Recover byte offsets from raw stream when cross reference source is corrupt

src/Document/CrossReference/CrossReferenceSourceParser.php

@@ -3,7 +3,9 @@
 
 namespace PrinsFrank\PdfParser\Document\CrossReference;
 
+use PrinsFrank\PdfParser\Document\CrossReference\RawStream\ObjectPositionsFromRawStreamParser;
 use PrinsFrank\PdfParser\Document\CrossReference\Source\CrossReferenceSource;
+use PrinsFrank\PdfParser\Document\CrossReference\Source\RecoveredCrossReferenceSource;
 use PrinsFrank\PdfParser\Document\CrossReference\Stream\CrossReferenceStreamParser;
 use PrinsFrank\PdfParser\Document\CrossReference\Table\CrossReferenceTableParser;
 use PrinsFrank\PdfParser\Document\Dictionary\DictionaryKey\DictionaryKey;
@@ -80,7 +82,15 @@ public static function parse(Stream $stream): CrossReferenceSource {
             $crossReferenceSections[] = $currentCrossReferenceSection;
         }
 
-        return new CrossReferenceSource(... $crossReferenceSections);
+        $crossReferenceSource = new CrossReferenceSource(... $crossReferenceSections);
+        if ($crossReferenceSource->hasInvalidByteOffset($stream)) {
+            return new RecoveredCrossReferenceSource(
+                ObjectPositionsFromRawStreamParser::parse($stream),
+                ...$crossReferenceSections,
+            );
+        }
+
+        return $crossReferenceSource;
     }
 
     private static function getCrossReferenceType(Stream $stream, int $byteOffsetLastCrossReferenceSection, int $byteOffsetEndOfCurrentLine): ?CrossReferenceType {

src/Document/CrossReference/RawStream/ObjectPositionsFromRawStreamParser.php

@@ -0,0 +1,67 @@
+<?php declare(strict_types=1);
+
+namespace PrinsFrank\PdfParser\Document\CrossReference\RawStream;
+
+use PrinsFrank\PdfParser\Stream\Stream;
+
+class ObjectPositionsFromRawStreamParser {
+    /** @return array<int, int> */
+    public static function parse(Stream $stream): array {
+        $inObjNr = $inObjGenerationNumber = $pendingObjMarker = false;
+        $startObjNrOffset = $objNrBuffer = $objMarkerBuffer = null;
+        $discoveredObjects = [];
+        foreach ($stream->chars(0, $stream->getSizeInBytes()) as $byteOffset => $char) {
+            if ($char === ' ') {
+                if ($inObjNr === true) {
+                    $inObjNr = false;
+                    $inObjGenerationNumber = true;
+                } elseif ($inObjGenerationNumber === true) {
+                    $inObjGenerationNumber = false;
+                    $pendingObjMarker = true;
+                } else {
+                    $inObjNr = $inObjGenerationNumber = $pendingObjMarker = false;
+                    $startObjNrOffset = $objNrBuffer = $objMarkerBuffer = null;
+                }
+            } else if ($char === '0'
+                || $char === '1'
+                || $char === '2'
+                || $char === '3'
+                || $char === '4'
+                || $char === '5'
+                || $char === '6'
+                || $char === '7'
+                || $char === '8'
+                || $char === '9') {
+                if ($pendingObjMarker === true) {
+                    $pendingObjMarker = false;
+                    $objNrBuffer = null;
+                } elseif ($inObjGenerationNumber === true) {
+                } elseif ($inObjNr === false) {
+                    $inObjNr = true;
+                    $startObjNrOffset = $byteOffset;
+                    $objNrBuffer = $char;
+                } elseif ($inObjNr === true) {
+                    $objNrBuffer .= $char;
+                }
+            } elseif ($pendingObjMarker === true) {
+                if ($objMarkerBuffer === null && $char === 'o') {
+                    $objMarkerBuffer = $char;
+                } elseif ($objMarkerBuffer === 'o' && $char === 'b') {
+                    $objMarkerBuffer .= $char;
+                } elseif ($objMarkerBuffer === 'ob' && $char === 'j') {
+                    $discoveredObjects[$startObjNrOffset] = (int) $objNrBuffer;
+                    $inObjNr = $inObjGenerationNumber = $pendingObjMarker = false;
+                    $startObjNrOffset = $objNrBuffer = $objMarkerBuffer = null;
+                } else {
+                    $inObjNr = $inObjGenerationNumber = $pendingObjMarker = false;
+                    $startObjNrOffset = $objNrBuffer = $objMarkerBuffer = null;
+                }
+            } else {
+                $inObjNr = $inObjGenerationNumber = $pendingObjMarker = false;
+                $startObjNrOffset = $objNrBuffer = $objMarkerBuffer = null;
+            }
+        }
+
+        return $discoveredObjects;
+    }
+}

src/Document/CrossReference/Source/CrossReferenceSource.php

@@ -13,6 +13,7 @@
 use PrinsFrank\PdfParser\Document\Dictionary\DictionaryValue\Name\NameValue;
 use PrinsFrank\PdfParser\Document\Dictionary\DictionaryValue\Reference\ReferenceValue;
 use PrinsFrank\PdfParser\Exception\ParseFailureException;
+use PrinsFrank\PdfParser\Stream\Stream;
 
 /** Can be both from a crossReferenceTable or a crossReferenceStream */
 class CrossReferenceSource {
@@ -75,4 +76,14 @@ public function getFirstId(): string {
 
         return $firstId;
     }
+
+    public function hasInvalidByteOffset(Stream $stream): bool {
+        foreach ($this->crossReferenceSections as $crossReferenceSection) {
+            if ($crossReferenceSection->hasInvalidByteOffset($stream)) {
+                return true;
+            }
+        }
+
+        return false;
+    }
 }

src/Document/CrossReference/Source/RecoveredCrossReferenceSource.php

@@ -0,0 +1,30 @@
+<?php declare(strict_types=1);
+
+namespace PrinsFrank\PdfParser\Document\CrossReference\Source;
+
+use PrinsFrank\PdfParser\Document\CrossReference\Source\Section\CrossReferenceSection;
+use PrinsFrank\PdfParser\Document\CrossReference\Source\Section\SubSection\Entry\CrossReferenceEntryCompressed;
+use PrinsFrank\PdfParser\Document\CrossReference\Source\Section\SubSection\Entry\CrossReferenceEntryInUseObject;
+
+class RecoveredCrossReferenceSource extends CrossReferenceSource {
+    /**
+     * @param array<int, int> $recoveredByteOffsetMap where the key is the byte offset and the value the object nr
+     * @no-named-arguments
+     */
+    public function __construct(
+        private array $recoveredByteOffsetMap,
+        CrossReferenceSection... $crossReferenceSections,
+    ) {
+        parent::__construct(...$crossReferenceSections);
+    }
+
+    public function getCrossReferenceEntry(int $objNumber): CrossReferenceEntryInUseObject|CrossReferenceEntryCompressed|null {
+        foreach ($this->recoveredByteOffsetMap as $byteOffset => $recoveredObjNr) {
+            if ($recoveredObjNr === $objNumber) {
+                return new CrossReferenceEntryInUseObject($byteOffset, 0);
+            }
+        }
+
+        return parent::getCrossReferenceEntry($objNumber);
+    }
+}

src/Document/CrossReference/Source/Section/CrossReferenceSection.php

@@ -6,6 +6,7 @@
 use PrinsFrank\PdfParser\Document\CrossReference\Source\Section\SubSection\Entry\CrossReferenceEntryCompressed;
 use PrinsFrank\PdfParser\Document\CrossReference\Source\Section\SubSection\Entry\CrossReferenceEntryInUseObject;
 use PrinsFrank\PdfParser\Document\Dictionary\Dictionary;
+use PrinsFrank\PdfParser\Stream\Stream;
 
 /** There are multiple crossReference sections if there are incremental updates. See 7.5.6 */
 readonly class CrossReferenceSection {
@@ -29,4 +30,14 @@ public function getCrossReferenceEntry(int $objNumber): CrossReferenceEntryInUse
 
         return null;
     }
+
+    public function hasInvalidByteOffset(Stream $stream): bool {
+        foreach ($this->crossReferenceSubSections as $crossReferenceSubSection) {
+            if ($crossReferenceSubSection->hasInvalidByteOffset($stream)) {
+                return true;
+            }
+        }
+
+        return false;
+    }
 }

src/Document/CrossReference/Source/Section/SubSection/CrossReferenceSubSection.php

@@ -8,6 +8,7 @@
 use PrinsFrank\PdfParser\Document\CrossReference\Source\Section\SubSection\Entry\CrossReferenceEntryInUseObject;
 use PrinsFrank\PdfParser\Exception\InvalidArgumentException;
 use PrinsFrank\PdfParser\Exception\RuntimeException;
+use PrinsFrank\PdfParser\Stream\Stream;
 
 readonly class CrossReferenceSubSection {
     /** @var array<CrossReferenceEntryInUseObject|CrossReferenceEntryFreeObject|CrossReferenceEntryCompressed> */
@@ -51,4 +52,24 @@ public function getCrossReferenceEntry(int $objNumber): CrossReferenceEntryInUse
 
         return $object;
     }
+
+    public function hasInvalidByteOffset(Stream $stream): bool {
+        foreach ($this->crossReferenceEntries as $index => $crossReferenceEntry) {
+            if ($crossReferenceEntry instanceof CrossReferenceEntryInUseObject === false) {
+                continue;
+            }
+
+            if ($crossReferenceEntry->byteOffsetInDecodedStream > $stream->getSizeInBytes()) {
+                return true;
+            }
+
+            $objNumber = $this->firstObjectNumber + $index;
+            $expectedObjMarker = $objNumber . ' ' . $crossReferenceEntry->generationNumber . ' obj';
+            if ($stream->read($crossReferenceEntry->byteOffsetInDecodedStream, strlen($expectedObjMarker)) !== $expectedObjMarker) {
+                return true;
+            }
+        }
+
+        return false;
+    }
 }

tests/Unit/Document/CrossReference/RawStream/ObjectPositionsFromRawStreamParserTest.php

@@ -0,0 +1,34 @@
+<?php declare(strict_types=1);
+
+namespace PrinsFrank\PdfParser\Tests\Unit\Document\CrossReference\RawStream;
+
+use PHPUnit\Framework\Attributes\CoversClass;
+use PHPUnit\Framework\TestCase;
+use PrinsFrank\PdfParser\Document\CrossReference\RawStream\ObjectPositionsFromRawStreamParser;
+use PrinsFrank\PdfParser\Stream\InMemoryStream;
+
+#[CoversClass(ObjectPositionsFromRawStreamParser::class)]
+class ObjectPositionsFromRawStreamParserTest extends TestCase {
+    public function testParse(): void {
+        static::assertSame(
+            [
+                10 => 1,
+                42 => 1232131,
+            ],
+            ObjectPositionsFromRawStreamParser::parse(
+                new InMemoryStream(
+                    <<<PDF
+                    %%PDF-1.7
+                    1 0 obj
+                    4 0 4 0 testobj
+                    endobj
+
+                    1232131 0 obj
+                    endobj
+
+                    PDF
+                )
+            )
+        );
+    }
+}