feat: Add LRUCache for font layout caching

Author: abihf

lib/font/embedded.js

@@ -1,3 +1,4 @@
+import { LRUCache } from 'lru-cache';
 import PDFFont from '../font';
 
 const toHex = function(num) {
@@ -24,7 +25,9 @@ class EmbeddedFont extends PDFFont {
     this.bbox = this.font.bbox;
 
     if (document.options.fontLayoutCache !== false) {
-      this.layoutCache = Object.create(null);
+      this.layoutCache = new LRUCache({ 
+        max: document.options.fontLayoutMaxCacheSize || 1000
+      });
     }
   }
 
@@ -49,12 +52,12 @@ class EmbeddedFont extends PDFFont {
       return this.layoutRun(text);
     }
     let cached;
-    if ((cached = this.layoutCache[text])) {
+    if ((cached = this.layoutCache.get(text))) {
       return cached;
     }
 
     const run = this.layoutRun(text);
-    this.layoutCache[text] = run;
+    this.layoutCache.set(text, run);
     return run;
   }
 

package.json

@@ -52,6 +52,7 @@
     "fontkit": "^1.8.1",
     "jpeg-exif": "^1.1.4",
     "linebreak": "^1.0.2",
+    "lru-cache": "^10.2.2",
     "png-js": "^1.0.0"
   },
   "scripts": {
@@ -89,4 +90,4 @@
       "<rootDir>/tests/unit/setupTests.js"
     ]
   }
-}
+}

yarn.lock

@@ -5016,6 +5016,11 @@ longest@^1.0.1:
   resolved "https://registry.yarnpkg.com/longest/-/longest-1.0.1.tgz#30a0b2da38f73770e8294a0d22e6625ed77d0097"
   integrity sha1-MKCy2jj3N3DoKUoNIuZiXtd9AJc=
 
+lru-cache@^10.2.2:
+  version "10.2.2"
+  resolved "https://registry.yarnpkg.com/lru-cache/-/lru-cache-10.2.2.tgz#48206bc114c1252940c41b25b41af5b545aca878"
+  integrity sha512-9hp3Vp2/hFQUiIwKo8XCeFVnrg8Pk3TYNPIR7tJADKi5YfcF7vEaK7avFHTlSy3kOKYaJQaalfEo6YuXdceBOQ==
+
 lru-cache@^5.1.1:
   version "5.1.1"
   resolved "https://registry.yarnpkg.com/lru-cache/-/lru-cache-5.1.1.tgz#1da27e6710271947695daf6848e847f01d84b920"