String element length

src/Neo/SmartContract/Native/StdLib.cs

@@ -16,6 +16,7 @@
 using System;
 using System.Globalization;
 using System.Numerics;
+using System.Text;
 
 namespace Neo.SmartContract.Native
 {
@@ -222,5 +223,39 @@ private static string[] StringSplit([MaxLength(MaxInputLength)] string str, stri
             StringSplitOptions options = removeEmptyEntries ? StringSplitOptions.RemoveEmptyEntries : StringSplitOptions.None;
             return str.Split(separator, options);
         }
+
+        [ContractMethod(CpuFee = 1 << 8)]
+        private static int StringByteLength([MaxLength(MaxInputLength)] string str)
+        {
+            // return the length of the string in bytes
+            // it should return 4 for "🦆" and 2 for "ã"
+            return Encoding.UTF8.GetByteCount(str);
+        }
+
+        [ContractMethod(CpuFee = 1 << 8)]
+        private static int StringCharLength([MaxLength(MaxInputLength)] string str)
+        {
+            // return the length of the string in characters
+            // it should return 2 for "🦆" and 1 for "ã"
+            return str.Length;
+        }
+
+        [ContractMethod(CpuFee = 1 << 8)]
+        private static int StringElementLength([MaxLength(MaxInputLength)] string str)
+        {
+            // return the length of the string in elements
+            // it should return 1 for both  "🦆" and "ã"
+
+            TextElementEnumerator enumerator = StringInfo.GetTextElementEnumerator(str);
+            int count = 0;
+
+            while (enumerator.MoveNext())
+            {
+                count++;
+            }
+
+            return count;
+        }
+
     }
 }

tests/Neo.UnitTests/SmartContract/Native/UT_StdLib.cs

@@ -209,6 +209,59 @@ public void StringSplit()
             Assert.AreEqual("b", arr[1].GetString());
         }
 
+        [TestMethod]
+        public void StringByteLength()
+        {
+            var snapshot = TestBlockchain.GetTestSnapshot();
+
+            using var script = new ScriptBuilder();
+            script.EmitDynamicCall(NativeContract.StdLib.Hash, "stringByteLength", "🦆");
+
+            using var engine = ApplicationEngine.Create(TriggerType.Application, null, snapshot, settings: TestBlockchain.TheNeoSystem.Settings);
+            engine.LoadScript(script.ToArray());
+
+            Assert.AreEqual(engine.Execute(), VMState.HALT);
+            Assert.AreEqual(1, engine.ResultStack.Count);
+
+            var res = engine.ResultStack.Pop<Integer>();
+            Assert.AreEqual(4, res);
+        }
+
+        [TestMethod]
+        public void StringCharLength()
+        {
+            var snapshot = TestBlockchain.GetTestSnapshot();
+
+            using var script = new ScriptBuilder();
+            script.EmitDynamicCall(NativeContract.StdLib.Hash, "stringCharLength", "🦆");
+
+            using var engine = ApplicationEngine.Create(TriggerType.Application, null, snapshot, settings: TestBlockchain.TheNeoSystem.Settings);
+            engine.LoadScript(script.ToArray());
+
+            Assert.AreEqual(engine.Execute(), VMState.HALT);
+            Assert.AreEqual(1, engine.ResultStack.Count);
+
+            var res = engine.ResultStack.Pop<Integer>();
+            Assert.AreEqual(2, res);
+        }
+        [TestMethod]
+        public void StringElementLength()
+        {
+            var snapshot = TestBlockchain.GetTestSnapshot();
+
+            using var script = new ScriptBuilder();
+            script.EmitDynamicCall(NativeContract.StdLib.Hash, "stringElementLength", "🦆");
+
+            using var engine = ApplicationEngine.Create(TriggerType.Application, null, snapshot, settings: TestBlockchain.TheNeoSystem.Settings);
+            engine.LoadScript(script.ToArray());
+
+            Assert.AreEqual(engine.Execute(), VMState.HALT);
+            Assert.AreEqual(1, engine.ResultStack.Count);
+
+            var res = engine.ResultStack.Pop<Integer>();
+            Assert.AreEqual(1, res);
+        }
+
         [TestMethod]
         public void Json_Deserialize()
         {