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A lightweight library to execute external processes from Java.
/*
* Copyright (C) 2014 ZeroTurnaround
* Contains fragments of code from Apache Commons Exec, rights owned
* by Apache Software Foundation (ASF).
*
* 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.zeroturnaround.exec.stream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.OutputStream;
/**
* Base class to connect a logging system to the output and/or
* error stream of then external process. The implementation
* parses the incoming data to construct a line and passes
* the complete line to an user-defined implementation.
*/
public abstract class LogOutputStream extends OutputStream {
/** Initial buffer size. */
private static final int INTIAL_SIZE = 132;
/** Carriage return */
private static final int CR = 0x0d;
/** Linefeed */
private static final int LF = 0x0a;
/** the internal buffer */
private final ByteArrayOutputStream buffer = new ByteArrayOutputStream(
INTIAL_SIZE);
private boolean skip = false;
/**
* Write the data to the buffer and flush the buffer, if a line separator is
* detected.
*
* @param cc data to log (byte).
* @see java.io.OutputStream#write(int)
*/
public void write(final int cc) throws IOException {
final byte c = (byte) cc;
if ((c == '\n') || (c == '\r')) {
if (!skip) {
processBuffer();
}
} else {
buffer.write(cc);
}
skip = (c == '\r');
}
/**
* Flush this log stream.
*
* @see java.io.OutputStream#flush()
*/
public void flush() {
if (buffer.size() > 0) {
processBuffer();
}
}
/**
* Writes all remaining data from the buffer.
*
* @see java.io.OutputStream#close()
*/
public void close() throws IOException {
if (buffer.size() > 0) {
processBuffer();
}
super.close();
}
/**
* Write a block of characters to the output stream
*
* @param b the array containing the data
* @param off the offset into the array where data starts
* @param len the length of block
* @throws java.io.IOException if the data cannot be written into the stream.
* @see java.io.OutputStream#write(byte[], int, int)
*/
public void write(final byte[] b, final int off, final int len)
throws IOException {
// find the line breaks and pass other chars through in blocks
int offset = off;
int blockStartOffset = offset;
int remaining = len;
while (remaining > 0) {
while (remaining > 0 && b[offset] != LF && b[offset] != CR) {
offset++;
remaining--;
}
// either end of buffer or a line separator char
int blockLength = offset - blockStartOffset;
if (blockLength > 0) {
buffer.write(b, blockStartOffset, blockLength);
}
while (remaining > 0 && (b[offset] == LF || b[offset] == CR)) {
write(b[offset]);
offset++;
remaining--;
}
blockStartOffset = offset;
}
}
/**
* Converts the buffer to a string and sends it to processLine.
*/
protected void processBuffer() {
processLine(buffer.toString());
buffer.reset();
}
/**
* Logs a line to the log system of the user.
*
* @param line
* the line to log.
*/
protected abstract void processLine(String line);
}