Use hash function that is deterministic across runs

Author: kostorr

include/ReadoutCard/InterprocessLock.h

@@ -11,7 +11,7 @@
 #include <chrono>
 #include <sys/socket.h>
 #include <sys/un.h>
-#include <iostream>
+#include <Utilities/Util.h>
 
 #define LOCK_TIMEOUT 5 //5 second timeout in case we wait for the lock (e.g PDA)
 #define UNIX_SOCK_NAME_LENGTH 104 //108 for most UNIXs, 104 for macOS
@@ -73,11 +73,8 @@ class Lock
       if (mSocketName.length() >= UNIX_SOCK_NAME_LENGTH) {
         std::string lockType = mSocketName.substr(0, 17); // isolate the class that created the lock
                                                           // Alice_O2_RoC_XYZ_*
-        std::cout << "mSocketName: " << mSocketName << std::endl;
-        std::cout << "cstr: " << mSocketName.c_str() << std::endl;
-        std::size_t lockNameHash = std::hash<std::string>{} (mSocketName.c_str()); // hash the mutable part
+        unsigned long lockNameHash = Utilities::hashDjb2(mSocketName.c_str(), mSocketName.size()); // hash the mutable part
         std::string safeLockName = lockType + std::to_string(lockNameHash) + "_lock"; // return conformant name
-        std::cout << "lockNameHash: " << lockNameHash << std::endl;
         return safeLockName;
       } else {
         return mSocketName;

src/Utilities/Util.h

@@ -95,6 +95,14 @@ inline bool checkAlignment(void* address, uint64_t alignment)
   return (uint64_t(address) % alignment) == 0;
 }
 
+inline unsigned long hashDjb2(const char *str, size_t length) 
+{
+  unsigned long hash = 5381;
+  for (size_t i = 0; i < length; ++i)
+    hash = 33 * hash + (unsigned char)str[i];
+  return hash;
+}
+
 } // namespace Util
 } // namespace roc
 } // namespace AliceO2