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/*
* Copyright (C) 2012 The Guava Authors
*
* 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.google.common.io;
import static com.google.common.base.Preconditions.checkNotNull;
import java.io.BufferedOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.io.Writer;
import java.nio.charset.Charset;
/**
* A destination to which bytes can be written, such as a file. Unlike an {@link OutputStream}, a
* {@code ByteSink} is not an open, stateful stream that can be written to and closed. Instead, it
* is an immutable <i>supplier</i> of {@code OutputStream} instances.
*
* <p>{@code ByteSink} provides two kinds of methods:
* <ul>
* <li><b>Methods that return a stream:</b> These methods should return a <i>new</i>, independent
* instance each time they are called. The caller is responsible for ensuring that the returned
* stream is closed.
* <li><b>Convenience methods:</b> These are implementations of common operations that are
* typically implemented by opening a stream using one of the methods in the first category, doing
* something and finally closing the stream or channel that was opened.
* </ul>
*
* @since 14.0
* @author Colin Decker
*/
public abstract class ByteSink {
/**
* Returns a {@link CharSink} view of this {@code ByteSink} that writes characters to this sink
* as bytes encoded with the given {@link Charset charset}.
*/
public CharSink asCharSink(Charset charset) {
return new AsCharSink(charset);
}
/**
* Opens a new {@link OutputStream} for writing to this sink. This method should return a new,
* independent stream each time it is called.
*
* <p>The caller is responsible for ensuring that the returned stream is closed.
*
* @throws IOException if an I/O error occurs in the process of opening the stream
*/
public abstract OutputStream openStream() throws IOException;
/**
* Opens a new {@link BufferedOutputStream} for writing to this sink. This method should return a
* new, independent stream each time it is called.
*
* <p>The caller is responsible for ensuring that the returned stream is closed.
*
* @throws IOException if an I/O error occurs in the process of opening the stream
*/
public BufferedOutputStream openBufferedStream() throws IOException {
OutputStream out = openStream();
return (out instanceof BufferedOutputStream)
? (BufferedOutputStream) out
: new BufferedOutputStream(out);
}
/**
* Writes all the given bytes to this sink.
*
* @throws IOException if an I/O occurs in the process of writing to this sink
*/
public void write(byte[] bytes) throws IOException {
checkNotNull(bytes);
Closer closer = Closer.create();
try {
OutputStream out = closer.register(openStream());
out.write(bytes);
} catch (Throwable e) {
throw closer.rethrow(e);
} finally {
closer.close();
}
}
/**
* Writes all the bytes from the given {@code InputStream} to this sink. Does not close
* {@code input}.
*
* @throws IOException if an I/O occurs in the process of reading from {@code input} or writing to
* this sink
*/
public long writeFrom(InputStream input) throws IOException {
checkNotNull(input);
Closer closer = Closer.create();
try {
OutputStream out = closer.register(openStream());
return ByteStreams.copy(input, out);
} catch (Throwable e) {
throw closer.rethrow(e);
} finally {
closer.close();
}
}
/**
* A char sink that encodes written characters with a charset and writes resulting bytes to this
* byte sink.
*/
private final class AsCharSink extends CharSink {
private final Charset charset;
private AsCharSink(Charset charset) {
this.charset = checkNotNull(charset);
}
@Override
public Writer openStream() throws IOException {
return new OutputStreamWriter(ByteSink.this.openStream(), charset);
}
@Override
public String toString() {
return ByteSink.this.toString() + ".asCharSink(" + charset + ")";
}
}
}
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