[lldb/Plugins] Introduce Scripted Interface Factory

This patch splits the previous `ScriptedProcessPythonInterface` into
multiple specific classes:

1. The `ScriptedInterface` abstract class that carries the interface
   instance object and its virtual pure abstract creation method.

2. The `ScriptedPythonInterface` that holds a generic `Dispatch` method that
   can be used by various interfaces to call python methods and also keeps a
   reference to the Python Script Interpreter instance.

3. The `ScriptedProcessInterface` that describes the base Scripted
   Process model with all the methods used in the underlying script.

All these components are used to refactor the `ScriptedProcessPythonInterface`
class, making it more modular.

This patch is also a requirement for the upcoming work on `ScriptedThread`.

Differential Revision: https://reviews.llvm.org/D107521

Signed-off-by: Med Ismail Bennani <medismail.bennani@gmail.com>

1 files changed, 155 insertions, 0 deletions

diff --git a/lldb/source/Plugins/ScriptInterpreter/Python/ScriptedPythonInterface.h b/lldb/source/Plugins/ScriptInterpreter/Python/ScriptedPythonInterface.h
new file mode 100644
index 0000000..85ec167
--- /dev/null
+++ b/lldb/source/Plugins/ScriptInterpreter/Python/ScriptedPythonInterface.h
@@ -0,0 +1,155 @@
+//===-- ScriptedPythonInterface.h -------------------------------*- 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
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLDB_PLUGINS_SCRIPTINTERPRETER_PYTHON_SCRIPTEDPYTHONINTERFACE_H
+#define LLDB_PLUGINS_SCRIPTINTERPRETER_PYTHON_SCRIPTEDPYTHONINTERFACE_H
+
+#include "lldb/Host/Config.h"
+
+#if LLDB_ENABLE_PYTHON
+
+#include "lldb/Interpreter/ScriptedInterface.h"
+#include "lldb/Utility/DataBufferHeap.h"
+
+#include "PythonDataObjects.h"
+#include "SWIGPythonBridge.h"
+#include "ScriptInterpreterPythonImpl.h"
+
+namespace lldb_private {
+class ScriptInterpreterPythonImpl;
+class ScriptedPythonInterface : virtual public ScriptedInterface {
+public:
+  ScriptedPythonInterface(ScriptInterpreterPythonImpl &interpreter);
+  virtual ~ScriptedPythonInterface() = default;
+
+protected:
+  template <typename T = StructuredData::ObjectSP>
+  T ExtractValueFromPythonObject(python::PythonObject &p, Status &error) {
+    return p.CreateStructuredObject();
+  }
+
+  template <>
+  Status ExtractValueFromPythonObject<Status>(python::PythonObject &p,
+                                              Status &error) {
+    if (lldb::SBError *sb_error = reinterpret_cast<lldb::SBError *>(
+            LLDBSWIGPython_CastPyObjectToSBError(p.get())))
+      error = m_interpreter.GetStatusFromSBError(*sb_error);
+    else
+      error.SetErrorString("Couldn't cast lldb::SBError to lldb::Status.");
+
+    return error;
+  }
+
+  template <>
+  lldb::DataExtractorSP
+  ExtractValueFromPythonObject<lldb::DataExtractorSP>(python::PythonObject &p,
+                                                      Status &error) {
+    lldb::SBData *sb_data = reinterpret_cast<lldb::SBData *>(
+        LLDBSWIGPython_CastPyObjectToSBData(p.get()));
+
+    if (!sb_data) {
+      error.SetErrorString("Couldn't cast lldb::SBError to lldb::Status.");
+      return nullptr;
+    }
+
+    return m_interpreter.GetDataExtractorFromSBData(*sb_data);
+  }
+
+  template <typename T = StructuredData::ObjectSP, typename... Args>
+  T Dispatch(llvm::StringRef method_name, Status &error, Args... args) {
+    using namespace python;
+    using Locker = ScriptInterpreterPythonImpl::Locker;
+
+    auto error_with_message = [&method_name, &error](llvm::StringRef message) {
+      error.SetErrorStringWithFormatv(
+          "ScriptedPythonInterface::{0} ({1}) ERROR = {2}", __FUNCTION__,
+          method_name, message);
+      return T();
+    };
+
+    if (!m_object_instance_sp)
+      return error_with_message("Python object ill-formed");
+
+    Locker py_lock(&m_interpreter, Locker::AcquireLock | Locker::NoSTDIN,
+                   Locker::FreeLock);
+
+    PythonObject implementor(PyRefType::Borrowed,
+                             (PyObject *)m_object_instance_sp->GetValue());
+
+    if (!implementor.IsAllocated())
+      return error_with_message("Python implementor not allocated.");
+
+    PythonObject pmeth(
+        PyRefType::Owned,
+        PyObject_GetAttrString(implementor.get(), method_name.str().c_str()));
+
+    if (PyErr_Occurred())
+      PyErr_Clear();
+
+    if (!pmeth.IsAllocated())
+      return error_with_message("Python method not allocated.");
+
+    if (PyCallable_Check(pmeth.get()) == 0) {
+      if (PyErr_Occurred())
+        PyErr_Clear();
+      return error_with_message("Python method not callable.");
+    }
+
+    if (PyErr_Occurred())
+      PyErr_Clear();
+
+    // TODO: make `const char *` when removing support for Python 2.
+    char *format = nullptr;
+    std::string format_buffer;
+
+    if (sizeof...(Args) > 0) {
+      FormatArgs(format_buffer, args...);
+      // TODO: make `const char *` when removing support for Python 2.
+      format = const_cast<char *>(format_buffer.c_str());
+    }
+
+    // TODO: make `const char *` when removing support for Python 2.
+    PythonObject py_return(
+        PyRefType::Owned,
+        PyObject_CallMethod(implementor.get(),
+                            const_cast<char *>(method_name.data()), format,
+                            args...));
+
+    if (PyErr_Occurred()) {
+      PyErr_Print();
+      PyErr_Clear();
+      return error_with_message("Python method could not be called.");
+    }
+
+    if (!py_return.IsAllocated())
+      return error_with_message("Returned object is null.");
+
+    return ExtractValueFromPythonObject<T>(py_return, error);
+  }
+
+  Status GetStatusFromMethod(llvm::StringRef method_name);
+
+  template <typename T, typename... Args>
+  void FormatArgs(std::string &fmt, T arg, Args... args) const {
+    FormatArgs(fmt, arg);
+    FormatArgs(fmt, args...);
+  }
+
+  template <typename T> void FormatArgs(std::string &fmt, T arg) const {
+    fmt += GetPythonValueFormatString(arg);
+  }
+
+  void FormatArgs(std::string &fmt) const {}
+
+  // The lifetime is managed by the ScriptInterpreter
+  ScriptInterpreterPythonImpl &m_interpreter;
+};
+} // namespace lldb_private
+
+#endif // LLDB_ENABLE_PYTHON
+#endif // LLDB_PLUGINS_SCRIPTINTERPRETER_PYTHON_SCRIPTEDPYTHONINTERFACE_H