Add StructuredData plugin type; showcase with new DarwinLog feature

Take 2, with missing cmake line fixed.  Build tested on
Ubuntu 14.04 with clang-3.6.

See docs/structured_data/StructuredDataPlugins.md for details.

differential review: https://reviews.llvm.org/D22976

reviewers: clayborg, jingham
llvm-svn: 279202

lldb/source/Target/StructuredDataPlugin.cpp

@@ -0,0 +1,90 @@
+//===-- StructuredDataPlugin.cpp --------------------------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "lldb/Target/StructuredDataPlugin.h"
+
+#include "lldb/Core/Debugger.h"
+#include "lldb/Interpreter/CommandInterpreter.h"
+#include "lldb/Interpreter/CommandObjectMultiword.h"
+
+using namespace lldb;
+using namespace lldb_private;
+
+namespace
+{
+    class CommandStructuredData : public CommandObjectMultiword
+    {
+    public:
+        CommandStructuredData(CommandInterpreter &interpreter) :
+            CommandObjectMultiword(interpreter,
+                               "structured-data",
+                               "Parent for per-plugin structured data commands",
+                               "plugin structured-data <plugin>")
+        {
+        }
+
+        ~CommandStructuredData()
+        {
+        }
+    };
+}
+
+StructuredDataPlugin::StructuredDataPlugin(const ProcessWP &process_wp) :
+    PluginInterface(),
+    m_process_wp(process_wp)
+{
+}
+
+StructuredDataPlugin::~StructuredDataPlugin()
+{
+}
+
+bool
+StructuredDataPlugin::GetEnabled(const ConstString &type_name) const
+{
+    // By default, plugins are always enabled.  Plugin authors should override
+    // this if there is an enabled/disabled state for their plugin.
+    return true;
+}
+
+ProcessSP
+StructuredDataPlugin::GetProcess() const
+{
+    return m_process_wp.lock();
+}
+
+void
+StructuredDataPlugin::InitializeBasePluginForDebugger(Debugger &debugger)
+{
+    // Create our mutliword command anchor if it doesn't already exist.
+    auto &interpreter = debugger.GetCommandInterpreter();
+    if (!interpreter.GetCommandObject("plugin structured-data"))
+    {
+        // Find the parent command.
+        auto parent_command =
+            debugger.GetCommandInterpreter().GetCommandObject("plugin");
+        if (!parent_command)
+            return;
+
+        // Create the structured-data ommand object.
+        auto command_name = "structured-data";
+        auto command_sp =
+            CommandObjectSP(new CommandStructuredData(interpreter));
+
+        // Hook it up under the top-level plugin command.
+        parent_command->LoadSubCommand(command_name,
+                                       command_sp);
+    }
+}
+
+void
+StructuredDataPlugin::ModulesDidLoad(Process &process, ModuleList &module_list)
+{
+    // Default implementation does nothing.
+}