DataOutput


1   /*
2    * @(#)DataOutput.java  1.21 04/05/13
3    *
4    * Copyright 2004 Sun Microsystems, Inc. All rights reserved.
5    * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
6    */
7   
8   package java.io;
9   
10  /**
11   * The <code>DataOutput</code> interface provides
12   * for converting data from any of the Java
13   * primitive types to a series of bytes and
14   * writing these bytes to a binary stream.
15   * There is  also a facility for converting
16   * a <code>String</code> into
17   * <a HREF="DataInput.html#modified-utf-8">modified UTF-8</a>
18   * format and writing the resulting series
19   * of bytes.
20   * <p>
21   * For all the methods in this interface that
22   * write bytes, it is generally true that if
23   * a byte cannot be written for any reason,
24   * an <code>IOException</code> is thrown.
25   *
26   * @author  Frank Yellin
27   * @version 1.21, 05/13/04
28   * @see     java.io.DataInput
29   * @see     java.io.DataOutputStream
30   * @since   JDK1.0
31   */
32  public
33  interface DataOutput {
34      /**
35       * Writes to the output stream the eight
36       * low-order bits of the argument <code>b</code>.
37       * The 24 high-order  bits of <code>b</code>
38       * are ignored.
39       *
40       * @param      b   the byte to be written.
41       * @exception  IOException  if an I/O error occurs.
42       */
43      void write(int b) throws IOException  ;
44  
45      /**
46       * Writes to the output stream all the bytes in array <code>b</code>.
47       * If <code>b</code> is <code>null</code>,
48       * a <code>NullPointerException</code> is thrown.
49       * If <code>b.length</code> is zero, then
50       * no bytes are written. Otherwise, the byte
51       * <code>b[0]</code> is written first, then
52       * <code>b[1]</code>, and so on; the last byte
53       * written is <code>b[b.length-1]</code>.
54       *
55       * @param      b   the data.
56       * @exception  IOException  if an I/O error occurs.
57       */
58      void write(byte b[]) throws IOException  ;
59  
60      /**
61       * Writes <code>len</code> bytes from array
62       * <code>b</code>, in order,  to
63       * the output stream.  If <code>b</code>
64       * is <code>null</code>, a <code>NullPointerException</code>
65       * is thrown.  If <code>off</code> is negative,
66       * or <code>len</code> is negative, or <code>off+len</code>
67       * is greater than the length of the array
68       * <code>b</code>, then an <code>IndexOutOfBoundsException</code>
69       * is thrown.  If <code>len</code> is zero,
70       * then no bytes are written. Otherwise, the
71       * byte <code>b[off]</code> is written first,
72       * then <code>b[off+1]</code>, and so on; the
73       * last byte written is <code>b[off+len-1]</code>.
74       *
75       * @param      b     the data.
76       * @param      off   the start offset in the data.
77       * @param      len   the number of bytes to write.
78       * @exception  IOException  if an I/O error occurs.
79       */
80      void write(byte b[], int off, int len) throws IOException  ;
81  
82      /**
83       * Writes a <code>boolean</code> value to this output stream.
84       * If the argument <code>v</code>
85       * is <code>true</code>, the value <code>(byte)1</code>
86       * is written; if <code>v</code> is <code>false</code>,
87       * the  value <code>(byte)0</code> is written.
88       * The byte written by this method may
89       * be read by the <code>readBoolean</code>
90       * method of interface <code>DataInput</code>,
91       * which will then return a <code>boolean</code>
92       * equal to <code>v</code>.
93       *
94       * @param      v   the boolean to be written.
95       * @exception  IOException  if an I/O error occurs.
96       */
97      void writeBoolean(boolean v) throws IOException  ;
98  
99      /**
100      * Writes to the output stream the eight low-
101      * order bits of the argument <code>v</code>.
102      * The 24 high-order bits of <code>v</code>
103      * are ignored. (This means  that <code>writeByte</code>
104      * does exactly the same thing as <code>write</code>
105      * for an integer argument.) The byte written
106      * by this method may be read by the <code>readByte</code>
107      * method of interface <code>DataInput</code>,
108      * which will then return a <code>byte</code>
109      * equal to <code>(byte)v</code>.
110      *
111      * @param      v   the byte value to be written.
112      * @exception  IOException  if an I/O error occurs.
113      */
114     void writeByte(int v) throws IOException  ;
115 
116     /**
117      * Writes two bytes to the output
118      * stream to represent the value of the argument.
119      * The byte values to be written, in the  order
120      * shown, are: <p>
121      * <pre><code>
122      * (byte)(0xff &amp; (v &gt;&gt; 8))
123      * (byte)(0xff &amp; v)
124      * </code> </pre> <p>
125      * The bytes written by this method may be
126      * read by the <code>readShort</code> method
127      * of interface <code>DataInput</code> , which
128      * will then return a <code>short</code> equal
129      * to <code>(short)v</code>.
130      *
131      * @param      v   the <code>short</code> value to be written.
132      * @exception  IOException  if an I/O error occurs.
133      */
134     void writeShort(int v) throws IOException  ;
135 
136     /**
137      * Writes a <code>char</code> value, which
138      * is comprised of two bytes, to the
139      * output stream.
140      * The byte values to be written, in the  order
141      * shown, are:
142      * <p><pre><code>
143      * (byte)(0xff &amp; (v &gt;&gt; 8))
144      * (byte)(0xff &amp; v)
145      * </code></pre><p>
146      * The bytes written by this method may be
147      * read by the <code>readChar</code> method
148      * of interface <code>DataInput</code> , which
149      * will then return a <code>char</code> equal
150      * to <code>(char)v</code>.
151      *
152      * @param      v   the <code>char</code> value to be written.
153      * @exception  IOException  if an I/O error occurs.
154      */
155     void writeChar(int v) throws IOException  ;
156 
157     /**
158      * Writes an <code>int</code> value, which is
159      * comprised of four bytes, to the output stream.
160      * The byte values to be written, in the  order
161      * shown, are:
162      * <p><pre><code>
163      * (byte)(0xff &amp; (v &gt;&gt; 24))
164      * (byte)(0xff &amp; (v &gt;&gt; 16))
165      * (byte)(0xff &amp; (v &gt;&gt; &#32; &#32;8))
166      * (byte)(0xff &amp; v)
167      * </code></pre><p>
168      * The bytes written by this method may be read
169      * by the <code>readInt</code> method of interface
170      * <code>DataInput</code> , which will then
171      * return an <code>int</code> equal to <code>v</code>.
172      *
173      * @param      v   the <code>int</code> value to be written.
174      * @exception  IOException  if an I/O error occurs.
175      */
176     void writeInt(int v) throws IOException  ;
177 
178     /**
179      * Writes a <code>long</code> value, which is
180      * comprised of eight bytes, to the output stream.
181      * The byte values to be written, in the  order
182      * shown, are:
183      * <p><pre><code>
184      * (byte)(0xff &amp; (v &gt;&gt; 56))
185      * (byte)(0xff &amp; (v &gt;&gt; 48))
186      * (byte)(0xff &amp; (v &gt;&gt; 40))
187      * (byte)(0xff &amp; (v &gt;&gt; 32))
188      * (byte)(0xff &amp; (v &gt;&gt; 24))
189      * (byte)(0xff &amp; (v &gt;&gt; 16))
190      * (byte)(0xff &amp; (v &gt;&gt;  8))
191      * (byte)(0xff &amp; v)
192      * </code></pre><p>
193      * The bytes written by this method may be
194      * read by the <code>readLong</code> method
195      * of interface <code>DataInput</code> , which
196      * will then return a <code>long</code> equal
197      * to <code>v</code>.
198      *
199      * @param      v   the <code>long</code> value to be written.
200      * @exception  IOException  if an I/O error occurs.
201      */
202     void writeLong(long v) throws IOException  ;
203 
204     /**
205      * Writes a <code>float</code> value,
206      * which is comprised of four bytes, to the output stream.
207      * It does this as if it first converts this
208      * <code>float</code> value to an <code>int</code>
209      * in exactly the manner of the <code>Float.floatToIntBits</code>
210      * method  and then writes the <code>int</code>
211      * value in exactly the manner of the  <code>writeInt</code>
212      * method.  The bytes written by this method
213      * may be read by the <code>readFloat</code>
214      * method of interface <code>DataInput</code>,
215      * which will then return a <code>float</code>
216      * equal to <code>v</code>.
217      *
218      * @param      v   the <code>float</code> value to be written.
219      * @exception  IOException  if an I/O error occurs.
220      */
221     void writeFloat(float v) throws IOException  ;
222 
223     /**
224      * Writes a <code>double</code> value,
225      * which is comprised of eight bytes, to the output stream.
226      * It does this as if it first converts this
227      * <code>double</code> value to a <code>long</code>
228      * in exactly the manner of the <code>Double.doubleToLongBits</code>
229      * method  and then writes the <code>long</code>
230      * value in exactly the manner of the  <code>writeLong</code>
231      * method. The bytes written by this method
232      * may be read by the <code>readDouble</code>
233      * method of interface <code>DataInput</code>,
234      * which will then return a <code>double</code>
235      * equal to <code>v</code>.
236      *
237      * @param      v   the <code>double</code> value to be written.
238      * @exception  IOException  if an I/O error occurs.
239      */
240     void writeDouble(double v) throws IOException  ;
241 
242     /**
243      * Writes a string to the output stream.
244      * For every character in the string
245      * <code>s</code>,  taken in order, one byte
246      * is written to the output stream.  If
247      * <code>s</code> is <code>null</code>, a <code>NullPointerException</code>
248      * is thrown.<p>  If <code>s.length</code>
249      * is zero, then no bytes are written. Otherwise,
250      * the character <code>s[0]</code> is written
251      * first, then <code>s[1]</code>, and so on;
252      * the last character written is <code>s[s.length-1]</code>.
253      * For each character, one byte is written,
254      * the low-order byte, in exactly the manner
255      * of the <code>writeByte</code> method . The
256      * high-order eight bits of each character
257      * in the string are ignored.
258      *
259      * @param      s   the string of bytes to be written.
260      * @exception  IOException  if an I/O error occurs.
261      */
262     void writeBytes(String   s) throws IOException  ;
263 
264     /**
265      * Writes every character in the string <code>s</code>,
266      * to the output stream, in order,
267      * two bytes per character. If <code>s</code>
268      * is <code>null</code>, a <code>NullPointerException</code>
269      * is thrown.  If <code>s.length</code>
270      * is zero, then no characters are written.
271      * Otherwise, the character <code>s[0]</code>
272      * is written first, then <code>s[1]</code>,
273      * and so on; the last character written is
274      * <code>s[s.length-1]</code>. For each character,
275      * two bytes are actually written, high-order
276      * byte first, in exactly the manner of the
277      * <code>writeChar</code> method.
278      *
279      * @param      s   the string value to be written.
280      * @exception  IOException  if an I/O error occurs.
281      */
282     void writeChars(String   s) throws IOException  ;
283 
284     /**
285      * Writes two bytes of length information
286      * to the output stream, followed
287      * by the
288      * <a HREF="DataInput.html#modified-utf-8">modified UTF-8</a>
289      * representation
290      * of  every character in the string <code>s</code>.
291      * If <code>s</code> is <code>null</code>,
292      * a <code>NullPointerException</code> is thrown.
293      * Each character in the string <code>s</code>
294      * is converted to a group of one, two, or
295      * three bytes, depending on the value of the
296      * character.<p>
297      * If a character <code>c</code>
298      * is in the range <code>&#92;u0001</code> through
299      * <code>&#92;u007f</code>, it is represented
300      * by one byte:<p>
301      * <pre>(byte)c </pre>  <p>
302      * If a character <code>c</code> is <code>&#92;u0000</code>
303      * or is in the range <code>&#92;u0080</code>
304      * through <code>&#92;u07ff</code>, then it is
305      * represented by two bytes, to be written
306      * in the order shown:<p> <pre><code>
307      * (byte)(0xc0 | (0x1f &amp; (c &gt;&gt; 6)))
308      * (byte)(0x80 | (0x3f &amp; c))
309      *  </code></pre>  <p> If a character
310      * <code>c</code> is in the range <code>&#92;u0800</code>
311      * through <code>uffff</code>, then it is
312      * represented by three bytes, to be written
313      * in the order shown:<p> <pre><code>
314      * (byte)(0xe0 | (0x0f &amp; (c &gt;&gt; 12)))
315      * (byte)(0x80 | (0x3f &amp; (c &gt;&gt;  6)))
316      * (byte)(0x80 | (0x3f &amp; c))
317      *  </code></pre>  <p> First,
318      * the total number of bytes needed to represent
319      * all the characters of <code>s</code> is
320      * calculated. If this number is larger than
321      * <code>65535</code>, then a <code>UTFDataFormatException</code>
322      * is thrown. Otherwise, this length is written
323      * to the output stream in exactly the manner
324      * of the <code>writeShort</code> method;
325      * after this, the one-, two-, or three-byte
326      * representation of each character in the
327      * string <code>s</code> is written.<p>  The
328      * bytes written by this method may be read
329      * by the <code>readUTF</code> method of interface
330      * <code>DataInput</code> , which will then
331      * return a <code>String</code> equal to <code>s</code>.
332      *
333      * @param      str   the string value to be written.
334      * @exception  IOException  if an I/O error occurs.
335      */
336     void writeUTF(String   str) throws IOException  ;
337 }
338
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