WIP: Strongly-typed MMTk options

After the MMTKBuilder refactoring in mmtk-core, mmtk-ruby now has access
to the strongly-typed Options struct.  We no longer have to use
environment variables or any string-parsing API for setting things like
the plan and the number of MMTk threads.

Author: wks

mmtk/src/api.rs

@@ -1,25 +1,51 @@
 // All functions here are extern function. There is no point for marking them as unsafe.
 #![allow(clippy::not_unsafe_ptr_arg_deref)]
 
+use std::ffi::CStr;
+
 use crate::abi;
 use crate::Ruby;
 use crate::mmtk;
 use crate::binding::RubyBinding;
 use mmtk::MMTKBuilder;
 use mmtk::memory_manager;
+use mmtk::memory_manager::mmtk_init;
 use mmtk::scheduler::{GCController, GCWorker};
 use mmtk::util::constants::MIN_OBJECT_SIZE;
+use mmtk::util::options::PlanSelector;
 use mmtk::util::{Address, ObjectReference};
 use mmtk::util::{VMMutatorThread, VMThread, VMWorkerThread};
 use mmtk::AllocationSemantics;
 use mmtk::Mutator;
+use mmtk::util::options::Options;
+
+#[no_mangle]
+pub extern "C" fn mmtk_options_default() -> *mut Options {
+    Box::into_raw(Box::new(Options::default()))
+}
 
 #[no_mangle]
-pub extern "C" fn mmtk_init_binding(heap_size: usize, upcalls: *const abi::RubyUpcalls) {
-    let mut builder = MMTKBuilder::default();
-    builder.options.heap_size.set(heap_size);
-    let mmtk = builder.build();
-    let mmtk_static = Box::leak(Box::new(mmtk));
+pub extern "C" fn mmtk_options_set_heap_size(options: *mut Options, heap_size: usize) {
+    let options = unsafe { &mut *options };
+    options.heap_size.set(heap_size);
+}
+
+#[no_mangle]
+pub extern "C" fn mmtk_options_set_plan(options: *mut Options, plan_name: *const libc::c_char) {
+    let options = unsafe { &mut *options };
+    let plan_name_cstr = unsafe { CStr::from_ptr(plan_name) };
+    let plan_name_str = plan_name_cstr.to_str().unwrap();
+    let plan_selector = plan_name_str.parse::<PlanSelector>().unwrap();
+    options.plan.set(plan_selector);
+}
+
+#[no_mangle]
+pub extern "C" fn mmtk_init_binding(options: *mut Options, upcalls: *const abi::RubyUpcalls) {
+    let options = unsafe { Box::from_raw(options) };
+    let builder = MMTKBuilder { options: *options };
+    let mmtk_boxed = mmtk_init(&builder);
+    let mmtk_static = Box::leak(Box::new(mmtk_boxed));
+
     let binding = RubyBinding::new(mmtk_static, upcalls);
 
     crate::BINDING.set(binding).unwrap_or_else(|_| {