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