com.itextpdf.kernel.pdf.MemoryLimitsAwareHandler Maven / Gradle / Ivy
/*
This file is part of the iText (R) project.
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Authors: iText Software.
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
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*/
package com.itextpdf.kernel.pdf;
import com.itextpdf.kernel.exceptions.KernelExceptionMessageConstant;
import com.itextpdf.kernel.exceptions.MemoryLimitsAwareException;
import java.util.HashSet;
/**
* A {@link MemoryLimitsAwareHandler} handles memory allocation and prevents decompressed
* pdf streams from occupation of more space than allowed.
*
* A configured MemoryLimitsAwareHandler can be set as a property of {@link ReaderProperties}
* instance which is passed to {@link PdfReader}.
*
* @see ReaderProperties#setMemoryLimitsAwareHandler(MemoryLimitsAwareHandler)
*/
public class MemoryLimitsAwareHandler {
private static final int SINGLE_SCALE_COEFFICIENT = 100;
private static final int SUM_SCALE_COEFFICIENT = 500;
private static final int MAX_NUMBER_OF_ELEMENTS_IN_XREF_STRUCTURE = 50000000;
private static final int SINGLE_DECOMPRESSED_PDF_STREAM_MIN_SIZE = Integer.MAX_VALUE / 100;
private static final long SUM_OF_DECOMPRESSED_PDF_STREAMS_MIN_SIZE = Integer.MAX_VALUE / 20;
private int maxSizeOfSingleDecompressedPdfStream;
private long maxSizeOfDecompressedPdfStreamsSum;
private int maxNumberOfElementsInXrefStructure;
private long allMemoryUsedForDecompression = 0;
private long memoryUsedForCurrentPdfStreamDecompression = 0;
boolean considerCurrentPdfStream = false;
/**
* Creates a {@link MemoryLimitsAwareHandler} which will be used to handle decompression of pdf streams.
* The max allowed memory limits will be generated by default.
*/
public MemoryLimitsAwareHandler() {
this(SINGLE_DECOMPRESSED_PDF_STREAM_MIN_SIZE, SUM_OF_DECOMPRESSED_PDF_STREAMS_MIN_SIZE,
MAX_NUMBER_OF_ELEMENTS_IN_XREF_STRUCTURE);
}
/**
* Creates a {@link MemoryLimitsAwareHandler} which will be used to handle decompression of pdf streams.
* The max allowed memory limits will be generated by default, based on the size of the document.
*
* @param documentSize the size of the document, which is going to be handled by iText.
*/
public MemoryLimitsAwareHandler(long documentSize) {
this((int) calculateDefaultParameter(documentSize, SINGLE_SCALE_COEFFICIENT,
SINGLE_DECOMPRESSED_PDF_STREAM_MIN_SIZE), calculateDefaultParameter(documentSize, SUM_SCALE_COEFFICIENT,
SUM_OF_DECOMPRESSED_PDF_STREAMS_MIN_SIZE), MAX_NUMBER_OF_ELEMENTS_IN_XREF_STRUCTURE);
}
private MemoryLimitsAwareHandler(int maxSizeOfSingleDecompressedPdfStream, long maxSizeOfDecompressedPdfStreamsSum,
int maxNumberOfElementsInXrefStructure) {
this.maxSizeOfSingleDecompressedPdfStream = maxSizeOfSingleDecompressedPdfStream;
this.maxSizeOfDecompressedPdfStreamsSum = maxSizeOfDecompressedPdfStreamsSum;
this.maxNumberOfElementsInXrefStructure = maxNumberOfElementsInXrefStructure;
}
/**
* Gets the maximum allowed size which can be occupied by a single decompressed pdf stream.
*
* @return the maximum allowed size which can be occupied by a single decompressed pdf stream.
*/
public int getMaxSizeOfSingleDecompressedPdfStream() {
return maxSizeOfSingleDecompressedPdfStream;
}
/**
* Sets the maximum allowed size which can be occupied by a single decompressed pdf stream.
* This value correlates with maximum heap size. This value should not exceed limit of the heap size.
*
*
iText will throw an exception if during decompression a pdf stream which was identified as
* requiring memory limits awareness occupies more memory than allowed.
*
* @param maxSizeOfSingleDecompressedPdfStream the maximum allowed size which can be occupied by a single
* decompressed pdf stream.
* @return this {@link MemoryLimitsAwareHandler} instance.
* @see MemoryLimitsAwareHandler#isMemoryLimitsAwarenessRequiredOnDecompression(PdfArray)
*/
public MemoryLimitsAwareHandler setMaxSizeOfSingleDecompressedPdfStream(int maxSizeOfSingleDecompressedPdfStream) {
this.maxSizeOfSingleDecompressedPdfStream = maxSizeOfSingleDecompressedPdfStream;
return this;
}
/**
* Gets the maximum allowed size which can be occupied by all decompressed pdf streams.
*
* @return the maximum allowed size value which streams may occupy
*/
public long getMaxSizeOfDecompressedPdfStreamsSum() {
return maxSizeOfDecompressedPdfStreamsSum;
}
/**
* Sets the maximum allowed size which can be occupied by all decompressed pdf streams.
* This value can be limited by the maximum expected PDF file size when it's completely decompressed.
* Setting this value correlates with the maximum processing time spent on document reading
*
*
iText will throw an exception if during decompression pdf streams which were identified as
* requiring memory limits awareness occupy more memory than allowed.
*
* @param maxSizeOfDecompressedPdfStreamsSum he maximum allowed size which can be occupied by all decompressed pdf
* streams.
* @return this {@link MemoryLimitsAwareHandler} instance.
* @see MemoryLimitsAwareHandler#isMemoryLimitsAwarenessRequiredOnDecompression(PdfArray)
*/
public MemoryLimitsAwareHandler setMaxSizeOfDecompressedPdfStreamsSum(long maxSizeOfDecompressedPdfStreamsSum) {
this.maxSizeOfDecompressedPdfStreamsSum = maxSizeOfDecompressedPdfStreamsSum;
return this;
}
/**
* Performs a check if the {@link PdfStream} with provided setup of the filters requires
* memory limits awareness during decompression.
*
* @param filters is an {@link PdfArray} of names of filters
* @return true if PDF stream is suspicious and false otherwise
*/
public boolean isMemoryLimitsAwarenessRequiredOnDecompression(PdfArray filters) {
final HashSet filterSet = new HashSet<>();
for (int index = 0; index < filters.size(); index++) {
final PdfName filterName = filters.getAsName(index);
if (!filterSet.add(filterName)) {
return true;
}
}
return false;
}
/**
* Gets maximum number of elements in xref structure.
*
* @return maximum number of elements in xref structure.
*/
public int getMaxNumberOfElementsInXrefStructure() {
return maxNumberOfElementsInXrefStructure;
}
/**
* Sets maximum number of elements in xref structure.
*
* @param maxNumberOfElementsInXrefStructure maximum number of elements in xref structure.
*/
public void setMaxNumberOfElementsInXrefStructure(int maxNumberOfElementsInXrefStructure) {
this.maxNumberOfElementsInXrefStructure = maxNumberOfElementsInXrefStructure;
}
/**
* Performs a check of possible extension of xref structure.
*
* @param requestedCapacity capacity to which we need to expand xref array.
*/
public void checkIfXrefStructureExceedsTheLimit(int requestedCapacity) {
// Objects in xref structures are using 1-based indexes, so to store maxNumberOfElementsInXrefStructure
// amount of elements we need maxNumberOfElementsInXrefStructure + 1 capacity.
if (requestedCapacity - 1 > maxNumberOfElementsInXrefStructure) {
throw new MemoryLimitsAwareException(KernelExceptionMessageConstant.XREF_STRUCTURE_SIZE_EXCEEDED_THE_LIMIT);
}
}
/**
* Considers the number of bytes which are occupied by the decompressed pdf stream.
* If memory limits have not been faced, throws an exception.
*
* @param numOfOccupiedBytes the number of bytes which are occupied by the decompressed pdf stream.
* @return this {@link MemoryLimitsAwareHandler} instance.
* @see MemoryLimitsAwareException
*/
MemoryLimitsAwareHandler considerBytesOccupiedByDecompressedPdfStream(long numOfOccupiedBytes) {
if (considerCurrentPdfStream && memoryUsedForCurrentPdfStreamDecompression < numOfOccupiedBytes) {
memoryUsedForCurrentPdfStreamDecompression = numOfOccupiedBytes;
if (memoryUsedForCurrentPdfStreamDecompression > maxSizeOfSingleDecompressedPdfStream) {
throw new MemoryLimitsAwareException(
KernelExceptionMessageConstant.DURING_DECOMPRESSION_SINGLE_STREAM_OCCUPIED_MORE_MEMORY_THAN_ALLOWED);
}
}
return this;
}
/**
* Begins handling of current pdf stream decompression.
*
* @return this {@link MemoryLimitsAwareHandler} instance.
*/
MemoryLimitsAwareHandler beginDecompressedPdfStreamProcessing() {
ensureCurrentStreamIsReset();
considerCurrentPdfStream = true;
return this;
}
/**
* Ends handling of current pdf stream decompression.
* If memory limits have not been faced, throws an exception.
*
* @return this {@link MemoryLimitsAwareHandler} instance.
* @see MemoryLimitsAwareException
*/
MemoryLimitsAwareHandler endDecompressedPdfStreamProcessing() {
allMemoryUsedForDecompression += memoryUsedForCurrentPdfStreamDecompression;
if (allMemoryUsedForDecompression > maxSizeOfDecompressedPdfStreamsSum) {
throw new MemoryLimitsAwareException(
KernelExceptionMessageConstant.DURING_DECOMPRESSION_MULTIPLE_STREAMS_IN_SUM_OCCUPIED_MORE_MEMORY_THAN_ALLOWED);
}
ensureCurrentStreamIsReset();
considerCurrentPdfStream = false;
return this;
}
long getAllMemoryUsedForDecompression() {
return allMemoryUsedForDecompression;
}
private static long calculateDefaultParameter(long documentSize, int scale, long min) {
long result = documentSize * scale;
if (result < min) {
result = min;
}
if (result > min * scale) {
result = min * scale;
}
return result;
}
private void ensureCurrentStreamIsReset() {
memoryUsedForCurrentPdfStreamDecompression = 0;
}
}