From e620fbde5717afd339385762d0cc3bb0f76bc05a Mon Sep 17 00:00:00 2001
From: Yota Toyama <raviqqe@gmail.com>
Date: Sat, 13 Apr 2019 20:22:56 +0000
Subject: [PATCH] Initialize src

---
 .gitignore   |  1 +
 Cargo.lock   | 16 +++++++++++
 Cargo.toml   |  9 ++++++
 src/error.rs | 22 +++++++++++++++
 src/lib.rs   | 79 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 5 files changed, 127 insertions(+)
 create mode 100644 .gitignore
 create mode 100644 Cargo.lock
 create mode 100644 Cargo.toml
 create mode 100644 src/error.rs
 create mode 100644 src/lib.rs

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..eb5a316
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1 @@
+target
diff --git a/Cargo.lock b/Cargo.lock
new file mode 100644
index 0000000..c4e887e
--- /dev/null
+++ b/Cargo.lock
@@ -0,0 +1,16 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+[[package]]
+name = "gc"
+version = "0.1.0"
+dependencies = [
+ "libc 0.2.51 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
+[[package]]
+name = "libc"
+version = "0.2.51"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+
+[metadata]
+"checksum libc 0.2.51 (registry+https://github.com/rust-lang/crates.io-index)" = "bedcc7a809076656486ffe045abeeac163da1b558e963a31e29fbfbeba916917"
diff --git a/Cargo.toml b/Cargo.toml
new file mode 100644
index 0000000..e77f856
--- /dev/null
+++ b/Cargo.toml
@@ -0,0 +1,9 @@
+[package]
+name = "gc"
+version = "0.1.0"
+authors = ["swgillespie <sean.william.g@gmail.com>", "Yota Toyama <raviqqe@gmail.com>"]
+publish = false
+edition = "2018"
+
+[dependencies]
+libc = "0.2"
diff --git a/src/error.rs b/src/error.rs
new file mode 100644
index 0000000..ea6deb2
--- /dev/null
+++ b/src/error.rs
@@ -0,0 +1,22 @@
+#[derive(Debug)]
+pub struct Error {
+    description: &'static str,
+}
+
+impl Error {
+    pub fn new(description: &'static str) -> Error {
+        Error { description }
+    }
+}
+
+impl std::fmt::Display for Error {
+    fn fmt(&self, formatter: &mut std::fmt::Formatter) -> std::fmt::Result {
+        write!(formatter, "{}", self.description)
+    }
+}
+
+impl std::error::Error for Error {
+    fn description(&self) -> &str {
+        self.description
+    }
+}
diff --git a/src/lib.rs b/src/lib.rs
new file mode 100644
index 0000000..1086f09
--- /dev/null
+++ b/src/lib.rs
@@ -0,0 +1,79 @@
+extern crate libc;
+
+mod error;
+
+use libc::{c_int, c_void, size_t};
+use std::alloc::{GlobalAlloc, Layout};
+
+const GC_SUCCESS: c_int = 0;
+
+#[repr(C)]
+struct GCStackBase {
+    mem_base: *const c_void,
+    reg_base: *const c_void,
+}
+
+#[link(name = "gc")]
+extern "C" {
+    fn GC_allow_register_threads() -> c_void;
+    fn GC_free(ptr: *mut c_void);
+    fn GC_get_stack_base(stack_base: *mut GCStackBase) -> c_int;
+    fn GC_init() -> c_void;
+    fn GC_malloc(size: size_t) -> *mut c_void;
+    fn GC_malloc_uncollectable(size: size_t) -> *mut c_void;
+    fn GC_register_my_thread(stack_base: *const GCStackBase) -> c_int;
+    fn GC_unregister_my_thread();
+}
+
+static mut GC_STARTED: bool = false;
+pub struct Allocator;
+
+impl Allocator {
+    pub unsafe fn initialize() {
+        GC_init();
+        GC_allow_register_threads();
+    }
+
+    pub unsafe fn start_gc() {
+        GC_STARTED = true
+    }
+
+    pub fn register_current_thread() -> Result<(), error::Error> {
+        let mut base = GCStackBase {
+            mem_base: std::ptr::null(),
+            reg_base: std::ptr::null(),
+        };
+
+        if unsafe { GC_get_stack_base(&mut base) } != GC_SUCCESS {
+            return Err(error::Error::new("failed to get stack base"));
+        }
+
+        if unsafe { GC_register_my_thread(&base) } != GC_SUCCESS {
+            return Err(error::Error::new("failed to register a thread for GC"));
+        }
+
+        Ok(())
+    }
+
+    pub fn unregister_current_thread() {
+        unsafe { GC_unregister_my_thread() }
+    }
+
+    pub fn alloc(size: usize) -> *mut u8 {
+        unsafe { Allocator.alloc(Layout::from_size_align_unchecked(size, 8)) }
+    }
+}
+
+unsafe impl GlobalAlloc for Allocator {
+    unsafe fn alloc(&self, layout: Layout) -> *mut u8 {
+        return if GC_STARTED {
+            GC_malloc(layout.size())
+        } else {
+            GC_malloc_uncollectable(layout.size())
+        } as *mut u8;
+    }
+
+    unsafe fn dealloc(&self, ptr: *mut u8, _layout: Layout) {
+        GC_free(ptr as *mut c_void)
+    }
+}