Mega Code Archive
Writer that places all output on an {@link Appendable} target
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/* Copyright (c) 2008 Google Inc.
*
* 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.gdata.util.common.io;
import java.io.Closeable;
import java.io.Flushable;
import java.io.Writer;
import java.io.IOException;
/**
* Writer that places all output on an {@link Appendable} target. If the target
* is {@link Flushable} or {@link Closeable}, flush()es and close()s will also
* be delegated to the target.
*
*
*
*/
class AppendableWriter extends Writer {
private final Appendable target;
private boolean closed;
/**
* Creates a new writer that appends everything it writes to {@code target}.
*
* @param target target to which to append output
*/
AppendableWriter(Appendable target) {
this.target = target;
}
/*
* Abstract methods from Writer
*/
@Override public void write(char cbuf[], int off, int len)
throws IOException {
checkNotClosed();
// It turns out that creating a new String is usually as fast, or faster
// than wrapping cbuf in a light-weight CharSequence. See benchmark code
// in comments of http://cl/9327627 and results at
// https://spreadsheets.google.com/a/google.com/ccc?key=pABoWmCP48mrC_J8v4xh1ZA
target.append(new String(cbuf, off, len));
}
@Override public void flush() throws IOException {
checkNotClosed();
if (target instanceof Flushable) {
((Flushable) target).flush();
}
}
@Override public void close() throws IOException {
this.closed = true;
if (target instanceof Closeable) {
((Closeable) target).close();
}
}
/*
* Override a few functions for performance reasons to avoid creating
* unnecessary strings.
*/
@Override public void write(int c) throws IOException {
checkNotClosed();
target.append((char) c);
}
@Override public void write(String str) throws IOException {
checkNotClosed();
target.append(str);
}
@Override public void write(String str, int off, int len) throws IOException {
checkNotClosed();
// tricky: append takes start, end pair...
target.append(str, off, off + len);
}
@Override public Writer append(char c) throws IOException {
checkNotClosed();
target.append(c);
return this;
}
@Override public Writer append(CharSequence charSeq) throws IOException {
checkNotClosed();
target.append(charSeq);
return this;
}
@Override public Writer append(CharSequence charSeq, int start, int end)
throws IOException {
checkNotClosed();
target.append(charSeq, start, end);
return this;
}
private void checkNotClosed() throws IOException {
if (closed) {
throw new IOException("Cannot write to a closed writer.");
}
}
}
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