CharSink.java
/*
* 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 <i>supplier</i> of {@code Writer} instances.
*
* <p>{@code CharSink} provides two kinds of methods:
*
* <ul>
* <li><b>Methods that return a writer:</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 writer is closed.
* <li><b>Convenience methods:</b> 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.
* </ul>
*
* <p>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
@ElementTypesAreNonnullByDefault
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.
*
* <p>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.
*
* <p>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<? extends CharSequence> 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<? extends CharSequence> 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<? extends CharSequence> 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<? extends CharSequence> lines, String lineSeparator)
throws IOException {
writeLines(lines.iterator(), lineSeparator);
}
private void writeLines(Iterator<? extends CharSequence> 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();
}
}
}