Reduce function creation when using Map.prototype.getOrInsertComputed()

With the exception of the first invocation the callback function is unused, which means that a lot of pointless functions may be created.
To avoid this we introduce helper functions for simple cases, such as creating `Map`s and `Objects`s.

Author: Snuffleupagus

src/core/xfa/fonts.js

@@ -13,9 +13,9 @@
  * limitations under the License.
  */
 
+import { makeObj, warn } from "../../shared/util.js";
 import { $globalData } from "./symbol_utils.js";
 import { stripQuotes } from "./utils.js";
-import { warn } from "../../shared/util.js";
 
 class FontFinder {
   constructor(pdfFonts) {
@@ -48,9 +48,7 @@ class FontFinder {
   addPdfFont(pdfFont) {
     const cssFontInfo = pdfFont.cssFontInfo;
     const name = cssFontInfo.fontFamily;
-    const font = this.fonts.getOrInsertComputed(name, () =>
-      Object.create(null)
-    );
+    const font = this.fonts.getOrInsertComputed(name, makeObj);
     this.defaultFont ??= font;
 
     let property = "";

src/core/xfa/som.js

@@ -19,7 +19,7 @@ import {
   $getChildrenByName,
   $getParent,
 } from "./symbol_utils.js";
-import { warn } from "../../shared/util.js";
+import { makeMap, warn } from "../../shared/util.js";
 
 const namePattern = /^[^.[]+/;
 const indexPattern = /^[^\]]+/;
@@ -193,7 +193,7 @@ function searchNode(
       let children, cached;
 
       if (useCache) {
-        cached = somCache.getOrInsertComputed(node, () => new Map());
+        cached = somCache.getOrInsertComputed(node, makeMap);
         children = cached.get(cacheName);
       }
 

src/display/annotation_storage.js

@@ -13,7 +13,7 @@
  * limitations under the License.
  */
 
-import { shadow, unreachable } from "../shared/util.js";
+import { makeMap, shadow, unreachable } from "../shared/util.js";
 import { AnnotationEditor } from "./editor/editor.js";
 import { MurmurHash3_64 } from "../shared/murmurhash3.js";
 
@@ -260,7 +260,7 @@ class AnnotationStorage {
         if (key === "type") {
           continue;
         }
-        const counters = map.getOrInsertComputed(key, () => new Map());
+        const counters = map.getOrInsertComputed(key, makeMap);
         counters.set(val, (counters.get(val) ?? 0) + 1);
       }
     }

src/display/api.js

@@ -25,6 +25,7 @@ import {
   getVerbosityLevel,
   info,
   isNodeJS,
+  makeObj,
   MathClamp,
   RenderingIntentFlag,
   setVerbosityLevel,
@@ -1502,8 +1503,9 @@ class PDFPageProxy {
     optionalContentConfigPromise ||=
       this._transport.getOptionalContentConfig(renderingIntent);
 
-    const intentState = this._intentStates.getOrInsertComputed(cacheKey, () =>
-      Object.create(null)
+    const intentState = this._intentStates.getOrInsertComputed(
+      cacheKey,
+      makeObj
     );
     // Ensure that a pending `streamReader` cancel timeout is always aborted.
     if (intentState.streamReaderCancelTimeout) {
@@ -1675,7 +1677,7 @@ class PDFPageProxy {
     );
     const intentState = this._intentStates.getOrInsertComputed(
       intentArgs.cacheKey,
-      () => Object.create(null)
+      makeObj
     );
     let opListTask;
 

src/display/canvas.js

@@ -22,6 +22,7 @@ import {
   FONT_IDENTITY_MATRIX,
   ImageKind,
   info,
+  makeMap,
   OPS,
   shadow,
   TextRenderingMode,
@@ -989,10 +990,7 @@ class CanvasGraphics {
           : [currentTransform.slice(0, 4), fillColor]
       );
 
-      cache = this._cachedBitmapsMap.getOrInsertComputed(
-        mainKey,
-        () => new Map()
-      );
+      cache = this._cachedBitmapsMap.getOrInsertComputed(mainKey, makeMap);
       const cachedImage = cache.get(cacheKey);
       if (cachedImage && !isPatternFill) {
         const offsetX = Math.round(

src/display/pdf_objects.js

@@ -15,6 +15,11 @@
 
 const INITIAL_DATA = Symbol("INITIAL_DATA");
 
+const dataObj = () => ({
+  ...Promise.withResolvers(),
+  data: INITIAL_DATA,
+});
+
 /**
  * A PDF document and page is built of many objects. E.g. there are objects for
  * fonts, images, rendering code, etc. These objects may get processed inside of
@@ -30,10 +35,7 @@ class PDFObjects {
    * @returns {Object}
    */
   #ensureObj(objId) {
-    return this.#objs.getOrInsertComputed(objId, () => ({
-      ...Promise.withResolvers(),
-      data: INITIAL_DATA,
-    }));
+    return this.#objs.getOrInsertComputed(objId, dataObj);
   }
 
   /**

src/pdf.js

@@ -33,6 +33,8 @@ import {
   getUuid,
   ImageKind,
   InvalidPDFException,
+  makeMap,
+  makeObj,
   MathClamp,
   normalizeUnicode,
   OPS,
@@ -123,6 +125,8 @@ globalThis.pdfjsLib = {
   isDataScheme,
   isPdfFile,
   isValidExplicitDest,
+  makeMap,
+  makeObj,
   MathClamp,
   noContextMenu,
   normalizeUnicode,
@@ -182,6 +186,8 @@ export {
   isDataScheme,
   isPdfFile,
   isValidExplicitDest,
+  makeMap,
+  makeObj,
   MathClamp,
   noContextMenu,
   normalizeUnicode,

src/shared/util.js

@@ -1234,6 +1234,11 @@ function _isValidExplicitDest(validRef, validName, dest) {
   return true;
 }
 
+// Helpers for simple `Map.prototype.getOrInsertComputed()` invocations,
+// to avoid duplicate function creation.
+const makeMap = () => new Map();
+const makeObj = () => Object.create(null);
+
 // TODO: Replace all occurrences of this function with `Math.clamp` once
 //       https://github.com/tc39/proposal-math-clamp/ is generally available.
 function MathClamp(v, min, max) {
@@ -1331,6 +1336,8 @@ export {
   isNodeJS,
   LINE_DESCENT_FACTOR,
   LINE_FACTOR,
+  makeMap,
+  makeObj,
   MathClamp,
   MeshFigureType,
   normalizeUnicode,

test/unit/pdf_spec.js

@@ -24,6 +24,8 @@ import {
   getUuid,
   ImageKind,
   InvalidPDFException,
+  makeMap,
+  makeObj,
   MathClamp,
   normalizeUnicode,
   OPS,
@@ -107,6 +109,8 @@ const expectedAPI = Object.freeze({
   isDataScheme,
   isPdfFile,
   isValidExplicitDest,
+  makeMap,
+  makeObj,
   MathClamp,
   noContextMenu,
   normalizeUnicode,

web/pdfjs.js

@@ -44,6 +44,8 @@ const {
   isDataScheme,
   isPdfFile,
   isValidExplicitDest,
+  makeMap,
+  makeObj,
   MathClamp,
   noContextMenu,
   normalizeUnicode,
@@ -103,6 +105,8 @@ export {
   isDataScheme,
   isPdfFile,
   isValidExplicitDest,
+  makeMap,
+  makeObj,
   MathClamp,
   noContextMenu,
   normalizeUnicode,