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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 com.google.common.annotations.GwtIncompatible;
import com.google.errorprone.annotations.CanIgnoreReturnValue;
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 supplier of {@code OutputStream} instances.
 *
 * 

{@code ByteSink} provides two kinds of methods: * *

    *
  • Methods that return a stream: These methods should return a new, independent * instance each time they are called. The caller is responsible for ensuring that the * returned stream is closed. *
  • Convenience methods: 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. *
* * @since 14.0 * @author Colin Decker */ @GwtIncompatible public abstract class ByteSink { /** Constructor for use by subclasses. */ protected 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 returns a new, * independent stream each time it is called. * *

The caller is responsible for ensuring that the returned stream is closed. * * @throws IOException if an I/O error occurs while opening the stream */ public abstract OutputStream openStream() throws IOException; /** * Opens a new buffered {@link OutputStream} for writing to this sink. The returned stream is not * required to be a {@link BufferedOutputStream} in order to allow implementations to simply * delegate to {@link #openStream()} when the stream returned by that method does not benefit from * additional buffering (for example, a {@code ByteArrayOutputStream}). This method returns a new, * independent stream each time it is called. * *

The caller is responsible for ensuring that the returned stream is closed. * * @throws IOException if an I/O error occurs while opening the stream * @since 15.0 (in 14.0 with return type {@link BufferedOutputStream}) */ public OutputStream 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 while 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); out.flush(); // https://code.google.com/p/guava-libraries/issues/detail?id=1330 } 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}. * * @return the number of bytes written * @throws IOException if an I/O occurs while reading from {@code input} or writing to this sink */ @CanIgnoreReturnValue public long writeFrom(InputStream input) throws IOException { checkNotNull(input); Closer closer = Closer.create(); try { OutputStream out = closer.register(openStream()); long written = ByteStreams.copy(input, out); out.flush(); // https://code.google.com/p/guava-libraries/issues/detail?id=1330 return written; } 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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