134 lines
3.9 KiB
Rust
134 lines
3.9 KiB
Rust
//! # Schemes
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//! A scheme is a primitive for handling filesystem syscalls in Redox.
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//! Schemes accept paths from the kernel for `open`, and file descriptors that they generate
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//! are then passed for operations like `close`, `read`, `write`, etc.
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//!
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//! The kernel validates paths and file descriptors before they are passed to schemes,
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//! also stripping the scheme identifier of paths if necessary.
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use alloc::arc::Arc;
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use alloc::boxed::Box;
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use collections::BTreeMap;
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use spin::{Once, Mutex, RwLock, RwLockReadGuard, RwLockWriteGuard};
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use syscall::{Error, Result};
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use self::debug::DebugScheme;
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use self::initfs::InitFsScheme;
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/// Debug scheme
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pub mod debug;
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/// InitFS scheme
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pub mod initfs;
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/// Limit on number of schemes
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pub const SCHEME_MAX_SCHEMES: usize = 65536;
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/// Scheme list type
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pub struct SchemeList {
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map: BTreeMap<usize, Arc<Mutex<Box<Scheme + Send>>>>,
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names: BTreeMap<Box<[u8]>, usize>,
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next_id: usize
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}
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impl SchemeList {
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/// Create a new scheme list.
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pub fn new() -> Self {
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SchemeList {
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map: BTreeMap::new(),
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names: BTreeMap::new(),
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next_id: 1
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}
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}
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/// Get the nth scheme.
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pub fn get(&self, id: usize) -> Option<&Arc<Mutex<Box<Scheme + Send>>>> {
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self.map.get(&id)
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}
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pub fn get_name(&self, name: &[u8]) -> Option<(usize, &Arc<Mutex<Box<Scheme + Send>>>)> {
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if let Some(&id) = self.names.get(name) {
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self.get(id).map(|scheme| (id, scheme))
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} else {
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None
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}
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}
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/// Create a new context.
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pub fn insert(&mut self, name: Box<[u8]>, scheme: Arc<Mutex<Box<Scheme + Send>>>) -> Result<&Arc<Mutex<Box<Scheme + Send>>>> {
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if self.names.contains_key(&name) {
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return Err(Error::FileExists);
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}
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if self.next_id >= SCHEME_MAX_SCHEMES {
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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 >= SCHEME_MAX_SCHEMES {
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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, scheme).is_none());
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assert!(self.names.insert(name, id).is_none());
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Ok(self.map.get(&id).expect("Failed to insert new scheme. ID is out of bounds."))
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}
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}
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/// Schemes list
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static SCHEMES: Once<RwLock<SchemeList>> = Once::new();
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/// Initialize schemes, called if needed
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fn init_schemes() -> RwLock<SchemeList> {
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let mut list: SchemeList = SchemeList::new();
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list.insert(Box::new(*b"debug"), Arc::new(Mutex::new(Box::new(DebugScheme)))).expect("failed to insert debug: scheme");
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list.insert(Box::new(*b"initfs"), Arc::new(Mutex::new(Box::new(InitFsScheme::new())))).expect("failed to insert initfs: scheme");
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RwLock::new(list)
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}
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/// Get the global schemes list, const
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pub fn schemes() -> RwLockReadGuard<'static, SchemeList> {
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SCHEMES.call_once(init_schemes).read()
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}
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/// Get the global schemes list, mutable
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pub fn schemes_mut() -> RwLockWriteGuard<'static, SchemeList> {
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SCHEMES.call_once(init_schemes).write()
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}
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/// A scheme trait, implemented by a scheme handler
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pub trait Scheme {
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/// Open the file at `path` with `flags`.
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///
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/// Returns a file descriptor or an error
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fn open(&mut self, path: &[u8], flags: usize) -> Result<usize>;
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/// Duplicate an open file descriptor
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///
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/// Returns a file descriptor or an error
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fn dup(&mut self, file: usize) -> Result<usize>;
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/// Read from some file descriptor into the `buffer`
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///
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/// Returns the number of bytes read
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fn read(&mut self, file: usize, buffer: &mut [u8]) -> Result<usize>;
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/// Write the `buffer` to the file descriptor
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///
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/// Returns the number of bytes written
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fn write(&mut self, file: usize, buffer: &[u8]) -> Result<usize>;
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/// Close the file descriptor
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fn close(&mut self, file: usize) -> Result<()>;
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}
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