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/*
This file is part of the iText (R) project.
Copyright (c) 1998-2022 iText Group NV
Authors: Bruno Lowagie, Paulo Soares, et al.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU Affero General Public License version 3
as published by the Free Software Foundation with the addition of the
following permission added to Section 15 as permitted in Section 7(a):
FOR ANY PART OF THE COVERED WORK IN WHICH THE COPYRIGHT IS OWNED BY
ITEXT GROUP. ITEXT GROUP DISCLAIMS THE WARRANTY OF NON INFRINGEMENT
OF THIRD PARTY RIGHTS
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 should have received a copy of the GNU Affero General Public License
along with this program; if not, see http://www.gnu.org/licenses or write to
the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
Boston, MA, 02110-1301 USA, or download the license from the following URL:
http://itextpdf.com/terms-of-use/
The interactive user interfaces in modified source and object code versions
of this program must display Appropriate Legal Notices, as required under
Section 5 of the GNU Affero General Public License.
In accordance with Section 7(b) of the GNU Affero General Public License,
a covered work must retain the producer line in every PDF that is created
or manipulated using iText.
You can be released from the requirements of the license by purchasing
a commercial license. Buying such a license is mandatory as soon as you
develop commercial activities involving the iText software without
disclosing the source code of your own applications.
These activities include: offering paid services to customers as an ASP,
serving PDFs on the fly in a web application, shipping iText with a closed
source product.
For more information, please contact iText Software Corp. at this
address: [email protected]
*/
package com.itextpdf.io.source;
import com.itextpdf.io.logs.IoLogMessageConstant;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import java.nio.channels.FileChannel;
import java.util.Iterator;
import java.util.LinkedList;
/**
* A RandomAccessSource that is based on an underlying {@link java.nio.channels.FileChannel}. The channel is mapped into memory using a paging scheme to allow for efficient reads of very large files.
* As an implementation detail, we use {@link GroupedRandomAccessSource} functionality, but override to make determination of the underlying
* mapped page more efficient - and to close each page as another is opened
*/
class PagedChannelRandomAccessSource extends GroupedRandomAccessSource implements IRandomAccessSource {
// these values were selected based on parametric testing with extracting text content from a 2.3GB file. These settings resulted in the best improvement over
// the single size MRU case (24% speed improvement)
public static final int DEFAULT_TOTAL_BUFSIZE = 1 << 26;
public static final int DEFAULT_MAX_OPEN_BUFFERS = 16;
/**
* The size of each of the buffers to use when mapping files into memory. This must be greater than 0 and less than {@link Integer#MAX_VALUE}
*/
private final int bufferSize;
/**
* The channel this source is based on
*/
private final FileChannel channel;
/**
* Most recently used list used to hold a number of mapped pages open at a time
*/
private final MRU mru;
/**
* Constructs a new {@link PagedChannelRandomAccessSource} based on the specified FileChannel, with a default buffer configuration.
* The default buffer configuration is currently 2^26 total paged bytes, spread across a maximum of 16 active buffers. This arrangement
* resulted in a 24% speed improvement over the single buffer case in parametric tests extracting text from a 2.3 GB file.
* @param channel the channel to use as the backing store
* @throws java.io.IOException if the channel cannot be opened or mapped
*/
public PagedChannelRandomAccessSource(FileChannel channel) throws java.io.IOException {
this(channel, DEFAULT_TOTAL_BUFSIZE, DEFAULT_MAX_OPEN_BUFFERS);
}
/**
* Constructs a new {@link PagedChannelRandomAccessSource} based on the specified FileChannel, with a specific buffer size
* @param channel the channel to use as the backing store
* @param totalBufferSize total buffer size
* @param maxOpenBuffers open buffers
* @throws java.io.IOException if the channel cannot be opened or mapped
*/
public PagedChannelRandomAccessSource(FileChannel channel, int totalBufferSize, int maxOpenBuffers) throws java.io.IOException {
super(buildSources(channel, totalBufferSize/maxOpenBuffers));
this.channel = channel;
this.bufferSize = totalBufferSize/maxOpenBuffers;
this.mru = new MRU(maxOpenBuffers);
}
/**
* Constructs a set of {@link MappedChannelRandomAccessSource}s for each page (of size bufferSize) of the underlying channel
* @param channel the underlying channel
* @param bufferSize the size of each page (the last page may be shorter)
* @return a list of sources that represent the pages of the channel
* @throws java.io.IOException if IO fails for any reason
*/
private static IRandomAccessSource[] buildSources(FileChannel channel, int bufferSize) throws java.io.IOException{
long size = channel.size();
if (size <= 0)
throw new java.io.IOException("File size must be greater than zero");
int bufferCount = (int)(size/bufferSize) + (size % bufferSize == 0 ? 0 : 1);
MappedChannelRandomAccessSource[] sources = new MappedChannelRandomAccessSource[bufferCount];
for (int i = 0; i < bufferCount; i++){
long pageOffset = (long)i*bufferSize;
long pageLength = Math.min(size - pageOffset, bufferSize);
sources[i] = new MappedChannelRandomAccessSource(channel, pageOffset, pageLength);
}
return sources;
}
/**
* {@inheritDoc}
*/
@Override
protected int getStartingSourceIndex(long offset) {
return (int) (offset / bufferSize);
}
/**
* {@inheritDoc}
* For now, close the source that is no longer being used. In the future, we may implement an MRU that allows multiple pages to be opened at a time
*/
@Override
protected void sourceReleased(IRandomAccessSource source) throws java.io.IOException {
IRandomAccessSource old = mru.enqueue(source);
if (old != null)
old.close();
}
/**
* {@inheritDoc}
* Ensure that the source is mapped. In the future, we may implement an MRU that allows multiple pages to be opened at a time
*/
@Override
protected void sourceInUse(IRandomAccessSource source) throws java.io.IOException {
((MappedChannelRandomAccessSource)source).open();
}
/**
* {@inheritDoc}
* Cleans the mapped bytebuffers and closes the channel
*/
@Override
public void close() throws java.io.IOException {
try {
super.close();
} finally {
try {
channel.close();
} catch (Exception ex) {
Logger logger = LoggerFactory.getLogger(PagedChannelRandomAccessSource.class);
logger.error(IoLogMessageConstant.FILE_CHANNEL_CLOSING_FAILED, ex);
}
}
}
private static class MRU {
/**
* The maximum number of entries held by this MRU
*/
private final int limit;
/**
* Backing list for managing the MRU
*/
private LinkedList queue = new LinkedList<>();
/**
* Constructs an MRU with the specified size
* @param limit the limit
*/
public MRU(int limit) {
this.limit = limit;
}
/**
* Adds an element to the MRU. If the element is already in the MRU, it is moved to the top.
* @param newElement the element to add
* @return the element that was removed from the MRU to make room for the new element, or null if no element needed to be removed
*/
public E enqueue(E newElement){
// TODO: this check may not be an effective optimization - the GroupedRandomAccessSource already tracks the 'current' source, so it seems unlikely that we would ever hit this code branch
if (queue.size() > 0 && queue.getFirst() == newElement)
return null;
for(Iterator it = queue.iterator(); it.hasNext();){
E element = it.next();
if (newElement == element){
it.remove();
queue.addFirst(newElement);
return null;
}
}
queue.addFirst(newElement);
if (queue.size() > limit)
return queue.removeLast();
return null;
}
}
}
