1 /*
2 * Copyright (c) 1995, 2013, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation. Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25
26 package java.io;
27
28 /**
29 * The <code>DataOutput</code> interface provides
30 * for converting data from any of the Java
31 * primitive types to a series of bytes and
32 * writing these bytes to a binary stream.
33 * There is also a facility for converting
34 * a <code>String</code> into
35 * <a href="DataInput.html#modified-utf-8">modified UTF-8</a>
36 * format and writing the resulting series
37 * of bytes.
38 * <p>
39 * For all the methods in this interface that
40 * write bytes, it is generally true that if
41 * a byte cannot be written for any reason,
42 * an <code>IOException</code> is thrown.
43 *
44 * @author Frank Yellin
45 * @see java.io.DataInput
46 * @see java.io.DataOutputStream
47 * @since JDK1.0
48 */
49 public
50 interface DataOutput {
51 /**
52 * Writes to the output stream the eight
53 * low-order bits of the argument <code>b</code>.
54 * The 24 high-order bits of <code>b</code>
55 * are ignored.
56 *
57 * @param b the byte to be written.
58 * @throws IOException if an I/O error occurs.
59 */
60 void write(int b) throws IOException;
61
62 /**
63 * Writes to the output stream all the bytes in array <code>b</code>.
64 * If <code>b</code> is <code>null</code>,
65 * a <code>NullPointerException</code> is thrown.
66 * If <code>b.length</code> is zero, then
67 * no bytes are written. Otherwise, the byte
68 * <code>b[0]</code> is written first, then
69 * <code>b[1]</code>, and so on; the last byte
70 * written is <code>b[b.length-1]</code>.
71 *
72 * @param b the data.
73 * @throws IOException if an I/O error occurs.
74 */
75 void write(byte b[]) throws IOException;
76
77 /**
78 * Writes <code>len</code> bytes from array
79 * <code>b</code>, in order, to
80 * the output stream. If <code>b</code>
81 * is <code>null</code>, a <code>NullPointerException</code>
82 * is thrown. If <code>off</code> is negative,
83 * or <code>len</code> is negative, or <code>off+len</code>
84 * is greater than the length of the array
85 * <code>b</code>, then an <code>IndexOutOfBoundsException</code>
86 * is thrown. If <code>len</code> is zero,
87 * then no bytes are written. Otherwise, the
88 * byte <code>b[off]</code> is written first,
89 * then <code>b[off+1]</code>, and so on; the
90 * last byte written is <code>b[off+len-1]</code>.
91 *
92 * @param b the data.
93 * @param off the start offset in the data.
94 * @param len the number of bytes to write.
95 * @throws IOException if an I/O error occurs.
96 */
97 void write(byte b[], int off, int len) throws IOException;
98
99 /**
100 * Writes a <code>boolean</code> value to this output stream.
101 * If the argument <code>v</code>
102 * is <code>true</code>, the value <code>(byte)1</code>
103 * is written; if <code>v</code> is <code>false</code>,
104 * the value <code>(byte)0</code> is written.
105 * The byte written by this method may
106 * be read by the <code>readBoolean</code>
107 * method of interface <code>DataInput</code>,
108 * which will then return a <code>boolean</code>
109 * equal to <code>v</code>.
110 *
111 * @param v the boolean to be written.
112 * @throws IOException if an I/O error occurs.
113 */
114 void writeBoolean(boolean v) throws IOException;
115
116 /**
117 * Writes to the output stream the eight low-
118 * order bits of the argument <code>v</code>.
119 * The 24 high-order bits of <code>v</code>
120 * are ignored. (This means that <code>writeByte</code>
121 * does exactly the same thing as <code>write</code>
122 * for an integer argument.) The byte written
123 * by this method may be read by the <code>readByte</code>
124 * method of interface <code>DataInput</code>,
125 * which will then return a <code>byte</code>
126 * equal to <code>(byte)v</code>.
127 *
128 * @param v the byte value to be written.
129 * @throws IOException if an I/O error occurs.
130 */
131 void writeByte(int v) throws IOException;
132
133 /**
134 * Writes two bytes to the output
135 * stream to represent the value of the argument.
136 * The byte values to be written, in the order
137 * shown, are:
138 * <pre>{@code
139 * (byte)(0xff & (v >> 8))
140 * (byte)(0xff & v)
141 * }</pre> <p>
142 * The bytes written by this method may be
143 * read by the <code>readShort</code> method
144 * of interface <code>DataInput</code> , which
145 * will then return a <code>short</code> equal
146 * to <code>(short)v</code>.
147 *
148 * @param v the <code>short</code> value to be written.
149 * @throws IOException if an I/O error occurs.
150 */
151 void writeShort(int v) throws IOException;
152
153 /**
154 * Writes a <code>char</code> value, which
155 * is comprised of two bytes, to the
156 * output stream.
157 * The byte values to be written, in the order
158 * shown, are:
159 * <pre>{@code
160 * (byte)(0xff & (v >> 8))
161 * (byte)(0xff & v)
162 * }</pre><p>
163 * The bytes written by this method may be
164 * read by the <code>readChar</code> method
165 * of interface <code>DataInput</code> , which
166 * will then return a <code>char</code> equal
167 * to <code>(char)v</code>.
168 *
169 * @param v the <code>char</code> value to be written.
170 * @throws IOException if an I/O error occurs.
171 */
172 void writeChar(int v) throws IOException;
173
174 /**
175 * Writes an <code>int</code> value, which is
176 * comprised of four bytes, to the output stream.
177 * The byte values to be written, in the order
178 * shown, are:
179 * <pre>{@code
180 * (byte)(0xff & (v >> 24))
181 * (byte)(0xff & (v >> 16))
182 * (byte)(0xff & (v >> 8))
183 * (byte)(0xff & v)
184 * }</pre><p>
185 * The bytes written by this method may be read
186 * by the <code>readInt</code> method of interface
187 * <code>DataInput</code> , which will then
188 * return an <code>int</code> equal to <code>v</code>.
189 *
190 * @param v the <code>int</code> value to be written.
191 * @throws IOException if an I/O error occurs.
192 */
193 void writeInt(int v) throws IOException;
194
195 /**
196 * Writes a <code>long</code> value, which is
197 * comprised of eight bytes, to the output stream.
198 * The byte values to be written, in the order
199 * shown, are:
200 * <pre>{@code
201 * (byte)(0xff & (v >> 56))
202 * (byte)(0xff & (v >> 48))
203 * (byte)(0xff & (v >> 40))
204 * (byte)(0xff & (v >> 32))
205 * (byte)(0xff & (v >> 24))
206 * (byte)(0xff & (v >> 16))
207 * (byte)(0xff & (v >> 8))
208 * (byte)(0xff & v)
209 * }</pre><p>
210 * The bytes written by this method may be
211 * read by the <code>readLong</code> method
212 * of interface <code>DataInput</code> , which
213 * will then return a <code>long</code> equal
214 * to <code>v</code>.
215 *
216 * @param v the <code>long</code> value to be written.
217 * @throws IOException if an I/O error occurs.
218 */
219 void writeLong(long v) throws IOException;
220
221 /**
222 * Writes a <code>float</code> value,
223 * which is comprised of four bytes, to the output stream.
224 * It does this as if it first converts this
225 * <code>float</code> value to an <code>int</code>
226 * in exactly the manner of the <code>Float.floatToIntBits</code>
227 * method and then writes the <code>int</code>
228 * value in exactly the manner of the <code>writeInt</code>
229 * method. The bytes written by this method
230 * may be read by the <code>readFloat</code>
231 * method of interface <code>DataInput</code>,
232 * which will then return a <code>float</code>
233 * equal to <code>v</code>.
234 *
235 * @param v the <code>float</code> value to be written.
236 * @throws IOException if an I/O error occurs.
237 */
238 void writeFloat(float v) throws IOException;
239
240 /**
241 * Writes a <code>double</code> value,
242 * which is comprised of eight bytes, to the output stream.
243 * It does this as if it first converts this
244 * <code>double</code> value to a <code>long</code>
245 * in exactly the manner of the <code>Double.doubleToLongBits</code>
246 * method and then writes the <code>long</code>
247 * value in exactly the manner of the <code>writeLong</code>
248 * method. The bytes written by this method
249 * may be read by the <code>readDouble</code>
250 * method of interface <code>DataInput</code>,
251 * which will then return a <code>double</code>
252 * equal to <code>v</code>.
253 *
254 * @param v the <code>double</code> value to be written.
255 * @throws IOException if an I/O error occurs.
256 */
257 void writeDouble(double v) throws IOException;
258
259 /**
260 * Writes a string to the output stream.
261 * For every character in the string
262 * <code>s</code>, taken in order, one byte
263 * is written to the output stream. If
264 * <code>s</code> is <code>null</code>, a <code>NullPointerException</code>
265 * is thrown.<p> If <code>s.length</code>
266 * is zero, then no bytes are written. Otherwise,
267 * the character <code>s[0]</code> is written
268 * first, then <code>s[1]</code>, and so on;
269 * the last character written is <code>s[s.length-1]</code>.
270 * For each character, one byte is written,
271 * the low-order byte, in exactly the manner
272 * of the <code>writeByte</code> method . The
273 * high-order eight bits of each character
274 * in the string are ignored.
275 *
276 * @param s the string of bytes to be written.
277 * @throws IOException if an I/O error occurs.
278 */
279 void writeBytes(String s) throws IOException;
280
281 /**
282 * Writes every character in the string <code>s</code>,
283 * to the output stream, in order,
284 * two bytes per character. If <code>s</code>
285 * is <code>null</code>, a <code>NullPointerException</code>
286 * is thrown. If <code>s.length</code>
287 * is zero, then no characters are written.
288 * Otherwise, the character <code>s[0]</code>
289 * is written first, then <code>s[1]</code>,
290 * and so on; the last character written is
291 * <code>s[s.length-1]</code>. For each character,
292 * two bytes are actually written, high-order
293 * byte first, in exactly the manner of the
294 * <code>writeChar</code> method.
295 *
296 * @param s the string value to be written.
297 * @throws IOException if an I/O error occurs.
298 */
299 void writeChars(String s) throws IOException;
300
301 /**
302 * Writes two bytes of length information
303 * to the output stream, followed
304 * by the
305 * <a href="DataInput.html#modified-utf-8">modified UTF-8</a>
306 * representation
307 * of every character in the string <code>s</code>.
308 * If <code>s</code> is <code>null</code>,
309 * a <code>NullPointerException</code> is thrown.
310 * Each character in the string <code>s</code>
311 * is converted to a group of one, two, or
312 * three bytes, depending on the value of the
313 * character.<p>
314 * If a character <code>c</code>
315 * is in the range <code>\u0001</code> through
316 * <code>\u007f</code>, it is represented
317 * by one byte:
318 * <pre>(byte)c </pre> <p>
319 * If a character <code>c</code> is <code>\u0000</code>
320 * or is in the range <code>\u0080</code>
321 * through <code>\u07ff</code>, then it is
322 * represented by two bytes, to be written
323 * in the order shown: <pre>{@code
324 * (byte)(0xc0 | (0x1f & (c >> 6)))
325 * (byte)(0x80 | (0x3f & c))
326 * }</pre> <p> If a character
327 * <code>c</code> is in the range <code>\u0800</code>
328 * through <code>uffff</code>, then it is
329 * represented by three bytes, to be written
330 * in the order shown: <pre>{@code
331 * (byte)(0xe0 | (0x0f & (c >> 12)))
332 * (byte)(0x80 | (0x3f & (c >> 6)))
333 * (byte)(0x80 | (0x3f & c))
334 * }</pre> <p> First,
335 * the total number of bytes needed to represent
336 * all the characters of <code>s</code> is
337 * calculated. If this number is larger than
338 * <code>65535</code>, then a <code>UTFDataFormatException</code>
339 * is thrown. Otherwise, this length is written
340 * to the output stream in exactly the manner
341 * of the <code>writeShort</code> method;
342 * after this, the one-, two-, or three-byte
343 * representation of each character in the
344 * string <code>s</code> is written.<p> The
345 * bytes written by this method may be read
346 * by the <code>readUTF</code> method of interface
347 * <code>DataInput</code> , which will then
348 * return a <code>String</code> equal to <code>s</code>.
349 *
350 * @param s the string value to be written.
351 * @throws IOException if an I/O error occurs.
352 */
353 void writeUTF(String s) throws IOException;
354 }