com.google.common.io.ByteSink.java Source code

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Here is the source code for com.google.common.io.ByteSink.java

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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 {

    /**
     * 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 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 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 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
     * @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 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);
            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}.
     *
     * @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());
            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 + ")";
        }
    }
}