optimize modbus

src/core/emsdevice.h

@@ -25,6 +25,8 @@
 #include "helpers.h"
 #include "emsdevicevalue.h"
 
+#include <unordered_map>
+
 namespace emsesp {
 
 class EMSdevice {
@@ -553,6 +555,26 @@ class EMSdevice {
 #endif
     std::vector<TelegramFunction> telegram_functions_; // each EMS device has its own set of registered telegram types
     std::vector<DeviceValue>      devicevalues_;       // all the device values
+
+    // added for modbus
+    // Hash map for O(1) lookup of device values by (tag, short_name) key
+    struct DeviceValueKey {
+        uint8_t     tag;
+        std::string short_name;
+
+        bool operator==(const DeviceValueKey & other) const {
+            return tag == other.tag && short_name == other.short_name;
+        }
+    };
+
+    struct DeviceValueKeyHash {
+        std::size_t operator()(const DeviceValueKey & key) const {
+            // Combine hash of tag and short_name
+            return std::hash<uint8_t>()(key.tag) ^ (std::hash<std::string>()(key.short_name) << 1);
+        }
+    };
+
+    std::unordered_map<DeviceValueKey, size_t, DeviceValueKeyHash> devicevalue_index_; // index: key -> devicevalues_ position
 };
 
 } // namespace emsesp