fix subset bug

Author: nicolaasuni

VERSION

@@ -1 +1 @@
-2.7.0
+2.7.1

src/Subset.php

@@ -243,10 +243,16 @@ public function getSubsetFont(): string
     protected function getTableChecksum(string $table, int $length): int
     {
         $sum = 0;
-        $tlen = ($length / 4);
+        $tlen = (int) floor(($length + 3) / 4);
         $offset = 0;
         for ($idx = 0; $idx < $tlen; ++$idx) {
-            $val = \unpack('Ni', \substr($table, $offset, 4));
+            $chunk = \substr($table, $offset, 4);
+            if (\strlen($chunk) < 4) {
+                // OpenType checksums use zero-padding for trailing partial words.
+                $chunk = \str_pad($chunk, 4, "\0", STR_PAD_RIGHT);
+            }
+
+            $val = \unpack('Ni', $chunk);
             if ($val === false) {
                 throw new FontException('Unable to unpack table data');
             }

test/SubsetTest.php

@@ -0,0 +1,66 @@
+<?php
+
+/**
+ * SubsetTest.php
+ *
+ * @since     2026-05-01
+ * @category  Library
+ * @package   PdfFont
+ * @author    Nicola Asuni <info@tecnick.com>
+ * @copyright 2011-2026 Nicola Asuni - Tecnick.com LTD
+ * @license   https://www.gnu.org/copyleft/lesser.html GNU-LGPL v3 (see LICENSE.TXT)
+ * @link      https://github.com/tecnickcom/tc-lib-pdf-font
+ *
+ * This file is part of tc-lib-pdf-font software library.
+ */
+
+namespace Test;
+
+/**
+ * Subset Test
+ *
+ * @since     2026-05-01
+ * @category  Library
+ * @package   PdfFont
+ * @author    Nicola Asuni <info@tecnick.com>
+ * @copyright 2011-2026 Nicola Asuni - Tecnick.com LTD
+ * @license   https://www.gnu.org/copyleft/lesser.html GNU-LGPL v3 (see LICENSE.TXT)
+ * @link      https://github.com/tecnickcom/tc-lib-pdf-font
+ */
+class SubsetTest extends TestUtil
+{
+    public function testTableChecksumPadsTrailingBytes(): void
+    {
+        $subset = new class () extends \Com\Tecnick\Pdf\Font\Subset {
+            public function __construct()
+            {
+            }
+
+            public function checksum(string $table, int $length): int
+            {
+                return $this->getTableChecksum($table, $length);
+            }
+        };
+
+        // 3-byte table must be zero-padded to a 4-byte word before summing.
+        $this->assertSame(0x01020300, $subset->checksum("\x01\x02\x03", 3));
+    }
+
+    public function testTableChecksumHandlesMixedFullAndPartialWords(): void
+    {
+        $subset = new class () extends \Com\Tecnick\Pdf\Font\Subset {
+            public function __construct()
+            {
+            }
+
+            public function checksum(string $table, int $length): int
+            {
+                return $this->getTableChecksum($table, $length);
+            }
+        };
+
+        $table = "\x11\x22\x33\x44\x55\x66\x77";
+        // 0x11223344 + 0x55667700, modulo 2^32
+        $this->assertSame(0x6688AA44, $subset->checksum($table, 7));
+    }
+}