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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.Beta;
import com.google.common.annotations.GwtIncompatible;
import com.google.errorprone.annotations.CanIgnoreReturnValue;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.Reader;
import java.io.Writer;
import java.nio.charset.Charset;
import java.util.Iterator;
import java.util.stream.Stream;

/**
 * A destination to which characters can be written, such as a text file. Unlike a {@link Writer}, a
 * {@code CharSink} is not an open, stateful stream that can be written to and closed. Instead, it
 * is an immutable supplier of {@code Writer} instances.
 *
 * 

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

    *
  • Methods that return a writer: These methods should return a new, independent * instance each time they are called. The caller is responsible for ensuring that the * returned writer is closed. *
  • Convenience methods: These are implementations of common operations that are * typically implemented by opening a writer using one of the methods in the first category, * doing something and finally closing the writer that was opened. *
* *

Any {@link ByteSink} may be viewed as a {@code CharSink} with a specific {@linkplain Charset * character encoding} using {@link ByteSink#asCharSink(Charset)}. Characters written to the * resulting {@code CharSink} will written to the {@code ByteSink} as encoded bytes. * * @since 14.0 * @author Colin Decker */ @GwtIncompatible public abstract class CharSink { /** Constructor for use by subclasses. */ protected CharSink() {} /** * Opens a new {@link Writer} for writing to this sink. This method returns a new, independent * writer each time it is called. * *

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

The caller is responsible for ensuring that the returned writer is closed. * * @throws IOException if an I/O error occurs while opening the writer * @since 15.0 (in 14.0 with return type {@link BufferedWriter}) */ public Writer openBufferedStream() throws IOException { Writer writer = openStream(); return (writer instanceof BufferedWriter) ? (BufferedWriter) writer : new BufferedWriter(writer); } /** * Writes the given character sequence to this sink. * * @throws IOException if an I/O error while writing to this sink */ public void write(CharSequence charSequence) throws IOException { checkNotNull(charSequence); Closer closer = Closer.create(); try { Writer out = closer.register(openStream()); out.append(charSequence); out.flush(); // https://code.google.com/p/guava-libraries/issues/detail?id=1330 } catch (Throwable e) { throw closer.rethrow(e); } finally { closer.close(); } } /** * Writes the given lines of text to this sink with each line (including the last) terminated with * the operating system's default line separator. This method is equivalent to {@code * writeLines(lines, System.getProperty("line.separator"))}. * * @throws IOException if an I/O error occurs while writing to this sink */ public void writeLines(Iterable lines) throws IOException { writeLines(lines, System.getProperty("line.separator")); } /** * Writes the given lines of text to this sink with each line (including the last) terminated with * the given line separator. * * @throws IOException if an I/O error occurs while writing to this sink */ public void writeLines(Iterable lines, String lineSeparator) throws IOException { writeLines(lines.iterator(), lineSeparator); } /** * Writes the given lines of text to this sink with each line (including the last) terminated with * the operating system's default line separator. This method is equivalent to {@code * writeLines(lines, System.getProperty("line.separator"))}. * * @throws IOException if an I/O error occurs while writing to this sink * @since 22.0 */ @Beta public void writeLines(Stream lines) throws IOException { writeLines(lines, System.getProperty("line.separator")); } /** * Writes the given lines of text to this sink with each line (including the last) terminated with * the given line separator. * * @throws IOException if an I/O error occurs while writing to this sink * @since 22.0 */ @Beta public void writeLines(Stream lines, String lineSeparator) throws IOException { writeLines(lines.iterator(), lineSeparator); } private void writeLines(Iterator lines, String lineSeparator) throws IOException { checkNotNull(lineSeparator); try (Writer out = openBufferedStream()) { while (lines.hasNext()) { out.append(lines.next()).append(lineSeparator); } } } /** * Writes all the text from the given {@link Readable} (such as a {@link Reader}) to this sink. * Does not close {@code readable} if it is {@code Closeable}. * * @return the number of characters written * @throws IOException if an I/O error occurs while reading from {@code readable} or writing to * this sink */ @CanIgnoreReturnValue public long writeFrom(Readable readable) throws IOException { checkNotNull(readable); Closer closer = Closer.create(); try { Writer out = closer.register(openStream()); long written = CharStreams.copy(readable, 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(); } } }





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