BackingStore tests

nova_vm/src/heap/array_buffer.rs

@@ -25,7 +25,7 @@ use super::{
 /// the capacity or length. The pointer can be None
 /// if the length of the buffer is zero.
 #[derive(Debug, Copy, Clone)]
-pub(crate) struct BackingStore {
+pub struct BackingStore {
     ptr: Option<NonNull<u8>>,
     cap: u32,
     byte_length: u32,
@@ -129,7 +129,7 @@ impl BackingStore {
     }
 
     fn as_ptr(&self, byte_offset: u32) -> Option<*const u8> {
-        if byte_offset > self.byte_length {
+        if byte_offset >= self.byte_length {
             None
         } else if let Some(data) = self.ptr {
             // SAFETY: The data is properly initialized, and the T being read is
@@ -141,7 +141,7 @@ impl BackingStore {
     }
 
     fn as_mut_ptr(&mut self, byte_offset: u32) -> Option<*mut u8> {
-        if byte_offset > self.byte_length {
+        if byte_offset >= self.byte_length {
             None
         } else if let Some(data) = self.ptr {
             // SAFETY: The data is properly initialized, and the T being read is
@@ -155,7 +155,7 @@ impl BackingStore {
     pub fn get<T: Viewable>(&self, offset: u32) -> Option<T> {
         let size = std::mem::size_of::<T>() as u32;
         let byte_offset = offset * size;
-        if byte_offset > self.byte_length {
+        if byte_offset >= self.byte_length {
             None
         } else if let Some(data) = self.ptr {
             // SAFETY: The data is properly initialized, and the T being read is
@@ -192,20 +192,20 @@ impl BackingStore {
             // SAFETY: Source buffer length is valid, destination buffer
             // is likewise at least equal in length to source, and both
             // are properly aligned for bytes.
-            unsafe { std::ptr::copy::<u8>(src, dst, byte_length) }
+            unsafe { std::ptr::copy::<u8>(src, dst, byte_length as usize) }
         }
     }
 }
 
 #[derive(Debug)]
-pub(crate) enum InternalBuffer {
+pub enum InternalBuffer {
     Detached,
     Growable(BackingStore),
     Static(BackingStore),
 }
 
 #[derive(Debug)]
-pub(crate) struct ArrayBufferHeapData {
+pub struct ArrayBufferHeapData {
     pub(super) object_index: Option<ObjectIndex>,
     pub(super) buffer: InternalBuffer,
     // detach_key
@@ -300,3 +300,84 @@ fn array_buffer_species(_heap: &mut Heap, this: Value, _args: &[Value]) -> JsRes
 fn array_buffer_todo(_heap: &mut Heap, _this: Value, _args: &[Value]) -> JsResult<Value> {
     todo!()
 }
+
+#[test]
+fn new_backing_store() {
+    let bs = BackingStore::new(0);
+    assert_eq!(bs.len(), 0);
+    assert_eq!(bs.capacity(), 0);
+    assert_eq!(bs.get::<u8>(0), None);
+
+    let bs = BackingStore::new(8);
+    assert_eq!(bs.len(), 8);
+    assert_eq!(bs.capacity(), 8);
+    for i in 0..8 {
+        assert_eq!(bs.get::<u8>(i as u32), Some(0));
+    }
+}
+
+#[test]
+fn new_backing_store_with_capacity() {
+    let bs = BackingStore::new_with_capacity(0, 8);
+    assert_eq!(bs.len(), 0);
+    assert_eq!(bs.capacity(), 8);
+    for i in 0..8 {
+        assert_eq!(bs.get::<u8>(i as u32), None);
+    }
+
+    let bs = BackingStore::new_with_capacity(8, 16);
+    assert_eq!(bs.len(), 8);
+    assert_eq!(bs.capacity(), 16);
+    for i in 0..8 {
+        assert_eq!(bs.get::<u8>(i as u32), Some(0));
+    }
+    for i in 8..16 {
+        assert_eq!(bs.get::<u8>(i as u32), None);
+    }
+}
+
+#[test]
+fn backing_store_set() {
+    let mut bs = BackingStore::new(8);
+    assert_eq!(bs.len(), 8);
+    assert_eq!(bs.capacity(), 8);
+    for i in 0..8 {
+        assert_eq!(bs.get::<u8>(i as u32), Some(0));
+    }
+
+    for i in 0..8 {
+        bs.set::<u8>(i as u32, i + 1);
+    }
+
+    for i in 0..8 {
+        assert_eq!(bs.get::<u8>(i as u32), Some(i + 1));
+    }
+}
+
+#[test]
+fn backing_store_resize() {
+    let mut bs = BackingStore::new_with_capacity(0, 8);
+    bs.resize(8);
+    assert_eq!(bs.len(), 8);
+    assert_eq!(bs.capacity(), 8);
+    for i in 0..8 {
+        assert_eq!(bs.get::<u8>(i as u32), Some(0));
+    }
+
+    for i in 0..8 {
+        bs.set::<u8>(i as u32, i + 1);
+    }
+
+    let ptr = bs.as_ptr(0).unwrap();
+    bs.resize(0);
+
+    // SAFETY: Backing store is not deallocated: Zero index pointer is still valid
+    // and is not read beyond its allocated capacity. The only usual safety requirement
+    // broken is to read beyond the buffer length, which is safe as the outside is still
+    // properly initialized u8s.
+    unsafe {
+        for i in 0..8 {
+            assert_eq!(ptr.add(i).read(), 0);
+        }
+    }
+}