1 /* 2 * Copyright (C) 2006 The Guava Authors 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 package com.google.common.io; 18 19 import static com.google.common.base.Preconditions.checkNotNull; 20 21 import java.io.Closeable; 22 import java.io.Flushable; 23 import java.io.IOException; 24 import java.io.Writer; 25 26 import javax.annotation.Nullable; 27 28 /** 29 * Writer that places all output on an {@link Appendable} target. If the target 30 * is {@link Flushable} or {@link Closeable}, flush()es and close()s will also 31 * be delegated to the target. 32 * 33 * @author Alan Green 34 * @author Sebastian Kanthak 35 * @since 1.0 36 */ 37 class AppendableWriter extends Writer { 38 private final Appendable target; 39 private boolean closed; 40 41 /** 42 * Creates a new writer that appends everything it writes to {@code target}. 43 * 44 * @param target target to which to append output 45 */ 46 AppendableWriter(Appendable target) { 47 this.target = checkNotNull(target); 48 } 49 50 /* 51 * Abstract methods from Writer 52 */ 53 54 @Override public void write(char cbuf[], int off, int len) 55 throws IOException { 56 checkNotClosed(); 57 // It turns out that creating a new String is usually as fast, or faster 58 // than wrapping cbuf in a light-weight CharSequence. 59 target.append(new String(cbuf, off, len)); 60 } 61 62 @Override public void flush() throws IOException { 63 checkNotClosed(); 64 if (target instanceof Flushable) { 65 ((Flushable) target).flush(); 66 } 67 } 68 69 @Override public void close() throws IOException { 70 this.closed = true; 71 if (target instanceof Closeable) { 72 ((Closeable) target).close(); 73 } 74 } 75 76 /* 77 * Override a few functions for performance reasons to avoid creating 78 * unnecessary strings. 79 */ 80 81 @Override public void write(int c) throws IOException { 82 checkNotClosed(); 83 target.append((char) c); 84 } 85 86 @Override public void write(@Nullable String str) throws IOException { 87 checkNotClosed(); 88 target.append(str); 89 } 90 91 @Override public void write(@Nullable String str, int off, int len) throws IOException { 92 checkNotClosed(); 93 // tricky: append takes start, end pair... 94 target.append(str, off, off + len); 95 } 96 97 @Override public Writer append(char c) throws IOException { 98 checkNotClosed(); 99 target.append(c); 100 return this; 101 } 102 103 @Override public Writer append(@Nullable CharSequence charSeq) throws IOException { 104 checkNotClosed(); 105 target.append(charSeq); 106 return this; 107 } 108 109 @Override public Writer append(@Nullable CharSequence charSeq, int start, int end) 110 throws IOException { 111 checkNotClosed(); 112 target.append(charSeq, start, end); 113 return this; 114 } 115 116 private void checkNotClosed() throws IOException { 117 if (closed) { 118 throw new IOException("Cannot write to a closed writer."); 119 } 120 } 121 } 122
