hotwire haku2 into rkgk

really a bodge job right now and it crashes but it's a start

crates/haku2/src/haku2.zig

@@ -9,7 +9,11 @@ const Scratch = @import("scratch.zig");
 const value = @import("value.zig");
 const Vm = @import("vm.zig");
 
-const allocator = if (builtin.cpu.arch == .wasm32) std.heap.wasm_allocator else @import("allocator.zig").hostAllocator;
+const allocator =
+    if (builtin.cpu.arch == .wasm32)
+        std.heap.wasm_allocator
+    else
+        @import("allocator.zig").hostAllocator;
 
 // Scratch
 
@@ -28,7 +32,9 @@ export fn haku2_scratch_reset(scratch: *Scratch) void {
 // Limits
 
 export fn haku2_limits_new() ?*Vm.Limits {
-    return allocator.create(Vm.Limits) catch null;
+    const limits = allocator.create(Vm.Limits) catch return null;
+    limits.* = .{};
+    return limits;
 }
 
 export fn haku2_limits_destroy(limits: *Vm.Limits) void {
@@ -102,9 +108,15 @@ export fn haku2_vm_run_main(
     return true;
 }
 
+export fn haku2_vm_has_cont(vm: *const Vm) bool {
+    if (vm.stack.len == 0) return false;
+    const top = vm.top();
+    return top == .ref and top.ref.* == .reticle;
+}
+
 export fn haku2_vm_is_dotter(vm: *const Vm) bool {
     if (vm.stack.len == 0) return false;
-    const top = vm.stack[vm.stack_top];
+    const top = vm.top();
     return top == .ref and top.ref.* == .reticle and top.ref.reticle == .dotter;
 }
 

crates/haku2/src/lib.rs

@@ -3,6 +3,7 @@ use std::{
     error::Error,
     fmt::{self, Display},
     marker::{PhantomData, PhantomPinned},
+    mem::forget,
     ptr::{self, NonNull},
 };
 
@@ -91,6 +92,7 @@ extern "C" {
         code_len: usize,
         local_count: u8,
     ) -> bool;
+    fn haku2_vm_has_cont(vm: *const VmC) -> bool;
     fn haku2_vm_is_dotter(vm: *const VmC) -> bool;
     fn haku2_vm_run_dotter(
         vm: *mut VmC,
@@ -211,10 +213,38 @@ impl Drop for Defs {
     }
 }
 
+#[derive(Debug)]
+pub struct Code {
+    defs: Defs,
+    main_chunk: Vec<u8>,
+    main_local_count: u8,
+}
+
+impl Code {
+    /// Creates a new instance of `Code` from a valid vector of bytes.
+    ///
+    /// # Safety
+    ///
+    /// This does not perform any validation, and there is no way to perform such
+    /// validation before constructing this. The bytecode must simply be valid, which is the case
+    /// for bytecode emitted directly by the compiler.
+    ///
+    /// Untrusted bytecode should never ever be loaded under any circumstances.
+    pub unsafe fn new(defs: Defs, main_chunk: Vec<u8>, main_local_count: u8) -> Self {
+        Self {
+            defs,
+            main_chunk,
+            main_local_count,
+        }
+    }
+}
+
+/// A VM that is ready to run and loaded with valid bytecode.
 #[derive(Debug)]
 pub struct Vm {
     scratch: Scratch,
-    raw: NonNull<VmC>,
+    code: Code,
+    inner: VmInner,
 }
 
 #[derive(Debug)]
@@ -236,17 +266,24 @@ pub struct Dotter {
 }
 
 impl Vm {
-    pub fn new(scratch: Scratch, defs: &Defs, limits: &Limits) -> Self {
+    pub fn new(scratch: Scratch, code: Code, limits: &Limits) -> Self {
         Self {
             // SAFETY:
-            // - Ownership of s is passed to the VM, so the VM cannot outlive the scratch space.
+            // - Ownership of scratch is passed to the VM, so the VM cannot outlive the scratch space.
             //   - The VM never gives you any references back, so this is safe to do.
             // - The other arguments are only borrowed immutably for construction.
-            raw: NonNull::new(unsafe {
-                haku2_vm_new(scratch.raw.as_ptr(), defs.raw.as_ptr(), limits.raw.as_ptr())
-            })
-            .expect("out of memory"),
+            inner: VmInner {
+                raw: NonNull::new(unsafe {
+                    haku2_vm_new(
+                        scratch.raw.as_ptr(),
+                        code.defs.raw.as_ptr(),
+                        limits.raw.as_ptr(),
+                    )
+                })
+                .expect("out of memory"),
+            },
             scratch,
+            code,
         }
     }
 
@@ -255,19 +292,14 @@ impl Vm {
     ///
     /// Calling `begin` again during this process will work correctly, and result in another
     /// continuation being stack on top of the old one---at the expense of a stack slot.
-    ///
-    /// # Safety
-    ///
-    /// The bytecode passed in must be valid, because bytecode validation is done on a best-effort
-    /// basis. Bytecode retrieved out of the compiler is guaranteed to be safe.
-    pub unsafe fn begin(&mut self, code: &[u8], local_count: u8) -> Result<(), Exception> {
+    pub fn begin(&mut self) -> Result<(), Exception> {
         let ok = unsafe {
             haku2_vm_run_main(
-                self.raw.as_ptr(),
+                self.inner.raw.as_ptr(),
                 self.scratch.raw.as_ptr(),
-                code.as_ptr(),
-                code.len(),
-                local_count,
+                self.code.main_chunk.as_ptr(),
+                self.code.main_chunk.len(),
+                self.code.main_local_count,
             )
         };
         if ok {
@@ -277,9 +309,14 @@ impl Vm {
         }
     }
 
+    /// Returns whether `cont()` can be called to run the next continuation.
+    pub fn has_cont(&self) -> bool {
+        unsafe { haku2_vm_has_cont(self.inner.raw.as_ptr()) }
+    }
+
     fn is_dotter(&self) -> bool {
         // SAFETY: The pointer is valid.
-        unsafe { haku2_vm_is_dotter(self.raw.as_ptr()) }
+        unsafe { haku2_vm_is_dotter(self.inner.raw.as_ptr()) }
     }
 
     /// Returns how the VM should continue executing after the previous execution.
@@ -291,12 +328,12 @@ impl Vm {
     }
 
     /// Renders the current scribble on top of the stack.
-    /// If the value on top is not a scribble, throws an exception (indicated by the return type.)
+    /// If the value on top is not a scribble, throws an exception.
     ///
     /// The rendering is performed by calling into the [`Canvas`] trait.
     pub fn render(&mut self, canvas: &mut dyn Canvas, max_depth: usize) -> Result<(), Exception> {
         let mut wrapped = CanvasC { inner: canvas };
-        let ok = unsafe { haku2_render(self.raw.as_ptr(), &mut wrapped, max_depth) };
+        let ok = unsafe { haku2_render(self.inner.raw.as_ptr(), &mut wrapped, max_depth) };
         if ok {
             Ok(())
         } else {
@@ -308,7 +345,7 @@ impl Vm {
     /// Returns `None` if there's no exception.
     pub fn exception(&self) -> Option<Exception> {
         // SAFETY: The pointer passed to this function is valid.
-        let len = unsafe { haku2_vm_exception_len(self.raw.as_ptr()) };
+        let len = unsafe { haku2_vm_exception_len(self.inner.raw.as_ptr()) };
         if len == 0 {
             return None;
         }
@@ -316,12 +353,24 @@ impl Vm {
         let mut buffer = vec![0; len];
         // SAFETY: The length of the buffer is as indicated by haku2_vm_exception_len.
         unsafe {
-            haku2_vm_exception_render(self.raw.as_ptr(), buffer.as_mut_ptr());
+            haku2_vm_exception_render(self.inner.raw.as_ptr(), buffer.as_mut_ptr());
         }
         Some(Exception {
             message: String::from_utf8_lossy(&buffer).into_owned(),
         })
     }
+
+    /// Take the `Scratch` out of the VM for reuse in another one.
+    /// The scratch memory will be reset (no bytes will be consumed.)
+    pub fn into_scratch(self) -> Scratch {
+        let Vm {
+            mut scratch,
+            code: _,
+            inner: _,
+        } = self;
+        scratch.reset();
+        scratch
+    }
 }
 
 impl ContDotter<'_> {
@@ -334,7 +383,7 @@ impl ContDotter<'_> {
 
         let ok = unsafe {
             haku2_vm_run_dotter(
-                self.vm.raw.as_ptr(),
+                self.vm.inner.raw.as_ptr(),
                 self.vm.scratch.raw.as_ptr(),
                 from_x,
                 from_y,
@@ -351,7 +400,12 @@ impl ContDotter<'_> {
     }
 }
 
-impl Drop for Vm {
+#[derive(Debug)]
+struct VmInner {
+    raw: NonNull<VmC>,
+}
+
+impl Drop for VmInner {
     fn drop(&mut self) {
         // SAFETY: The pointer passed is non-null.
         unsafe {

crates/haku2/src/render.zig

@@ -54,6 +54,6 @@ fn renderRec(vm: *Vm, canvas: *Canvas, val: Value, depth: usize, max_depth: usiz
 }
 
 pub fn render(vm: *Vm, canvas: *Canvas, max_depth: usize) !void {
-    const val = try vm.pop();
+    const val = vm.stack[vm.stack_top - 1];
     try renderRec(vm, canvas, val, 0, max_depth);
 }

crates/haku2/src/vm.zig

@@ -113,6 +113,14 @@ pub fn pop(vm: *Vm) Error!Value {
     return vm.stack[vm.stack_top];
 }
 
+pub fn top(vm: *const Vm) Value {
+    if (vm.stack_top > 0) {
+        return vm.stack[vm.stack_top - 1];
+    } else {
+        return .nil;
+    }
+}
+
 pub fn pushCall(vm: *Vm, frame: CallFrame) Error!void {
     if (vm.call_stack_top >= vm.call_stack.len) {
         return vm.throw("too much recursion", .{});