resize

nova_vm/src/heap/array_buffer.rs

@@ -1,6 +1,6 @@
 use std::{
     alloc::{alloc_zeroed, handle_alloc_error, Layout},
-    ptr::{read_unaligned, write_unaligned, NonNull},
+    ptr::{read_unaligned, write_bytes, write_unaligned, NonNull},
 };
 
 use crate::{
@@ -101,6 +101,20 @@ impl BackingStore {
         self.cap
     }
 
+    pub fn resize(&mut self, size: u32) {
+        debug_assert!(size <= self.cap);
+        let len = self.len;
+        self.len = size;
+        if size < len {
+            // Zero out the "dropped" bytes.
+            if let Some(data) = self.ptr {
+                // SAFETY: The data is properly initialized, and the T being written is
+                // checked to be fully within the length of the data allocation.
+                unsafe { write_bytes(data.as_ptr().add(size as usize), 0, (len - size) as usize) }
+            }
+        }
+    }
+
     pub fn view_len<T: Viewable>(&self, offset: u32) -> u32 {
         let size = std::mem::size_of::<T>() as u32;
         (self.len - offset) / size