1 /*
2 * ====================================================================
3 * Licensed to the Apache Software Foundation (ASF) under one
4 * or more contributor license agreements. See the NOTICE file
5 * distributed with this work for additional information
6 * regarding copyright ownership. The ASF licenses this file
7 * to you under the Apache License, Version 2.0 (the
8 * "License"); you may not use this file except in compliance
9 * with the License. You may obtain a copy of the License at
10 *
11 * http://www.apache.org/licenses/LICENSE-2.0
12 *
13 * Unless required by applicable law or agreed to in writing,
14 * software distributed under the License is distributed on an
15 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
16 * KIND, either express or implied. See the License for the
17 * specific language governing permissions and limitations
18 * under the License.
19 * ====================================================================
20 *
21 * This software consists of voluntary contributions made by many
22 * individuals on behalf of the Apache Software Foundation. For more
23 * information on the Apache Software Foundation, please see
24 * <http://www.apache.org/>.
25 *
26 */
27
28 package com.foxinmy.weixin4j.util;
29
30 import java.io.Serializable;
31
32 /**
33 * A resizable byte array.
34 *
35 * @since 4.0
36 */
37 public final class ByteArrayBuffer implements Serializable {
38
39 private static final long serialVersionUID = 4359112959524048036L;
40
41 private byte[] buffer;
42 private int len;
43
44 /**
45 * Creates an instance of {@link ByteArrayBuffer} with the given initial
46 * capacity.
47 *
48 * @param capacity the capacity
49 */
50 public ByteArrayBuffer(final int capacity) {
51 super();
52 this.buffer = new byte[capacity];
53 }
54
55 private void expand(final int newlen) {
56 final byte newbuffer[] = new byte[Math.max(this.buffer.length << 1, newlen)];
57 System.arraycopy(this.buffer, 0, newbuffer, 0, this.len);
58 this.buffer = newbuffer;
59 }
60
61 /**
62 * Appends {@code len} bytes to this buffer from the given source
63 * array starting at index {@code off}. The capacity of the buffer
64 * is increased, if necessary, to accommodate all {@code len} bytes.
65 *
66 * @param b the bytes to be appended.
67 * @param off the index of the first byte to append.
68 * @param len the number of bytes to append.
69 * @throws IndexOutOfBoundsException if {@code off} if out of
70 * range, {@code len} is negative, or
71 * {@code off} + {@code len} is out of range.
72 */
73 public void append(final byte[] b, final int off, final int len) {
74 if (b == null) {
75 return;
76 }
77 if ((off < 0) || (off > b.length) || (len < 0) ||
78 ((off + len) < 0) || ((off + len) > b.length)) {
79 throw new IndexOutOfBoundsException("off: "+off+" len: "+len+" b.length: "+b.length);
80 }
81 if (len == 0) {
82 return;
83 }
84 final int newlen = this.len + len;
85 if (newlen > this.buffer.length) {
86 expand(newlen);
87 }
88 System.arraycopy(b, off, this.buffer, this.len, len);
89 this.len = newlen;
90 }
91
92 /**
93 * Appends {@code b} byte to this buffer. The capacity of the buffer
94 * is increased, if necessary, to accommodate the additional byte.
95 *
96 * @param b the byte to be appended.
97 */
98 public void append(final int b) {
99 final int newlen = this.len + 1;
100 if (newlen > this.buffer.length) {
101 expand(newlen);
102 }
103 this.buffer[this.len] = (byte)b;
104 this.len = newlen;
105 }
106
107 /**
108 * Appends {@code len} chars to this buffer from the given source
109 * array starting at index {@code off}. The capacity of the buffer
110 * is increased if necessary to accommodate all {@code len} chars.
111 * <p>
112 * The chars are converted to bytes using simple cast.
113 *
114 * @param b the chars to be appended.
115 * @param off the index of the first char to append.
116 * @param len the number of bytes to append.
117 * @throws IndexOutOfBoundsException if {@code off} if out of
118 * range, {@code len} is negative, or
119 * {@code off} + {@code len} is out of range.
120 */
121 public void append(final char[] b, final int off, final int len) {
122 if (b == null) {
123 return;
124 }
125 if ((off < 0) || (off > b.length) || (len < 0) ||
126 ((off + len) < 0) || ((off + len) > b.length)) {
127 throw new IndexOutOfBoundsException("off: "+off+" len: "+len+" b.length: "+b.length);
128 }
129 if (len == 0) {
130 return;
131 }
132 final int oldlen = this.len;
133 final int newlen = oldlen + len;
134 if (newlen > this.buffer.length) {
135 expand(newlen);
136 }
137 for (int i1 = off, i2 = oldlen; i2 < newlen; i1++, i2++) {
138 this.buffer[i2] = (byte) b[i1];
139 }
140 this.len = newlen;
141 }
142
143 /**
144 * Appends {@code len} chars to this buffer from the given source
145 * char array buffer starting at index {@code off}. The capacity
146 * of the buffer is increased if necessary to accommodate all
147 * {@code len} chars.
148 * <p>
149 * The chars are converted to bytes using simple cast.
150 *
151 * @param b the chars to be appended.
152 * @param off the index of the first char to append.
153 * @param len the number of bytes to append.
154 * @throws IndexOutOfBoundsException if {@code off} if out of
155 * range, {@code len} is negative, or
156 * {@code off} + {@code len} is out of range.
157 */
158 public void append(final CharArrayBuffer b, final int off, final int len) {
159 if (b == null) {
160 return;
161 }
162 append(b.buffer(), off, len);
163 }
164
165 /**
166 * Clears content of the buffer. The underlying byte array is not resized.
167 */
168 public void clear() {
169 this.len = 0;
170 }
171
172 /**
173 * Converts the content of this buffer to an array of bytes.
174 *
175 * @return byte array
176 */
177 public byte[] toByteArray() {
178 final byte[] b = new byte[this.len];
179 if (this.len > 0) {
180 System.arraycopy(this.buffer, 0, b, 0, this.len);
181 }
182 return b;
183 }
184
185 /**
186 * Returns the {@code byte} value in this buffer at the specified
187 * index. The index argument must be greater than or equal to
188 * {@code 0}, and less than the length of this buffer.
189 *
190 * @param i the index of the desired byte value.
191 * @return the byte value at the specified index.
192 * @throws IndexOutOfBoundsException if {@code index} is
193 * negative or greater than or equal to {@link #length()}.
194 */
195 public int byteAt(final int i) {
196 return this.buffer[i];
197 }
198
199 /**
200 * Returns the current capacity. The capacity is the amount of storage
201 * available for newly appended bytes, beyond which an allocation
202 * will occur.
203 *
204 * @return the current capacity
205 */
206 public int capacity() {
207 return this.buffer.length;
208 }
209
210 /**
211 * Returns the length of the buffer (byte count).
212 *
213 * @return the length of the buffer
214 */
215 public int length() {
216 return this.len;
217 }
218
219 /**
220 * Ensures that the capacity is at least equal to the specified minimum.
221 * If the current capacity is less than the argument, then a new internal
222 * array is allocated with greater capacity. If the {@code required}
223 * argument is non-positive, this method takes no action.
224 *
225 * @param required the minimum required capacity.
226 *
227 * @since 4.1
228 */
229 public void ensureCapacity(final int required) {
230 if (required <= 0) {
231 return;
232 }
233 final int available = this.buffer.length - this.len;
234 if (required > available) {
235 expand(this.len + required);
236 }
237 }
238
239 /**
240 * Returns reference to the underlying byte array.
241 *
242 * @return the byte array.
243 */
244 public byte[] buffer() {
245 return this.buffer;
246 }
247
248 /**
249 * Sets the length of the buffer. The new length value is expected to be
250 * less than the current capacity and greater than or equal to
251 * {@code 0}.
252 *
253 * @param len the new length
254 * @throws IndexOutOfBoundsException if the
255 * {@code len} argument is greater than the current
256 * capacity of the buffer or less than {@code 0}.
257 */
258 public void setLength(final int len) {
259 if (len < 0 || len > this.buffer.length) {
260 throw new IndexOutOfBoundsException("len: "+len+" < 0 or > buffer len: "+this.buffer.length);
261 }
262 this.len = len;
263 }
264
265 /**
266 * Returns {@code true} if this buffer is empty, that is, its
267 * {@link #length()} is equal to {@code 0}.
268 * @return {@code true} if this buffer is empty, {@code false}
269 * otherwise.
270 */
271 public boolean isEmpty() {
272 return this.len == 0;
273 }
274
275 /**
276 * Returns {@code true} if this buffer is full, that is, its
277 * {@link #length()} is equal to its {@link #capacity()}.
278 * @return {@code true} if this buffer is full, {@code false}
279 * otherwise.
280 */
281 public boolean isFull() {
282 return this.len == this.buffer.length;
283 }
284
285 /**
286 * Returns the index within this buffer of the first occurrence of the
287 * specified byte, starting the search at the specified
288 * {@code beginIndex} and finishing at {@code endIndex}.
289 * If no such byte occurs in this buffer within the specified bounds,
290 * {@code -1} is returned.
291 * <p>
292 * There is no restriction on the value of {@code beginIndex} and
293 * {@code endIndex}. If {@code beginIndex} is negative,
294 * it has the same effect as if it were zero. If {@code endIndex} is
295 * greater than {@link #length()}, it has the same effect as if it were
296 * {@link #length()}. If the {@code beginIndex} is greater than
297 * the {@code endIndex}, {@code -1} is returned.
298 *
299 * @param b the byte to search for.
300 * @param from the index to start the search from.
301 * @param to the index to finish the search at.
302 * @return the index of the first occurrence of the byte in the buffer
303 * within the given bounds, or {@code -1} if the byte does
304 * not occur.
305 *
306 * @since 4.1
307 */
308 public int indexOf(final byte b, final int from, final int to) {
309 int beginIndex = from;
310 if (beginIndex < 0) {
311 beginIndex = 0;
312 }
313 int endIndex = to;
314 if (endIndex > this.len) {
315 endIndex = this.len;
316 }
317 if (beginIndex > endIndex) {
318 return -1;
319 }
320 for (int i = beginIndex; i < endIndex; i++) {
321 if (this.buffer[i] == b) {
322 return i;
323 }
324 }
325 return -1;
326 }
327
328 /**
329 * Returns the index within this buffer of the first occurrence of the
330 * specified byte, starting the search at {@code 0} and finishing
331 * at {@link #length()}. If no such byte occurs in this buffer within
332 * those bounds, {@code -1} is returned.
333 *
334 * @param b the byte to search for.
335 * @return the index of the first occurrence of the byte in the
336 * buffer, or {@code -1} if the byte does not occur.
337 *
338 * @since 4.1
339 */
340 public int indexOf(final byte b) {
341 return indexOf(b, 0, this.len);
342 }
343 }