Set up for Rust-cpp Protobuf implementation message matcher.

PiperOrigin-RevId: 658397591

rust/cpp.rs

@@ -319,6 +319,19 @@ pub fn debug_string(_private: Private, msg: RawMessage, f: &mut fmt::Formatter<'
     write!(f, "{dbg_str}")
 }
 
+extern "C" {
+    /// # Safety
+    /// - `msg1` and `msg2` legally dereferencable MessageLite* pointers.
+    fn proto2_rust_messagelite_equals(msg1: RawMessage, msg2: RawMessage) -> bool;
+}
+
+/// # Safety
+/// - `msg1` and `msg2` legally dereferencable MessageLite* pointers.
+pub unsafe fn raw_message_equals(_private: Private, msg1: RawMessage, msg2: RawMessage) -> bool {
+    // SAFETY: Same constraints placed on caller.
+    unsafe { proto2_rust_messagelite_equals(msg1, msg2) }
+}
+
 pub type RawMapIter = UntypedMapIterator;
 
 /// The raw contents of every generated message.

rust/cpp_kernel/BUILD

@@ -5,12 +5,14 @@ load("@rules_rust//rust:defs.bzl", "rust_library")
 cc_library(
     name = "cpp_api",
     srcs = [
+        "compare.cc",
         "debug.cc",
         "map.cc",
         "repeated.cc",
         "strings.cc",
     ],
     hdrs = [
+        "compare.h",
         "debug.h",
         "map.h",
         "rust_alloc_for_cpp_api.h",
@@ -25,6 +27,7 @@ cc_library(
         ":rust_alloc_for_cpp_api",  # buildcleaner: keep
         "//src/google/protobuf",
         "//src/google/protobuf:protobuf_lite",
+        "//src/google/protobuf/io",
         "@com_google_absl//absl/log:absl_check",
         "@com_google_absl//absl/log:absl_log",
         "@com_google_absl//absl/strings:string_view",

rust/cpp_kernel/compare.cc

@@ -0,0 +1,26 @@
+#include "rust/cpp_kernel/compare.h"
+
+#include <string>
+
+#include "google/protobuf/io/zero_copy_stream_impl_lite.h"
+#include "google/protobuf/message_lite.h"
+
+static std::string SerializeDeterministically(const google::protobuf::MessageLite& m) {
+  std::string serialized;
+  {
+    google::protobuf::io::StringOutputStream output_stream(&serialized);
+    google::protobuf::io::CodedOutputStream coded_stream(&output_stream);
+    coded_stream.SetSerializationDeterministic(true);
+    m.SerializePartialToCodedStream(&coded_stream);
+  }
+  return serialized;
+}
+
+extern "C" {
+
+bool proto2_rust_messagelite_equals(const google::protobuf::MessageLite* msg1,
+                                    const google::protobuf::MessageLite* msg2) {
+  return SerializeDeterministically(*msg1) == SerializeDeterministically(*msg2);
+}
+
+}  // extern "C"

rust/cpp_kernel/compare.h

@@ -0,0 +1,13 @@
+#ifndef GOOGLE_PROTOBUF_RUST_CPP_KERNEL_COMPARE_H__
+#define GOOGLE_PROTOBUF_RUST_CPP_KERNEL_COMPARE_H__
+
+#include "google/protobuf/message_lite.h"
+
+extern "C" {
+
+bool proto2_rust_messagelite_equals(const google::protobuf::MessageLite* msg1,
+                                    const google::protobuf::MessageLite* msg2);
+
+}  // extern "C"
+
+#endif  // GOOGLE_PROTOBUF_RUST_CPP_KERNEL_COMPARE_H__