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path: root/pkgs/games/build-support/monogame-patcher/src/patcher.cs
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using System.Collections.Generic;
using System.IO;
using System.Linq;
using System;

using Mono.Cecil.Cil;
using Mono.Cecil.Rocks;
using Mono.Cecil;

using CommandLine;

class Command {
    protected string infile;
    protected string outfile;
    protected ModuleDefinition module;

    public Command(GenericOptions options) {
        if (options.outputFile == null)
            this.outfile = options.inputFile;
        else
            this.outfile = options.outputFile;
        this.infile = options.inputFile;

        var resolver = new DefaultAssemblyResolver();
        resolver.AddSearchDirectory(Path.GetDirectoryName(this.infile));

        var rp = new ReaderParameters {
            ReadWrite = this.infile == this.outfile,
            AssemblyResolver = resolver
        };
        this.module = ModuleDefinition.ReadModule(this.infile, rp);
    }

    protected MethodReference find_method_ref(string fullSig) {
        foreach (var aref in this.module.AssemblyReferences) {
            var resolved = this.module.AssemblyResolver.Resolve(aref);
            foreach (var type in resolved.MainModule.Types) {
                foreach (var ctor in type.GetConstructors()) {
                    if (ctor.ToString() != fullSig) continue;
                    return this.module.ImportReference(ctor);
                }
                foreach (var meth in type.GetMethods()) {
                    if (meth.ToString() != fullSig) continue;
                    return this.module.ImportReference(meth);
                }
            }
        }

        throw new Exception($"Method reference for {fullSig} not found.");
    }

    public void save() {
        if (this.outfile == this.infile)
            this.module.Write();
        else
            this.module.Write(this.outfile);
    }
}

class FixFileStreams : Command {
    private MethodReference betterFileStream;

    public FixFileStreams(FixFileStreamsCmd options) : base(options) {
        var filtered = this.module.Types
            .Where(p => options.typesToPatch.Contains(p.Name));

        this.betterFileStream = this.find_method_ref(
            "System.Void System.IO.FileStream::.ctor" +
            "(System.String,System.IO.FileMode,System.IO.FileAccess)"
        );

        foreach (var toPatch in filtered)
            patch_type(toPatch);

        this.save();
    }

    private void patch_method(MethodDefinition md) {
        var il = md.Body.GetILProcessor();

        var fileStreams = md.Body.Instructions
            .Where(i => i.OpCode == OpCodes.Newobj)
            .Where(i => (i.Operand as MethodReference).DeclaringType
                    .FullName == "System.IO.FileStream");

        foreach (Instruction i in fileStreams.ToList()) {
            var fileAccessRead = il.Create(OpCodes.Ldc_I4_1);
            il.InsertBefore(i, fileAccessRead);
            il.Replace(i, il.Create(OpCodes.Newobj, this.betterFileStream));
        }
    }

    private void patch_type(TypeDefinition td) {
        foreach (var nested in td.NestedTypes) patch_type(nested);
        foreach (MethodDefinition md in td.Methods) patch_method(md);
    }
}

class ReplaceCall : Command {
    private string search;
    private MethodReference replace;

    public ReplaceCall(ReplaceCallCmd options) : base(options) {
        this.search = options.replaceMethod;
        this.replace = this.find_method_ref(options.replacementMethod);

        var filtered = this.module.Types
            .Where(p => options.typesToPatch.Contains(p.Name));

        foreach (var toPatch in filtered)
            patch_type(toPatch);

        this.save();
    }

    private void patch_method(MethodDefinition md) {
        var il = md.Body.GetILProcessor();

        var found = md.Body.Instructions
            .Where(i => i.OpCode == OpCodes.Call)
            .Where(i => i.Operand.ToString() == this.search);

        foreach (Instruction i in found.ToList())
            il.Replace(i, il.Create(OpCodes.Call, this.replace));
    }

    private void patch_type(TypeDefinition td) {
        foreach (var nested in td.NestedTypes) patch_type(nested);
        foreach (MethodDefinition md in td.Methods) patch_method(md);
    }
}

public class patcher {
    public static int Main(string[] args) {
        var parser = new Parser((settings) => {
            settings.EnableDashDash = true;
            settings.HelpWriter = Console.Error;

            // XXX: When not running in a terminal the width is 0, but the
            //      CommandLine library expects it to be greater than zero.
            if (Console.WindowWidth == 0)
                settings.MaximumDisplayWidth = 80;
        });

        parser.ParseArguments<FixFileStreamsCmd, ReplaceCallCmd>(args)
            .WithParsed<FixFileStreamsCmd>(opts => new FixFileStreams(opts))
            .WithParsed<ReplaceCallCmd>(opts => new ReplaceCall(opts));
        return 0;
    }
}