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255 lines
8.1 KiB
Java
255 lines
8.1 KiB
Java
/*
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* Copyright (c) 1994, 2023, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation. Oracle designates this
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* particular file as subject to the "Classpath" exception as provided
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* by Oracle in the LICENSE file that accompanied this code.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*/
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package java.io;
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import java.util.Arrays;
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import jdk.internal.misc.InternalLock;
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import jdk.internal.misc.VM;
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/**
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* The class implements a buffered output stream. By setting up such
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* an output stream, an application can write bytes to the underlying
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* output stream without necessarily causing a call to the underlying
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* system for each byte written.
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*
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* @author Arthur van Hoff
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* @since 1.0
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*/
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public class BufferedOutputStream extends FilterOutputStream {
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private static final int DEFAULT_INITIAL_BUFFER_SIZE = 512;
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private static final int DEFAULT_MAX_BUFFER_SIZE = 8192;
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// initialized to null when BufferedOutputStream is sub-classed
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private final InternalLock lock;
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/**
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* The internal buffer where data is stored.
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*/
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protected byte[] buf;
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/**
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* The number of valid bytes in the buffer. This value is always
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* in the range {@code 0} through {@code buf.length}; elements
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* {@code buf[0]} through {@code buf[count-1]} contain valid
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* byte data.
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*/
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protected int count;
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/**
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* Max size of the internal buffer.
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*/
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private final int maxBufSize;
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/**
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* Returns the buffer size to use when no output buffer size specified.
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*/
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private static int initialBufferSize() {
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if (VM.isBooted() && Thread.currentThread().isVirtual()) {
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return DEFAULT_INITIAL_BUFFER_SIZE;
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} else {
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return DEFAULT_MAX_BUFFER_SIZE;
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}
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}
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/**
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* Creates a new buffered output stream.
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*/
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private BufferedOutputStream(OutputStream out, int initialSize, int maxSize) {
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super(out);
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if (initialSize <= 0) {
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throw new IllegalArgumentException("Buffer size <= 0");
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}
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if (getClass() == BufferedOutputStream.class) {
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// use InternalLock and resizable buffer when not sub-classed
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this.lock = InternalLock.newLockOrNull();
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this.buf = new byte[initialSize]; // resizable
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} else {
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// use monitors and no resizing when sub-classed
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this.lock = null;
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this.buf = new byte[maxSize];
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}
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this.maxBufSize = maxSize;
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}
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/**
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* Creates a new buffered output stream to write data to the
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* specified underlying output stream.
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*
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* @param out the underlying output stream.
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*/
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public BufferedOutputStream(OutputStream out) {
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this(out, initialBufferSize(), DEFAULT_MAX_BUFFER_SIZE);
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}
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/**
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* Creates a new buffered output stream to write data to the
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* specified underlying output stream with the specified buffer
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* size.
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*
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* @param out the underlying output stream.
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* @param size the buffer size.
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* @throws IllegalArgumentException if size <= 0.
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*/
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public BufferedOutputStream(OutputStream out, int size) {
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this(out, size, size);
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}
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/** Flush the internal buffer */
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private void flushBuffer() throws IOException {
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if (count > 0) {
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out.write(buf, 0, count);
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count = 0;
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}
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}
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/**
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* Grow buf to fit an additional len bytes if needed.
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* If possible, it grows by len+1 to avoid flushing when len bytes
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* are added. A no-op if the buffer is not resizable.
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*
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* This method should only be called while holding the lock.
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*/
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private void growIfNeeded(int len) {
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int neededSize = count + len + 1;
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if (neededSize < 0)
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neededSize = Integer.MAX_VALUE;
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int bufSize = buf.length;
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if (neededSize > bufSize && bufSize < maxBufSize) {
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int newSize = Math.min(neededSize, maxBufSize);
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buf = Arrays.copyOf(buf, newSize);
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}
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}
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/**
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* Writes the specified byte to this buffered output stream.
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*
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* @param b the byte to be written.
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* @throws IOException if an I/O error occurs.
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*/
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@Override
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public void write(int b) throws IOException {
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if (lock != null) {
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lock.lock();
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try {
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implWrite(b);
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} finally {
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lock.unlock();
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}
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} else {
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synchronized (this) {
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implWrite(b);
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}
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}
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}
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private void implWrite(int b) throws IOException {
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growIfNeeded(1);
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if (count >= buf.length) {
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flushBuffer();
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}
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buf[count++] = (byte)b;
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}
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/**
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* Writes {@code len} bytes from the specified byte array
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* starting at offset {@code off} to this buffered output stream.
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*
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* <p> Ordinarily this method stores bytes from the given array into this
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* stream's buffer, flushing the buffer to the underlying output stream as
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* needed. If the requested length is at least as large as this stream's
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* buffer, however, then this method will flush the buffer and write the
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* bytes directly to the underlying output stream. Thus redundant
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* {@code BufferedOutputStream}s will not copy data unnecessarily.
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*
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* @param b the data.
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* @param off the start offset in the data.
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* @param len the number of bytes to write.
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* @throws IOException if an I/O error occurs.
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* @throws IndexOutOfBoundsException {@inheritDoc}
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*/
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@Override
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public void write(byte[] b, int off, int len) throws IOException {
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if (lock != null) {
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lock.lock();
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try {
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implWrite(b, off, len);
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} finally {
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lock.unlock();
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}
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} else {
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synchronized (this) {
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implWrite(b, off, len);
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}
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}
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}
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private void implWrite(byte[] b, int off, int len) throws IOException {
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if (len >= maxBufSize) {
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/* If the request length exceeds the max size of the output buffer,
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flush the output buffer and then write the data directly.
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In this way buffered streams will cascade harmlessly. */
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flushBuffer();
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out.write(b, off, len);
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return;
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}
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growIfNeeded(len);
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if (len > buf.length - count) {
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flushBuffer();
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}
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System.arraycopy(b, off, buf, count, len);
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count += len;
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}
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/**
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* Flushes this buffered output stream. This forces any buffered
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* output bytes to be written out to the underlying output stream.
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*
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* @throws IOException if an I/O error occurs.
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* @see java.io.FilterOutputStream#out
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*/
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@Override
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public void flush() throws IOException {
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if (lock != null) {
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lock.lock();
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try {
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implFlush();
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} finally {
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lock.unlock();
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}
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} else {
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synchronized (this) {
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implFlush();
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}
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}
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}
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private void implFlush() throws IOException {
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flushBuffer();
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out.flush();
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}
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}
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