Create SFS and check magic.

Cargo.toml

@@ -5,3 +5,4 @@ authors = ["WangRunji <wangrunji0408@163.com>"]
 
 [dependencies]
 spin = "0.4"
+bit-set = "0.5"

src/lib.rs

@@ -1,10 +1,15 @@
 #![feature(alloc)]
 #![no_std]
 
+#[cfg(test)]
+#[macro_use]
+extern crate std;
+
 extern crate spin;
 extern crate alloc;
+extern crate bit_set;
 
-mod vfs;
+mod sfs;
 mod structs;
 #[cfg(test)]
 mod tests;

src/sfs.rs

@@ -0,0 +1,69 @@
+use spin::Mutex;
+use bit_set::BitSet;
+use alloc::{boxed::Box, Vec};
+use super::structs::*;
+use core::mem::{uninitialized, size_of};
+use core::slice;
+
+/// Interface for SFS to read & write
+///     TODO: use std::io::{Read, Write}
+pub trait Device {
+    fn read_at(&mut self, offset: u64, buf: &mut [u8]) -> Option<usize>;
+    fn write_at(&mut self, offset: u64, buf: &[u8]) -> Option<usize>;
+}
+
+/// inode for sfs
+pub struct Inode {
+    /// on-disk inode
+    disk_inode: *mut DiskInode,
+    /// inode number
+    id: u32,
+    /// true if inode modified
+    dirty: bool,
+    /// kill inode if it hits zero
+    reclaim_count: u32,
+    /// semaphore for din
+    mutex: Mutex<()>,
+}
+
+/// filesystem for sfs
+pub struct SimpleFileSystem {
+    /// on-disk superblock
+    super_block: SuperBlock,
+    /// blocks in use are mared 0
+    free_map: BitSet,
+    /// true if super/freemap modified
+    super_dirty: bool,
+    /// buffer for non-block aligned io
+//    buffer: u8,
+    /// semaphore for fs
+//    fs_mutex: Mutex<()>,
+    /// semaphore for link/unlink and rename
+//    link_mutex: Mutex<()>,
+    /// inode list
+//    inodes: Vec<Inode>,
+    /// device
+    device: Mutex<Box<Device>>,
+}
+
+impl SimpleFileSystem {
+    /// Create a new SFS with device
+    pub fn new(mut device: Box<Device>) -> Option<Self> {
+        let mut super_block: SuperBlock = unsafe{ uninitialized() };
+        let slice = unsafe{ slice::from_raw_parts_mut(
+            &mut super_block as *mut SuperBlock as *mut u8, size_of::<SuperBlock>()) };
+        if device.read_at(0, slice).is_none() {
+            return None;
+        }
+        if super_block.check() == false {
+            return None;
+        }
+
+        Some(SimpleFileSystem {
+            super_block,
+            free_map: BitSet::new(),
+            super_dirty: false,
+            device: Mutex::new(device),
+        })
+    }
+}

src/structs.rs

@@ -1,81 +1,49 @@
-use spin::Mutex;
-use alloc::Vec;
-//use core::fmt::{Debug, Formatter, Error};
-
 /// On-disk superblock
 #[repr(C, packed)]
-struct SuperBlock {
+pub struct SuperBlock {
     /// magic number, should be SFS_MAGIC
-    magic: u32,
+    pub magic: u32,
     /// number of blocks in fs
-    blocks: u32,
+    pub blocks: u32,
     /// number of unused blocks in fs
-    unused_blocks: u32,
+    pub unused_blocks: u32,
     /// infomation for sfs
-    info: [u8; MAX_INFO_LEN + 1],
+    pub info: [u8; MAX_INFO_LEN + 1],
 }
 
 /// inode (on disk)
 #[repr(C, packed)]
 #[derive(Debug)]
-struct DiskInode {
+pub struct DiskInode {
     /// size of the file (in bytes)
-    size: u32,
+    pub size: u32,
     /// one of SYS_TYPE_* above
-    type_: u16,
+    pub type_: u16,
     /// number of hard links to this file
-    nlinks: u16,
+    pub nlinks: u16,
     /// number of blocks
-    blocks: u32,
+    pub blocks: u32,
     /// direct blocks
-    direct: [u32; NDIRECT],
+    pub direct: [u32; NDIRECT],
     /// indirect blocks
-    indirect: u32,
+    pub indirect: u32,
     /// double indirect blocks
-    db_indirect: u32,
+    pub db_indirect: u32,
 }
 
 /// file entry (on disk)
 #[repr(C, packed)]
-struct DiskEntry {
+pub struct DiskEntry {
     /// inode number
-    inode_number: u32,
+    pub inode_number: u32,
     /// file name
-    name: [u8; MAX_FNAME_LEN + 1],
+    pub name: [u8; MAX_FNAME_LEN + 1],
 }
 
-/// inode for sfs
+impl SuperBlock {
-struct Inode {
+    pub fn check(&self) -> bool {
-    /// on-disk inode
+        self.magic == MAGIC
-    disk_inode: *mut DiskInode,
-    /// inode number
-    id: u32,
-    /// true if inode modified
-    dirty: bool,
-    /// kill inode if it hits zero
-    reclaim_count: u32,
-    /// semaphore for din
-    mutex: Mutex<()>,
     }
-
-/// filesystem for sfs
-struct SimpleFileSystem {
-    /// on-disk superblock
-    super_block: SuperBlock,
-    /// blocks in use are mared 0
-    free_map: [u8; 0],
-    /// true if super/freemap modified
-    super_dirty: bool,
-    /// buffer for non-block aligned io
-    buffer: [u8; 0],
-    /// semaphore for fs
-    fs_mutex: Mutex<()>,
-    /// semaphore for io
-    io_mutex: Mutex<()>,
-    /// semaphore for link/unlink and rename
-    link_mutex: Mutex<()>,
-    /// inode list
-    inodes: Vec<DiskInode>
 }
 
 /*
@@ -83,29 +51,29 @@ struct SimpleFileSystem {
  * and is used by tools that work on SFS volumes, such as mksfs.
  */
 /// magic number for sfs
-const MAGIC: usize = 0x2f8dbe2a;
+pub const MAGIC: u32 = 0x2f8dbe2a;
 /// size of block
-const BLKSIZE: usize = 4096;
+pub const BLKSIZE: usize = 4096;
 /// number of direct blocks in inode
-const NDIRECT: usize = 12;
+pub const NDIRECT: usize = 12;
 /// max length of infomation
-const MAX_INFO_LEN: usize = 31;
+pub const MAX_INFO_LEN: usize = 31;
 /// max length of filename
-const MAX_FNAME_LEN: usize = 255;
+pub const MAX_FNAME_LEN: usize = 255;
 /// max file size (128M)
-const MAX_FILE_SIZE: usize = 1024 * 1024 * 128;
+pub const MAX_FILE_SIZE: usize = 1024 * 1024 * 128;
 /// block the superblock lives in
-const BLKN_SUPER: usize = 0;
+pub const BLKN_SUPER: usize = 0;
 /// location of the root dir inode
-const BLKN_ROOT: usize = 1;
+pub const BLKN_ROOT: usize = 1;
 /// 1st block of the freemap
-const BLKN_FREEMAP: usize = 2;
+pub const BLKN_FREEMAP: usize = 2;
 /// number of bits in a block
-const BLKBITS: usize = BLKSIZE * 8;
+pub const BLKBITS: usize = BLKSIZE * 8;
 /// number of entries in a block
-const BLK_NENTRY: usize = BLKSIZE / 4;
+pub const BLK_NENTRY: usize = BLKSIZE / 4;
 
 /// file types
-enum FileType {
+pub enum FileType {
     Invalid = 0, File = 1, Dir = 2, Link = 3,
 }

src/tests.rs

@@ -1,4 +1,28 @@
+use std::fs::File;
+use std::io::{Read, Write, Seek, SeekFrom};
+use std::boxed::Box;
+use super::sfs::*;
+
+impl Device for File {
+    fn read_at(&mut self, offset: u64, buf: &mut [u8]) -> Option<usize> {
+        match self.seek(SeekFrom::Start(offset)) {
+            Ok(real_offset) if real_offset == offset => self.read(buf).ok(),
+            _ => None,
+        }
+    }
+
+    fn write_at(&mut self, offset: u64, buf: &[u8]) -> Option<usize> {
+        match self.seek(SeekFrom::Start(offset)) {
+            Ok(real_offset) if real_offset == offset => self.write(buf).ok(),
+            _ => None,
+        }
+    }
+}
+
 #[test]
 fn test() {
-
+    let file = File::open("sfs.img")
+        .expect("failed to open sfs.img");
+    let sfs = SimpleFileSystem::new(Box::new(file))
+        .expect("failed to create SFS");
 }