blob: cfade5777457f541768dcec98bcf6dad43d54d9e (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
|
/*
* Copyright 2002-2004 Apache Software Foundation
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
*/
package org.apache.tools.ant.filters;
import java.io.IOException;
import java.io.Reader;
import java.util.LinkedList;
import org.apache.tools.ant.types.Parameter;
import org.apache.tools.ant.util.LineTokenizer;
/**
* Reads the last <code>n</code> lines of a stream. (Default is last10 lines.)
*
* Example:
*
* <pre><tailfilter lines="3"/></pre>
*
* Or:
*
* <pre><filterreader classname="org.apache.tools.ant.filters.TailFilter">
* <param name="lines" value="3"/>
* </filterreader></pre>
*
* @author Magesh Umasankar
*/
public final class TailFilter extends BaseParamFilterReader
implements ChainableReader {
/** Parameter name for the number of lines to be returned. */
private static final String LINES_KEY = "lines";
/** Parameter name for the number of lines to be skipped. */
private static final String SKIP_KEY = "skip";
/** Default number of lines to show */
private static final int DEFAULT_NUM_LINES = 10;
/** Number of lines to be returned in the filtered stream. */
private long lines = DEFAULT_NUM_LINES;
/** Number of lines to be skipped. */
private long skip = 0;
/** Whether or not read-ahead been completed. */
private boolean completedReadAhead = false;
/** A line tokenizer */
private LineTokenizer lineTokenizer = null;
/** the current line from the input stream */
private String line = null;
/** the position in the current line */
private int linePos = 0;
private LinkedList lineList = new LinkedList();
/**
* Constructor for "dummy" instances.
*
* @see BaseFilterReader#BaseFilterReader()
*/
public TailFilter() {
super();
}
/**
* Creates a new filtered reader.
*
* @param in A Reader object providing the underlying stream.
* Must not be <code>null</code>.
*/
public TailFilter(final Reader in) {
super(in);
lineTokenizer = new LineTokenizer();
lineTokenizer.setIncludeDelims(true);
}
/**
* Returns the next character in the filtered stream. If the read-ahead
* has been completed, the next character in the buffer is returned.
* Otherwise, the stream is read to the end and buffered (with the buffer
* growing as necessary), then the appropriate position in the buffer is
* set to read from.
*
* @return the next character in the resulting stream, or -1
* if the end of the resulting stream has been reached
*
* @exception IOException if the underlying stream throws an IOException
* during reading
*/
public final int read() throws IOException {
if (!getInitialized()) {
initialize();
setInitialized(true);
}
while (line == null || line.length() == 0) {
line = lineTokenizer.getToken(in);
line = tailFilter(line);
if (line == null) {
return -1;
}
linePos = 0;
}
int ch = line.charAt(linePos);
linePos++;
if (linePos == line.length()) {
line = null;
}
return ch;
}
/**
* Sets the number of lines to be returned in the filtered stream.
*
* @param lines the number of lines to be returned in the filtered stream
*/
public final void setLines(final long lines) {
this.lines = lines;
}
/**
* Returns the number of lines to be returned in the filtered stream.
*
* @return the number of lines to be returned in the filtered stream
*/
private final long getLines() {
return lines;
}
/**
* Sets the number of lines to be skipped in the filtered stream.
*
* @param skip the number of lines to be skipped in the filtered stream
*/
public final void setSkip(final long skip) {
this.skip = skip;
}
/**
* Returns the number of lines to be skipped in the filtered stream.
*
* @return the number of lines to be skipped in the filtered stream
*/
private final long getSkip() {
return skip;
}
/**
* Creates a new TailFilter using the passed in
* Reader for instantiation.
*
* @param rdr A Reader object providing the underlying stream.
* Must not be <code>null</code>.
*
* @return a new filter based on this configuration, but filtering
* the specified reader
*/
public final Reader chain(final Reader rdr) {
TailFilter newFilter = new TailFilter(rdr);
newFilter.setLines(getLines());
newFilter.setSkip(getSkip());
newFilter.setInitialized(true);
return newFilter;
}
/**
* Scans the parameters list for the "lines" parameter and uses
* it to set the number of lines to be returned in the filtered stream.
* also scan for "skip" parameter.
*/
private final void initialize() {
Parameter[] params = getParameters();
if (params != null) {
for (int i = 0; i < params.length; i++) {
if (LINES_KEY.equals(params[i].getName())) {
setLines(new Long(params[i].getValue()).longValue());
continue;
}
if (SKIP_KEY.equals(params[i].getName())) {
skip = new Long(params[i].getValue()).longValue();
continue;
}
}
}
}
/**
* implement a tail filter on a stream of lines.
* line = null is the end of the stream.
* @return "" while reading in the lines,
* line while outputting the lines
* null at the end of outputting the lines
*/
private String tailFilter(String line) {
if (!completedReadAhead) {
if (line != null) {
lineList.add(line);
if (lines == -1) {
if (lineList.size() > skip) {
return (String) lineList.removeFirst();
}
} else {
long linesToKeep = lines + (skip > 0 ? skip : 0);
if (linesToKeep < lineList.size()) {
lineList.removeFirst();
}
}
return "";
}
completedReadAhead = true;
if (skip > 0) {
for (int i = 0; i < skip; ++i) {
lineList.removeLast();
}
}
if (lines > -1) {
while (lineList.size() > lines) {
lineList.removeFirst();
}
}
}
if (lineList.size() > 0) {
return (String) lineList.removeFirst();
}
return null;
}
}
|