Update README.md

Author: winscripter

README.md

@@ -1 +1,98 @@
-# ILSourceParser
+# ILSourceParser
+This library for .NET provides functionality to parse IL source code. If you're not aware, Microsoft Intermediate Language (IL or CIL, formerly known as MSIL) is
+what the .NET application typically consists of. C#, Visual Basic, F#, and other well-known official .NET languages compile to IL bytecode. However,
+IL actually has its syntax as well. ILSourceParser parses the IL syntax into syntax nodes, making it easier to analyze IL.
+
+This library does not rely on any existing project and is not a port from another language, so chances are there could be some issues with this library. If
+you encounter one, please create a new issue post about it!
+
+The known issue is that ILSourceParser might not be the fastest thing in the world, because it took nearly 1 second to analyze a 200-line of code IL file. Maybe
+it just needs some additional JIT warming, although there could be a different reason - parsing IL is generally harder than parsing C#, mostly because IL has almost 300
+instructions, and we have to do over 300 checks when parsing method body to parse one instruction.
+
+### Example
+```cs
+var syntaxTree = ILSyntaxTree.ParseText(@".assembly MyAssembly { }");
+var root = syntaxTree.GetRoot();
+foreach (SyntaxNode node in root.DescendantNodes)
+{
+    // do something with node
+}
+```
+ILSourceParser is generally really similar to [Roslyn](https://github.com/dotnet/roslyn), even though it doesn't rely on it at all.
+
+A more complex example here:
+```cs
+using ILSourceParser;
+using ILSourceParser.Syntax;
+using ILSourceParser.Syntax.Instructions;
+using Sprache;
+
+string input = @".assembly MyAssembly
+{
+    .ver 1:2:3:4
+}
+.assembly extern System.Runtime
+{
+}
+.assembly extern System.Console
+{
+}
+
+// My Cool Application !
+
+.imagebase 0x00400000
+.line 123
+
+.class public sequential auto ansi beforefieldinit MyValueType extends [System.Runtime]System.ValueType
+{
+    .field private static initonly string s_myString
+
+    .method public static hidebysig void .cctor() cil managed
+    {
+        ldstr ""Hello, World!""
+        stsfld string MyValueType::s_myString
+    }
+    
+    .method public static void PrintText() cil managed
+    {
+        .maxstack 8
+        
+        ldsfld string MyValueType::s_myString
+        call void [System.Console]System.Console::WriteLine(string)
+        
+        ret
+    }
+}";
+var syntaxRoot = ILSyntaxTree.ParseText(input).GetRoot();
+
+foreach (var descendant in syntaxRoot.DescendantNodes)
+{
+    switch (descendant)
+    {
+        case AssemblyDeclarationSyntax asm:
+            Console.WriteLine($"Assembly {asm.AssemblyName}, is external: {asm.IsExtern}");
+            break;
+        case BaseCommentSyntax comment:
+            if (comment is InlineCommentSyntax inline)
+            {
+                Console.WriteLine($"Inline comment, text: {inline.CommentText}");
+            }
+            else if (comment is MultilineCommentSyntax multiline)
+            {
+                Console.WriteLine($"Multiline comment, text: {multiline.CommentText}");
+            }
+            break;
+        case ImageBaseDirectiveSyntax imageBase:
+            Console.WriteLine($"Image base {imageBase.ImageBase}");
+            break;
+        case LineDirectiveSyntax line:
+            Console.WriteLine($"Line {line.Line}");
+            break;
+        case ClassDeclarationSyntax @class:
+            string flags = string.Join(", ", @class.Flags);
+            Console.WriteLine($"Class named {@class.Name}; flags: {flags}");
+            break;
+    }
+}
+```