Reverse engineered TRE checksum function

TreFile.cc

@@ -267,7 +267,11 @@ void TreFile::dumpAll(std::string path) const
     std::string name = path;
     name.append(crcStr);
 
-    dumpIdx_(name, ent.second);
+    try {
+      dumpIdx_(name, ent.second);
+    } catch (Exception &ex) {
+      continue;
+    }
   }
 
   for (auto ent : table2_) {
@@ -301,13 +305,37 @@ void TreFile::printStructure()
 	   std::get<2>(table3_[ent.second]),
 	   std::get<3>(table3_[ent.second]));
   }
+
+  printf("CRC<->Name:\n");
+  for (auto const& ent1 : table1_) {
+    for (auto const& ent2 : table2_) {
+      if (ent1.second == ent2.second)
+	printf("\t%.8x\t%s\n", ent1.first, ent2.first.c_str());
+    }
+  }
 }
 
+uint32_t TreFile::calcCRC(std::string const& path)
+{
+  uint32_t sum = 0;
+  for(unsigned char c: path) {
+    sum = (sum << 3) | ((sum>>29)&0x7);
+    sum += c;
+  }
+
+  return sum;
+}
+  
 size_t TreFile::findName_(std::string const& name) const
 {
   auto it = table2_.find(name);
-  if (it == table2_.end())
+  if (it == table2_.end()) {
-    throw Exception{name + " not found"};
+    try {
+      return findCRC_(calcCRC(name));
+    } catch (Exception &ex) {
+      throw Exception{name + " not found"};
+    }
+  }
 
   return it->second;
 }

TreFile.hh

@@ -23,6 +23,10 @@ public:
 
   void printStructure();
 
+  /* Calculate the XTRE "CRC" (in reality a cheap checksum) of
+     'path' */
+  static uint32_t calcCRC(std::string const& path);
+  
   class Object {
   public:
     Object() : base_(nullptr), length_(0) {