PDFBOX-6193: avoid AIOOBE due to a negative hash based on a proposal by Stefan Ziegler

git-svn-id: https://svn.apache.org/repos/asf/pdfbox/trunk@1934290 13f79535-47bb-0310-9956-ffa450edef68

Author: lehmi

pdfbox/src/main/java/org/apache/pdfbox/pdmodel/font/TrueTypeEmbedder.java

@@ -364,9 +364,8 @@ protected abstract void buildSubset(InputStream ttfSubset, String tag,
      */
     public String getTag(Map<Integer, Integer> gidToCid)
     {
-        // deterministic
-        long num = gidToCid.hashCode();
-
+        // hash might be negative due to an overflow if the map contains lots of values
+        long num = Math.abs(gidToCid.hashCode());
         // base25 encode
         StringBuilder sb = new StringBuilder();
         do