Speed up usage of differences by caching any encountered codepoints (20%-25% speed improvements on samples with differences arrays)

Author: PrinsFrank

src/Document/ContentStream/PositionedText/TextSegment/TextSegment.php

@@ -17,7 +17,7 @@ public function __construct(
     public function getText(?DifferencesArrayValue $differences, ?EncodingNameValue $encoding, ?ToUnicodeCMap $toUnicodeCMap): string {
         $binaryString = $this->textString->getBinaryString();
         if (strlen($binaryString) === 1 && ($glyph = $differences?->getGlyph(ord($binaryString))) !== null) {
-            $text = $glyph->getChar();
+            $text = $glyph;
         } elseif (in_array($encoding, [EncodingNameValue::MacExpertEncoding, EncodingNameValue::WinAnsiEncoding], true)
             && $differences === null) {
             $text = $encoding->decodeString($binaryString);

src/Document/Dictionary/DictionaryValue/Array/DifferencesArrayValue.php

@@ -9,6 +9,9 @@
 use PrinsFrank\PdfParser\Document\Dictionary\DictionaryValue\Reference\ReferenceValueArray;
 
 class DifferencesArrayValue implements DictionaryValue {
+    /** @var array<int, string|null> */
+    private array $glyphCache = [];
+
     /** @param list<DifferenceRange> $differenceRanges */
     public function __construct(
         private readonly array $differenceRanges,
@@ -44,13 +47,17 @@ public static function fromValue(string $valueString): ?self {
         return new self($differenceRanges);
     }
 
-    public function getGlyph(int $int): ?AGlyphList {
+    public function getGlyph(int $codePoint): ?string {
+        if (array_key_exists($codePoint, $this->glyphCache)) {
+            return $this->glyphCache[$codePoint];
+        }
+
         foreach ($this->differenceRanges as $differenceRange) {
-            if ($differenceRange->contains($int)) {
-                return $differenceRange->getGlyph($int);
+            if ($differenceRange->contains($codePoint)) {
+                return $this->glyphCache[$codePoint] = $differenceRange->getGlyph($codePoint)?->getChar();
             }
         }
 
-        return null;
+        return $this->glyphCache[$codePoint] = null;
     }
 }

tests/Unit/Document/Dictionary/DictionaryValue/Array/DifferencesArrayValueTest.php

@@ -36,7 +36,7 @@ public function testFromValue(): void {
 
     public function testGetGlyph(): void {
         static::assertSame(
-            AglyphList::grave,
+            "\u{0060}",
             (new DifferencesArrayValue([new DifferenceRange(36, [AGlyphList::grave])]))
                 ->getGlyph(36),
         );