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The Apache Commons IO library contains utility classes, stream implementations, file filters,
file comparators, endian transformation classes, and much more.
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You 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 org.apache.commons.io.input.buffer;
import java.io.BufferedInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.util.Objects;
/**
* Implementation of a buffered input stream, which is internally based on the
* {@link CircularByteBuffer}. Unlike the {@link BufferedInputStream}, this one
* doesn't need to reallocate byte arrays internally.
*/
public class CircularBufferInputStream extends InputStream {
protected final InputStream in;
protected final CircularByteBuffer buffer;
protected final int bufferSize;
private boolean eofSeen;
/** Creates a new instance, which filters the given input stream, and
* uses the given buffer size.
* @param pIn The input stream, which is being buffered.
* @param pBufferSize The size of the {@link CircularByteBuffer}, which is
* used internally.
*/
public CircularBufferInputStream(InputStream pIn, int pBufferSize) {
Objects.requireNonNull(pIn, "InputStream");
if (pBufferSize <= 0) {
throw new IllegalArgumentException("Invalid buffer size: " + pBufferSize);
}
in = pIn;
buffer = new CircularByteBuffer(pBufferSize);
bufferSize = pBufferSize;
eofSeen = false;
}
/** Creates a new instance, which filters the given input stream, and
* uses a reasonable default buffer size (8192).
* @param pIn The input stream, which is being buffered.
*/
public CircularBufferInputStream(InputStream pIn) {
this(pIn, 8192);
}
protected void fillBuffer() throws IOException {
if (eofSeen) {
return;
}
int space = buffer.getSpace();
final byte[] buf = new byte[space];
while (space > 0) {
final int res = in.read(buf, 0, space);
if (res == -1) {
eofSeen = true;
return;
} else if (res > 0) {
buffer.add(buf, 0, res);
space -= res;
}
}
}
protected boolean haveBytes(int pNumber) throws IOException {
if (buffer.getCurrentNumberOfBytes() < pNumber) {
fillBuffer();
}
return buffer.hasBytes();
}
@Override
public int read() throws IOException {
if (!haveBytes(1)) {
return -1;
}
return buffer.read();
}
@Override
public int read(byte[] pBuffer) throws IOException {
return read(pBuffer, 0, pBuffer.length);
}
@Override
public int read(byte[] pBuffer, int pOffset, int pLength) throws IOException {
Objects.requireNonNull(pBuffer, "Buffer");
if (pOffset < 0) {
throw new IllegalArgumentException("Offset must not be negative");
}
if (pLength < 0) {
throw new IllegalArgumentException("Length must not be negative");
}
if (!haveBytes(pLength)) {
return -1;
}
final int result = Math.min(pLength, buffer.getCurrentNumberOfBytes());
for (int i = 0; i < result; i++) {
pBuffer[pOffset+i] = buffer.read();
}
return result;
}
@Override
public void close() throws IOException {
in.close();
eofSeen = true;
buffer.clear();
}
}