feat(serde_v8): deserialize ArrayBuffers (#13436)

Previously we would only deserialize `ArrayBufferView`s as zero-copy bufs

This avoids rewrapping `ArrayBuffers` in `ArrayBufferView`s when implementing APIs that take [BufferSource](https://webidl.spec.whatwg.org/#BufferSource) args passed through the op-layer

2 files changed, 56 insertions, 33 deletions

diff --git a/serde_v8/src/magic/buffer.rs b/serde_v8/src/magic/buffer.rs
index 80f2f8bc7..e6f85324e 100644
--- a/serde_v8/src/magic/buffer.rs
+++ b/serde_v8/src/magic/buffer.rs
@@ -1,5 +1,6 @@
 // Copyright 2018-2022 the Deno authors. All rights reserved. MIT license.
 
+use std::convert::TryFrom;
 use std::fmt;
 use std::ops::Deref;
 use std::ops::DerefMut;
@@ -15,22 +16,29 @@ pub enum MagicBuffer {
 }
 
 impl MagicBuffer {
-  pub fn new<'s>(
-    scope: &mut v8::HandleScope<'s>,
-    view: v8::Local<v8::ArrayBufferView>,
-  ) -> Self {
-    Self::try_new(scope, view).unwrap()
+  pub fn empty() -> Self {
+    MagicBuffer::ToV8(Mutex::new(Some(vec![0_u8; 0].into_boxed_slice())))
   }
+}
 
-  pub fn try_new<'s>(
-    scope: &mut v8::HandleScope<'s>,
-    view: v8::Local<v8::ArrayBufferView>,
-  ) -> Result<Self, v8::DataError> {
-    Ok(Self::FromV8(ZeroCopyBuf::try_new(scope, view)?))
+impl<'s> TryFrom<v8::Local<'s, v8::ArrayBuffer>> for MagicBuffer {
+  type Error = v8::DataError;
+  fn try_from(buffer: v8::Local<v8::ArrayBuffer>) -> Result<Self, Self::Error> {
+    Ok(Self::FromV8(ZeroCopyBuf::try_from(buffer)?))
   }
+}
 
-  pub fn empty() -> Self {
-    MagicBuffer::ToV8(Mutex::new(Some(vec![0_u8; 0].into_boxed_slice())))
+// TODO(@AaronO): consider streamlining this as "ScopedValue" ?
+type ScopedView<'a, 'b, 's> = (
+  &'s mut v8::HandleScope<'a>,
+  v8::Local<'b, v8::ArrayBufferView>,
+);
+impl<'a, 'b, 's> TryFrom<ScopedView<'a, 'b, 's>> for MagicBuffer {
+  type Error = v8::DataError;
+  fn try_from(
+    scoped_view: ScopedView<'a, 'b, 's>,
+  ) -> Result<Self, Self::Error> {
+    Ok(Self::FromV8(ZeroCopyBuf::try_from(scoped_view)?))
   }
 }
 
diff --git a/serde_v8/src/magic/zero_copy_buf.rs b/serde_v8/src/magic/zero_copy_buf.rs
index b536f5859..30acd8137 100644
--- a/serde_v8/src/magic/zero_copy_buf.rs
+++ b/serde_v8/src/magic/zero_copy_buf.rs
@@ -25,31 +25,46 @@ pub struct ZeroCopyBuf {
 unsafe impl Send for ZeroCopyBuf {}
 
 impl ZeroCopyBuf {
-  pub fn new<'s>(
-    scope: &mut v8::HandleScope<'s>,
-    view: v8::Local<v8::ArrayBufferView>,
-  ) -> Self {
-    Self::try_new(scope, view).unwrap()
-  }
-
-  pub fn try_new<'s>(
-    scope: &mut v8::HandleScope<'s>,
-    view: v8::Local<v8::ArrayBufferView>,
+  pub fn from_buffer(
+    buffer: v8::Local<v8::ArrayBuffer>,
+    byte_offset: usize,
+    byte_length: usize,
   ) -> Result<Self, v8::DataError> {
-    let backing_store = view.buffer(scope).unwrap().get_backing_store();
-    if backing_store.is_shared() {
-      return Err(v8::DataError::BadType {
+    let backing_store = buffer.get_backing_store();
+    match backing_store.is_shared() {
+      true => Err(v8::DataError::BadType {
         actual: "shared ArrayBufferView",
         expected: "non-shared ArrayBufferView",
-      });
+      }),
+      false => Ok(Self {
+        backing_store,
+        byte_offset,
+        byte_length,
+      }),
     }
-    let byte_offset = view.byte_offset();
-    let byte_length = view.byte_length();
-    Ok(Self {
-      backing_store,
-      byte_offset,
-      byte_length,
-    })
+  }
+}
+
+impl<'s> TryFrom<v8::Local<'s, v8::ArrayBuffer>> for ZeroCopyBuf {
+  type Error = v8::DataError;
+  fn try_from(buffer: v8::Local<v8::ArrayBuffer>) -> Result<Self, Self::Error> {
+    Self::from_buffer(buffer, 0, buffer.byte_length())
+  }
+}
+
+// TODO(@AaronO): consider streamlining this as "ScopedValue" ?
+type ScopedView<'a, 'b, 's> = (
+  &'s mut v8::HandleScope<'a>,
+  v8::Local<'b, v8::ArrayBufferView>,
+);
+impl<'a, 'b, 's> TryFrom<ScopedView<'a, 'b, 's>> for ZeroCopyBuf {
+  type Error = v8::DataError;
+  fn try_from(
+    scoped_view: ScopedView<'a, 'b, 's>,
+  ) -> Result<Self, Self::Error> {
+    let (scope, view) = scoped_view;
+    let buffer = view.buffer(scope).unwrap();
+    Self::from_buffer(buffer, view.byte_offset(), view.byte_length())
   }
 }