123 lines
3.1 KiB
Rust
123 lines
3.1 KiB
Rust
//! Context management
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use collections::{BTreeMap, Vec};
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use core::sync::atomic::{AtomicUsize, ATOMIC_USIZE_INIT, Ordering};
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use spin::{Once, RwLock, RwLockReadGuard, RwLockWriteGuard};
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use syscall::{Error, Result};
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/// File operations
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pub mod file;
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/// Limit on number of contexts
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pub const CONTEXT_MAX_CONTEXTS: usize = 65536;
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/// Maximum context files
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pub const CONTEXT_MAX_FILES: usize = 65536;
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/// Context list type
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pub struct ContextList {
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map: BTreeMap<usize, RwLock<Context>>,
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next_id: usize
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}
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impl ContextList {
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pub fn new() -> Self {
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ContextList {
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map: BTreeMap::new(),
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next_id: 1
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}
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}
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pub fn get(&self, id: usize) -> Option<&RwLock<Context>> {
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self.map.get(&id)
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}
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pub fn current(&self) -> Option<&RwLock<Context>> {
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self.map.get(&CONTEXT_ID.load(Ordering::SeqCst))
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}
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pub fn new_context(&mut self) -> Result<&RwLock<Context>> {
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if self.next_id >= CONTEXT_MAX_CONTEXTS {
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self.next_id = 1;
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}
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while self.map.contains_key(&self.next_id) {
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self.next_id += 1;
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}
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if self.next_id >= CONTEXT_MAX_CONTEXTS {
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return Err(Error::TryAgain);
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}
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let id = self.next_id;
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self.next_id += 1;
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assert!(self.map.insert(id, RwLock::new(Context::new(id))).is_none());
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Ok(self.map.get(&id).expect("failed to insert new context"))
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}
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}
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/// Contexts list
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static CONTEXTS: Once<RwLock<ContextList>> = Once::new();
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#[thread_local]
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static CONTEXT_ID: AtomicUsize = ATOMIC_USIZE_INIT;
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pub fn init() {
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let mut contexts = contexts_mut();
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let context_lock = contexts.new_context().expect("could not initialize first context");
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let context = context_lock.read();
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CONTEXT_ID.store(context.id, Ordering::SeqCst);
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}
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/// Initialize contexts, called if needed
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fn init_contexts() -> RwLock<ContextList> {
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RwLock::new(ContextList::new())
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}
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/// Get the global schemes list, const
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pub fn contexts() -> RwLockReadGuard<'static, ContextList> {
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CONTEXTS.call_once(init_contexts).read()
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}
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/// Get the global schemes list, mutable
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pub fn contexts_mut() -> RwLockWriteGuard<'static, ContextList> {
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CONTEXTS.call_once(init_contexts).write()
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}
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/// A context, which identifies either a process or a thread
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#[derive(Debug)]
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pub struct Context {
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/// The ID of this context
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pub id: usize,
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/// The open files in the scheme
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pub files: Vec<Option<file::File>>
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}
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impl Context {
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pub fn new(id: usize) -> Context {
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Context {
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id: id,
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files: Vec::new()
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}
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}
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/// Add a file to the lowest available slot.
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/// Return the file descriptor number or None if no slot was found
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pub fn add_file(&mut self, file: file::File) -> Option<usize> {
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for (i, mut file_option) in self.files.iter_mut().enumerate() {
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if file_option.is_none() {
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*file_option = Some(file);
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return Some(i);
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}
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}
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let len = self.files.len();
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if len < CONTEXT_MAX_FILES {
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self.files.push(Some(file));
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Some(len)
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} else {
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None
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}
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}
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}
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