1 files changed, 87 insertions, 0 deletions
diff --git a/deps/sol2/examples/source/environment_snooping.cpp b/deps/sol2/examples/source/environment_snooping.cpp
new file mode 100644
index 0000000..1c3fdf1
--- /dev/null
+++ b/deps/sol2/examples/source/environment_snooping.cpp
@@ -0,0 +1,87 @@
+#define SOL_ALL_SAFETIES_ON 1
+#include <sol/sol.hpp>
+
+#include "assert.hpp"
+#include <iostream>
+
+// Simple sol3 version of the below
+void simple(sol::this_state ts, sol::this_environment te) {
+	sol::state_view lua = ts;
+	if (te) {
+		sol::environment& env = te;
+		sol::environment freshenv = lua["freshenv"];
+		bool is_same_env = freshenv == env;
+		std::cout << "this_environment -- env == freshenv : " << is_same_env << std::endl;
+	}
+	std::cout << "this_environment -- no environment present" << std::endl;
+}
+
+// NOTE:
+// THIS IS A LOW-LEVEL EXAMPLE, using pieces of sol2
+// to facilitate better usage
+// It is recommended you just do the simple version, as it is basically this code
+// but it is sometimes useful to show the hoops you need to jump through to use the Lua C API
+void complicated(sol::this_state ts) {
+	lua_State* L = ts;
+
+	lua_Debug info;
+	// Level 0 means current function (this C function, which is useless for our purposes)
+	// Level 1 means next call frame up the stack. This is probably the environment we're looking for?
+	int level = 1;
+	int pre_stack_size = lua_gettop(L);
+	if (lua_getstack(L, level, &info) != 1) {
+		// failure: call it quits
+		std::cout << "error: unable to traverse the stack" << std::endl;
+		lua_settop(L, pre_stack_size);
+		return;
+	}
+	// the "f" identifier is the most important here
+	// it pushes the function running at `level` onto the stack:
+	// we can get the environment from this
+	// the rest is for printing / debugging purposes
+	if (lua_getinfo(L, "fnluS", &info) == 0) {
+		// failure?
+		std::cout << "manually -- error: unable to get stack information" << std::endl;
+		lua_settop(L, pre_stack_size);
+		return;
+	}
+
+	// Okay, so all the calls worked.
+	// Print out some information about this "level"
+	std::cout << "manually -- [" << level << "] " << info.short_src << ":" << info.currentline
+		<< " -- " << (info.name ? info.name : "<unknown>") << "[" << info.what << "]" << std::endl;
+
+	// Grab the function off the top of the stack
+	// remember: -1 means top, -2 means 1 below the top, and so on...
+	// 1 means the very bottom of the stack, 
+	// 2 means 1 more up, and so on to the top value...
+	sol::function f(L, -1);
+	// The environment can now be ripped out of the function
+	sol::environment env(sol::env_key, f);
+	if (!env.valid()) {
+		std::cout << "manually -- error: no environment to get" << std::endl;
+		lua_settop(L, pre_stack_size);
+		return;
+	}
+	sol::state_view lua(L);
+	sol::environment freshenv = lua["freshenv"];
+	bool is_same_env = freshenv == env;
+	std::cout << "manually -- env == freshenv : " << is_same_env << std::endl;
+}
+
+int main() {
+	std::cout << "=== environment snooping ===" << std::endl;
+	sol::state lua;
+
+	sol::environment freshenv(lua, sol::create, lua.globals());
+	lua["freshenv"] = freshenv;
+	lua.set_function("f", simple);
+	lua.set_function("g", complicated);
+
+	lua.script("f()", freshenv);
+	lua.script("g()", freshenv);
+
+	std::cout << std::endl;
+
+	return 0;
+}