Avoid hanging the worker-thread for CMap data with ridiculously large ranges (issue 11922)

This patch was inspired by ad2b64f124/xpdf/CharCodeToUnicode.cc (L480-L484)

src/core/cmap.js

@@ -198,6 +198,10 @@ var BUILT_IN_CMAPS = [
   "WP-Symbol",
 ];
 
+// Heuristic to avoid hanging the worker-thread for CMap data with ridiculously
+// large ranges, such as e.g. 0xFFFFFFFF (fixes issue11922_reduced.pdf).
+const MAX_MAP_RANGE = 2 ** 24 - 1; // = 0xFFFFFF
+
 // CMap, not to be confused with TrueType's cmap.
 class CMap {
   constructor(builtInCMap = false) {
@@ -223,12 +227,18 @@ class CMap {
   }
 
   mapCidRange(low, high, dstLow) {
+    if (high - low > MAX_MAP_RANGE) {
+      throw new Error("mapCidRange - ignoring data above MAX_MAP_RANGE.");
+    }
     while (low <= high) {
       this._map[low++] = dstLow++;
     }
   }
 
   mapBfRange(low, high, dstLow) {
+    if (high - low > MAX_MAP_RANGE) {
+      throw new Error("mapBfRange - ignoring data above MAX_MAP_RANGE.");
+    }
     var lastByte = dstLow.length - 1;
     while (low <= high) {
       this._map[low++] = dstLow;
@@ -240,6 +250,9 @@ class CMap {
   }
 
   mapBfRangeToArray(low, high, array) {
+    if (high - low > MAX_MAP_RANGE) {
+      throw new Error("mapBfRangeToArray - ignoring data above MAX_MAP_RANGE.");
+    }
     const ii = array.length;
     let i = 0;
     while (low <= high && i < ii) {

test/pdfs/.gitignore

@@ -50,6 +50,7 @@
 !issue7665.pdf
 !issue7696.pdf
 !issue7835.pdf
+!issue11922_reduced.pdf
 !issue7855.pdf
 !issue7872.pdf
 !issue7901.pdf

test/test_manifest.json

@@ -726,6 +726,12 @@
        "annotations": true,
        "about": "Annotation with Rect array containing indirect objects."
     },
+    {  "id": "issue11922",
+       "file": "pdfs/issue11922_reduced.pdf",
+       "md5": "711bb4b4bf92d967644b4f88d11a93db",
+       "rounds": 1,
+       "type": "load"
+    },
     {  "id": "file_url_link",
        "file": "pdfs/file_url_link.pdf",
        "md5": "b0253c96c38d43bc49259bbf36db938a",