/* * 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; import java.io.EOFException; import java.io.IOException; import java.io.InputStream; /** * A functional, light weight {@link InputStream} that emulates * a stream of a specified size. *
* This implementation provides a light weight * object for testing with an {@link InputStream} * where the contents don't matter. *
* One use case would be for testing the handling of * large {@link InputStream} as it can emulate that * scenario without the overhead of actually processing * large numbers of bytes - significantly speeding up * test execution times. *
* This implementation returns zero from the method that
* reads a byte and leaves the array unchanged in the read
* methods that are passed a byte array.
* If alternative data is required the processByte()
and
* processBytes()
methods can be implemented to generate
* data, for example:
*
*
* public class TestInputStream extends NullInputStream { * public TestInputStream(int size) { * super(size); * } * protected int processByte() { * return ... // return required value here * } * protected void processBytes(byte[] bytes, int offset, int length) { * for (int i = offset; i < length; i++) { * bytes[i] = ... // set array value here * } * } * } ** * @since Commons IO 1.3 * @version $Revision: 463529 $ */ public class NullInputStream extends InputStream { private long size; private long position; private long mark = -1; private long readlimit; private boolean eof; private boolean throwEofException; private boolean markSupported; /** * Create an {@link InputStream} that emulates a specified size * which supports marking and does not throw EOFException. * * @param size The size of the input stream to emulate. */ public NullInputStream(long size) { this(size, true, false); } /** * Create an {@link InputStream} that emulates a specified * size with option settings. * * @param size The size of the input stream to emulate. * @param markSupported Whether this instance will support * the
mark()
functionality.
* @param throwEofException Whether this implementation
* will throw an {@link EOFException} or return -1 when the
* end of file is reached.
*/
public NullInputStream(long size, boolean markSupported, boolean throwEofException) {
this.size = size;
this.markSupported = markSupported;
this.throwEofException = throwEofException;
}
/**
* Return the current position.
*
* @return the current position.
*/
public long getPosition() {
return position;
}
/**
* Return the size this {@link InputStream} emulates.
*
* @return The size of the input stream to emulate.
*/
public long getSize() {
return size;
}
/**
* Return the number of bytes that can be read.
*
* @return The number of bytes that can be read.
*/
public int available() {
long avail = size - position;
if (avail <= 0) {
return 0;
} else if (avail > Integer.MAX_VALUE) {
return Integer.MAX_VALUE;
} else {
return (int)avail;
}
}
/**
* Close this input stream - resets the internal state to
* the initial values.
*
* @throws IOException If an error occurs.
*/
public void close() throws IOException {
eof = false;
position = 0;
mark = -1;
}
/**
* Mark the current position.
*
* @param readlimit The number of bytes before this marked position
* is invalid.
* @throws UnsupportedOperationException if mark is not supported.
*/
public synchronized void mark(int readlimit) {
if (!markSupported) {
throw new UnsupportedOperationException("Mark not supported");
}
mark = position;
this.readlimit = readlimit;
}
/**
* Indicates whether mark is supported.
*
* @return Whether mark is supported or not.
*/
public boolean markSupported() {
return markSupported;
}
/**
* Read a byte.
*
* @return Either The byte value returned by processByte()
* or -1
if the end of file has been reached and
* throwEofException
is set to false
.
* @throws EOFException if the end of file is reached and
* throwEofException
is set to true
.
* @throws IOException if trying to read past the end of file.
*/
public int read() throws IOException {
if (eof) {
throw new IOException("Read after end of file");
}
if (position == size) {
return doEndOfFile();
}
position++;
return processByte();
}
/**
* Read some bytes into the specified array.
*
* @param bytes The byte array to read into
* @return The number of bytes read or -1
* if the end of file has been reached and
* throwEofException
is set to false
.
* @throws EOFException if the end of file is reached and
* throwEofException
is set to true
.
* @throws IOException if trying to read past the end of file.
*/
public int read(byte[] bytes) throws IOException {
return read(bytes, 0, bytes.length);
}
/**
* Read the specified number bytes into an array.
*
* @param bytes The byte array to read into.
* @param offset The offset to start reading bytes into.
* @param length The number of bytes to read.
* @return The number of bytes read or -1
* if the end of file has been reached and
* throwEofException
is set to false
.
* @throws EOFException if the end of file is reached and
* throwEofException
is set to true
.
* @throws IOException if trying to read past the end of file.
*/
public int read(byte[] bytes, int offset, int length) throws IOException {
if (eof) {
throw new IOException("Read after end of file");
}
if (position == size) {
return doEndOfFile();
}
position += length;
int returnLength = length;
if (position > size) {
returnLength = length - (int)(position - size);
position = size;
}
processBytes(bytes, offset, returnLength);
return returnLength;
}
/**
* Reset the stream to the point when mark was last called.
*
* @throws UnsupportedOperationException if mark is not supported.
* @throws IOException If no position has been marked
* or the read limit has been exceed since the last position was
* marked.
*/
public synchronized void reset() throws IOException {
if (!markSupported) {
throw new UnsupportedOperationException("Mark not supported");
}
if (mark < 0) {
throw new IOException("No position has been marked");
}
if (position > (mark + readlimit)) {
throw new IOException("Marked position [" + mark +
"] is no longer valid - passed the read limit [" +
readlimit + "]");
}
position = mark;
eof = false;
}
/**
* Skip a specified number of bytes.
*
* @param numberOfBytes The number of bytes to skip.
* @return The number of bytes skipped or -1
* if the end of file has been reached and
* throwEofException
is set to false
.
* @throws EOFException if the end of file is reached and
* throwEofException
is set to true
.
* @throws IOException if trying to read past the end of file.
*/
public long skip(long numberOfBytes) throws IOException {
if (eof) {
throw new IOException("Skip after end of file");
}
if (position == size) {
return doEndOfFile();
}
position += numberOfBytes;
long returnLength = numberOfBytes;
if (position > size) {
returnLength = numberOfBytes - (position - size);
position = size;
}
return returnLength;
}
/**
* Return a byte value for the read()
method.
*
* This implementation returns zero.
*
* @return This implementation always returns zero.
*/
protected int processByte() {
// do nothing - overridable by subclass
return 0;
}
/**
* Process the bytes for the read(byte[], offset, length)
* method.
*
* This implementation leaves the byte array unchanged.
*
* @param bytes The byte array
* @param offset The offset to start at.
* @param length The number of bytes.
*/
protected void processBytes(byte[] bytes, int offset, int length) {
// do nothing - overridable by subclass
}
/**
* Handle End of File.
*
* @return -1
if throwEofException
is
* set to false
* @throws EOFException if throwEofException
is set
* to true
.
*/
private int doEndOfFile() throws EOFException {
eof = true;
if (throwEofException) {
throw new EOFException();
}
return -1;
}
}