umagesh 02/02/17 19:07:30
Added:
proposal/sandbox/filterreaders/src/main/org/apache/tools/ant/filters
TailFilter.java
Log:
Filter to read the last 'n' lines.
Revision Changes Path
1.1
jakarta-ant/proposal/sandbox/filterreaders/src/main/org/apache/tools/ant/filters/TailFilter.java
Index: TailFilter.java
===================================================================
package org.apache.tools.ant.filters;
import java.io.FilterReader;
import java.io.IOException;
import java.io.Reader;
import org.apache.tools.ant.types.Parameter;
import org.apache.tools.ant.types.Parameterizable;
/**
* Read the last n lines. Default is last 10 lines.
*
* Example:
* =======
*
* <filterreader classname="org.apache.tools.ant.filters.TailFilter">
* <param name="lines" value="3"/>
* </filterreader>
*
* @author <a href="mailto:[EMAIL PROTECTED]">Magesh Umasankar</a>
*/
public final class TailFilter
extends FilterReader
implements Parameterizable
{
private static final String LINES_KEY = "lines";
private Parameter[] parameters;
private boolean initialized = false;
private long linesRead = 0;
private long lines = 10;
private boolean ignoreLineFeed = false;
private char[] buffer = new char[4096];
private int returnedCharPos = -1;
private boolean completedReadAhead = false;
private int bufferPos = 0;
/**
* Create a new filtered reader.
*
* @param in a Reader object providing the underlying stream.
*/
public TailFilter(final Reader in) {
super(in);
}
/**
* Read ahead and keep in buffer last n lines only at any given
* point. Grow buffer as needed.
*/
public final int read() throws IOException {
if (!initialized) {
initialize();
initialized = true;
}
if (!completedReadAhead) {
int ch = -1;
while ((ch = in.read()) != -1) {
if (buffer.length == bufferPos) {
if (returnedCharPos != -1) {
final char[] tmpBuffer = new char[buffer.length];
System.arraycopy(buffer, returnedCharPos + 1,
tmpBuffer,
0, buffer.length - (returnedCharPos
+ 1));
buffer = tmpBuffer;
bufferPos = bufferPos - (returnedCharPos + 1);
returnedCharPos = -1;
} else {
final char[] tmpBuffer = new char[buffer.length * 2];
System.arraycopy(buffer, 0, tmpBuffer, 0, bufferPos);
buffer = tmpBuffer;
}
}
if (ignoreLineFeed) {
if (ch == '\n') {
ch = in.read();
}
ignoreLineFeed = false;
}
switch (ch) {
case '\r':
ch = '\n';
ignoreLineFeed = true;
//fall through
case '\n':
linesRead++;
if (linesRead == lines + 1) {
int i = 0;
for (i = returnedCharPos + 1; buffer[i] != '\n';
i++) {
}
returnedCharPos = i;
linesRead--;
}
break;
}
if (ch == -1) {
break;
}
buffer[bufferPos] = (char) ch;
bufferPos++;
}
completedReadAhead = true;
}
++returnedCharPos;
if (returnedCharPos >= bufferPos) {
return -1;
} else {
return buffer[returnedCharPos];
}
}
public final int read(final char cbuf[], final int off,
final int len) throws IOException {
for (int i = 0; i < len; i++) {
final int ch = read();
if (ch == -1) {
if (i == 0) {
return -1;
} else {
return i;
}
}
cbuf[off + i] = (char) ch;
}
return len;
}
public final long skip(long n) throws IOException {
for (long i = 0; i < n; i++) {
if (in.read() == -1) {
return i;
}
}
return n;
}
/**
* Set Parameters
*/
public final void setParameters(final Parameter[] parameters) {
this.parameters = parameters;
initialized = false;
}
private final void initialize() {
if (parameters != null) {
for (int i = 0; i < parameters.length; i++) {
if (LINES_KEY.equals(parameters[i].getName())) {
lines = new Long(parameters[i].getValue()).longValue();
break;
}
}
}
}
}
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