Re-factor the isLittleEndian/isEvalSupported caching

This functionality is very old, hence we should be able to improve the caching a little bit with modern JavaScript features.

src/core/function.js

@@ -15,9 +15,9 @@
 
 import { Dict, Ref } from "./primitives.js";
 import {
+  FeatureTest,
   FormatError,
   info,
-  IsEvalSupportedCached,
   shadow,
   unreachable,
 } from "../shared/util.js";
@@ -438,7 +438,7 @@ class PDFFunction {
     const parser = new PostScriptParser(lexer);
     const code = parser.parse();
 
-    if (isEvalSupported && IsEvalSupportedCached.value) {
+    if (isEvalSupported && FeatureTest.isEvalSupported) {
       const compiled = new PostScriptCompiler().compile(code, domain, range);
       if (compiled) {
         // Compiled function consists of simple expressions such as addition,

src/display/canvas.js

@@ -14,11 +14,11 @@
  */
 
 import {
+  FeatureTest,
   FONT_IDENTITY_MATRIX,
   IDENTITY_MATRIX,
   ImageKind,
   info,
-  IsLittleEndianCached,
   OPS,
   shadow,
   TextRenderingMode,
@@ -702,7 +702,7 @@ function putBinaryImageData(ctx, imgData, transferMaps = null) {
     const dest32DataLength = dest32.length;
     const fullSrcDiff = (width + 7) >> 3;
     let white = 0xffffffff;
-    let black = IsLittleEndianCached.value ? 0xff000000 : 0x000000ff;
+    let black = FeatureTest.isLittleEndian ? 0xff000000 : 0x000000ff;
 
     if (transferMapGray) {
       if (transferMapGray[0] === 0xff && transferMapGray[0xff] === 0) {

src/display/font_loader.js

@@ -16,7 +16,7 @@
 import {
   assert,
   bytesToString,
-  IsEvalSupportedCached,
+  FeatureTest,
   shadow,
   string32,
   unreachable,
@@ -455,7 +455,7 @@ class FontFaceObject {
     }
 
     // If we can, compile cmds into JS for MAXIMUM SPEED...
-    if (this.isEvalSupported && IsEvalSupportedCached.value) {
+    if (this.isEvalSupported && FeatureTest.isEvalSupported) {
       const jsBuf = [];
       for (const current of cmds) {
         const args = current.args !== undefined ? current.args.join(",") : "";

src/shared/util.js

@@ -682,11 +682,6 @@ function isLittleEndian() {
   const view32 = new Uint32Array(buffer8.buffer, 0, 1);
   return view32[0] === 1;
 }
-const IsLittleEndianCached = {
-  get value() {
-    return shadow(this, "value", isLittleEndian());
-  },
-};
 
 // Checks if it's possible to eval JS expressions.
 function isEvalSupported() {
@@ -697,11 +692,16 @@ function isEvalSupported() {
     return false;
   }
 }
-const IsEvalSupportedCached = {
+
-  get value() {
+class FeatureTest {
-    return shadow(this, "value", isEvalSupported());
+  static get isLittleEndian() {
-  },
+    return shadow(this, "isLittleEndian", isLittleEndian());
-};
+  }
+
+  static get isEvalSupported() {
+    return shadow(this, "isEvalSupported", isEvalSupported());
+  }
+}
 
 const hexNumbers = [...Array(256).keys()].map(n =>
   n.toString(16).padStart(2, "0")
@@ -1103,6 +1103,7 @@ export {
   createValidAbsoluteUrl,
   DocumentActionEventType,
   escapeString,
+  FeatureTest,
   FONT_IDENTITY_MATRIX,
   FontType,
   FormatError,
@@ -1115,8 +1116,6 @@ export {
   isArrayBuffer,
   isArrayEqual,
   isAscii,
-  IsEvalSupportedCached,
-  IsLittleEndianCached,
   MissingPDFException,
   objectFromMap,
   objectSize,