Converting scheme ids into a new type SchemeId

Keeping scheme ids (and pids, and file handles, ...) as usize is a
footgun. Let's remove it.

kernel/scheme/debug.rs

@@ -1,14 +1,15 @@
 use core::str;
-use core::sync::atomic::{AtomicUsize, Ordering, ATOMIC_USIZE_INIT};
+use core::sync::atomic::Ordering;
 use spin::Once;
 
 use context;
+use scheme::*;
 use sync::WaitQueue;
 use syscall::error::*;
 use syscall::flag::EVENT_READ;
 use syscall::scheme::Scheme;
 
-pub static DEBUG_SCHEME_ID: AtomicUsize = ATOMIC_USIZE_INIT;
+pub static DEBUG_SCHEME_ID: AtomicSchemeId = ATOMIC_SCHEMEID_INIT;
 
 /// Input queue
 static INPUT: Once<WaitQueue<u8>> = Once::new();

kernel/scheme/irq.rs

@@ -1,14 +1,15 @@
 use core::{mem, str};
-use core::sync::atomic::{AtomicUsize, ATOMIC_USIZE_INIT, Ordering};
+use core::sync::atomic::Ordering;
 use spin::Mutex;
 
 use arch::interrupt::irq::acknowledge;
 use context;
+use scheme::{AtomicSchemeId, ATOMIC_SCHEMEID_INIT};
 use syscall::error::*;
 use syscall::flag::EVENT_READ;
 use syscall::scheme::Scheme;
 
-pub static IRQ_SCHEME_ID: AtomicUsize = ATOMIC_USIZE_INIT;
+pub static IRQ_SCHEME_ID: AtomicSchemeId = ATOMIC_SCHEMEID_INIT;
 
 /// IRQ queues
 static ACKS: Mutex<[usize; 16]> = Mutex::new([0; 16]);

kernel/scheme/mod.rs

@@ -9,7 +9,7 @@
 use alloc::arc::Arc;
 use alloc::boxed::Box;
 use collections::BTreeMap;
-use core::sync::atomic::Ordering;
+use core::sync::atomic::{AtomicUsize, Ordering};
 use spin::{Once, RwLock, RwLockReadGuard, RwLockWriteGuard};
 
 use syscall::error::*;
@@ -62,10 +62,15 @@ pub mod zero;
 /// Limit on number of schemes
 pub const SCHEME_MAX_SCHEMES: usize = 65536;
 
+/// Unique identifier for a scheme.
+int_like!(SchemeId, AtomicSchemeId, usize, AtomicUsize);
+
+pub const ATOMIC_SCHEMEID_INIT: AtomicSchemeId = AtomicSchemeId::default();
+
 /// Scheme list type
 pub struct SchemeList {
-    map: BTreeMap<usize, Arc<Box<Scheme + Send + Sync>>>,
-    names: BTreeMap<Box<[u8]>, usize>,
+    map: BTreeMap<SchemeId, Arc<Box<Scheme + Send + Sync>>>,
+    names: BTreeMap<Box<[u8]>, SchemeId>,
     next_id: usize
 }
 
@@ -79,20 +84,20 @@ impl SchemeList {
         }
     }
 
-    pub fn iter(&self) -> ::collections::btree_map::Iter<usize, Arc<Box<Scheme + Send + Sync>>> {
+    pub fn iter(&self) -> ::collections::btree_map::Iter<SchemeId, Arc<Box<Scheme + Send + Sync>>> {
         self.map.iter()
     }
 
-    pub fn iter_name(&self) -> ::collections::btree_map::Iter<Box<[u8]>, usize> {
+    pub fn iter_name(&self) -> ::collections::btree_map::Iter<Box<[u8]>, SchemeId> {
         self.names.iter()
     }
 
     /// Get the nth scheme.
-    pub fn get(&self, id: usize) -> Option<&Arc<Box<Scheme + Send + Sync>>> {
+    pub fn get(&self, id: SchemeId) -> Option<&Arc<Box<Scheme + Send + Sync>>> {
         self.map.get(&id)
     }
 
-    pub fn get_name(&self, name: &[u8]) -> Option<(usize, &Arc<Box<Scheme + Send + Sync>>)> {
+    pub fn get_name(&self, name: &[u8]) -> Option<(SchemeId, &Arc<Box<Scheme + Send + Sync>>)> {
         if let Some(&id) = self.names.get(name) {
             self.get(id).map(|scheme| (id, scheme))
         } else {
@@ -101,7 +106,7 @@ impl SchemeList {
     }
 
     /// Create a new scheme.
-    pub fn insert(&mut self, name: Box<[u8]>, scheme: Arc<Box<Scheme + Send + Sync>>) -> Result<usize> {
+    pub fn insert(&mut self, name: Box<[u8]>, scheme: Arc<Box<Scheme + Send + Sync>>) -> Result<SchemeId> {
         if self.names.contains_key(&name) {
             return Err(Error::new(EEXIST));
         }
@@ -110,7 +115,7 @@ impl SchemeList {
             self.next_id = 1;
         }
 
-        while self.map.contains_key(&self.next_id) {
+        while self.map.contains_key(&SchemeId(self.next_id)) {
             self.next_id += 1;
         }
 
@@ -118,12 +123,11 @@ impl SchemeList {
             return Err(Error::new(EAGAIN));
         }
 
-        let id = self.next_id;
+        let id = SchemeId(self.next_id);
         self.next_id += 1;
 
         assert!(self.map.insert(id, scheme).is_none());
         assert!(self.names.insert(name, id).is_none());
-
         Ok(id)
     }
 }

kernel/scheme/pipe.rs

@@ -2,6 +2,7 @@ use alloc::arc::{Arc, Weak};
 use collections::{BTreeMap, VecDeque};
 use core::sync::atomic::{AtomicUsize, ATOMIC_USIZE_INIT, Ordering};
 use spin::{Mutex, Once, RwLock, RwLockReadGuard, RwLockWriteGuard};
+use scheme::{AtomicSchemeId, ATOMIC_SCHEMEID_INIT};
 
 use sync::WaitCondition;
 use syscall::error::{Error, Result, EBADF, EPIPE};
@@ -9,7 +10,7 @@ use syscall::flag::O_NONBLOCK;
 use syscall::scheme::Scheme;
 
 /// Pipes list
-pub static PIPE_SCHEME_ID: AtomicUsize = ATOMIC_USIZE_INIT;
+pub static PIPE_SCHEME_ID: AtomicSchemeId = ATOMIC_SCHEMEID_INIT;
 static PIPE_NEXT_ID: AtomicUsize = ATOMIC_USIZE_INIT;
 static PIPES: Once<RwLock<(BTreeMap<usize, PipeRead>, BTreeMap<usize, PipeWrite>)>> = Once::new();
 

kernel/scheme/root.rs

@@ -1,16 +1,16 @@
 use alloc::arc::Arc;
 use alloc::boxed::Box;
 use collections::BTreeMap;
-use core::sync::atomic::{AtomicUsize, ATOMIC_USIZE_INIT, Ordering};
+use core::sync::atomic::{AtomicUsize, Ordering};
 use spin::RwLock;
 
 use context;
 use syscall::error::*;
 use syscall::scheme::Scheme;
-use scheme;
+use scheme::{self, AtomicSchemeId, ATOMIC_SCHEMEID_INIT};
 use scheme::user::{UserInner, UserScheme};
 
-pub static ROOT_SCHEME_ID: AtomicUsize = ATOMIC_USIZE_INIT;
+pub static ROOT_SCHEME_ID: AtomicSchemeId = ATOMIC_SCHEMEID_INIT;
 
 pub struct RootScheme {
     next_id: AtomicUsize,

kernel/scheme/user.rs

@@ -1,6 +1,6 @@
 use alloc::arc::{Arc, Weak};
 use collections::BTreeMap;
-use core::sync::atomic::{AtomicUsize, AtomicU64, Ordering};
+use core::sync::atomic::{AtomicU64, Ordering};
 use core::{mem, slice, usize};
 use spin::{Mutex, RwLock};
 
@@ -10,6 +10,7 @@ use arch::paging::temporary_page::TemporaryPage;
 use context::{self, Context};
 use context::memory::Grant;
 use scheme::root::ROOT_SCHEME_ID;
+use scheme::{AtomicSchemeId, ATOMIC_SCHEMEID_INIT};
 use sync::{WaitQueue, WaitMap};
 use syscall::data::{Packet, Stat};
 use syscall::error::*;
@@ -20,7 +21,7 @@ use syscall::scheme::Scheme;
 pub struct UserInner {
     handle_id: usize,
     flags: usize,
-    pub scheme_id: AtomicUsize,
+    pub scheme_id: AtomicSchemeId,
     next_id: AtomicU64,
     context: Weak<RwLock<Context>>,
     todo: WaitQueue<Packet>,
@@ -33,7 +34,7 @@ impl UserInner {
         UserInner {
             handle_id: handle_id,
             flags: flags,
-            scheme_id: AtomicUsize::new(0),
+            scheme_id: ATOMIC_SCHEMEID_INIT,
             next_id: AtomicU64::new(1),
             context: context,
             todo: WaitQueue::new(),