Optimise shader cache string generation

src/ammonite/core/fileManager.cpp

@@ -1,4 +1,5 @@
 #include <cstddef>
+#include <cstdint>
 #include <chrono>
 #include <filesystem>
 #include <string>
@@ -24,15 +25,30 @@ namespace ammonite {
       }
 
       namespace {
-        //Hash input filenames together to create a unique cache string
+        //Don't use this for security, you'll lose your job
         static std::string generateCacheString(std::string* filePaths,
                                                unsigned int fileCount) {
-          std::string inputString = std::string("");
+          uint8_t output[8] = {0};
+          uint8_t prev = 0;
+
+          /*
+           - XOR the first byte of the hash with each character of each path
+           - After each character, sequentially XOR every byte of the hash with the result of
+             the previous XOR
+          */
           for (unsigned int i = 0; i < fileCount; i++) {
-            inputString += filePaths[i] + std::string(";");
+            uint8_t* filePath = (uint8_t*)filePaths[i].c_str();
+            int pathLength = filePaths[i].length();
+            for (int i = 0; i < pathLength; i++) {
+              output[0] ^= filePath[i];
+              for (int j = 0; j < 8; j++) {
+                output[j] ^= prev;
+                prev = output[j];
+              }
+            }
           }
 
-          return std::to_string(std::hash<std::string>{}(inputString));
+          return std::to_string(*(uint64_t*)output);
         }
       }