[ESI] Factor out gRPC/proto usage in Cosim backend (#9350)

To facilitate reuse of the gRPC/protobuf generated files, and to equally hide these dependencies from the user, this PR factors out all references of gRPC and `cosim.grpc.pb.h` into a stand-alone library.

Author: mortbopet

lib/Dialect/ESI/runtime/CMakeLists.txt

@@ -287,48 +287,66 @@ if(ESI_COSIM)
     find_package(gRPC REQUIRED CONFIG)
   endif()
 
-  add_library(CosimBackend SHARED
-    ${CMAKE_CURRENT_SOURCE_DIR}/cpp/lib/backends/Cosim.cpp
+  set(PROTO_BINARY_DIR "${CMAKE_CURRENT_BINARY_DIR}/generated")
+
+  # CosimRpc library - wraps gRPC/protobuf dependencies
+  add_library(CosimRpc SHARED
+    ${CMAKE_CURRENT_SOURCE_DIR}/cpp/lib/backends/RpcClient.cpp
     ${CMAKE_CURRENT_SOURCE_DIR}/cpp/lib/backends/RpcServer.cpp
     ${CMAKE_CURRENT_SOURCE_DIR}/cosim.proto
   )
   set(ESICppRuntimeBackendHeaders
     ${ESICppRuntimeBackendHeaders}
-    ${CMAKE_CURRENT_SOURCE_DIR}/cpp/include/esi/backends/Cosim.h
+    ${CMAKE_CURRENT_SOURCE_DIR}/cpp/include/esi/backends/RpcClient.h
     ${CMAKE_CURRENT_SOURCE_DIR}/cpp/include/esi/backends/RpcServer.h
   )
 
-  target_link_libraries(CosimBackend PUBLIC
+  target_link_libraries(CosimRpc PUBLIC
     ESICppRuntime
     protobuf::libprotobuf
     gRPC::grpc++
   )
-  set(PROTO_BINARY_DIR "${CMAKE_CURRENT_BINARY_DIR}/generated")
-  target_include_directories(CosimBackend PUBLIC "$<BUILD_INTERFACE:${PROTO_BINARY_DIR}>")
+  target_include_directories(CosimRpc PUBLIC "$<BUILD_INTERFACE:${PROTO_BINARY_DIR}>")
   protobuf_generate(
-      TARGET CosimBackend
+      TARGET CosimRpc
       PROTOC_OUT_DIR "${PROTO_BINARY_DIR}")
   protobuf_generate(
-      TARGET CosimBackend
+      TARGET CosimRpc
       LANGUAGE grpc
       GENERATE_EXTENSIONS .grpc.pb.h .grpc.pb.cc
       PLUGIN "protoc-gen-grpc=\$<TARGET_FILE:gRPC::grpc_cpp_plugin>"
       PROTOC_OUT_DIR "${PROTO_BINARY_DIR}")
 
+
+  # CosimBackend library - the ESI backend plugin
+  add_library(CosimBackend SHARED
+    ${CMAKE_CURRENT_SOURCE_DIR}/cpp/lib/backends/Cosim.cpp
+  )
+  set(ESICppRuntimeBackendHeaders
+    ${ESICppRuntimeBackendHeaders}
+    ${CMAKE_CURRENT_SOURCE_DIR}/cpp/include/esi/backends/Cosim.h
+  )
+
+  target_link_libraries(CosimBackend PUBLIC
+    ESICppRuntime
+    CosimRpc
+  )
+  target_include_directories(CosimBackend PUBLIC "$<BUILD_INTERFACE:${PROTO_BINARY_DIR}>")
+
   add_dependencies(ESIRuntime CosimBackend)
 
   if(WIN32)
     # Windows cosim backend carries a lot of runtime dependencies, mainly
     # transitively through gRPC. Make sure they're installed as well.
-    install(TARGETS CosimBackend
+    install(TARGETS CosimRpc CosimBackend
       DESTINATION ${ESIRT_INSTALL_LIBDIR}
       RUNTIME_DEPENDENCIES
         PRE_EXCLUDE_REGEXES "api-ms-" "ext-ms-"
         POST_EXCLUDE_REGEXES ".*system32/.*\\.dll"
       COMPONENT ESIRuntime
     )
   else()
-    install(TARGETS CosimBackend
+    install(TARGETS CosimRpc CosimBackend
       DESTINATION ${ESIRT_INSTALL_LIBDIR}
       COMPONENT ESIRuntime
     )

lib/Dialect/ESI/runtime/cpp/cmake/esiaccelConfig.cmake.in

@@ -14,10 +14,27 @@ else()
   )
 endif()
 
+add_library(esiaccel::CosimRpc SHARED IMPORTED)
+set_target_properties(esiaccel::CosimRpc PROPERTIES
+  INTERFACE_INCLUDE_DIRECTORIES "${CMAKE_CURRENT_LIST_DIR}/../include"
+  INTERFACE_LINK_LIBRARIES esiaccel::ESICppRuntime
+)
+
+if(WIN32)
+  set_target_properties(esiaccel::CosimRpc PROPERTIES
+    IMPORTED_LOCATION "${CMAKE_CURRENT_LIST_DIR}/../CosimRpc.dll"
+    IMPORTED_IMPLIB "${CMAKE_CURRENT_LIST_DIR}/../CosimRpc.lib"
+  )
+else()
+  set_target_properties(esiaccel::CosimRpc PROPERTIES
+    IMPORTED_LOCATION "${CMAKE_CURRENT_LIST_DIR}/../@ESIRT_INSTALL_LIBDIR@/libCosimRpc.so"
+  )
+endif()
+
 add_library(esiaccel::CosimBackend SHARED IMPORTED)
 set_target_properties(esiaccel::CosimBackend PROPERTIES
   INTERFACE_INCLUDE_DIRECTORIES "${CMAKE_CURRENT_LIST_DIR}/../include"
-  INTERFACE_LINK_LIBRARIES esiaccel::ESICppRuntime
+  INTERFACE_LINK_LIBRARIES "esiaccel::ESICppRuntime;esiaccel::CosimRpc"
 )
 
 if(WIN32)

lib/Dialect/ESI/runtime/cpp/include/esi/backends/Cosim.h

@@ -7,8 +7,8 @@
 //===----------------------------------------------------------------------===//
 //
 // This is a specialization of the ESI C++ API (backend) for connection into a
-// simulation of an ESI system. Currently uses Cap'nProto RPC, but that could
-// change. Requires Cap'nProto C++ library.
+// simulation of an ESI system. Currently uses gRPC, but that could change.
+// Requires gRPC C++ library.
 //
 // DO NOT EDIT!
 // This file is distributed as part of an ESI package. The source for this file
@@ -26,13 +26,11 @@
 #include <set>
 
 namespace esi {
-namespace cosim {
-class ChannelDesc;
-}
-
 namespace backends {
 namespace cosim {
+
 class CosimEngine;
+class RpcClient;
 
 /// Connect to an ESI simulation.
 class CosimAccelerator : public esi::AcceleratorConnection {
@@ -53,11 +51,6 @@ class CosimAccelerator : public esi::AcceleratorConnection {
   // Set the way this connection will retrieve the manifest.
   void setManifestMethod(ManifestMethod method);
 
-  // C++ doesn't have a mechanism to forward declare a nested class and we don't
-  // want to include the generated header here. So we have to wrap it in a
-  // forward-declared struct we write ourselves.
-  struct StubContainer;
-
   void createEngine(const std::string &engineTypeName, AppIDPath idPath,
                     const ServiceImplDetails &details,
                     const HWClientDetails &clients) override;
@@ -69,7 +62,7 @@ class CosimAccelerator : public esi::AcceleratorConnection {
                                  const HWClientDetails &clients) override;
 
 private:
-  StubContainer *rpcClient;
+  std::unique_ptr<RpcClient> rpcClient;
 
   // We own all channels connected to rpcClient since their lifetime is tied to
   // rpcClient.

lib/Dialect/ESI/runtime/cpp/include/esi/backends/RpcClient.h

@@ -0,0 +1,97 @@
+//===- RpcClient.h - ESI Cosim RPC client -----------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// This file contains the gRPC client implementation for ESI cosimulation.
+// It wraps all gRPC/protobuf dependencies so they don't leak into other
+// headers.
+//
+// DO NOT EDIT!
+// This file is distributed as part of an ESI package. The source for this file
+// should always be modified within CIRCT (lib/dialect/ESI/runtime/cpp).
+//
+//===----------------------------------------------------------------------===//
+
+// NOLINTNEXTLINE(llvm-header-guard)
+#ifndef ESI_BACKENDS_RPCCLIENT_H
+#define ESI_BACKENDS_RPCCLIENT_H
+
+#include "esi/Common.h"
+
+#include <functional>
+#include <memory>
+#include <string>
+#include <vector>
+
+namespace esi {
+namespace backends {
+namespace cosim {
+
+/// A gRPC client for communicating with the cosimulation server.
+/// This class wraps all gRPC/protobuf dependencies.
+class RpcClient {
+public:
+  RpcClient(const std::string &hostname, uint16_t port);
+  ~RpcClient();
+
+  // Non-copyable.
+  RpcClient(const RpcClient &) = delete;
+  RpcClient &operator=(const RpcClient &) = delete;
+
+  /// Get the ESI version from the manifest.
+  uint32_t getEsiVersion() const;
+
+  /// Get the compressed manifest from the server.
+  std::vector<uint8_t> getCompressedManifest() const;
+
+  /// Channel direction as reported by the server.
+  enum class ChannelDirection { ToServer, ToClient };
+
+  /// Description of a channel from the server.
+  struct ChannelDesc {
+    std::string name;
+    std::string type;
+    ChannelDirection dir;
+  };
+
+  /// Get the channel description for a channel name.
+  /// Returns true if the channel was found.
+  bool getChannelDesc(const std::string &channelName, ChannelDesc &desc) const;
+
+  /// List all channels available on the server.
+  std::vector<ChannelDesc> listChannels() const;
+
+  /// Send a message to a server-bound channel.
+  void writeToServer(const std::string &channelName, const MessageData &data);
+
+  /// Callback type for receiving messages from a client-bound channel.
+  /// Return true if the message was consumed, false to retry.
+  using ReadCallback = std::function<bool(const MessageData &)>;
+
+  /// Abstract handle for a read channel connection.
+  /// Destructor disconnects from the channel.
+  class ReadChannelConnection {
+  public:
+    virtual ~ReadChannelConnection() = default;
+    virtual void disconnect() = 0;
+  };
+
+  /// Connect to a client-bound channel and receive messages via callback.
+  /// Returns a handle that disconnects when destroyed.
+  std::unique_ptr<ReadChannelConnection>
+  connectClientReceiver(const std::string &channelName, ReadCallback callback);
+
+private:
+  class Impl;
+  std::unique_ptr<Impl> impl;
+};
+
+} // namespace cosim
+} // namespace backends
+} // namespace esi
+
+#endif // ESI_BACKENDS_RPCCLIENT_H