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      1 /*
      2  * Copyright (C) 2006 Google Inc.
      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 java.io.Closeable;
     20 import java.io.Flushable;
     21 import java.io.Writer;
     22 import java.io.IOException;
     23 
     24 /**
     25  * Writer that places all output on an {@link Appendable} target. If the target
     26  * is {@link Flushable} or {@link Closeable}, flush()es and close()s will also
     27  * be delegated to the target.
     28  *
     29  * @author Alan Green
     30  * @author Sebastian Kanthak
     31  * @since 2009.09.15 <b>tentative</b>
     32  */
     33 class AppendableWriter extends Writer {
     34   private final Appendable target;
     35   private boolean closed;
     36 
     37   /**
     38    * Creates a new writer that appends everything it writes to {@code target}.
     39    *
     40    * @param target target to which to append output
     41    */
     42   AppendableWriter(Appendable target) {
     43     this.target = target;
     44   }
     45 
     46   /*
     47    * Abstract methods from Writer
     48    */
     49 
     50   @Override public void write(char cbuf[], int off, int len)
     51       throws IOException {
     52     checkNotClosed();
     53     // It turns out that creating a new String is usually as fast, or faster
     54     // than wrapping cbuf in a light-weight CharSequence.
     55     target.append(new String(cbuf, off, len));
     56   }
     57 
     58   @Override public void flush() throws IOException {
     59     checkNotClosed();
     60     if (target instanceof Flushable) {
     61       ((Flushable) target).flush();
     62     }
     63   }
     64 
     65   @Override public void close() throws IOException {
     66     this.closed = true;
     67     if (target instanceof Closeable) {
     68       ((Closeable) target).close();
     69     }
     70   }
     71 
     72   /*
     73    * Override a few functions for performance reasons to avoid creating
     74    * unnecessary strings.
     75    */
     76 
     77   @Override public void write(int c) throws IOException {
     78     checkNotClosed();
     79     target.append((char) c);
     80   }
     81 
     82   @Override public void write(String str) throws IOException {
     83     checkNotClosed();
     84     target.append(str);
     85   }
     86 
     87   @Override public void write(String str, int off, int len) throws IOException {
     88     checkNotClosed();
     89     // tricky: append takes start, end pair...
     90     target.append(str, off, off + len);
     91   }
     92 
     93   @Override public Writer append(char c) throws IOException {
     94     checkNotClosed();
     95     target.append(c);
     96     return this;
     97   }
     98 
     99   @Override public Writer append(CharSequence charSeq) throws IOException {
    100     checkNotClosed();
    101     target.append(charSeq);
    102     return this;
    103   }
    104 
    105   @Override public Writer append(CharSequence charSeq, int start, int end)
    106       throws IOException {
    107     checkNotClosed();
    108     target.append(charSeq, start, end);
    109     return this;
    110   }
    111 
    112   private void checkNotClosed() throws IOException {
    113     if (closed) {
    114       throw new IOException("Cannot write to a closed writer.");
    115     }
    116   }
    117 }
    118