[lldb[RPC] Upstream RPC server interface emitters

This commit upstreams the LLDB RPC server interface emitters. These
emitters generate the server-side API interfaces for RPC, which
communicate directly with liblldb itself out of process using the SB
API.

https://discourse.llvm.org/t/rfc-upstreaming-lldb-rpc/85804

Author: chelcassanova

lldb/tools/lldb-rpc/lldb-rpc-gen/server/RPCServerHeaderEmitter.cpp

@@ -0,0 +1,75 @@
+//===-- RPCServerHeaderEmitter.cpp ----------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#include "RPCServerHeaderEmitter.h"
+#include "RPCCommon.h"
+
+#include "clang/AST/AST.h"
+#include "clang/AST/Mangle.h"
+#include "clang/Frontend/CompilerInstance.h"
+
+#include "llvm/ADT/StringRef.h"
+#include "llvm/Support/ToolOutputFile.h"
+#include "llvm/Support/raw_ostream.h"
+
+using namespace clang;
+using namespace lldb_rpc_gen;
+
+void RPCServerHeaderEmitter::EmitMethod(const Method &method) {
+  // We'll be using the mangled name in order to disambiguate
+  // overloaded methods.
+  const std::string &MangledName = method.MangledName;
+
+  EmitLine("class " + MangledName +
+           " : public rpc_common::RPCFunctionInstance {");
+  EmitLine("public:");
+  IndentLevel++;
+  EmitConstructor(MangledName);
+  EmitDestructor(MangledName);
+  EmitHandleRPCCall();
+  IndentLevel--;
+  EmitLine("};");
+}
+
+void RPCServerHeaderEmitter::EmitHandleRPCCall() {
+  EmitLine("bool HandleRPCCall(rpc_common::Connection &connection, "
+           "rpc_common::RPCStream &send, rpc_common::RPCStream &response) "
+           "override;");
+}
+
+void RPCServerHeaderEmitter::EmitConstructor(const std::string &MangledName) {
+  EmitLine(MangledName + "() : RPCFunctionInstance(\"" + MangledName +
+           "\") {}");
+}
+
+void RPCServerHeaderEmitter::EmitDestructor(const std::string &MangledName) {
+  EmitLine("~" + MangledName + "() override {}");
+}
+
+std::string RPCServerHeaderEmitter::GetHeaderGuard() {
+  const std::string UpperFilenameNoExt =
+      llvm::sys::path::stem(
+          llvm::sys::path::filename(OutputFile->getFilename()))
+          .upper();
+  return "GENERATED_LLDB_RPC_SERVER_" + UpperFilenameNoExt + "_H";
+}
+
+void RPCServerHeaderEmitter::Begin() {
+  const std::string HeaderGuard = GetHeaderGuard();
+  EmitLine("#ifndef " + HeaderGuard);
+  EmitLine("#define " + HeaderGuard);
+  EmitLine("");
+  EmitLine("#include <lldb-rpc/common/RPCFunction.h>");
+  EmitLine("");
+  EmitLine("namespace rpc_server {");
+}
+
+void RPCServerHeaderEmitter::End() {
+  EmitLine("} // namespace rpc_server");
+  EmitLine("#endif // " + GetHeaderGuard());
+}

lldb/tools/lldb-rpc/lldb-rpc-gen/server/RPCServerHeaderEmitter.h

@@ -0,0 +1,47 @@
+//===-- RPCServerHeaderEmitter.h ----------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLDB_RPC_GEN_RPCSERVERHEADEREMITTER_H
+#define LLDB_RPC_GEN_RPCSERVERHEADEREMITTER_H
+
+#include "RPCCommon.h"
+
+#include "clang/AST/AST.h"
+#include "llvm/Support/ToolOutputFile.h"
+
+using namespace clang;
+
+namespace lldb_rpc_gen {
+/// Emit the source code for server-side *.h files.
+class RPCServerHeaderEmitter : public FileEmitter {
+public:
+  RPCServerHeaderEmitter(std::unique_ptr<llvm::ToolOutputFile> &&OutputFile)
+      : FileEmitter(std::move(OutputFile)) {
+    Begin();
+  }
+
+  ~RPCServerHeaderEmitter() { End(); }
+
+  void EmitMethod(const Method &method);
+
+private:
+  void EmitHandleRPCCall();
+
+  void EmitConstructor(const std::string &MangledName);
+
+  void EmitDestructor(const std::string &MangledName);
+
+  std::string GetHeaderGuard();
+
+  void Begin();
+
+  void End();
+};
+} // namespace lldb_rpc_gen
+
+#endif // LLDB_RPC_GEN_RPCSERVERHEADEREMITTER_H