001/*
002 * Copyright (C) 2012 The Guava Authors
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License");
005 * you may not use this file except in compliance with the License.
006 * You may obtain a copy of the License at
007 *
008 * http://www.apache.org/licenses/LICENSE-2.0
009 *
010 * Unless required by applicable law or agreed to in writing, software
011 * distributed under the License is distributed on an "AS IS" BASIS,
012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013 * See the License for the specific language governing permissions and
014 * limitations under the License.
015 */
016
017package com.google.common.io;
018
019import static com.google.common.base.Preconditions.checkNotNull;
020
021import java.io.BufferedWriter;
022import java.io.IOException;
023import java.io.Reader;
024import java.io.Writer;
025import java.nio.charset.Charset;
026
027/**
028 * A destination to which characters can be written, such as a text file. Unlike a {@link Writer}, a
029 * {@code CharSink} is not an open, stateful stream that can be written to and closed. Instead, it
030 * is an immutable <i>supplier</i> of {@code Writer} instances.
031 *
032 * <p>{@code CharSink} provides two kinds of methods:
033 * <ul>
034 *   <li><b>Methods that return a writer:</b> These methods should return a <i>new</i>,
035 *   independent instance each time they are called. The caller is responsible for ensuring that the
036 *   returned writer is closed.
037 *   <li><b>Convenience methods:</b> These are implementations of common operations that are
038 *   typically implemented by opening a writer using one of the methods in the first category,
039 *   doing something and finally closing the writer that was opened.
040 * </ul>
041 *
042 * <p>Any {@link ByteSink} may be viewed as a {@code CharSink} with a specific {@linkplain Charset
043 * character encoding} using {@link ByteSink#asCharSink(Charset)}. Characters written to the
044 * resulting {@code CharSink} will written to the {@code ByteSink} as encoded bytes.
045 *
046 * @since 14.0
047 * @author Colin Decker
048 */
049public abstract class CharSink implements OutputSupplier<Writer> {
050
051  /**
052   * Constructor for use by subclasses.
053   */
054  protected CharSink() {}
055
056  /**
057   * Opens a new {@link Writer} for writing to this sink. This method should return a new,
058   * independent writer each time it is called.
059   *
060   * <p>The caller is responsible for ensuring that the returned writer is closed.
061   *
062   * @throws IOException if an I/O error occurs in the process of opening the writer
063   */
064  public abstract Writer openStream() throws IOException;
065
066  /**
067   * This method is a temporary method provided for easing migration from suppliers to sources and
068   * sinks.
069   *
070   * @since 15.0
071   * @deprecated This method is only provided for temporary compatibility with the
072   *     {@link OutputSupplier} interface and should not be called directly. Use
073   *     {@link #openStream} instead. This method is scheduled for removal in Guava 18.0.
074   */
075  @Override
076  @Deprecated
077  public final Writer getOutput() throws IOException {
078    return openStream();
079  }
080
081  /**
082   * Opens a new buffered {@link Writer} for writing to this sink. The returned stream is not
083   * required to be a {@link BufferedWriter} in order to allow implementations to simply delegate
084   * to {@link #openStream()} when the stream returned by that method does not benefit from
085   * additional buffering. This method should return a new, independent writer each time it is
086   * called.
087   *
088   * <p>The caller is responsible for ensuring that the returned writer is closed.
089   *
090   * @throws IOException if an I/O error occurs in the process of opening the writer
091   * @since 15.0 (in 14.0 with return type {@link BufferedWriter})
092   */
093  public Writer openBufferedStream() throws IOException {
094    Writer writer = openStream();
095    return (writer instanceof BufferedWriter)
096        ? (BufferedWriter) writer
097        : new BufferedWriter(writer);
098  }
099
100  /**
101   * Writes the given character sequence to this sink.
102   *
103   * @throws IOException if an I/O error in the process of writing to this sink
104   */
105  public void write(CharSequence charSequence) throws IOException {
106    checkNotNull(charSequence);
107
108    Closer closer = Closer.create();
109    try {
110      Writer out = closer.register(openStream());
111      out.append(charSequence);
112      out.flush(); // https://code.google.com/p/guava-libraries/issues/detail?id=1330
113    } catch (Throwable e) {
114      throw closer.rethrow(e);
115    } finally {
116      closer.close();
117    }
118  }
119
120  /**
121   * Writes the given lines of text to this sink with each line (including the last) terminated with
122   * the operating system's default line separator. This method is equivalent to
123   * {@code writeLines(lines, System.getProperty("line.separator"))}.
124   *
125   * @throws IOException if an I/O error occurs in the process of writing to this sink
126   */
127  public void writeLines(Iterable<? extends CharSequence> lines) throws IOException {
128    writeLines(lines, System.getProperty("line.separator"));
129  }
130
131  /**
132   * Writes the given lines of text to this sink with each line (including the last) terminated with
133   * the given line separator.
134   *
135   * @throws IOException if an I/O error occurs in the process of writing to this sink
136   */
137  public void writeLines(Iterable<? extends CharSequence> lines, String lineSeparator)
138      throws IOException {
139    checkNotNull(lines);
140    checkNotNull(lineSeparator);
141
142    Closer closer = Closer.create();
143    try {
144      Writer out = closer.register(openBufferedStream());
145      for (CharSequence line : lines) {
146        out.append(line).append(lineSeparator);
147      }
148      out.flush(); // https://code.google.com/p/guava-libraries/issues/detail?id=1330
149    } catch (Throwable e) {
150      throw closer.rethrow(e);
151    } finally {
152      closer.close();
153    }
154  }
155
156  /**
157   * Writes all the text from the given {@link Readable} (such as a {@link Reader}) to this sink.
158   * Does not close {@code readable} if it is {@code Closeable}.
159   *
160   * @throws IOException if an I/O error occurs in the process of reading from {@code readable} or
161   *     writing to this sink
162   */
163  public long writeFrom(Readable readable) throws IOException {
164    checkNotNull(readable);
165
166    Closer closer = Closer.create();
167    try {
168      Writer out = closer.register(openStream());
169      long written = CharStreams.copy(readable, out);
170      out.flush(); // https://code.google.com/p/guava-libraries/issues/detail?id=1330
171      return written;
172    } catch (Throwable e) {
173      throw closer.rethrow(e);
174    } finally {
175      closer.close();
176    }
177  }
178}