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Using non-blocking java nio InputStream/ByteChannels #1

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Using non-blocking java nio InputStream/ByteChannels #1

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2 changes: 1 addition & 1 deletion src/com/tools/jtail/TailFile.java
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Original file line number Diff line number Diff line change
Expand Up @@ -27,6 +27,6 @@
public interface TailFile
{

public void tail(PrintStream out) throws FileNotFoundException, IOException;
void tail(PrintStream out) throws FileNotFoundException, IOException;

}
104 changes: 50 additions & 54 deletions src/com/tools/jtail/TailFileFactory.java
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Original file line number Diff line number Diff line change
Expand Up @@ -16,20 +16,23 @@
*/
package com.tools.jtail;

import java.io.BufferedReader;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.io.PrintStream;
import java.io.RandomAccessFile;
import java.util.LinkedList;
import java.util.List;
import java.io.*;
import java.nio.ByteBuffer;
import java.nio.channels.SeekableByteChannel;
import java.nio.charset.Charset;
import java.nio.file.Files;
import java.util.ArrayDeque;
import java.util.EnumSet;
import java.util.logging.Level;
import java.util.logging.Logger;

import static java.nio.file.StandardOpenOption.READ;

/**
* Creates TailFile implementations depending on the requirements.
* <img src="../../../images/TailFileFactory.png"/>
* <br/>
* Uses non-blocking java nio InputStream/ByteChannels (i.e. file can be deleted while opened here).
*
* @author maartenl
*
Expand Down Expand Up @@ -97,7 +100,8 @@ private static class TailFileBytes implements TailFile
{

private final FileInfo info;

private static final String encoding = System.getProperty("file.encoding");
private static final Charset charset = Charset.forName(encoding);
private final boolean showFilenames;

private TailFileBytes(FileInfo info, boolean showFilenames)
Expand All @@ -113,21 +117,26 @@ public void tail(PrintStream out) throws FileNotFoundException, IOException
{
out.println("==> " + info.getFilename() + " <==");
}
byte[] buffer = new byte[BUFFER_SIZE];
// We use a ByteBuffer to read (BUFER_SIZE)
ByteBuffer buffer = ByteBuffer.allocate(BUFFER_SIZE);
// Position is set to 0
buffer.clear();
if (info.getPosition() > info.getSize())
{
out.println("jtail: " + info.getFilename() + ": file truncated");
info.setPosition(0);
}
try (RandomAccessFile reader = new RandomAccessFile(info.getFile().toFile(), "r");)
{
reader.seek(info.getPosition());
while ((reader.read(buffer))
!= -1)
{
out.print(new String(buffer));
try (SeekableByteChannel reader = Files.newByteChannel(info.getFile(), EnumSet.of(READ))) {
reader.position(info.getPosition());
// While the number of bytes from the channel are > 0
while(reader.read(buffer)>0) {
// after reading into the buffer we have to flip it in order to write it to out.
buffer.flip();
out.print(charset.decode(buffer));
// Prepare the buffer for a new read
buffer.clear();
}
info.setPosition(reader.getFilePointer());
info.setPosition(reader.position());
}
}
}
Expand Down Expand Up @@ -157,7 +166,7 @@ public void tail(PrintStream out) throws FileNotFoundException, IOException
}
int currentLine = 0;
boolean found = false;
try (BufferedReader reader = new BufferedReader(new FileReader(info.getFile().toFile())))
try (BufferedReader reader = new BufferedReader(new InputStreamReader(Files.newInputStream(info.getFile()))))
{
String lineRead;
while ((lineRead = reader.readLine()) != null)
Expand Down Expand Up @@ -185,7 +194,8 @@ private static class TailFileLinesFromEnd implements TailFile
private final FileInfo info;

private final boolean showFilenames;

private static final String encoding = System.getProperty("file.encoding");
private static final Charset charset = Charset.forName(encoding);
private long lines;

private TailFileLinesFromEnd(FileInfo info, long lines, boolean showFilenames)
Expand All @@ -196,64 +206,50 @@ private TailFileLinesFromEnd(FileInfo info, long lines, boolean showFilenames)
}

@Override
public void tail(PrintStream out) throws FileNotFoundException, IOException
{
if (showFilenames)
{
public void tail(PrintStream out) throws FileNotFoundException, IOException {
if (showFilenames) {
out.println("==> " + info.getFilename() + " <==");
}
// We use a ByteBuffer to read (BUFFER_SIZE)
ByteBuffer buffer = ByteBuffer.allocate(BUFFER_SIZE);
// Position is set to 0
buffer.clear();
int linesRead = 0;
byte[] buffer = new byte[BUFFER_SIZE];
List<String> totalRead = new LinkedList<>();
if (info.getPosition() > info.getSize())
{
ArrayDeque<String> totalRead = new ArrayDeque<>();
if (info.getPosition() > info.getSize()) {
out.println("jtail: " + info.getFilename() + ": file truncated");
info.setPosition(0);
}
info.setPosition(info.getSize() - BUFFER_SIZE);
try (RandomAccessFile reader = new RandomAccessFile(info.getFile().toFile(), "r");)
info.setPosition(Math.max(info.getSize() - BUFFER_SIZE, 0));
try (SeekableByteChannel reader = Files.newByteChannel(info.getFile(), EnumSet.of(READ)))
{
do
{
reader.seek(info.getPosition());
reader.position(info.getPosition());
reader.read(buffer);
String s = new String(buffer);
buffer.flip();
String s = charset.decode(buffer).toString();
buffer.clear();
String[] split = s.split("\n");
logger.log(Level.FINEST, "split: {0}...{1}:{2}", new Object[]
{
split[0], split.length, split[split.length - 1]
});
if (totalRead.isEmpty())
{
linesRead += split.length;
for (int i = 0; i < split.length; i++)
{
totalRead.add(i, split[i]);
}
} else
linesRead += split.length;
for (int i = split.length-1; i >= 0 && totalRead.size() < lines; i--)
{
totalRead.set(0, split[split.length - 1] + totalRead.get(0));
for (int i = 0; i < split.length - 1; i++)
{
totalRead.add(i, split[i]);
}
totalRead.addFirst(split[i]);
}
if (linesRead > lines)
{
break;
}
info.setPosition(info.getPosition() - BUFFER_SIZE);
} while (info.getPosition() != 0);
// info.setPosition(reader.getFilePointer());
} while (info.getPosition() > 0);

// write it to the output
for (long i = lines - 1; i >= 0; i--)
{
if (i <= totalRead.size() - 1)
{
out.println(totalRead.get((int) (totalRead.size() - 1 - i)));
}
}
totalRead.forEach(out::println);
// set the position to the end of the file
info.setPosition(info.getSize());
}
}
Expand Down
6 changes: 3 additions & 3 deletions src/com/tools/jtail/Watcher.java
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Original file line number Diff line number Diff line change
Expand Up @@ -34,10 +34,10 @@
public interface Watcher
{

public void eventDetected(FileInfo info) throws IOException;
void eventDetected(FileInfo info) throws IOException;

public void startWatching() throws IOException;
void startWatching() throws IOException;

public void watch(FileInfo fileInfo) throws IOException;
void watch(FileInfo fileInfo) throws IOException;

}