tidy up deno_core modules (#5923)

1 files changed, 67 insertions, 0 deletions

diff --git a/core/zero_copy_buf.rs b/core/zero_copy_buf.rs
new file mode 100644
index 000000000..b10c14045
--- /dev/null
+++ b/core/zero_copy_buf.rs
@@ -0,0 +1,67 @@
+use crate::bindings;
+use rusty_v8 as v8;
+use std::ops::Deref;
+use std::ops::DerefMut;
+
+/// A ZeroCopyBuf encapsulates a slice that's been borrowed from a JavaScript
+/// ArrayBuffer object. JavaScript objects can normally be garbage collected,
+/// but the existence of a ZeroCopyBuf inhibits this until it is dropped. It
+/// behaves much like an Arc<[u8]>, although a ZeroCopyBuf currently can't be
+/// cloned.
+pub struct ZeroCopyBuf {
+  backing_store: v8::SharedRef<v8::BackingStore>,
+  byte_offset: usize,
+  byte_length: usize,
+}
+
+unsafe impl Send for ZeroCopyBuf {}
+
+impl ZeroCopyBuf {
+  pub fn new(view: v8::Local<v8::ArrayBufferView>) -> Self {
+    let backing_store = view.buffer().unwrap().get_backing_store();
+    let byte_offset = view.byte_offset();
+    let byte_length = view.byte_length();
+    Self {
+      backing_store,
+      byte_offset,
+      byte_length,
+    }
+  }
+}
+
+impl Deref for ZeroCopyBuf {
+  type Target = [u8];
+  fn deref(&self) -> &[u8] {
+    unsafe {
+      bindings::get_backing_store_slice(
+        &self.backing_store,
+        self.byte_offset,
+        self.byte_length,
+      )
+    }
+  }
+}
+
+impl DerefMut for ZeroCopyBuf {
+  fn deref_mut(&mut self) -> &mut [u8] {
+    unsafe {
+      bindings::get_backing_store_slice_mut(
+        &self.backing_store,
+        self.byte_offset,
+        self.byte_length,
+      )
+    }
+  }
+}
+
+impl AsRef<[u8]> for ZeroCopyBuf {
+  fn as_ref(&self) -> &[u8] {
+    &*self
+  }
+}
+
+impl AsMut<[u8]> for ZeroCopyBuf {
+  fn as_mut(&mut self) -> &mut [u8] {
+    &mut *self
+  }
+}