C++: Output il2cpp-api-functions.h with unavailable exports elided

Il2CppInspector.Common/Cpp/UnityHeaders/UnityHeaders.cs

@@ -173,11 +173,15 @@ namespace Il2CppInspector.Cpp.UnityHeaders
         }
 
         // Convert il2cpp-api-functions.h from "DO_API(r, n, p)" to "typedef r (*n)(p)"
-        internal static string GetTypedefsFromAPIHeader(string text) {
+        private static readonly Regex APILineRegex = new Regex(@"^DO_API(?:_NO_RETURN)?\((.*?),(.*?),\s*\((.*?)\)\s*\);", RegexOptions.Multiline);
-            var rgx = new Regex(@"^DO_API(?:_NO_RETURN)?\((.*?),(.*?),\s*\((.*?)\)\s*\);", RegexOptions.Multiline);
+
-            return rgx.Replace(text, "typedef $1 (*$2)($3);");
+        internal static string GetFunctionNameFromAPILine(string line) {
+            var match = APILineRegex.Match(line);
+            return match.Success ? match.Groups[2].ToString().Trim() : string.Empty;
         }
 
+        internal static string GetTypedefsFromAPIHeader(string text) => APILineRegex.Replace(text, "typedef $1 (*$2)($3);");
+
         // Get a list of function names from il2cpp-api-functions.h, taking #ifs into account
         private static IEnumerable<string> GetFunctionNamesFromAPIHeaderText(string text) {
             var defText = GetTypedefsFromAPIHeader(text);

Il2CppInspector.Common/Outputs/CppScaffolding.cs

@@ -9,6 +9,7 @@ using System.Text;
 using System.Text.RegularExpressions;
 using Il2CppInspector.Reflection;
 using Il2CppInspector.Cpp;
+using Il2CppInspector.Cpp.UnityHeaders;
 using Il2CppInspector.Model;
 using Il2CppInspector.Properties;
 
@@ -50,6 +51,27 @@ namespace Il2CppInspector.Outputs
 
             writer.Close();
 
+            // Write selected Unity API function file to il2cpp-api-functions.h
+            // (this is a copy of the header file from an actual Unity install)
+            var il2cppApiFile = Path.Combine(outputPath, "il2cpp-api-functions.h");
+            var apiHeaderText = model.UnityHeaders.GetAPIHeaderText();
+
+            using var fsApi = new FileStream(il2cppApiFile, FileMode.Create);
+            writer = new StreamWriter(fsApi, Encoding.UTF8);
+
+            writeHeader();
+
+            // Elide APIs that aren't in the binary to avoid compile errors
+            foreach (var line in apiHeaderText.Split('\n')) {
+                var fnName = UnityHeaders.GetFunctionNameFromAPILine(line);
+
+                if (string.IsNullOrEmpty(fnName))
+                    writer.WriteLine(line);
+                else if (model.AvailableAPIs.ContainsKey(fnName))
+                    writer.WriteLine(line);
+            }
+            writer.Close();
+
             // Write API function pointers to il2cpp-function-ptr.h
             var il2cppFnPtrFile = Path.Combine(outputPath, "il2cpp-function-ptr.h");
 
@@ -59,7 +81,9 @@ namespace Il2CppInspector.Outputs
             writeHeader();
             writeSectionHeader("IL2CPP API function pointers");
 
-            // TODO: Use model.APIExports instead once it is implemented
+            // We could use model.AvailableAPIs here but that would exclude outputting the address
+            // of API exports which for some reason aren't defined in our selected API header,
+            // so although it doesn't affect the C++ compilation, we use GetAPIExports() instead for completeness
             var exports = model.Package.Binary.GetAPIExports();
 
             foreach (var export in exports) {