add formula evaluation for watch overrides

Cargo.lock

@@ -703,6 +703,7 @@ dependencies = [
  "glutin",
  "hex",
  "libloading 0.5.2",
+ "meval",
  "mini_gl_fb",
  "structopt",
  "winit",
@@ -1132,6 +1133,16 @@ dependencies = [
  "autocfg",
 ]
 
+[[package]]
+name = "meval"
+version = "0.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f79496a5651c8d57cd033c5add8ca7ee4e3d5f7587a4777484640d9cb60392d9"
+dependencies = [
+ "fnv",
+ "nom 1.2.4",
+]
+
 [[package]]
 name = "mini_gl_fb"
 version = "0.9.0"
@@ -1269,6 +1280,12 @@ dependencies = [
  "libc",
 ]
 
+[[package]]
+name = "nom"
+version = "1.2.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a5b8c256fd9471521bcb84c3cdba98921497f1a331cbc15b8030fc63b82050ce"
+
 [[package]]
 name = "nom"
 version = "6.2.1"
@@ -2425,7 +2442,7 @@ version = "0.3.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "3a9a231574ae78801646617cefd13bfe94be907c0e4fa979cfd8b770aa3c5d08"
 dependencies = [
- "nom",
+ "nom 6.2.1",
 ]
 
 [[package]]

Cargo.toml

@@ -25,4 +25,5 @@ winit = "0.25"
 
 gilrs = "0.8.1"
 find_folder="0.3.0"
-hex = "0.4.3"
+hex = "0.4.3"
+meval = "0.2.0"

src/main.rs

@@ -7,6 +7,7 @@ extern crate conrod_core;
 extern crate failure;
 extern crate glutin;
 extern crate hex;
+extern crate meval;
 
 use mini_gl_fb::glutin::event_loop::EventLoop;
 

src/ui/debug_window.rs

@@ -3,6 +3,7 @@ use std::{cell::RefCell, collections::HashSet, io::{Read, Write}, pin::Pin, rc::
 use conrod_core::{Borderable, Colorable, Dimensions, Labelable, Positionable, Sizeable, Widget, position::Place, widget, widget_ids};
 use glium::Surface;
 use glutin::{dpi::LogicalSize, event::{ElementState, Event, KeyboardInput, VirtualKeyCode, WindowEvent}, event_loop::EventLoop, window::WindowId};
+use meval::Context;
 use mini_gl_fb::{config, get_fancy};
 
 use crate::{MyEmulator, memory::search::MemorySearch, ui::memory_watch::remove_temporary_watches};
@@ -125,6 +126,9 @@ impl TrackedWindow for DebugWindow {
 
                 let mut ui = self.ui.set_widgets();
 
+                let mut meval_context = meval::Context::new();
+                meval_context.var("t", emu.frame as f64);
+
                 widget::Canvas::new()
                     .color(conrod_core::color::DARK_PURPLE)
                     .set(self.ids.canvas, &mut ui);
@@ -241,7 +245,7 @@ impl TrackedWindow for DebugWindow {
 
                 // Refresh watches
                 for watch in &mut self.watches{
-                    watch.refresh(memory);
+                    watch.refresh(memory, &meval_context);
                 }
 
                 widget::BorderedRectangle::new([500.0, 230.0])

src/ui/memory_watch.rs

@@ -1,5 +1,7 @@
 use std::{collections::HashSet, fmt::Display};
 
+use meval::{Context, Expr};
+
 
 pub struct MemoryWatch {
     pub start: usize,
@@ -24,7 +26,7 @@ impl MemoryWatch {
         }
     }
 
-    pub fn refresh(&mut self, data: &mut [u8]) {
+    pub fn refresh(&mut self, data: &mut [u8], meval_context: &Context) {
         if self.start + self.length > data.len() {
             self.last_seen_value = None;
             self.status = WatchStatus::OutOfBounds;
@@ -36,14 +38,39 @@ impl MemoryWatch {
         }
 
         if let Some(user_input)  = &self.user_input {
-            match hex::decode(user_input) {
-                Ok(user_input_bytes) => {
-                    if user_input_bytes.len() == self.length {
-                        data[self.start..self.start + self.length].copy_from_slice(user_input_bytes.as_slice());
-                        self.status = WatchStatus::Ok;
+            if user_input.starts_with("=") && self.length == 1{ // only support one byte for expressions for now
+                // evaluate formula
+                match &user_input[1..].parse::<Expr>() {
+                    Ok(expr) => {
+                        match expr.eval_with_context(meval_context){
+                            Ok(result) => {
+                                // truncate to a byte.
+                                let truncated_result = result.min(255.0).max(0.0).round();
+                                let byte_result = truncated_result as u8;
+                                data[self.start] = byte_result;
+                            }
+                            Err(e) => {
+                                println!("Failed to evaluate expression '{}', {}", user_input, e);
+                            }
+                        }
+
+                    }
+                    Err(e) => {
+                        println!("Failed to parse expression '{}', {}", user_input, e);
                     }
                 }
-                Err(_) => {self.status = WatchStatus::InputDecodeFailed;}
+
+            }
+            else { // it's data
+                match hex::decode(user_input) {
+                    Ok(user_input_bytes) => {
+                        if user_input_bytes.len() == self.length {
+                            data[self.start..self.start + self.length].copy_from_slice(user_input_bytes.as_slice());
+                            self.status = WatchStatus::Ok;
+                        }
+                    }
+                    Err(_) => {self.status = WatchStatus::InputDecodeFailed;}
+                }
             }
         }