
     *
     * @exception  IOException  if an I/O error occurs.
     * @see        java.io.FilterOutputStream#out
     * @see        java.io.OutputStream#flush()
     */
    public void flush() throws IOException {
        out.flush();
    }

    
Writes a boolean to the underlying output stream as
a 1-byte value. The value true is written out as the
value (byte)1; the value false is
written out as the value (byte)0. If no exception is
thrown, the counter written is incremented by
1.

Params:
  • v –   a boolean value to be written.
Throws:
See Also:
/**
     * Writes a <code>boolean</code> to the underlying output stream as
     * a 1-byte value. The value <code>true</code> is written out as the
     * value <code>(byte)1</code>; the value <code>false</code> is
     * written out as the value <code>(byte)0</code>. If no exception is
     * thrown, the counter <code>written</code> is incremented by
     * <code>1</code>.
     *
     * @param      v   a <code>boolean</code> value to be written.
     * @exception  IOException  if an I/O error occurs.
     * @see        java.io.FilterOutputStream#out
     */
    public final void writeBoolean(boolean v) throws IOException {
        out.write(v ? 1 : 0);
        incCount(1);
    }

    
Writes out a byte to the underlying output stream as
a 1-byte value. If no exception is thrown, the counter
written is incremented by 1.

Params:
  • v –   a byte value to be written.
Throws:
See Also:
/**
     * Writes out a <code>byte</code> to the underlying output stream as
     * a 1-byte value. If no exception is thrown, the counter
     * <code>written</code> is incremented by <code>1</code>.
     *
     * @param      v   a <code>byte</code> value to be written.
     * @exception  IOException  if an I/O error occurs.
     * @see        java.io.FilterOutputStream#out
     */
    public final void writeByte(int v) throws IOException {
        out.write(v);
        incCount(1);
    }

    
Writes a short to the underlying output stream as two
bytes, high byte first. If no exception is thrown, the counter
written is incremented by 2.

Params:
  • v –   a short to be written.
Throws:
See Also:
/**
     * Writes a <code>short</code> to the underlying output stream as two
     * bytes, high byte first. If no exception is thrown, the counter
     * <code>written</code> is incremented by <code>2</code>.
     *
     * @param      v   a <code>short</code> to be written.
     * @exception  IOException  if an I/O error occurs.
     * @see        java.io.FilterOutputStream#out
     */
    public final void writeShort(int v) throws IOException {
        out.write((v >>> 8) & 0xFF);
        out.write((v >>> 0) & 0xFF);
        incCount(2);
    }

    
Writes a char to the underlying output stream as a
2-byte value, high byte first. If no exception is thrown, the
counter written is incremented by 2.

Params:
  • v –   a char value to be written.
Throws:
See Also:
/**
     * Writes a <code>char</code> to the underlying output stream as a
     * 2-byte value, high byte first. If no exception is thrown, the
     * counter <code>written</code> is incremented by <code>2</code>.
     *
     * @param      v   a <code>char</code> value to be written.
     * @exception  IOException  if an I/O error occurs.
     * @see        java.io.FilterOutputStream#out
     */
    public final void writeChar(int v) throws IOException {
        out.write((v >>> 8) & 0xFF);
        out.write((v >>> 0) & 0xFF);
        incCount(2);
    }

    
Writes an int to the underlying output stream as four
bytes, high byte first. If no exception is thrown, the counter
written is incremented by 4.

Params:
  • v –   an int to be written.
Throws:
See Also:
/**
     * Writes an <code>int</code> to the underlying output stream as four
     * bytes, high byte first. If no exception is thrown, the counter
     * <code>written</code> is incremented by <code>4</code>.
     *
     * @param      v   an <code>int</code> to be written.
     * @exception  IOException  if an I/O error occurs.
     * @see        java.io.FilterOutputStream#out
     */
    public final void writeInt(int v) throws IOException {
        out.write((v >>> 24) & 0xFF);
        out.write((v >>> 16) & 0xFF);
        out.write((v >>>  8) & 0xFF);
        out.write((v >>>  0) & 0xFF);
        incCount(4);
    }

    private byte writeBuffer[] = new byte[8];

    
Writes a long to the underlying output stream as eight
bytes, high byte first. In no exception is thrown, the counter
written is incremented by 8.

Params:
  • v –   a long to be written.
Throws:
See Also:
/**
     * Writes a <code>long</code> to the underlying output stream as eight
     * bytes, high byte first. In no exception is thrown, the counter
     * <code>written</code> is incremented by <code>8</code>.
     *
     * @param      v   a <code>long</code> to be written.
     * @exception  IOException  if an I/O error occurs.
     * @see        java.io.FilterOutputStream#out
     */
    public final void writeLong(long v) throws IOException {
        writeBuffer[0] = (byte)(v >>> 56);
        writeBuffer[1] = (byte)(v >>> 48);
        writeBuffer[2] = (byte)(v >>> 40);
        writeBuffer[3] = (byte)(v >>> 32);
        writeBuffer[4] = (byte)(v >>> 24);
        writeBuffer[5] = (byte)(v >>> 16);
        writeBuffer[6] = (byte)(v >>>  8);
        writeBuffer[7] = (byte)(v >>>  0);
        out.write(writeBuffer, 0, 8);
        incCount(8);
    }

    
Converts the float argument to an int using the
floatToIntBits method in class Float,
and then writes that int value to the underlying
output stream as a 4-byte quantity, high byte first. If no
exception is thrown, the counter written is
incremented by 4.

Params:
  • v –   a float value to be written.
Throws:
See Also:
/**
     * Converts the float argument to an <code>int</code> using the
     * <code>floatToIntBits</code> method in class <code>Float</code>,
     * and then writes that <code>int</code> value to the underlying
     * output stream as a 4-byte quantity, high byte first. If no
     * exception is thrown, the counter <code>written</code> is
     * incremented by <code>4</code>.
     *
     * @param      v   a <code>float</code> value to be written.
     * @exception  IOException  if an I/O error occurs.
     * @see        java.io.FilterOutputStream#out
     * @see        java.lang.Float#floatToIntBits(float)
     */
    public final void writeFloat(float v) throws IOException {
        writeInt(Float.floatToIntBits(v));
    }

    
Converts the double argument to a long using the
doubleToLongBits method in class Double,
and then writes that long value to the underlying
output stream as an 8-byte quantity, high byte first. If no
exception is thrown, the counter written is
incremented by 8.

Params:
  • v –   a double value to be written.
Throws:
See Also:
/**
     * Converts the double argument to a <code>long</code> using the
     * <code>doubleToLongBits</code> method in class <code>Double</code>,
     * and then writes that <code>long</code> value to the underlying
     * output stream as an 8-byte quantity, high byte first. If no
     * exception is thrown, the counter <code>written</code> is
     * incremented by <code>8</code>.
     *
     * @param      v   a <code>double</code> value to be written.
     * @exception  IOException  if an I/O error occurs.
     * @see        java.io.FilterOutputStream#out
     * @see        java.lang.Double#doubleToLongBits(double)
     */
    public final void writeDouble(double v) throws IOException {
        writeLong(Double.doubleToLongBits(v));
    }

    
Writes out the string to the underlying output stream as a
sequence of bytes. Each character in the string is written out, in
sequence, by discarding its high eight bits. If no exception is
thrown, the counter written is incremented by the
length of s.

Params:
  • s –   a string of bytes to be written.
Throws:
See Also:
/**
     * Writes out the string to the underlying output stream as a
     * sequence of bytes. Each character in the string is written out, in
     * sequence, by discarding its high eight bits. If no exception is
     * thrown, the counter <code>written</code> is incremented by the
     * length of <code>s</code>.
     *
     * @param      s   a string of bytes to be written.
     * @exception  IOException  if an I/O error occurs.
     * @see        java.io.FilterOutputStream#out
     */
    public final void writeBytes(String s) throws IOException {
        int len = s.length();
        for (int i = 0 ; i < len ; i++) {
            out.write((byte)s.charAt(i));
        }
        incCount(len);
    }

    
Writes a string to the underlying output stream as a sequence of
characters. Each character is written to the data output stream as
if by the writeChar method. If no exception is
thrown, the counter written is incremented by twice
the length of s.

Params:
  • s –   a String value to be written.
Throws:
See Also:
/**
     * Writes a string to the underlying output stream as a sequence of
     * characters. Each character is written to the data output stream as
     * if by the <code>writeChar</code> method. If no exception is
     * thrown, the counter <code>written</code> is incremented by twice
     * the length of <code>s</code>.
     *
     * @param      s   a <code>String</code> value to be written.
     * @exception  IOException  if an I/O error occurs.
     * @see        java.io.DataOutputStream#writeChar(int)
     * @see        java.io.FilterOutputStream#out
     */
    public final void writeChars(String s) throws IOException {
        int len = s.length();
        for (int i = 0 ; i < len ; i++) {
            int v = s.charAt(i);
            out.write((v >>> 8) & 0xFF);
            out.write((v >>> 0) & 0xFF);
        }
        incCount(len * 2);
    }

    
Writes a string to the underlying output stream using
modified UTF-8
encoding in a machine-independent manner.


First, two bytes are written to the output stream as if by the
writeShort method giving the number of bytes to
follow. This value is the number of bytes actually written out,
not the length of the string. Following the length, each character
of the string is output, in sequence, using the modified UTF-8 encoding
for the character. If no exception is thrown, the counter
written is incremented by the total number of
bytes written to the output stream. This will be at least two
plus the length of str, and at most two plus
thrice the length of str.

Params:
  • str –   a string to be written.
Throws:
/**
     * Writes a string to the underlying output stream using
     * <a href="DataInput.html#modified-utf-8">modified UTF-8</a>
     * encoding in a machine-independent manner.
     * <p>
     * First, two bytes are written to the output stream as if by the
     * <code>writeShort</code> method giving the number of bytes to
     * follow. This value is the number of bytes actually written out,
     * not the length of the string. Following the length, each character
     * of the string is output, in sequence, using the modified UTF-8 encoding
     * for the character. If no exception is thrown, the counter
     * <code>written</code> is incremented by the total number of
     * bytes written to the output stream. This will be at least two
     * plus the length of <code>str</code>, and at most two plus
     * thrice the length of <code>str</code>.
     *
     * @param      str   a string to be written.
     * @exception  IOException  if an I/O error occurs.
     */
    public final void writeUTF(String str) throws IOException {
        writeUTF(str, this);
    }

    
Writes a string to the specified DataOutput using
modified UTF-8
encoding in a machine-independent manner.


First, two bytes are written to out as if by the writeShort
method giving the number of bytes to follow. This value is the number of
bytes actually written out, not the length of the string. Following the
length, each character of the string is output, in sequence, using the
modified UTF-8 encoding for the character. If no exception is thrown, the
counter written is incremented by the total number of
bytes written to the output stream. This will be at least two
plus the length of str, and at most two plus
thrice the length of str.

Params:
  • str –   a string to be written.
  • out –   destination to write to
Throws:
Returns:    The number of bytes written out.
/**
     * Writes a string to the specified DataOutput using
     * <a href="DataInput.html#modified-utf-8">modified UTF-8</a>
     * encoding in a machine-independent manner.
     * <p>
     * First, two bytes are written to out as if by the <code>writeShort</code>
     * method giving the number of bytes to follow. This value is the number of
     * bytes actually written out, not the length of the string. Following the
     * length, each character of the string is output, in sequence, using the
     * modified UTF-8 encoding for the character. If no exception is thrown, the
     * counter <code>written</code> is incremented by the total number of
     * bytes written to the output stream. This will be at least two
     * plus the length of <code>str</code>, and at most two plus
     * thrice the length of <code>str</code>.
     *
     * @param      str   a string to be written.
     * @param      out   destination to write to
     * @return     The number of bytes written out.
     * @exception  IOException  if an I/O error occurs.
     */
    static int writeUTF(String str, DataOutput out) throws IOException {
        int strlen = str.length();
        int utflen = 0;
        int c, count = 0;

        /* use charAt instead of copying String to char array */
        for (int i = 0; i < strlen; i++) {
            c = str.charAt(i);
            if ((c >= 0x0001) && (c <= 0x007F)) {
                utflen++;
            } else if (c > 0x07FF) {
                utflen += 3;
            } else {
                utflen += 2;
            }
        }

        if (utflen > 65535)
            throw new UTFDataFormatException(
                "encoded string too long: " + utflen + " bytes");

        byte[] bytearr = null;
        if (out instanceof DataOutputStream) {
            DataOutputStream dos = (DataOutputStream)out;
            if(dos.bytearr == null || (dos.bytearr.length < (utflen+2)))
                dos.bytearr = new byte[(utflen*2) + 2];
            bytearr = dos.bytearr;
        } else {
            bytearr = new byte[utflen+2];
        }

        bytearr[count++] = (byte) ((utflen >>> 8) & 0xFF);
        bytearr[count++] = (byte) ((utflen >>> 0) & 0xFF);

        int i=0;
        for (i=0; i<strlen; i++) {
           c = str.charAt(i);
           if (!((c >= 0x0001) && (c <= 0x007F))) break;
           bytearr[count++] = (byte) c;
        }

        for (;i < strlen; i++){
            c = str.charAt(i);
            if ((c >= 0x0001) && (c <= 0x007F)) {
                bytearr[count++] = (byte) c;

            } else if (c > 0x07FF) {
                bytearr[count++] = (byte) (0xE0 | ((c >> 12) & 0x0F));
                bytearr[count++] = (byte) (0x80 | ((c >>  6) & 0x3F));
                bytearr[count++] = (byte) (0x80 | ((c >>  0) & 0x3F));
            } else {
                bytearr[count++] = (byte) (0xC0 | ((c >>  6) & 0x1F));
                bytearr[count++] = (byte) (0x80 | ((c >>  0) & 0x3F));
            }
        }
        out.write(bytearr, 0, utflen+2);
        return utflen + 2;
    }

    
Returns the current value of the counter written,
the number of bytes written to this data output stream so far.
If the counter overflows, it will be wrapped to Integer.MAX_VALUE.

See Also:
Returns: the value of the written field.
/**
     * Returns the current value of the counter <code>written</code>,
     * the number of bytes written to this data output stream so far.
     * If the counter overflows, it will be wrapped to Integer.MAX_VALUE.
     *
     * @return  the value of the <code>written</code> field.
     * @see     java.io.DataOutputStream#written
     */
    public final int size() {
        return written;
    }
}