package com.alibaba.common.lang.io;
import com.alibaba.common.lang.ByteArray;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
/**
* 非同步的<code>ByteArrayOutputStream</code>替换方案, 执行<code>toByteArray()</code>方法时返回的是只读的内部字节数组,
* 避免了没有必要的字节复制. 本代码移植自IBM developer works精彩文章, 参见package文档.
*
* @author Michael Zhou
* @version $Id: ByteArrayOutputStream.java 593 2004-02-26 13:47:19Z baobao $
*/
public class ByteArrayOutputStream extends OutputStream {
private static final int DEFAULT_INITIAL_BUFFER_SIZE = 8192;
// internal buffer
private byte[] buffer;
private int index;
private int capacity;
// is the stream closed?
private boolean closed;
// is the buffer shared?
private boolean shared;
public ByteArrayOutputStream() {
this(DEFAULT_INITIAL_BUFFER_SIZE);
}
public ByteArrayOutputStream(int initialBufferSize) {
capacity = initialBufferSize;
buffer = new byte[capacity];
}
public void write(int datum) throws IOException {
if (closed) {
throw new IOException("Stream closed");
} else {
if (index >= capacity) {
// expand the internal buffer
capacity = (capacity * 2) + 1;
byte[] tmp = new byte[capacity];
System.arraycopy(buffer, 0, tmp, 0, index);
buffer = tmp;
// the new buffer is not shared
shared = false;
}
// store the byte
buffer[index++] = (byte) datum;
}
}
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 (closed) {
throw new IOException("Stream closed");
} else {
if ((index + length) > capacity) {
// expand the internal buffer
capacity = (capacity * 2) + length;
byte[] tmp = new byte[capacity];
System.arraycopy(buffer, 0, tmp, 0, index);
buffer = tmp;
// the new buffer is not shared
shared = false;
}
// copy in the subarray
System.arraycopy(data, offset, buffer, index, length);
index += length;
}
}
public void close() {
closed = true;
}
public void writeTo(OutputStream out) throws IOException {
// write the internal buffer directly
out.write(buffer, 0, index);
}
public ByteArray toByteArray() {
shared = true;
return new ByteArray(buffer, 0, index);
}
public InputStream toInputStream() {
// return a stream reading from the shared internal buffer
shared = true;
return new ByteArrayInputStream(buffer, 0, index);
}
public void reset() throws IOException {
if (closed) {
throw new IOException("Stream closed");
} else {
if (shared) {
// create a new buffer if it is shared
buffer = new byte[capacity];
shared = false;
}
// reset index
index = 0;
}
}
}