VFS: Updated the API and worked on some implementation

drivers/vfs/src/cache.rs

@@ -0,0 +1,42 @@
+pub struct Cache {
+    // A limit on how many open files can be in this cache
+    // Usefull to prevent hundreds of processes caching thousands of files
+    // 0 == No Limit
+    file_id_limit: u64,
+
+    // Total bytes allowed to be cached before a file is pushed out of the cache
+    total_byte_size: u64,
+    current_byte_size: u64,
+    cache: Vec<(FileID, Vec<u8>)>,
+}
+
+impl Cache {
+    fn default() -> Self {
+        Self {
+            file_id_limit: 1024,
+            total_byte_size: 1024 * 16,
+            current_byte_size: 0,
+            cache: Vec::new(),
+        }
+    }
+    fn recalculate_cache(&mut self) {
+        let mut current: u64 = 0;
+        for (_, file) in &self.cache {
+            current += file.len() as u64;
+        }
+        self.current_byte_size = current;
+    }
+}
+
+#[test]
+fn recalc_cache_test() {
+    let mut cache = Cache::default();
+    let mut temp_file_vec: Vec<u8> = Vec::new();
+    for x in 0u64..=10 {
+        temp_file_vec.push(x.try_into().unwrap());
+        let file = (x, temp_file_vec.clone());
+        cache.cache.push(file);
+    }
+    cache.recalculate_cache();
+    assert_eq!(cache.current_byte_size, 66);
+}

drivers/vfs/src/main.rs

@@ -1,18 +1,105 @@
 // #![no_std]
+#![feature(async_fn_in_trait)]
 
-use std::path::Path;
-// use std::prelude::rust_2021::alloc;
+pub mod cache;
 extern crate alloc;
+
 use alloc::vec::Vec;
+pub type Path = String;
 
-fn main() {}
+fn main() {
+    let vfs = VFS::new();
+    // TODO: load config for the vfs
 
-pub type File = Vec<u8>;
-// TODO: implement better VFS api
-pub trait FileIO {
-    fn read(file: &mut File, file_address: u64, read_length: u64);
-    fn write(file: &mut File, file_address: u64, dest_ptr: u64, src_len: usize);
-    fn open(path: Path);
-    fn close(file: &mut File);
+    // advertise the VFS service
+    // wait on proccesses to subscribe and send messages
+}
+
+// NOTE: in the implementation this should be a basevalue of some randomized value to
+// prevent the ability to check how many files are open on the system
+pub type FileID = u64;
+
+pub trait FileIO {
+    // Store the FileID in the VFS to allow multiple programs to have a FileID without conflicting
+    fn s_open(path: Path) -> Result<FileID, FileIOError>;
+    async fn a_open(path: Path) -> Result<FileID, FileIOError>;
+
+    // Close the file and flush changes to disk
+    fn s_close(file_id: FileID) -> Result<(), FileIOError>;
+    async fn a_close(file_id: FileID) -> Result<(), FileIOError>;
+
+    // Offset into the file to allow for things like reading a specific value
+    // Length from the offset
+    fn s_read(file_id: FileID, offset: usize, length: u64) -> Result<Vec<u8>, FileIOError>;
+    async fn a_read(file_id: FileID, offset: usize, length: u64) -> Result<Vec<u8>, FileIOError>;
+
+    // Offset into the file to allow for things like reading a specific value
+    fn s_write(file_id: FileID, offset: usize, data: Vec<u8>) -> Result<(), FileIOError>;
+    async fn a_write(file_id: FileID, offset: usize, data: Vec<u8>) -> Result<(), FileIOError>;
+}
+
+pub enum FileIOError {
+    NoMountPoint,
+}
+
+pub struct MountPoint {
+    mount: Path,
+    // Use this to send the file requests to the right filesystem driver
+    filesystem_proc_id: u64,
+}
+
+pub struct VFS {
+    // If a file is used twice move it from first cache to second cache
+    // This is under the assumption that if you write to a file twice you will write again
+    first_layer:      Cache,
+    second_layer:     Cache,
+    mount_point_list: Vec<MountPoint>,
+}
+impl VFS {
+    fn new() -> Self {
+        Self {
+            first_layer:      Cache::default(),
+            second_layer:     Cache::default(),
+            mount_point_list: Vec::new(),
+        }
+    }
+
+    fn resolve_mountpoint(self, path: Path) -> Result<MountPoint, FileIOError> {
+        return Err(FileIOError::NoMountPoint);
+    }
+}
+
+impl FileIO for VFS {
+    fn s_open(path: Path) -> Result<FileID, FileIOError> {
+        // Break up the path into a mountpoint and a path fragment
+        todo!()
+    }
+
+    async fn a_open(path: Path) -> Result<FileID, FileIOError> {
+        todo!()
+    }
+
+    fn s_close(file_id: FileID) -> Result<(), FileIOError> {
+        todo!()
+    }
+
+    async fn a_close(file_id: FileID) -> Result<(), FileIOError> {
+        todo!()
+    }
+
+    fn s_read(file_id: FileID, offset: usize, length: u64) -> Result<Vec<u8>, FileIOError> {
+        todo!()
+    }
+
+    async fn a_read(file_id: FileID, offset: usize, length: u64) -> Result<Vec<u8>, FileIOError> {
+        todo!()
+    }
+
+    fn s_write(file_id: FileID, offset: usize, data: Vec<u8>) -> Result<(), FileIOError> {
+        todo!()
+    }
+
+    async fn a_write(file_id: FileID, offset: usize, data: Vec<u8>) -> Result<(), FileIOError> {
+        todo!()
+    }
 }
-pub enum FileError {}

libraries/os_core/src/lib.rs

@@ -26,5 +26,5 @@ pub struct Result<T> {
 }
 
 pub struct Path {
-    parts: String,
+    parts: OSString,
 }

libraries/std/src/allocator.rs

@@ -0,0 +1,16 @@
+use alloc::alloc::{GlobalAlloc, Layout};
+
+struct MyAllocator;
+
+unsafe impl GlobalAlloc for MyAllocator {
+    unsafe fn alloc(&self, layout: Layout) -> *mut u8 {
+        panic!();
+    }
+
+    unsafe fn dealloc(&self, ptr: *mut u8, layout: Layout) {
+        panic!();
+    }
+}
+
+#[global_allocator]
+static GLOBAL: MyAllocator = MyAllocator;

libraries/std/src/lib.rs

@@ -9,6 +9,7 @@ pub mod env;
 pub mod exit;
 pub mod io;
 
+pub mod allocator;
 #[cfg(not(test))]
 pub mod panic;