refactor(core): remove ZeroCopyBuf's dep on the bindings mod (#10232)

Also cleanup `bindings::deserialize()/decode()` so they 
use the `ZeroCopyBuf` abstraction rather than reimplementing it.

This cleanup will facilitate moving `ZeroCopyBuf` to `serde_v8` 
since it's now self contained and there are no other 
`get_backing_store_slice()` callers.

core/bindings.rs

@@ -12,7 +12,6 @@ use crate::ZeroCopyBuf;
 use rusty_v8 as v8;
 use serde::Serialize;
 use serde_v8::to_v8;
-use std::cell::Cell;
 use std::convert::TryFrom;
 use std::convert::TryInto;
 use std::io::{stdout, Write};
@@ -287,29 +286,6 @@ pub extern "C" fn promise_reject_callback(message: v8::PromiseRejectMessage) {
   };
 }
 
-pub(crate) unsafe fn get_backing_store_slice(
-  backing_store: &v8::SharedRef<v8::BackingStore>,
-  byte_offset: usize,
-  byte_length: usize,
-) -> &[u8] {
-  let cells: *const [Cell<u8>] =
-    &backing_store[byte_offset..byte_offset + byte_length];
-  let bytes = cells as *const [u8];
-  &*bytes
-}
-
-#[allow(clippy::mut_from_ref)]
-pub(crate) unsafe fn get_backing_store_slice_mut(
-  backing_store: &v8::SharedRef<v8::BackingStore>,
-  byte_offset: usize,
-  byte_length: usize,
-) -> &mut [u8] {
-  let cells: *const [Cell<u8>] =
-    &backing_store[byte_offset..byte_offset + byte_length];
-  let bytes = cells as *const _ as *mut [u8];
-  &mut *bytes
-}
-
 fn print(
   scope: &mut v8::HandleScope,
   args: v8::FunctionCallbackArguments,
@@ -599,14 +575,8 @@ fn decode(
     }
   };
 
-  let backing_store = view.buffer(scope).unwrap().get_backing_store();
+  let zero_copy = ZeroCopyBuf::new(scope, view);
-  let buf = unsafe {
+  let buf = &zero_copy;
-    get_backing_store_slice(
-      &backing_store,
-      view.byte_offset(),
-      view.byte_length(),
-    )
-  };
 
   // Strip BOM
   let buf =
@@ -694,14 +664,8 @@ fn deserialize(
     }
   };
 
-  let backing_store = view.buffer(scope).unwrap().get_backing_store();
+  let zero_copy = ZeroCopyBuf::new(scope, view);
-  let buf = unsafe {
+  let buf = &zero_copy;
-    get_backing_store_slice(
-      &backing_store,
-      view.byte_offset(),
-      view.byte_length(),
-    )
-  };
 
   let serialize_deserialize = Box::new(SerializeDeserialize {});
   let mut value_deserializer =

core/zero_copy_buf.rs

@@ -1,7 +1,7 @@
 // Copyright 2018-2021 the Deno authors. All rights reserved. MIT license.
 
-use crate::bindings;
 use rusty_v8 as v8;
+use std::cell::Cell;
 use std::ops::Deref;
 use std::ops::DerefMut;
 
@@ -45,7 +45,7 @@ impl Deref for ZeroCopyBuf {
   type Target = [u8];
   fn deref(&self) -> &[u8] {
     unsafe {
-      bindings::get_backing_store_slice(
+      get_backing_store_slice(
         &self.backing_store,
         self.byte_offset,
         self.byte_length,
@@ -57,7 +57,7 @@ impl Deref for ZeroCopyBuf {
 impl DerefMut for ZeroCopyBuf {
   fn deref_mut(&mut self) -> &mut [u8] {
     unsafe {
-      bindings::get_backing_store_slice_mut(
+      get_backing_store_slice_mut(
         &self.backing_store,
         self.byte_offset,
         self.byte_length,
@@ -77,3 +77,26 @@ impl AsMut<[u8]> for ZeroCopyBuf {
     &mut *self
   }
 }
+
+unsafe fn get_backing_store_slice(
+  backing_store: &v8::SharedRef<v8::BackingStore>,
+  byte_offset: usize,
+  byte_length: usize,
+) -> &[u8] {
+  let cells: *const [Cell<u8>] =
+    &backing_store[byte_offset..byte_offset + byte_length];
+  let bytes = cells as *const [u8];
+  &*bytes
+}
+
+#[allow(clippy::mut_from_ref)]
+unsafe fn get_backing_store_slice_mut(
+  backing_store: &v8::SharedRef<v8::BackingStore>,
+  byte_offset: usize,
+  byte_length: usize,
+) -> &mut [u8] {
+  let cells: *const [Cell<u8>] =
+    &backing_store[byte_offset..byte_offset + byte_length];
+  let bytes = cells as *const _ as *mut [u8];
+  &mut *bytes
+}