added custom functions to expression builder

application/src/main/java/org/thingsboard/server/service/cf/ctx/state/CalculatedFieldCtx.java

@@ -18,6 +18,8 @@ package org.thingsboard.server.service.cf.ctx.state;
 import lombok.Data;
 import net.objecthunter.exp4j.Expression;
 import net.objecthunter.exp4j.ExpressionBuilder;
+import net.objecthunter.exp4j.function.Function;
+import net.objecthunter.exp4j.function.Functions;
 import org.mvel2.MVEL;
 import org.thingsboard.script.api.tbel.TbelInvokeService;
 import org.thingsboard.server.common.data.AttributeScope;
@@ -111,6 +113,7 @@ public class CalculatedFieldCtx {
             if (isValidExpression(expression)) {
                 this.customExpression = ThreadLocal.withInitial(() ->
                         new ExpressionBuilder(expression)
+                                .functions(userDefinedFunctions)
                                 .implicitMultiplication(true)
                                 .variables(this.arguments.keySet())
                                 .build()
@@ -279,4 +282,50 @@ public class CalculatedFieldCtx {
         return "Failed to init CF state. State size exceeds limit of " + (maxStateSize / 1024) + "Kb!";
     }
 
+    private static final List<Function> userDefinedFunctions = List.of(
+            new Function("ln") {
+                @Override
+                public double apply(double... args) {
+                    return Math.log(args[0]);
+                }
+            },
+            new Function("lg") {
+                @Override
+                public double apply(double... args) {
+                    return Math.log10(args[0]);
+                }
+            },
+            new Function("logab", 2) {
+                @Override
+                public double apply(double... args) {
+                    return Math.log(args[1]) / Math.log(args[0]);
+                }
+            },
+
+            // Manually listing built-in functions to avoid inefficient equals-based lookup in Functions.getBuiltinFunction during each evaluation.
+            Functions.getBuiltinFunction("sin"),
+            Functions.getBuiltinFunction("cos"),
+            Functions.getBuiltinFunction("tan"),
+            Functions.getBuiltinFunction("cot"),
+            Functions.getBuiltinFunction("log"),
+            Functions.getBuiltinFunction("log2"),
+            Functions.getBuiltinFunction("log10"),
+            Functions.getBuiltinFunction("log1p"),
+            Functions.getBuiltinFunction("abs"),
+            Functions.getBuiltinFunction("acos"),
+            Functions.getBuiltinFunction("asin"),
+            Functions.getBuiltinFunction("atan"),
+            Functions.getBuiltinFunction("cbrt"),
+            Functions.getBuiltinFunction("floor"),
+            Functions.getBuiltinFunction("sinh"),
+            Functions.getBuiltinFunction("sqrt"),
+            Functions.getBuiltinFunction("tanh"),
+            Functions.getBuiltinFunction("cosh"),
+            Functions.getBuiltinFunction("ceil"),
+            Functions.getBuiltinFunction("pow"),
+            Functions.getBuiltinFunction("exp"),
+            Functions.getBuiltinFunction("expm1"),
+            Functions.getBuiltinFunction("signum")
+    );
+
 }