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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.IOException;
import java.io.InputStream;
import java.util.Objects;
/**
* Implements a buffered input stream, which allows to peek into the buffers first bytes. This comes in handy when
* manually implementing scanners, lexers, parsers, and the like.
*/
public class PeekableInputStream extends CircularBufferInputStream {
/**
* Creates a new instance, which filters the given input stream, and uses the given buffer size.
*
* @param inputStream The input stream, which is being buffered.
* @param bufferSize The size of the {@link CircularByteBuffer}, which is used internally.
*/
public PeekableInputStream(final InputStream inputStream, final int bufferSize) {
super(inputStream, bufferSize);
}
/**
* Creates a new instance, which filters the given input stream, and uses a reasonable default buffer size (8192).
*
* @param inputStream The input stream, which is being buffered.
*/
public PeekableInputStream(final InputStream inputStream) {
super(inputStream);
}
/**
* Returns whether the next bytes in the buffer are as given by {@code sourceBuffer}. This is equivalent to
* {@link #peek(byte[], int, int)} with {@code offset} == 0, and {@code length} == {@code sourceBuffer.length}
*
* @param sourceBuffer the buffer to compare against
* @return true if the next bytes are as given
* @throws IOException Refilling the buffer failed.
*/
public boolean peek(final byte[] sourceBuffer) throws IOException {
Objects.requireNonNull(sourceBuffer, "sourceBuffer");
return peek(sourceBuffer, 0, sourceBuffer.length);
}
/**
* Returns whether the next bytes in the buffer are as given by {@code sourceBuffer}, {code offset}, and
* {@code length}.
*
* @param sourceBuffer the buffer to compare against
* @param offset the start offset
* @param length the length to compare
* @return true if the next bytes in the buffer are as given
* @throws IOException if there is a problem calling fillBuffer()
*/
public boolean peek(final byte[] sourceBuffer, final int offset, final int length) throws IOException {
Objects.requireNonNull(sourceBuffer, "sourceBuffer");
if (sourceBuffer.length > bufferSize) {
throw new IllegalArgumentException("Peek request size of " + sourceBuffer.length
+ " bytes exceeds buffer size of " + bufferSize + " bytes");
}
if (buffer.getCurrentNumberOfBytes() < sourceBuffer.length) {
fillBuffer();
}
return buffer.peek(sourceBuffer, offset, length);
}
}