Refactor context list

kernel/context/mod.rs

@@ -1,22 +1,52 @@
 //! Context management
 
+use alloc::arc::Arc;
+use collections::{BTreeMap, Vec};
+use spin::{Once, RwLock, RwLockReadGuard, RwLockWriteGuard};
+
 /// File operations
 pub mod file;
 
-/// Context list
-pub static mut CONTEXT: Context = Context::new();
+/// Maximum context files
+pub const CONTEXT_MAX_FILES: usize = 65536;
+
+/// Context ID
+pub type ContextId = u16;
+
+/// Context list type
+pub type ContextList = BTreeMap<ContextId, Arc<RwLock<Context>>>;
+
+/// Contexts list
+static CONTEXTS: Once<RwLock<ContextList>> = Once::new();
+
+/// Initialize contexts, called if needed
+fn init_contexts() -> RwLock<ContextList> {
+    let mut map: ContextList = BTreeMap::new();
+    map.insert(0, Arc::new(RwLock::new(Context::new())));
+    RwLock::new(map)
+}
+
+/// Get the global schemes list, const
+pub fn contexts() -> RwLockReadGuard<'static, ContextList> {
+    CONTEXTS.call_once(init_contexts).read()
+}
+
+/// Get the global schemes list, mutable
+pub fn contexts_mut() -> RwLockWriteGuard<'static, ContextList> {
+    CONTEXTS.call_once(init_contexts).write()
+}
 
 /// A context, which identifies either a process or a thread
-#[derive(Copy, Clone, Debug)]
+#[derive(Clone, Debug)]
 pub struct Context {
     /// The open files in the scheme
-    pub files: [Option<file::File>; 32]
+    pub files: Vec<Option<file::File>>
 }
 
 impl Context {
-    pub const fn new() -> Context {
+    pub fn new() -> Context {
         Context {
-            files: [None; 32]
+            files: Vec::new()
         }
     }
 
@@ -29,6 +59,12 @@ impl Context {
                 return Some(i);
             }
         }
-        None
+        let len = self.files.len();
+        if len < CONTEXT_MAX_FILES {
+            self.files.push(Some(file));
+            Some(len)
+        } else {
+            None
+        }
     }
 }