com.google.common.io.MultiReader Maven / Gradle / Ivy
/*
* Copyright (C) 2008 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 com.google.common.base.Preconditions;
import java.io.IOException;
import java.io.Reader;
import java.util.Iterator;
import javax.annotation.Nullable;
/**
* A {@link Reader} that concatenates multiple readers.
*
* @author Bin Zhu
* @since 1.0
*/
class MultiReader extends Reader {
private final Iterator it;
private Reader current;
MultiReader(Iterator readers) throws IOException {
this.it = readers;
advance();
}
/**
* Closes the current reader and opens the next one, if any.
*/
private void advance() throws IOException {
close();
if (it.hasNext()) {
current = it.next().openStream();
}
}
@Override public int read(@Nullable char cbuf[], int off, int len) throws IOException {
if (current == null) {
return -1;
}
int result = current.read(cbuf, off, len);
if (result == -1) {
advance();
return read(cbuf, off, len);
}
return result;
}
@Override public long skip(long n) throws IOException {
Preconditions.checkArgument(n >= 0, "n is negative");
if (n > 0) {
while (current != null) {
long result = current.skip(n);
if (result > 0) {
return result;
}
advance();
}
}
return 0;
}
@Override public boolean ready() throws IOException {
return (current != null) && current.ready();
}
@Override public void close() throws IOException {
if (current != null) {
try {
current.close();
} finally {
current = null;
}
}
}
}