1 /*
2 * Copyright (C) 2008, 2015 Shawn O. Pearce <spearce@spearce.org>
3 * and other copyright owners as documented in the project's IP log.
4 *
5 * This program and the accompanying materials are made available
6 * under the terms of the Eclipse Distribution License v1.0 which
7 * accompanies this distribution, is reproduced below, and is
8 * available at http://www.eclipse.org/org/documents/edl-v10.php
9 *
10 * All rights reserved.
11 *
12 * Redistribution and use in source and binary forms, with or
13 * without modification, are permitted provided that the following
14 * conditions are met:
15 *
16 * - Redistributions of source code must retain the above copyright
17 * notice, this list of conditions and the following disclaimer.
18 *
19 * - Redistributions in binary form must reproduce the above
20 * copyright notice, this list of conditions and the following
21 * disclaimer in the documentation and/or other materials provided
22 * with the distribution.
23 *
24 * - Neither the name of the Eclipse Foundation, Inc. nor the
25 * names of its contributors may be used to endorse or promote
26 * products derived from this software without specific prior
27 * written permission.
28 *
29 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
30 * CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
31 * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
32 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
33 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
34 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
35 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
36 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
37 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
38 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
39 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
40 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
41 * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
42 */
43
44 package org.eclipse.jgit.util;
45
46 /** Conversion utilities for network byte order handling. */
47 public final class NB {
48 /**
49 * Compare a 32 bit unsigned integer stored in a 32 bit signed integer.
50 * <p>
51 * This function performs an unsigned compare operation, even though Java
52 * does not natively support unsigned integer values. Negative numbers are
53 * treated as larger than positive ones.
54 *
55 * @param a
56 * the first value to compare.
57 * @param b
58 * the second value to compare.
59 * @return < 0 if a < b; 0 if a == b; > 0 if a > b.
60 */
61 public static int compareUInt32(final int a, final int b) {
62 final int cmp = (a >>> 1) - (b >>> 1);
63 if (cmp != 0)
64 return cmp;
65 return (a & 1) - (b & 1);
66 }
67
68 /**
69 * Compare a 64 bit unsigned integer stored in a 64 bit signed integer.
70 * <p>
71 * This function performs an unsigned compare operation, even though Java
72 * does not natively support unsigned integer values. Negative numbers are
73 * treated as larger than positive ones.
74 *
75 * @param a
76 * the first value to compare.
77 * @param b
78 * the second value to compare.
79 * @return < 0 if a < b; 0 if a == b; > 0 if a > b.
80 * @since 4.3
81 */
82 public static int compareUInt64(final long a, final long b) {
83 long cmp = (a >>> 1) - (b >>> 1);
84 if (cmp > 0) {
85 return 1;
86 } else if (cmp < 0) {
87 return -1;
88 }
89 cmp = ((a & 1) - (b & 1));
90 if (cmp > 0) {
91 return 1;
92 } else if (cmp < 0) {
93 return -1;
94 } else {
95 return 0;
96 }
97 }
98
99 /**
100 * Convert sequence of 2 bytes (network byte order) into unsigned value.
101 *
102 * @param intbuf
103 * buffer to acquire the 2 bytes of data from.
104 * @param offset
105 * position within the buffer to begin reading from. This
106 * position and the next byte after it (for a total of 2 bytes)
107 * will be read.
108 * @return unsigned integer value that matches the 16 bits read.
109 */
110 public static int decodeUInt16(final byte[] intbuf, final int offset) {
111 int r = (intbuf[offset] & 0xff) << 8;
112 return r | (intbuf[offset + 1] & 0xff);
113 }
114
115 /**
116 * Convert sequence of 4 bytes (network byte order) into signed value.
117 *
118 * @param intbuf
119 * buffer to acquire the 4 bytes of data from.
120 * @param offset
121 * position within the buffer to begin reading from. This
122 * position and the next 3 bytes after it (for a total of 4
123 * bytes) will be read.
124 * @return signed integer value that matches the 32 bits read.
125 */
126 public static int decodeInt32(final byte[] intbuf, final int offset) {
127 int r = intbuf[offset] << 8;
128
129 r |= intbuf[offset + 1] & 0xff;
130 r <<= 8;
131
132 r |= intbuf[offset + 2] & 0xff;
133 return (r << 8) | (intbuf[offset + 3] & 0xff);
134 }
135
136 /**
137 * Convert sequence of 8 bytes (network byte order) into signed value.
138 *
139 * @param intbuf
140 * buffer to acquire the 8 bytes of data from.
141 * @param offset
142 * position within the buffer to begin reading from. This
143 * position and the next 7 bytes after it (for a total of 8
144 * bytes) will be read.
145 * @return signed integer value that matches the 64 bits read.
146 * @since 3.0
147 */
148 public static long decodeInt64(final byte[] intbuf, final int offset) {
149 long r = intbuf[offset] << 8;
150
151 r |= intbuf[offset + 1] & 0xff;
152 r <<= 8;
153
154 r |= intbuf[offset + 2] & 0xff;
155 r <<= 8;
156
157 r |= intbuf[offset + 3] & 0xff;
158 r <<= 8;
159
160 r |= intbuf[offset + 4] & 0xff;
161 r <<= 8;
162
163 r |= intbuf[offset + 5] & 0xff;
164 r <<= 8;
165
166 r |= intbuf[offset + 6] & 0xff;
167 return (r << 8) | (intbuf[offset + 7] & 0xff);
168 }
169
170 /**
171 * Convert sequence of 4 bytes (network byte order) into unsigned value.
172 *
173 * @param intbuf
174 * buffer to acquire the 4 bytes of data from.
175 * @param offset
176 * position within the buffer to begin reading from. This
177 * position and the next 3 bytes after it (for a total of 4
178 * bytes) will be read.
179 * @return unsigned integer value that matches the 32 bits read.
180 */
181 public static long decodeUInt32(final byte[] intbuf, final int offset) {
182 int low = (intbuf[offset + 1] & 0xff) << 8;
183 low |= (intbuf[offset + 2] & 0xff);
184 low <<= 8;
185
186 low |= (intbuf[offset + 3] & 0xff);
187 return ((long) (intbuf[offset] & 0xff)) << 24 | low;
188 }
189
190 /**
191 * Convert sequence of 8 bytes (network byte order) into unsigned value.
192 *
193 * @param intbuf
194 * buffer to acquire the 8 bytes of data from.
195 * @param offset
196 * position within the buffer to begin reading from. This
197 * position and the next 7 bytes after it (for a total of 8
198 * bytes) will be read.
199 * @return unsigned integer value that matches the 64 bits read.
200 */
201 public static long decodeUInt64(final byte[] intbuf, final int offset) {
202 return (decodeUInt32(intbuf, offset) << 32)
203 | decodeUInt32(intbuf, offset + 4);
204 }
205
206 /**
207 * Write a 16 bit integer as a sequence of 2 bytes (network byte order).
208 *
209 * @param intbuf
210 * buffer to write the 2 bytes of data into.
211 * @param offset
212 * position within the buffer to begin writing to. This position
213 * and the next byte after it (for a total of 2 bytes) will be
214 * replaced.
215 * @param v
216 * the value to write.
217 */
218 public static void encodeInt16(final byte[] intbuf, final int offset, int v) {
219 intbuf[offset + 1] = (byte) v;
220 v >>>= 8;
221
222 intbuf[offset] = (byte) v;
223 }
224
225 /**
226 * Write a 32 bit integer as a sequence of 4 bytes (network byte order).
227 *
228 * @param intbuf
229 * buffer to write the 4 bytes of data into.
230 * @param offset
231 * position within the buffer to begin writing to. This position
232 * and the next 3 bytes after it (for a total of 4 bytes) will be
233 * replaced.
234 * @param v
235 * the value to write.
236 */
237 public static void encodeInt32(final byte[] intbuf, final int offset, int v) {
238 intbuf[offset + 3] = (byte) v;
239 v >>>= 8;
240
241 intbuf[offset + 2] = (byte) v;
242 v >>>= 8;
243
244 intbuf[offset + 1] = (byte) v;
245 v >>>= 8;
246
247 intbuf[offset] = (byte) v;
248 }
249
250 /**
251 * Write a 64 bit integer as a sequence of 8 bytes (network byte order).
252 *
253 * @param intbuf
254 * buffer to write the 8 bytes of data into.
255 * @param offset
256 * position within the buffer to begin writing to. This position
257 * and the next 7 bytes after it (for a total of 8 bytes) will be
258 * replaced.
259 * @param v
260 * the value to write.
261 */
262 public static void encodeInt64(final byte[] intbuf, final int offset, long v) {
263 intbuf[offset + 7] = (byte) v;
264 v >>>= 8;
265
266 intbuf[offset + 6] = (byte) v;
267 v >>>= 8;
268
269 intbuf[offset + 5] = (byte) v;
270 v >>>= 8;
271
272 intbuf[offset + 4] = (byte) v;
273 v >>>= 8;
274
275 intbuf[offset + 3] = (byte) v;
276 v >>>= 8;
277
278 intbuf[offset + 2] = (byte) v;
279 v >>>= 8;
280
281 intbuf[offset + 1] = (byte) v;
282 v >>>= 8;
283
284 intbuf[offset] = (byte) v;
285 }
286
287 private NB() {
288 // Don't create instances of a static only utility.
289 }
290 }