/*
* Copyright (c) 2002-2012 Alibaba Group Holding Limited.
* All rights reserved.
*
* 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 com.alibaba.citrus.util.io;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
/**
* 从<code>OutputEngine</code>取得数据的输入流, 作为<code>PipedInputStream</code>的替换方案,
* 这个类提供了极高的性能. 本代码移植自IBM developer works文章:
* <ul>
* <li><a
* href="http://www.ibm.com/developerworks/cn/java/j-io1/index.shtml">彻底转变流,第 1
* 部分:从输出流中读取</a>
* <li><a
* href="http://www.ibm.com/developerworks/cn/java/j-io2/index.shtml">彻底转变流,第 2
* 部分:优化 Java 内部 I/O</a>
* </ul>
*
* @author Michael Zhou
*/
public class OutputEngineInputStream extends InputStream {
private static final int DEFAULT_INITIAL_BUFFER_SIZE = 8192;
private OutputEngine engine;
private byte[] buffer;
private int index;
private int limit;
private int capacity;
private boolean closed;
private boolean eof;
public OutputEngineInputStream(OutputEngine engine) throws IOException {
this(engine, DEFAULT_INITIAL_BUFFER_SIZE);
}
public OutputEngineInputStream(OutputEngine engine, int initialBufferSize) throws IOException {
this.engine = engine;
capacity = initialBufferSize;
buffer = new byte[capacity];
engine.open(new OutputStreamImpl());
}
private byte[] one = new byte[1];
@Override
public int read() throws IOException {
int amount = read(one, 0, 1);
return amount < 0 ? -1 : one[0] & 0xff;
}
@Override
public int read(byte[] data, int offset, int length) throws IOException {
if (data == null) {
throw new NullPointerException();
} else if (offset < 0 || offset + length > data.length || length < 0) {
throw new IndexOutOfBoundsException();
} else if (closed) {
throw new IOException("Stream closed");
} else {
while (index >= limit) {
if (eof) {
return -1;
}
engine.execute();
}
if (limit - index < length) {
length = limit - index;
}
System.arraycopy(buffer, index, data, offset, length);
index += length;
return length;
}
}
@Override
public long skip(long amount) throws IOException {
if (closed) {
throw new IOException("Stream closed");
} else if (amount <= 0) {
return 0;
} else {
while (index >= limit) {
if (eof) {
return 0;
}
engine.execute();
}
if (limit - index < amount) {
amount = limit - index;
}
index += (int) amount;
return amount;
}
}
@Override
public int available() throws IOException {
if (closed) {
throw new IOException("Stream closed");
} else {
return limit - index;
}
}
@Override
public void close() throws IOException {
if (!closed) {
closed = true;
engine.close();
}
}
private void writeImpl(byte[] data, int offset, int length) {
if (index >= limit) {
index = limit = 0;
}
if (limit + length > capacity) {
capacity = capacity * 2 + length;
byte[] tmp = new byte[capacity];
System.arraycopy(buffer, index, tmp, 0, limit - index);
buffer = tmp;
limit -= index;
index = 0;
}
System.arraycopy(data, offset, buffer, limit, length);
limit += length;
}
private class OutputStreamImpl extends OutputStream {
@Override
public void write(int datum) throws IOException {
one[0] = (byte) datum;
write(one, 0, 1);
}
@Override
public void write(byte[] data, int offset, int length) throws IOException {
if (data == null) {
throw new NullPointerException();
} else if (offset < 0 || offset + length > data.length || length < 0) {
throw new IndexOutOfBoundsException();
} else if (eof) {
throw new IOException("Stream closed");
} else {
writeImpl(data, offset, length);
}
}
@Override
public void close() {
eof = true;
}
}
}