InputStreamWrapper.java
/*
** Module : InputStreamWrapper.java
** Public : creates a Java InputStream which accesses a P2J Stream instance
** (which may be on a remote node)
**
** Copyright (c) 2011-2021, Golden Code Development Corporation.
**
** -#- -I- --Date-- ---------------------------------------Description----------------------------------------
** 001 GES 20110812 Created initial version.
** 002 CA 20210709 Refactored to read pristine bytes and not decoded characters.
** CA 20211001 Refactored read(byte[], off, len) to read the remote stream in chunks, as very large files
** can OOME the FWD client.
*/
/*
** This program is free software: you can redistribute it and/or modify
** it under the terms of the GNU Affero General Public License as
** published by the Free Software Foundation, either version 3 of the
** License, or (at your option) any later version.
**
** This program is distributed in the hope that it will be useful,
** but WITHOUT ANY WARRANTY; without even the implied warranty of
** MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
** GNU Affero General Public License for more details.
**
** You may find a copy of the GNU Affero GPL version 3 at the following
** location: https://www.gnu.org/licenses/agpl-3.0.en.html
**
** Additional terms under GNU Affero GPL version 3 section 7:
**
** Under Section 7 of the GNU Affero GPL version 3, the following additional
** terms apply to the works covered under the License. These additional terms
** are non-permissive additional terms allowed under Section 7 of the GNU
** Affero GPL version 3 and may not be removed by you.
**
** 0. Attribution Requirement.
**
** You must preserve all legal notices or author attributions in the covered
** work or Appropriate Legal Notices displayed by works containing the covered
** work. You may not remove from the covered work any author or developer
** credit already included within the covered work.
**
** 1. No License To Use Trademarks.
**
** This license does not grant any license or rights to use the trademarks
** Golden Code, FWD, any Golden Code or FWD logo, or any other trademarks
** of Golden Code Development Corporation. You are not authorized to use the
** name Golden Code, FWD, or the names of any author or contributor, for
** publicity purposes without written authorization.
**
** 2. No Misrepresentation of Affiliation.
**
** You may not represent yourself as Golden Code Development Corporation or FWD.
**
** You may not represent yourself for publicity purposes as associated with
** Golden Code Development Corporation, FWD, or any author or contributor to
** the covered work, without written authorization.
**
** 3. No Misrepresentation of Source or Origin.
**
** You may not represent the covered work as solely your work. All modified
** versions of the covered work must be marked in a reasonable way to make it
** clear that the modified work is not originating from Golden Code Development
** Corporation or FWD. All modified versions must contain the notices of
** attribution required in this license.
*/
package com.goldencode.p2j.util;
import java.io.*;
/**
* Provides a Java <code>InputStream</code> which accesses a contained
* {@link Stream} instance. This allows classes that use the standard Java
* I/O features (in package <code>java.io.*</code>) to transparently use
* a P2J stream instead. That stream may be on a remote node.
*/
public class InputStreamWrapper
extends InputStream
{
/**
* The chunk to read at once from the remote {@link #stream}, via in the {@link #read(byte[], int, int)}
* implementation.
*/
private static final int READ_CHUNK_SIZE = 1024 * 1024; // 1MB
/** The contained stream that does our real work. */
private Stream stream = null;
/** The marked position in the stream. */
private long mark = -1;
/**
* Construct an instance which wrappers the given stream.
*
* @param stream
* The P2J stream to wrap.
*/
public InputStreamWrapper(Stream stream)
{
this.stream = stream;
}
/**
* Get the wrapped FWD stream.
*
* @return The {@link #stream}.
*/
public Stream getStream()
{
return stream;
}
/**
* Reads the next byte of data from the input stream. Although the byte is
* returned as a 32-bit <code>int</code>, the actual value will always be
* between 0 and 255 inclusive. When the end of the stream has been reached,
* -1 is returned.
* <p>
* The underlying stream subclass determines the content of the result.
* Byte oriented streams such as pipes or files will return a byte while
* streams that generate keystrokes or characters may return a DBCS or
* Unicode character. Any data that is greater in size than a byte will
* be truncated!
* <p>
* This method blocks waiting for the data, the end of the stream or some
* exceptional condition.
*
* @return The next byte of data or -1 when the end of the stream is
* reached.
*/
public int read()
throws IOException
{
if (stream == null)
{
return -1;
}
int result = stream.readByte();
switch (result)
{
case -1:
// error
throw new IOException("Failure during stream read.");
case -2:
// EOF
result = -1;
break;
}
return result;
}
/**
* Read a chunk of bytes from the current read position in the stream to the
* offset calculated by given length or to the <code>EOF</code>, whichever
* comes first. The <code>EOF</code> character is not returned.
*
* @param array
* The array in which to save bytes.
* @param off
* The offset into the array at which to start saving bytes.
* @param len
* The maximum number of bytes to read.
*
* @return The number of bytes read or -1 if <code>EOF</code> has been
* reached). The number of bytes read will be the smaller
* of the <code>len</code> parameter or the actual bytes left
* before the <code>EOF</code>.
*
* @throws IOException
* If an I/O error occurs.
*/
public int read(byte[] array, int off, int len)
throws IOException
{
if (stream == null)
{
return -1;
}
ByteArrayOutputStream baos = new ByteArrayOutputStream(len);
int remaining = len;
while (remaining > 0)
{
// read at least 1MB of data and at most the remaining bytes
byte[] chunk = stream.readBytes(Math.min(remaining, READ_CHUNK_SIZE));
if (chunk == null)
{
if (remaining == len)
{
// couldn't read anything
return -1;
}
// something was read, EOF reached
break;
}
remaining -= chunk.length;
baos.write(chunk);
}
byte[] data = baos.toByteArray();
System.arraycopy(data, 0, array, off, data.length);
return data.length;
}
/**
* Obtains an estimate of the number of bytes that can be read from this
* stream without blocking. This number is not reliable in an absolute
* sense, but it does specify a minimum that can be used.
*
* @return The minimum number of bytes immediately.
*/
public int available()
throws IOException
{
if (stream == null)
{
throw new IOException("Stream is not open.");
}
return (int) stream.available();
}
/**
* Closes the input stream and releases OS resources associated with it.
*/
public void close()
{
if (stream != null)
{
stream.closeIn();
stream = null;
}
}
/**
* Mark the current position in the stream.
*
* @param readlimit
* This argument is not used.
*/
@Override
public synchronized void mark(int readlimit)
{
try
{
mark = stream == null ? -1l : stream.getPos();
}
catch (UnsupportedOperationException |
IOException e)
{
mark = -1;
}
}
/**
* Reset the stream to the marked position.
*/
@Override
public synchronized void reset()
throws IOException
{
if (stream == null)
{
throw new IOException("Stream is not open.");
}
if (mark == -1)
{
throw new IOException("Stream is not marked.");
}
stream.setPos(mark);
}
/**
* Tests if this stream supports the mark mode.
*
* @return Always<code>true</code>.
*/
@Override
public boolean markSupported()
{
return true;
}
}