Reduce allocations when using Map.prototype.getOrInsert() with Arrays

Change all these cases to use `Map.prototype.getOrInsertComputed()` instead, in combination with a helper function for creating the `Array`s (similar to the previous patch).

Author: Snuffleupagus

src/core/core_utils.js

@@ -18,6 +18,7 @@ import {
   assert,
   BaseException,
   hexNumbers,
+  makeArr,
   objectSize,
   stringToPDFString,
   Util,
@@ -669,7 +670,9 @@ function getNewAnnotationsMap(annotationStorage) {
     if (!key.startsWith(AnnotationEditorPrefix)) {
       continue;
     }
-    newAnnotationsByPage.getOrInsert(value.pageIndex, []).push(value);
+    newAnnotationsByPage
+      .getOrInsertComputed(value.pageIndex, makeArr)
+      .push(value);
   }
   return newAnnotationsByPage.size > 0 ? newAnnotationsByPage : null;
 }

src/core/document.js

@@ -20,6 +20,7 @@ import {
   info,
   InvalidPDFException,
   isArrayEqual,
+  makeArr,
   objectSize,
   PageActionEventType,
   RenderingIntentFlag,
@@ -1892,7 +1893,7 @@ class PDFDocument {
       orphanFields.put(fieldRef, parentRef);
     }
 
-    promises.getOrInsert(name, []).push(
+    promises.getOrInsertComputed(name, makeArr).push(
       AnnotationFactory.create(
         xref,
         fieldRef,

src/core/struct_tree.js

@@ -15,6 +15,7 @@
 
 import {
   AnnotationPrefix,
+  makeArr,
   stringToPDFString,
   stringToUTF8String,
   warn,
@@ -450,7 +451,7 @@ class StructTreeRoot {
     for (const element of elements) {
       if (element.structTreeParentId) {
         const id = parseInt(element.structTreeParentId.split("_mc")[1], 10);
-        idToElements.getOrInsert(id, []).push(element);
+        idToElements.getOrInsertComputed(id, makeArr).push(element);
       }
     }
 

src/core/xfa/builder.js

@@ -24,10 +24,10 @@ import {
   $resolvePrototypes,
   $root,
 } from "./symbol_utils.js";
+import { makeArr, warn } from "../../shared/util.js";
 import { NamespaceSetUp } from "./setup.js";
 import { Template } from "./template.js";
 import { UnknownNamespace } from "./unknown.js";
-import { warn } from "../../shared/util.js";
 import { XFAObject } from "./xfa_object.js";
 
 class Root extends XFAObject {
@@ -166,7 +166,9 @@ class Builder {
   _addNamespacePrefix(prefixes) {
     for (const { prefix, value } of prefixes) {
       const namespace = this._searchNamespace(value);
-      this._namespacePrefixes.getOrInsert(prefix, []).push(namespace);
+      this._namespacePrefixes
+        .getOrInsertComputed(prefix, makeArr)
+        .push(namespace);
     }
   }
 

src/display/annotation_layer.js

@@ -36,6 +36,7 @@ import {
   AnnotationType,
   FeatureTest,
   LINE_FACTOR,
+  makeArr,
   shadow,
   unreachable,
   Util,
@@ -3877,7 +3878,9 @@ class AnnotationLayer {
         this.#elements.push(element);
 
         if (data.popupRef) {
-          popupToElements.getOrInsert(data.popupRef, []).push(element);
+          popupToElements
+            .getOrInsertComputed(data.popupRef, makeArr)
+            .push(element);
         }
       }
 

src/pdf.js

@@ -33,6 +33,7 @@ import {
   getUuid,
   ImageKind,
   InvalidPDFException,
+  makeArr,
   makeMap,
   makeObj,
   MathClamp,
@@ -125,6 +126,7 @@ globalThis.pdfjsLib = {
   isDataScheme,
   isPdfFile,
   isValidExplicitDest,
+  makeArr,
   makeMap,
   makeObj,
   MathClamp,
@@ -186,6 +188,7 @@ export {
   isDataScheme,
   isPdfFile,
   isValidExplicitDest,
+  makeArr,
   makeMap,
   makeObj,
   MathClamp,

src/shared/util.js

@@ -1236,6 +1236,7 @@ function _isValidExplicitDest(validRef, validName, dest) {
 
 // Helpers for simple `Map.prototype.getOrInsertComputed()` invocations,
 // to avoid duplicate function creation.
+const makeArr = () => [];
 const makeMap = () => new Map();
 const makeObj = () => Object.create(null);
 
@@ -1336,6 +1337,7 @@ export {
   isNodeJS,
   LINE_DESCENT_FACTOR,
   LINE_FACTOR,
+  makeArr,
   makeMap,
   makeObj,
   MathClamp,

test/unit/pdf_spec.js

@@ -24,6 +24,7 @@ import {
   getUuid,
   ImageKind,
   InvalidPDFException,
+  makeArr,
   makeMap,
   makeObj,
   MathClamp,
@@ -109,6 +110,7 @@ const expectedAPI = Object.freeze({
   isDataScheme,
   isPdfFile,
   isValidExplicitDest,
+  makeArr,
   makeMap,
   makeObj,
   MathClamp,

web/pdf_viewer.js

@@ -33,6 +33,7 @@ import {
   AnnotationEditorType,
   AnnotationEditorUIManager,
   AnnotationMode,
+  makeArr,
   MathClamp,
   PermissionFlag,
   PixelsPerInch,
@@ -2281,7 +2282,7 @@ class PDFViewer {
           if (percent === 0 || widthPercent < 100) {
             continue;
           }
-          pageLayout.getOrInsert(y, []).push(id);
+          pageLayout.getOrInsertComputed(y, makeArr).push(id);
         }
         // Find the row of the current page.
         for (const yArray of pageLayout.values()) {

web/pdfjs.js

@@ -44,6 +44,7 @@ const {
   isDataScheme,
   isPdfFile,
   isValidExplicitDest,
+  makeArr,
   makeMap,
   makeObj,
   MathClamp,
@@ -105,6 +106,7 @@ export {
   isDataScheme,
   isPdfFile,
   isValidExplicitDest,
+  makeArr,
   makeMap,
   makeObj,
   MathClamp,