Updates on int.ToString(format)

Tests/Kernels/Cosmos.Compiler.Tests.Bcl.System/System/Int32Test.cs

@@ -1,5 +1,6 @@
 using System;
-
+using System.Linq;
+using Cosmos.Common.Extensions;
 using Cosmos.TestRunner;
 
 namespace Cosmos.Compiler.Tests.Bcl.System
@@ -37,13 +38,26 @@ public static void Execute()
             // actually the Hash Code of an Int32 is the same value
             Assert.IsTrue((resultAsInt == value), "Int32.GetHashCode() doesn't work");
 
-#if false
-            // Now let's try ToString() again but printed in hex (this test fails for now!)
-            result = value.ToString("X2");
-            expectedResult = "0x7FFFFFFF";
+            // Now let's try ToString() again but printed in hex
+            result = value.ToString("X");
+            expectedResult = "7FFFFFFF";
+
+            Assert.IsTrue((result == expectedResult), "Int32.ToString(X) brings incorrect result.");
+
+            // Ensure value is not overrided
+            Assert.IsTrue((value != 0), "Int32.ToString(X) overrides the value of the variable.");
+
+            // Hex with padding
+            value = 255;
+            result = value.ToString("X4");
+            expectedResult = "00FF";
+            Assert.IsTrue((result == expectedResult), "Int32.ToString(X4) brings incorrect result.");
 
-            Assert.IsTrue((result == expectedResult), "Int32.ToString(X2) doesn't work");
-#endif
+            // Test Decimal format wit padding
+            value = 10;
+            expectedResult = "0010";
+            result = value.ToString("D4");
+            Assert.IsTrue((result == expectedResult), "Int32.ToString(D4) brings incorrect result.");
 
             // basic bit operations
 

source/Cosmos.System2_Plugs/System/Int32Impl.cs

@@ -1,3 +1,4 @@
+using System.Text;
 using Cosmos.Common;
 using IL2CPU.API.Attribs;
 
@@ -13,46 +14,56 @@ public static string ToString(ref int aThis)
 
         public static string ToString(ref int aThis, string format)
         {
-            if (format.Equals("X"))
+            if (string.IsNullOrEmpty(format))
             {
-                string result = "";
+                return "0";
+            }
 
-                if(aThis == 0)
-                {
-                    result = "0";
-                }
+            StringBuilder sb = new();
 
-                while (aThis != 0)
-                {
-                    if (aThis % 16 < 10)
+            switch (format[0])
+            {
+                case 'X':
+                    if (aThis == 0)
                     {
-                        result = aThis % 16 + result;
+                        sb.Append('0');
+                        break;
                     }
-                    else
-                    {
-                        string temp = "";
 
-                        switch (aThis % 16)
+                    int value = aThis;
+
+                    while (value != 0)
+                    {
+                        int remainder = value % 16;
+                        if (remainder < 10)
                         {
-                            case 10: temp = "A"; break;
-                            case 11: temp = "B"; break;
-                            case 12: temp = "C"; break;
-                            case 13: temp = "D"; break;
-                            case 14: temp = "E"; break;
-                            case 15: temp = "F"; break;
+                            sb.Insert(0, remainder);
+                        }
+                        else
+                        {
+                            char temp = (char)('A' + (remainder - 10));
+                            sb.Insert(0, temp);
                         }
 
-                        result = temp + result;
+                        value /= 16;
                     }
+                    break;
+                case 'D':
+                    sb.Append(aThis);
+                    break;
+                default:
+                    return aThis.ToString();
+            }
 
-                    aThis /= 16;
-                }
+            var result = sb.ToString();
 
-                return result;
+            if (format.Length > 1)
+            {
+                return int.TryParse(format.AsSpan(1), out int number) ? result.PadLeft(number, '0') : aThis.ToString();
             }
             else
             {
-                return aThis.ToString();
+                return result;
             }
         }