From 0d090df3e206dd909849fd05cd869416e4489f74 Mon Sep 17 00:00:00 2001
From: Hong Shin <hongshin@google.com>
Date: Mon, 22 Jan 2024 14:16:26 -0800
Subject: [PATCH] Implement ProxiedWithRawVTable, ProxiedWithRawOptionalVTable,
 and ProxiedWithPresence for Messages

Stage 2 of 3.
Fleshed out the bodies required by the aforementioned contracts above.
We create MessageVTable and utilize the `unsafe fns` directly in `message.cc` -- a departure from PrimitiveVTables.

In the final followup CL, we will perform the field_entry swapover and update all unit tests.

PiperOrigin-RevId: 600567890
---
 rust/internal.rs                             |  4 +--
 rust/vtable.rs                               | 22 +++++++-----
 src/google/protobuf/compiler/rust/message.cc | 38 ++++++++++++++------
 3 files changed, 44 insertions(+), 20 deletions(-)

diff --git a/rust/internal.rs b/rust/internal.rs
index e66e7b1630..ac7d67367b 100644
--- a/rust/internal.rs
+++ b/rust/internal.rs
@@ -11,8 +11,8 @@
 
 pub use crate::r#enum::Enum;
 pub use crate::vtable::{
-    new_vtable_field_entry, BytesMutVTable, BytesOptionalMutVTable, MessageOptionalVTable,
-    MessageVTable, PrimitiveOptionalMutVTable, PrimitiveVTable, PrimitiveWithRawVTable,
+    new_vtable_field_entry, BytesMutVTable, BytesOptionalMutVTable, MessageVTable,
+    PrimitiveOptionalMutVTable, PrimitiveVTable, PrimitiveWithRawVTable,
     ProxiedWithRawOptionalVTable, ProxiedWithRawVTable, RawVTableMutator,
     RawVTableOptionalMutatorData,
 };
diff --git a/rust/vtable.rs b/rust/vtable.rs
index de44895907..f577f994fb 100644
--- a/rust/vtable.rs
+++ b/rust/vtable.rs
@@ -134,10 +134,14 @@ impl<'msg, T: ProxiedWithRawVTable + ?Sized> RawVTableMutator<'msg, T> {
         RawVTableMutator { msg_ref, vtable: NonNull::from(vtable).cast(), _phantom: PhantomData }
     }
 
-    fn vtable(self) -> &'static T::VTable {
+    pub fn vtable(self) -> &'static T::VTable {
         // SAFETY: This was cast from `&'static T::VTable`.
         unsafe { self.vtable.cast().as_ref() }
     }
+
+    pub fn msg_ref(self) -> MutatorMessageRef<'msg> {
+        self.msg_ref
+    }
 }
 
 /// [`RawVTableMutator`], but also includes has/clear.
@@ -197,7 +201,11 @@ impl<'msg, T: ProxiedWithRawOptionalVTable + ?Sized> RawVTableOptionalMutatorDat
         Self { msg_ref, optional_vtable: NonNull::from(vtable).cast(), _phantom: PhantomData }
     }
 
-    fn optional_vtable(self) -> &'static T::OptionalVTable {
+    pub fn msg_ref(self) -> MutatorMessageRef<'msg> {
+        self.msg_ref
+    }
+
+    pub fn optional_vtable(self) -> &'static T::OptionalVTable {
         // SAFETY: This was cast from `&'static T::OptionalVTable` in `new`.
         unsafe { self.optional_vtable.cast().as_ref() }
     }
@@ -507,10 +515,8 @@ impl<'msg, T: PrimitiveWithRawVTable> RawVTableOptionalMutatorData<'msg, T> {
 }
 
 #[derive(Debug)]
-#[allow(unused)]
-pub struct MessageOptionalVTable {
-    pub base: MessageVTable,
+pub struct MessageVTable {
+    pub getter: unsafe extern "C" fn(msg: RawMessage) -> RawMessage,
+    pub mut_getter: unsafe extern "C" fn(msg: RawMessage) -> RawMessage,
+    pub clearer: unsafe extern "C" fn(msg: RawMessage),
 }
-
-#[derive(Debug)]
-pub struct MessageVTable {}
diff --git a/src/google/protobuf/compiler/rust/message.cc b/src/google/protobuf/compiler/rust/message.cc
index 1c038935fa..2185babecc 100644
--- a/src/google/protobuf/compiler/rust/message.cc
+++ b/src/google/protobuf/compiler/rust/message.cc
@@ -586,25 +586,31 @@ void GenerateRs(Context& ctx, const Descriptor& msg) {
           type VTable = $pbi$::MessageVTable;
 
           fn make_view(_private: $pbi$::Private,
-                      _mut_inner: $pbi$::RawVTableMutator<'_, Self>)
+                      mut_inner: $pbi$::RawVTableMutator<'_, Self>)
                       -> $pb$::View<'_, Self> {
-            todo!()
+            let msg = unsafe {
+              (mut_inner.vtable().getter)(mut_inner.msg_ref().msg())
+            };
+            $Msg$View::new($pbi$::Private, msg)
           }
 
           fn make_mut(_private: $pbi$::Private,
-                      _inner: $pbi$::RawVTableMutator<'_, Self>)
+                      inner: $pbi$::RawVTableMutator<'_, Self>)
                       -> $pb$::Mut<'_, Self> {
-            todo!()
+            let raw_submsg = unsafe {
+              (inner.vtable().mut_getter)(inner.msg_ref().msg())
+            };
+            $Msg$Mut::from_parent($pbi$::Private, inner.msg_ref(), raw_submsg)
           }
         }
 
         impl $pbi$::ProxiedWithRawOptionalVTable for $Msg$ {
-          type OptionalVTable = $pbi$::MessageOptionalVTable;
+          type OptionalVTable = $pbi$::MessageVTable;
 
           fn upcast_vtable(_private: $pbi$::Private,
                            optional_vtable: &'static Self::OptionalVTable)
                           -> &'static Self::VTable {
-            &optional_vtable.base
+            &optional_vtable
           }
         }
 
@@ -612,14 +618,26 @@ void GenerateRs(Context& ctx, const Descriptor& msg) {
           type PresentMutData<'a> = $pbr$::MessagePresentMutData<'a, $Msg$>;
           type AbsentMutData<'a> = $pbr$::MessageAbsentMutData<'a, $Msg$>;
 
-          fn clear_present_field(_present_mutator: Self::PresentMutData<'_>)
+          fn clear_present_field(present_mutator: Self::PresentMutData<'_>)
              -> Self::AbsentMutData<'_> {
-            todo!();
+             // SAFETY: The raw ptr msg_ref is valid
+            unsafe {
+              (present_mutator.optional_vtable().clearer);
+              (present_mutator.msg_ref().msg());
+
+             $pbi$::RawVTableOptionalMutatorData::new($pbi$::Private,
+               present_mutator.msg_ref(),
+               present_mutator.optional_vtable())
+            }
           }
 
-          fn set_absent_to_default(_absent_mutator: Self::AbsentMutData<'_>)
+          fn set_absent_to_default(absent_mutator: Self::AbsentMutData<'_>)
              -> Self::PresentMutData<'_> {
-           todo!();
+           unsafe {
+             $pbi$::RawVTableOptionalMutatorData::new($pbi$::Private,
+               absent_mutator.msg_ref(),
+               absent_mutator.optional_vtable())
+           }
           }
         }