Finished snippet emulator (for now)

vweb/src/lib.rs

@@ -114,6 +114,14 @@ impl WasmCPU {
 
     pub fn halted(&self) -> bool { self.0.halted() }
 
+    pub fn get_stack(&self) -> Vec<i32> {
+        self.0.get_stack().into_iter().map(i32::from).collect()
+    }
+
+    pub fn get_call(&self) -> Vec<i32> {
+        self.0.get_call().into_iter().map(i32::from).collect()
+    }
+
     pub fn set_pc(&mut self, val: u32) {
         self.0.set_pc(Word::from(val))
     }
@@ -122,6 +130,14 @@ impl WasmCPU {
         self.0.run_to_halt()
     }
 
+    pub fn safe_run(&mut self, max_ticks: usize) {
+        let mut current = 0;
+        while !self.0.halted() && current < max_ticks {
+            current += 1;
+            self.tick()
+        }
+    }
+
     pub fn load(&mut self, rom: Vec<u8>) {
         for (i, b) in rom.iter().enumerate() {
             self.poke(0x400 + i as u32, *b)

vweb/src/snippet_emulator.jsx

@@ -3,6 +3,13 @@ import React, {useState, useCallback, useEffect} from 'react'
 import {WasmCPU, assemble_snippet, source_map, NovaForth} from '../pkg/vweb.js'
 
 export default function({ children }) {
+    // Use this by giving it some source as a body:
+    // <SnippetEmulator>
+    //   {`.org 0x400
+    //     push 3
+    //     hlt`}
+    // </SnippetEmulator>
+    // The string-in-braces is so that jsx doesn't eat the newlines and whitespace
     if (React.Children.count(children) !== 1) {
         throw 'Expects a single text node as a child'
     }
@@ -16,20 +23,30 @@ export default function({ children }) {
     const [cpu, setCpu] = useState(new WasmCPU()) // The actual CPU emulator itself
     const [activeLine, setActiveLine] = useState(null) // The (0-based) index of the
 
+    // Update which line is highlighted. This should be called in most button callbacks.
     const updateActiveLine = useCallback(() => {
         sourceMap && setActiveLine(sourceMap.get(cpu.pc()))
+        if (cpu.halted()) { setMessage('Halted') }
     }, [cpu, sourceMap])
 
+    // Reset the CPU
     const reset = useCallback(() => {
         cpu.reset()
-        cpu.start()
+        cpu.start() // Reset leaves Vulcan in a stopped state but since we're going to step through anyway...
         updateActiveLine()
     }, [cpu, updateActiveLine])
 
+    // Reset the CPU but also put in a message saying we did. This needs to be a separate fn because the
+    // rebuild handler calls the other one but it sets its own message which we don't want to overwrite
+    const resetBtn = useCallback(() => {
+        reset()
+        setMessage('Reset')
+    }, [reset])
+
     // A callback to build the binary from source
     const rebuild = useCallback((code) => {
         try {
-            const bin = assemble_snippet(code)
+            const bin = assemble_snippet(code) // Build the thing and its source map. This throws if there's a problem
             const sm = source_map(code)
             setBinary(bin)
             setSourceMap(sm.Ok || {})
@@ -40,11 +57,26 @@ export default function({ children }) {
         }
     }, [])
 
+    // Step forward one
     const step = useCallback(() => {
         cpu.tick()
+        setMessage('')
         updateActiveLine()
     }, [cpu, updateActiveLine])
 
+    // Run all the lines at once, until the CPU halts
+    const runToHalt = useCallback(() => {
+        setTimeout(() => {
+            cpu.safe_run(100_000) // Safe run, 100k cycles and pause
+            updateActiveLine()
+            // If we're not halted then we're probably in an infinite loop. That might be fine, but stop running, in case
+            // it's not. If they just hit [run] again then it'll keep on going. For snippets it's likely this indicates
+            // a bug though.
+            if (!cpu.halted()) { setMessage('Paused after 100k cycles')}
+        }, 0)
+        setMessage('Running...')
+    }, [cpu, updateActiveLine])
+
     // On load, clean the source and build the stuff
     useEffect(() => {
         const lines = React.Children.toArray(children)[0].split('\n')
@@ -78,10 +110,11 @@ export default function({ children }) {
                 <div className='message'>{message}</div>
                 <div className='buttons'>
                     <a className='step' onClick={step}>[Step]</a>
-                    <a className='step'>[Run]</a>
-                    <a className='reset' onClick={reset}>[Reset]</a>
+                    <a className='step' onClick={runToHalt}>[Run]</a>
+                    <a className='reset' onClick={resetBtn}>[Reset]</a>
                     <a className='edit' onClick={() => { setEditing(true); setMessage('') }}>[Edit]</a>
                 </div>
+                <StackDisplay data={cpu.get_stack()} call={cpu.get_call()}/>
             </div>
         )
     }
@@ -99,5 +132,10 @@ function SourceDisplay({ src, activeLine }) {
 }
 
 function StackDisplay({ data, call }) {
-
+    return (
+        <div className='stacks'>
+            {data && <div><span>Data:&nbsp;</span><span>{data.join(', ')}</span></div>}
+            {call && <div><span>Call:&nbsp;</span><span>{call.join(', ')}</span></div>}
+        </div>
+    )
 }