More mem sketching.

dvm-lib/src/vm/mem.rs

@@ -1,5 +1,9 @@
+use std::alloc::{Layout, alloc};
 use std::any::TypeId;
-use std::ptr::Pointee;
+use std::borrow::Borrow;
+use std::collections::HashSet;
+use std::hash::{Hash, Hasher};
+use std::ptr::{Pointee, slice_from_raw_parts_mut};
 use std::rc::Rc;
 use std::sync::OnceLock;
 
@@ -31,8 +35,24 @@ impl<T: Trace + ?Sized + 'static> Gc<T> {
     }
 }
 
-struct GcMut<T: Trace> {
-    inner: *mut GcInner<T>,
+impl<T: Trace + ?Sized> Clone for Gc<T> {
+    fn clone(&self) -> Self {
+        Gc::from_inner(self.inner)
+    }
+}
+
+impl<T: Trace + ?Sized + PartialEq> PartialEq for Gc<T> {
+    fn eq(&self, other: &Self) -> bool {
+        self.data().eq(other.data())
+    }
+}
+
+impl<T: Trace + ?Sized + Eq> Eq for Gc<T> {}
+
+impl<T: Trace + ?Sized + Hash> Hash for Gc<T> {
+    fn hash<H: Hasher>(&self, state: &mut H) {
+        self.data().hash(state)
+    }
 }
 
 struct GcInner<T: Trace + ?Sized> {
@@ -55,6 +75,54 @@ impl<T: Trace> GcInner<T> {
     }
 }
 
+impl<T: Trace + Clone> GcInner<T> {
+    fn from_slice(slice: &[T]) -> *mut GcInner<[T]> {
+        let data_layout = Layout::array::<T>(slice.len()).expect(&format!(
+            "Unable to create Layout for array size {}",
+            slice.len()
+        ));
+        let (gc_inner_layout, _) = Layout::new::<GcInner<()>>()
+            .extend(data_layout)
+            .expect("Unable to create and extend Layout for GcInner<()>");
+        let gc_inner_layout = gc_inner_layout.pad_to_align();
+
+        // alloc
+        let ptr = unsafe { alloc(gc_inner_layout) };
+        if ptr.is_null() {
+            panic!("Unable to allocate memory for GcInner<()>");
+        }
+
+        // get wide pointer
+        let gc_inner = slice_from_raw_parts_mut(ptr, slice.len()) as *mut GcInner<[T]>;
+
+        // init
+        unsafe {
+            (&raw mut (*gc_inner).borrow_count).write(0);
+            (&raw mut (*gc_inner).borrow_mut_count).write(false);
+            (&raw mut (*gc_inner).color).write(false);
+            (&raw mut (*gc_inner).next).write(None);
+
+            for (i, item) in slice.iter().enumerate() {
+                (&raw mut (*gc_inner).data[i]).write(item.clone());
+            }
+        }
+
+        gc_inner
+    }
+}
+
+impl<T: Trace + ?Sized> GcInner<T> {
+    fn from_dst(data_ptr: *mut T) -> *mut GcInner<T> {
+        todo!()
+    }
+}
+
+impl Trace for () {
+    fn grays(&self) -> Vec<GcAny> {
+        vec![]
+    }
+}
+
 struct GcAny {
     inner_ptr: *mut (),            // like void* in C
     inner_ptr_metadata: *const (), // type-erased metadata
@@ -112,6 +180,7 @@ struct GcAnyVTable {
     trace: fn(*const (), *const ()) -> Vec<GcAny>,
 }
 
+#[derive(Clone)]
 enum Value {
     Object(Gc<Object>),
     Int(i32),
@@ -121,6 +190,7 @@ enum Value {
 
 struct Class {
     name: Rc<str>,
+    field_count: usize, // just a place-holder
 }
 
 #[repr(C)]
@@ -141,8 +211,108 @@ impl Trace for str {
     }
 }
 
-impl From<&str> for Gc<str> {
-    fn from(value: &str) -> Self {
+impl<T: Trace + Clone> From<&[T]> for Gc<[T]> {
+    fn from(value: &[T]) -> Self {
+        Gc::from_inner(GcInner::from_slice(value))
+    }
+}
+
+impl<T: Trace> Trace for [T] {
+    fn grays(&self) -> Vec<GcAny> {
         todo!()
     }
 }
+
+impl Trace for u8 {
+    fn grays(&self) -> Vec<GcAny> {
+        vec![]
+    }
+}
+
+impl From<&str> for Gc<str> {
+    fn from(value: &str) -> Self {
+        let gc_inner = GcInner::from_slice(value.as_bytes()) as *mut GcInner<str>;
+        Gc::from_inner(gc_inner)
+    }
+}
+
+struct DvmHeap {
+    first: Option<GcAny>,
+    last: Option<GcAny>,
+}
+
+impl DvmHeap {
+    fn new() -> Self {
+        Self {
+            first: None,
+            last: None,
+        }
+    }
+
+    fn new_object(&mut self, class: &Class) -> Gc<Object> {
+        let mut fields = Vec::with_capacity(class.field_count);
+        for _ in 0..class.field_count {
+            fields.push(Value::Null);
+        }
+
+        let fields_layout = Layout::array::<Value>(class.field_count).unwrap();
+        let object_layout = Layout::new::<*const Class>()
+            .extend(fields_layout)
+            .unwrap()
+            .0
+            .pad_to_align();
+
+        let ptr = unsafe { alloc(object_layout) };
+        if ptr.is_null() {
+            panic!("Unable to allocate memory for new Object on DvmHeap");
+        }
+
+        let wide_ptr = slice_from_raw_parts_mut(ptr, class.field_count) as *mut Object;
+
+        unsafe {
+            (&raw mut (*wide_ptr).class).write(class);
+            for (i, value) in fields.iter().enumerate() {
+                (&raw mut (*wide_ptr).fields[i]).write(value.clone());
+            }
+        }
+
+        let gc = Gc::from_inner(GcInner::from_dst(wide_ptr));
+        // some logic for adjusting first and last pointers, etc., bookkeeping on the heap, ex:
+        self.first = Some(gc.erase());
+        self.last = Some(gc.erase());
+        gc
+    }
+
+    fn push<T: Trace>(&mut self, data: T) -> Gc<T> {
+        let inner = GcInner::new(data);
+        let inner_ptr = Box::into_raw(Box::new(inner));
+        Gc::from_inner(inner_ptr)
+    }
+}
+
+impl Borrow<str> for Gc<str> {
+    fn borrow(&self) -> &str {
+        self.data()
+    }
+}
+
+fn borrow_test() {
+    let s = Gc::from("hello");
+    let mut interned = HashSet::<Gc<str>>::new();
+    interned.insert(s.clone());
+    if interned.contains("hello") {
+        println!("yay")
+    }
+}
+
+impl Trace for i32 {
+    fn grays(&self) -> Vec<GcAny> {
+        vec![]
+    }
+}
+
+fn push_test() {
+    let num = 42_i32;
+    let mut heap = DvmHeap::new();
+    let gc_num = heap.push(num);
+}