wrapping doom via rust

Author: diekmann

doom/.cargo/config

@@ -0,0 +1,10 @@
+[target.i686-unknown-linux-gnu]
+runner = "./run_in_256colors.sh"
+
+
+[build]
+# doom is a 32bit application.
+target = "i686-unknown-linux-gnu"
+
+[net]
+offline = true

doom/Cargo.lock

@@ -0,0 +1,9 @@
+[package]
+name = "doom"
+version = "0.1.0"
+authors = ["diekmann <none@localhost>"]
+edition = "2018"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]

doom/Cargo.toml

@@ -7,7 +7,7 @@ But we want to build everything from scratch in this series, without Emscripten.
 
 ---
 
-We start with the original vanilla DOOM sources from https://github.com/id-Software/DOOM at [6ed1e40](https://github.com/diekmann/wasm-fizzbuzz/commit/6ed1e4067082bfe61a7b767b91dc981aa1517f94).
+We start with the original vanilla DOOM sources from <https://github.com/id-Software/DOOM> at [6ed1e40](https://github.com/diekmann/wasm-fizzbuzz/commit/6ed1e4067082bfe61a7b767b91dc981aa1517f94).
 
 Some minor tweaks are necessary to compile the 1997 sources on my 64bit Ubuntu 20.04.
 
@@ -28,3 +28,40 @@ With those tweaks, DOOM is starting with X11 rendering:
 ![DOOM is compiling and starting with X11 rendering (no WebAssembly used so far)](imgs/doom_booting_x11.png)
 
 Time to port this to WebAssembly next.
+
+---
+
+Following <https://surma.dev/things/c-to-webassembly/>, we want to compile DOOM as `wasm32`.
+But this will be a long journey.
+And we cannot play doom once we switch to `wasm32` untill the graphics driver for X11 is removed and replaced by a graphics driver for the web.
+Therefore, to test as much as possible and be able to play doom during development, I will develop on X86 for as long as possible and change architecture to `wasm32` reather late.
+
+First, let's replace the compiler from `gcc` to `clang`, turn on optimization, and disable debugging.
+This reduces binary size from `1,9M` to `383K`
+
+To get doom ready for the web, we need to do the following
+
+* Replace the X11 graphics driver with something that works in the browser.
+* Replace the sound driver with, .... my PC does not have speakers, let's just remove sound.
+* Replace all calls DOOM makes into the C stand library (such as `malloc` or `fopen`) with implementations that work in the browser. Either by implementing them in WebAssembly or JavaScript.
+
+Since the year is 2021, there is no reason to write new C code, ...
+
+```
+~/git/wasm-fizzbuzz/doom$ cargo init
+```
+
+To make the doom C code callable interoperable with rust, we no longer compile it into a binry, but build a static library (`liblinuxxdoom.a`) instead.
+Inspired by <https://docs.rust-embedded.org/book/interoperability/c-with-rust.html>, we should be able to call DOOM's `D_DoomMain` from rust then.
+
+We are essentially still working on a 32bit application, remeber?
+
+```
+cargo run --target=i686-unknown-linux-gnu
+```
+
+Adding a `.cargo/config` to select the default target and a runner...
+
+And we got DOOM starting from rust \m/
+
+![DOOM starting via cargo](imgs/doom_booting_x11_rust.png)

doom/README.md

@@ -0,0 +1,12 @@
+fn main() {
+    // TODO: go to linuxdoom-1.10 and `make linux/linuxxdoom.a` first
+    println!("cargo:rustc-link-search=linuxdoom-1.10/linux");
+    println!("cargo:rustc-link-lib=linuxxdoom");
+
+
+    // libraries which should be removed before going to wasm
+    println!("cargo:rustc-link-lib=Xext");
+    println!("cargo:rustc-link-lib=X11");
+    println!("cargo:rustc-link-lib=nsl");
+    println!("cargo:rustc-link-lib=m");
+}

doom/build.rs

@@ -0,0 +1 @@
+linuxdoom-1.10/doom1.wad

doom/doom1.wad

@@ -4,14 +4,14 @@
 #
 # $Log:$
 #
-CC=  clang
+CC=clang
+AR=llvm-ar-10
 
 # doom was written with the implicit assumption that ints and pointers are 32bit.
 # Adding -m32 to make it compile on 64bit archs.
 # on Ubuntu 20.04:
 # apt install gcc-multilib libx11-dev:i386 libxext-dev:i386
-
-CFLAGS=-m32 -O2 -Wall -flto -Wno-unused-const-variable -DNORMALUNIX -DLINUX
+CFLAGS=-m32 -O2 -Wall -Wno-unused-const-variable -DNORMALUNIX -DLINUX
 LDFLAGS=-L/usr/X11R6/lib
 LIBS=-lXext -lX11 -lnsl -lm
 
@@ -88,8 +88,9 @@ clean:
 	rm -f *.o *~ *.flc
 	rm -f $(O)/*
 
+# link-time optimization only when building the binary, but not when building the *.o files, since we want to link them with rust.
 $(O)/linuxxdoom:	$(OBJS) $(O)/i_main.o
-	$(CC) $(CFLAGS) $(LDFLAGS) $(OBJS) $(O)/i_main.o \
+	$(CC) -flto $(CFLAGS) $(LDFLAGS) $(OBJS) $(O)/i_main.o \
 	-o $(O)/linuxxdoom $(LIBS)
 
 $(O)/%.o:	%.c
@@ -101,6 +102,9 @@ run:	all
 	sleep 1 # ugly!! waiting for Xephyr to start.
 	DISPLAY=:1 ./$(O)/linuxxdoom -2
 
+$(O)/liblinuxxdoom.a: $(OBJS)
+	$(AR) rcs $@ $^
+
 #############################################################
 #
 #############################################################

doom/imgs/doom_booting_x11_rust.png

@@ -0,0 +1,4 @@
+#!/bin/sh
+Xephyr :1 -screen 640x400x8 -title DooM &
+sleep 1 # ugly!! waiting for Xephyr to start.
+DISPLAY=:1 "${1}" -2

doom/linuxdoom-1.10/Makefile

@@ -0,0 +1,12 @@
+extern "C" {
+    fn D_DoomMain() -> !;
+}
+
+fn main() {
+    println!("Hello, world from rust!");
+
+    // TODO: set global variables
+    // myargc=2 and myargv={"-2"}
+
+    unsafe { D_DoomMain() };
+}