1 | /* |
2 | Copyright (C) 2002-2005 MySQL AB |
3 | |
4 | This program is free software; you can redistribute it and/or modify |
5 | it under the terms of version 2 of the GNU General Public License as |
6 | published by the Free Software Foundation. |
7 | |
8 | There are special exceptions to the terms and conditions of the GPL |
9 | as it is applied to this software. View the full text of the |
10 | exception in file EXCEPTIONS-CONNECTOR-J in the directory of this |
11 | software distribution. |
12 | |
13 | This program is distributed in the hope that it will be useful, |
14 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
15 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
16 | GNU General Public License for more details. |
17 | |
18 | You should have received a copy of the GNU General Public License |
19 | along with this program; if not, write to the Free Software |
20 | Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA |
21 | |
22 | |
23 | */ |
24 | |
25 | package com.mysql.jdbc.util; |
26 | |
27 | import java.io.IOException; |
28 | import java.io.InputStream; |
29 | |
30 | import com.mysql.jdbc.log.Log; |
31 | |
32 | /** |
33 | * A non-blocking buffered input stream. Reads more if it can, won't block to |
34 | * fill the buffer, only blocks to satisfy a request of read(byte[]) |
35 | * |
36 | * @author Mark Matthews |
37 | * |
38 | * @version $Id: ReadAheadInputStream.java,v 1.1.2.1 2005/05/13 18:58:39 |
39 | * mmatthews Exp $ |
40 | */ |
41 | public class ReadAheadInputStream extends InputStream { |
42 | |
43 | private final static int DEFAULT_BUFFER_SIZE = 4096; |
44 | |
45 | private InputStream underlyingStream; |
46 | |
47 | private byte buf[]; |
48 | |
49 | protected int endOfCurrentData; |
50 | |
51 | protected int currentPosition; |
52 | |
53 | protected boolean doDebug = false; |
54 | |
55 | protected Log log; |
56 | |
57 | private void fill(int readAtLeastTheseManyBytes) throws IOException { |
58 | checkClosed(); |
59 | |
60 | this.currentPosition = 0; /* no mark: throw away the buffer */ |
61 | |
62 | this.endOfCurrentData = currentPosition; |
63 | |
64 | // Read at least as many bytes as the caller wants, but don't |
65 | // block to fill the whole buffer (like java.io.BufferdInputStream |
66 | // does) |
67 | |
68 | int bytesToRead = Math.min(this.buf.length - currentPosition, |
69 | readAtLeastTheseManyBytes); |
70 | |
71 | int bytesAvailable = this.underlyingStream.available(); |
72 | |
73 | if (bytesAvailable > bytesToRead) { |
74 | |
75 | // Great, there's more available, let's grab those |
76 | // bytes too! (read-ahead) |
77 | |
78 | bytesToRead = Math.min(this.buf.length - currentPosition, |
79 | bytesAvailable); |
80 | } |
81 | |
82 | if (this.doDebug) { |
83 | StringBuffer debugBuf = new StringBuffer(); |
84 | debugBuf.append(" ReadAheadInputStream.fill("); |
85 | debugBuf.append(readAtLeastTheseManyBytes); |
86 | debugBuf.append("), buffer_size="); |
87 | debugBuf.append(this.buf.length); |
88 | debugBuf.append(", current_position="); |
89 | debugBuf.append(currentPosition); |
90 | debugBuf.append(", need to read "); |
91 | debugBuf.append(Math.min(this.buf.length - currentPosition, |
92 | readAtLeastTheseManyBytes)); |
93 | debugBuf.append(" bytes to fill request,"); |
94 | |
95 | if (bytesAvailable > 0) { |
96 | debugBuf.append(" underlying InputStream reports "); |
97 | debugBuf.append(bytesAvailable); |
98 | |
99 | debugBuf.append(" total bytes available,"); |
100 | } |
101 | |
102 | debugBuf.append(" attempting to read "); |
103 | debugBuf.append(bytesToRead); |
104 | debugBuf.append(" bytes."); |
105 | |
106 | if (this.log != null) { |
107 | this.log.logTrace(debugBuf.toString()); |
108 | } else { |
109 | System.err.println(debugBuf.toString()); |
110 | } |
111 | } |
112 | |
113 | int n = this.underlyingStream.read(this.buf, currentPosition, |
114 | bytesToRead); |
115 | |
116 | if (n > 0) { |
117 | endOfCurrentData = n + currentPosition; |
118 | } |
119 | } |
120 | |
121 | private int readFromUnderlyingStreamIfNecessary(byte[] b, int off, int len) |
122 | throws IOException { |
123 | checkClosed(); |
124 | |
125 | int avail = endOfCurrentData - currentPosition; |
126 | |
127 | if (this.doDebug) { |
128 | StringBuffer debugBuf = new StringBuffer(); |
129 | debugBuf.append("ReadAheadInputStream.readIfNecessary("); |
130 | debugBuf.append(b); |
131 | debugBuf.append(","); |
132 | debugBuf.append(off); |
133 | debugBuf.append(","); |
134 | debugBuf.append(len); |
135 | debugBuf.append(")"); |
136 | |
137 | if (avail <= 0) { |
138 | debugBuf |
139 | .append(" not all data available in buffer, must read from stream"); |
140 | |
141 | if (len >= this.buf.length) { |
142 | debugBuf |
143 | .append(", amount requested > buffer, returning direct read() from stream"); |
144 | } |
145 | } |
146 | |
147 | if (this.log != null) { |
148 | this.log.logTrace(debugBuf.toString()); |
149 | } else { |
150 | System.err.println(debugBuf.toString()); |
151 | } |
152 | } |
153 | |
154 | if (avail <= 0) { |
155 | |
156 | if (len >= this.buf.length) { |
157 | return this.underlyingStream.read(b, off, len); |
158 | } |
159 | |
160 | fill(len); |
161 | |
162 | avail = endOfCurrentData - currentPosition; |
163 | |
164 | if (avail <= 0) |
165 | return -1; |
166 | } |
167 | |
168 | int bytesActuallyRead = (avail < len) ? avail : len; |
169 | |
170 | System.arraycopy(this.buf, currentPosition, b, off, bytesActuallyRead); |
171 | |
172 | this.currentPosition += bytesActuallyRead; |
173 | |
174 | return bytesActuallyRead; |
175 | } |
176 | |
177 | public synchronized int read(byte b[], int off, int len) throws IOException { |
178 | checkClosed(); // Check for closed stream |
179 | if ((off | len | (off + len) | (b.length - (off + len))) < 0) { |
180 | throw new IndexOutOfBoundsException(); |
181 | } else if (len == 0) { |
182 | return 0; |
183 | } |
184 | |
185 | int totalBytesRead = 0; |
186 | |
187 | while (true) { |
188 | int bytesReadThisRound = readFromUnderlyingStreamIfNecessary(b, off |
189 | + totalBytesRead, len - totalBytesRead); |
190 | |
191 | // end-of-stream? |
192 | if (bytesReadThisRound <= 0) { |
193 | if (totalBytesRead == 0) { |
194 | totalBytesRead = bytesReadThisRound; |
195 | } |
196 | |
197 | break; |
198 | } |
199 | |
200 | totalBytesRead += bytesReadThisRound; |
201 | |
202 | // Read _at_least_ enough bytes |
203 | if (totalBytesRead >= len) { |
204 | break; |
205 | } |
206 | |
207 | // Nothing to read? |
208 | if (this.underlyingStream.available() <= 0) { |
209 | break; |
210 | } |
211 | } |
212 | |
213 | return totalBytesRead; |
214 | } |
215 | |
216 | public int read() throws IOException { |
217 | checkClosed(); |
218 | |
219 | if (currentPosition >= endOfCurrentData) { |
220 | fill(1); |
221 | if (currentPosition >= endOfCurrentData) |
222 | return -1; |
223 | } |
224 | |
225 | return this.buf[currentPosition++] & 0xff; |
226 | } |
227 | |
228 | public int available() throws IOException { |
229 | checkClosed(); |
230 | |
231 | return this.underlyingStream.available() |
232 | + (this.endOfCurrentData - this.currentPosition); |
233 | } |
234 | |
235 | private void checkClosed() throws IOException { |
236 | |
237 | if (this.buf == null) { |
238 | throw new IOException("Stream closed"); |
239 | } |
240 | } |
241 | |
242 | /** |
243 | * |
244 | */ |
245 | public ReadAheadInputStream(InputStream toBuffer, boolean debug, Log logTo) { |
246 | this(toBuffer, DEFAULT_BUFFER_SIZE, debug, logTo); |
247 | } |
248 | |
249 | public ReadAheadInputStream(InputStream toBuffer, int bufferSize, |
250 | boolean debug, |
251 | Log logTo) { |
252 | this.underlyingStream = toBuffer; |
253 | this.buf = new byte[bufferSize]; |
254 | this.doDebug = debug; |
255 | this.log = logTo; |
256 | } |
257 | |
258 | /* |
259 | * (non-Javadoc) |
260 | * |
261 | * @see java.io.Closeable#close() |
262 | */ |
263 | public void close() throws IOException { |
264 | if (this.underlyingStream != null) { |
265 | try { |
266 | this.underlyingStream.close(); |
267 | } finally { |
268 | this.underlyingStream = null; |
269 | this.buf = null; |
270 | this.log = null; |
271 | } |
272 | } |
273 | } |
274 | |
275 | /* |
276 | * (non-Javadoc) |
277 | * |
278 | * @see java.io.InputStream#markSupported() |
279 | */ |
280 | public boolean markSupported() { |
281 | return false; |
282 | } |
283 | |
284 | /* |
285 | * (non-Javadoc) |
286 | * |
287 | * @see java.io.InputStream#skip(long) |
288 | */ |
289 | public long skip(long n) throws IOException { |
290 | checkClosed(); |
291 | if (n <= 0) { |
292 | return 0; |
293 | } |
294 | |
295 | long bytesAvailInBuffer = this.endOfCurrentData - this.currentPosition; |
296 | |
297 | if (bytesAvailInBuffer <= 0) { |
298 | |
299 | fill((int) n); |
300 | bytesAvailInBuffer = this.endOfCurrentData - this.currentPosition; |
301 | if (bytesAvailInBuffer <= 0) |
302 | return 0; |
303 | } |
304 | |
305 | long bytesSkipped = (bytesAvailInBuffer < n) ? bytesAvailInBuffer : n; |
306 | this.currentPosition += bytesSkipped; |
307 | return bytesSkipped; |
308 | } |
309 | } |