Add background task example plugin

Clarify BackgroundTask functionality (skip-note, skip-ci)

Providing clear documentation so it is understood that background tasks do not manage the execution of said the task.

Add background_task plugin to examples section

README.md

@@ -53,6 +53,7 @@ In addition to the default build setup, you may want to:
 
 There are many examples available. The [Python examples folder](https://github.com/Vector35/binaryninja-api/tree/dev/python/examples) demonstrates many different applications of the Python API, while C++ examples include:
 
+- [background_task](https://github.com/Vector35/binaryninja-api/tree/dev/examples/background_task) is a plugin that demonstrates managing a background task.\*
 - [bin-info](https://github.com/Vector35/binaryninja-api/tree/dev/examples/bin-info) is a standalone executable that prints some information about a given binary to the terminal.\*
 - [breakpoint](https://github.com/Vector35/binaryninja-api/tree/dev/examples/breakpoint) is a plugin that allows you to select a region within an x86 binary and use the context menu to fill it with breakpoint bytes.
 - [command-line disassm](https://github.com/Vector35/binaryninja-api/tree/dev/examples/cmdline_disasm) demonstrates how to dump disassembly to the command line.\*

binaryninjaapi.h

@@ -15513,8 +15513,20 @@ namespace BinaryNinja {
 	    public CoreRefCountObject<BNBackgroundTask, BNNewBackgroundTaskReference, BNFreeBackgroundTask>
 	{
 	  public:
-		BackgroundTask(BNBackgroundTask* task);
-		BackgroundTask(const std::string& initialText, bool canCancel);
+		BackgroundTask(BNBackgroundTask *task);
+
+		/*!
+			Provides a mechanism for reporting progress of
+			an optionally cancelable task to the user via the status bar in the UI.
+			If canCancel is is `True`, then the task can be cancelled either
+			programmatically or by the user via the UI.
+
+			\note This API does not provide a means to execute a task. The caller is responsible to execute (and possibly cancel) the task.
+
+			\param initialText Text description of the progress of the background task (displayed in status bar of the UI)
+			\param canCancel Whether the task can be cancelled
+		*/
+		BackgroundTask(const std::string &initialText, bool canCancel);
 
 		bool CanCancel() const;
 		bool IsCancelled() const;

examples/CMakeLists.txt

@@ -1,3 +1,4 @@
+add_subdirectory(background_task)
 add_subdirectory(bin-info)
 add_subdirectory(breakpoint)
 add_subdirectory(cmdline_disasm)

examples/background_task/CMakeLists.txt

@@ -0,0 +1,36 @@
+cmake_minimum_required(VERSION 3.13 FATAL_ERROR)
+
+project(background_task CXX C)
+
+file(GLOB SOURCES
+	src/*.cpp
+	src/*.h)
+
+add_library(background_task SHARED ${SOURCES})
+
+if(NOT BN_API_BUILD_EXAMPLES AND NOT BN_INTERNAL_BUILD)
+    # Out-of-tree build
+    find_path(
+        BN_API_PATH
+        NAMES binaryninjaapi.h
+        HINTS ../.. binaryninjaapi $ENV{BN_API_PATH}
+        REQUIRED
+    )
+    add_subdirectory(${BN_API_PATH} api)
+endif()
+
+target_link_libraries(background_task binaryninjaui)
+
+set_target_properties(background_task PROPERTIES
+    CXX_STANDARD 17
+	CXX_VISIBILITY_PRESET hidden
+	CXX_STANDARD_REQUIRED ON
+    VISIBILITY_INLINES_HIDDEN ON
+	POSITION_INDEPENDENT_CODE ON
+	LIBRARY_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/out/bin)
+
+if(BN_INTERNAL_BUILD)
+	ui_plugin_rpath(background_task)
+endif()
+
+bn_install_plugin(${PROJECT_NAME})

examples/background_task/src/backgroundtask.cpp

@@ -0,0 +1,80 @@
+#include <thread>
+#include <random>
+
+#include "binaryninjaapi.h"
+
+using namespace BinaryNinja;
+
+static Ref<BackgroundTask> inspireBackgroundTask = nullptr;
+
+uint64_t InspireWriteCallback(uint8_t *data, uint64_t len, void *ctxt)
+{
+	try
+	{
+		Json::Value json;
+		std::unique_ptr<Json::CharReader> reader(Json::CharReaderBuilder().newCharReader());
+		std::string errors;
+		if (!reader->parse((char *) data, (char *) data + len, &json, &errors))
+		{
+			LogError("Failed to parse! %s", errors.c_str());
+		}
+		else
+		{
+			std::random_device rd;
+			std::map<int, int> hist;
+			std::uniform_int_distribution<Json::ArrayIndex> dist(0, json.size());
+			auto randQuoteObj = json.get(dist(rd), 0);
+			if (randQuoteObj.isObject() && randQuoteObj.size() == 2)
+			{
+				std::string quote = randQuoteObj.get("text", Json::Value("INVALID")).asString();
+				LogInfo("%s", quote.c_str());
+				// Display quote in progress text for 3 seconds.
+				inspireBackgroundTask->SetProgressText(quote);
+				std::this_thread::sleep_for(std::chrono::seconds(3));
+			}
+		}
+	} catch (Json::Exception e)
+	{
+		LogError("JSON exception! %s", e.m_message.c_str());
+		inspireBackgroundTask->Cancel();
+	}
+	return len;
+}
+
+bool InspireProgressCallback(void *ctxt, uint64_t progress, uint64_t total)
+{
+	// Close connection on cancellation
+	return !inspireBackgroundTask->IsCancelled();
+}
+
+void Inspire(BinaryView *bv)
+{
+	inspireBackgroundTask = new BackgroundTask("Getting inspired!", true);
+	std::thread inspireThread([]() {
+		LogInfo("Getting inspired!");
+		BNDownloadInstanceOutputCallbacks outputCallbacks;
+		memset(&outputCallbacks, 0, sizeof(outputCallbacks));
+		outputCallbacks.writeCallback = InspireWriteCallback;
+		outputCallbacks.progressCallback = InspireProgressCallback;
+
+		auto downloadProvider = DownloadProvider::GetByName("CoreDownloadProvider");
+		auto downloadInstance = downloadProvider->CreateNewInstance();
+		inspireBackgroundTask->SetProgressText("Waiting for inspiration...");
+		if (downloadInstance->PerformRequest("https://type.fit/api/quotes", &outputCallbacks))
+			LogError("Inspiration failed!");
+
+		inspireBackgroundTask->Finish();
+	});
+	inspireThread.detach();
+}
+
+extern "C" {
+	BN_DECLARE_CORE_ABI_VERSION
+
+	BINARYNINJAPLUGIN bool CorePluginInit()
+	{
+		PluginCommand::Register("Inspire me!", "Print an inspirational quote to the log", Inspire);
+
+		return true;
+	}
+}