Cleanup schemes list, remove lazy_static

Cargo.toml

@@ -9,7 +9,6 @@ crate-type = ["staticlib"]
 
 [dependencies]
 bitflags = "*"
-lazy_static = "*"
 spin = "*"
 
 [dev-dependencies]

kernel/lib.rs

@@ -67,6 +67,7 @@
 #![feature(alloc)]
 #![feature(collections)]
 #![feature(const_fn)]
+#![feature(drop_types_in_const)]
 #![feature(question_mark)]
 #![no_std]
 
@@ -88,8 +89,6 @@ extern crate collections;
 
 #[macro_use]
 extern crate bitflags;
-#[macro_use]
-extern crate lazy_static;
 extern crate spin;
 
 /// Context management

kernel/scheme/mod.rs

@@ -11,7 +11,7 @@ use alloc::boxed::Box;
 
 use collections::BTreeMap;
 
-use spin::{Mutex, RwLock};
+use spin::{Once, Mutex, RwLock, RwLockReadGuard, RwLockWriteGuard};
 
 use syscall::Result;
 
@@ -20,13 +20,23 @@ use self::debug::DebugScheme;
 /// Debug scheme
 pub mod debug;
 
+pub type SchemeList = BTreeMap<Box<[u8]>, Arc<Mutex<Box<Scheme + Send>>>>;
+
 /// Schemes list
-lazy_static! {
+static SCHEMES: Once<RwLock<SchemeList>> = Once::new();
-    pub static ref SCHEMES: RwLock<BTreeMap<Box<[u8]>, Arc<Mutex<Box<Scheme + Send>>>>> = {
+
-        let mut map: BTreeMap<Box<[u8]>, Arc<Mutex<Box<Scheme + Send>>>> = BTreeMap::new();
+fn init_schemes() -> RwLock<SchemeList> {
+    let mut map: SchemeList = BTreeMap::new();
     map.insert(Box::new(*b"debug"), Arc::new(Mutex::new(Box::new(DebugScheme))));
     RwLock::new(map)
-    };
+}
+
+pub fn schemes() -> RwLockReadGuard<'static, SchemeList> {
+    SCHEMES.call_once(init_schemes).read()
+}
+
+pub fn schemes_mut() -> RwLockWriteGuard<'static, SchemeList> {
+    SCHEMES.call_once(init_schemes).write()
 }
 
 /// A scheme trait, implemented by a scheme handler

kernel/syscall/fs.rs

@@ -1,5 +1,7 @@
 //! Filesystem syscalls
 
+use scheme;
+
 use super::{Error, Result};
 
 /// Read syscall
@@ -33,7 +35,7 @@ pub fn open(path: &[u8], flags: usize) -> Result<usize> {
 
     let file = {
         if let Some(namespace) = namespace_opt {
-            let schemes = ::scheme::SCHEMES.read();
+            let schemes = scheme::schemes();
             if let Some(scheme_mutex) = schemes.get(namespace) {
                 scheme_mutex.lock().open(reference_opt.unwrap_or(b""), flags)
             } else {