fix: check that the previous xref is not the just processed xref (#727)

* fix: check that that previous xref is not the just processed xref * test: add unit test for Issue 727 * fix: code style issue * Update tests/PHPUnit/Integration/RawData/RawDataParserTest.php Co-authored-by: Konrad Abicht <[email protected]> --------- Co-authored-by: Konrad Abicht <[email protected]>
smalot · Aug 16, 2024 · ac8e667 · ac8e667
1 parent 7964d2e
commit ac8e667
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Showing 4 changed files with 25 additions and 3 deletions.
diff --git a/samples/bugs/Issue727.pdf b/samples/bugs/Issue727.pdf
diff --git a/src/Smalot/PdfParser/RawData/FilterHelper.php b/src/Smalot/PdfParser/RawData/FilterHelper.php
@@ -282,7 +282,7 @@ protected function decodeFilterLZWDecode(string $data): string
         // convert string to binary string
         $bitstring = '';
         for ($i = 0; $i < $data_length; ++$i) {
-            $bitstring .= sprintf('%08b', \ord($data[$i]));
+            $bitstring .= \sprintf('%08b', \ord($data[$i]));
         }
         // get the number of bits
         $data_length = \strlen($bitstring);

diff --git a/src/Smalot/PdfParser/RawData/RawDataParser.php b/src/Smalot/PdfParser/RawData/RawDataParser.php
@@ -214,8 +214,11 @@ protected function decodeXref(string $pdfData, int $startxref, array $xref = [])
                 }
             }
             if (preg_match('/Prev[\s]+([0-9]+)/i', $trailer_data, $matches) > 0) {
-                // get previous xref
-                $xref = $this->getXrefData($pdfData, (int) $matches[1], $xref);
+                $offset = (int) $matches[1];
+                if (0 != $offset) {
+                    // get previous xref
+                    $xref = $this->getXrefData($pdfData, $offset, $xref);
+                }
             }
         } else {
             throw new \Exception('Unable to find trailer');

diff --git a/tests/PHPUnit/Integration/RawData/RawDataParserTest.php b/tests/PHPUnit/Integration/RawData/RawDataParserTest.php
@@ -194,4 +194,23 @@ public function testGetXrefDataIssue673(): void
 
         self::assertStringContainsString('6 rue des Goutais', $text);
     }
+
+    /**
+     * Handle self referencing xref
+     *
+     * It seems that some PDF creators output `Prev 0` when there is no previous xref.
+     *
+     * @see https://github.com/smalot/pdfparser/pull/727
+     */
+    public function testDecodeXrefIssue727(): void
+    {
+        $filename = $this->rootDir.'/samples/bugs/Issue727.pdf';
+
+        // Parsing this document would previously cause an infinite loop
+        $parser = $this->getParserInstance();
+        $document = $parser->parseFile($filename);
+        $text = $document->getText();
+
+        self::assertStringContainsString('', $text);
+    }
 }