initial commit

3 files changed, 203 insertions, 0 deletions

diff --git a/src/disk/bitmap.rs b/src/disk/bitmap.rs
new file mode 100644
index 0000000..a5a9cc4
--- /dev/null
+++ b/src/disk/bitmap.rs
@@ -0,0 +1,49 @@
+use crate::block_device::{BlockDevice, BLOCK_SIZE};
+use std::sync::Arc;
+
+pub struct Bitmap {
+    pub starting_block: usize,
+    pub length: usize,
+    pub device: Arc<dyn BlockDevice>,
+    pub data: Vec<u8>,
+    pub dirty_blocks: Vec<usize>,
+}
+
+impl Bitmap {
+    pub fn new(starting_block: usize, length: usize, device: Arc<dyn BlockDevice>) -> Self {
+        Self {
+            starting_block,
+            length,
+            device,
+            data: vec![0u8; length * BLOCK_SIZE],
+            dirty_blocks: Vec::new(),
+        }
+    }
+    pub fn allocate(&mut self) -> usize {
+        for (i, byte) in self.data.iter_mut().enumerate() {
+            let leading_ones = byte.leading_ones();
+            if leading_ones != 8 {
+                *byte |= (1 << (7 - leading_ones)) as u8;
+                self.dirty_blocks.push(i / BLOCK_SIZE);
+                return i * 8 + leading_ones as usize;
+            }
+        }
+        panic!("No more space for allocation!")
+    }
+
+    pub fn query(&self, index: usize) -> bool {
+        self.data[index / 8] & ((1 << (7 - index % 8)) as u8) != 0
+    }
+
+    fn write_back(&mut self) {
+        for block_index_offset in self.dirty_blocks.iter() {
+            let buffer_front_index = BLOCK_SIZE * block_index_offset;
+            let buffer_back_index = BLOCK_SIZE * (block_index_offset + 1);
+            self.device.write(
+                self.starting_block + block_index_offset,
+                &self.data[buffer_front_index..buffer_back_index],
+            );
+        }
+        self.dirty_blocks = Vec::new();
+    }
+}
diff --git a/src/disk/inode.rs b/src/disk/inode.rs
new file mode 100644
index 0000000..f38508a
--- /dev/null
+++ b/src/disk/inode.rs
@@ -0,0 +1,152 @@
+use bitflags::bitflags;
+
+const DIRECT_NUMBER: usize = 15;
+
+#[derive(Debug)]
+pub struct InodeMode(u16);
+
+bitflags! {
+    impl InodeMode: u16 {
+        const IXOTH = 0x0001;
+        const IWOTH = 0x0002;
+        const IROTH = 0x0004;
+        const IXGRP = 0x0008;
+        const IWGRP = 0x0010;
+        const IRGRP = 0x0020;
+        const IXUSR = 0x0040;
+        const IWUSR = 0x0080;
+        const IRUSR = 0x0100;
+        const ISVTX = 0x0200;
+        const ISGID = 0x0400;
+        const ISUID = 0x0800;
+        // These are mutually-exclusive:
+        const IFIFO = 0x1000;
+        const IFCHR = 0x2000;
+        const IFDIR = 0x4000;
+        const IFBLK = 0x6000;
+        const IFREG = 0x8000;
+        const IFLNK = 0xA000;
+        const IFSOCK = 0xC000;
+    }
+}
+
+/// Pretty much the same with ext2, with minor changes:
+/// - removed OS dependent attributes (osd1 & osd2)
+/// - removed i_faddr since fragmentation is not supported
+/// - changed uid and gid from u16 to u32
+/// - added more direct blocks for a total size of 128 bytes
+/// TODO: do we need to extend time precision?
+#[repr(C)]
+#[derive(Debug)]
+pub struct Inode {
+    mode: InodeMode,
+    uid: u32,
+    size: u32,
+    atime: u32, // time in seconds
+    ctime: u32,
+    mtime: u32,
+    dtime: u32,
+    gid: u32,
+    n_links: u16,
+    n_blocks: u32,
+    flags: u32, // TODO: do we actually need this? maybe just return 0
+    direct: [u32; DIRECT_NUMBER],
+    single_indirect: u32,
+    double_indirect: u32,
+    triple_indirect: u32,
+    generation: u32,
+    file_acl: u32,
+    dir_acl: u32, // TODO do we have to implement ACL......?
+}
+
+impl Inode {
+    pub fn directory() -> Self {
+        Self {
+            mode: InodeMode::IFDIR
+                | InodeMode::IRUSR
+                | InodeMode::IWUSR
+                | InodeMode::IXUSR
+                | InodeMode::IRGRP
+                | InodeMode::IXGRP
+                | InodeMode::IROTH
+                | InodeMode::IXOTH,
+            // Directory, 755 permissions
+            uid: 0,
+            size: 0,
+            atime: 0,
+            ctime: 0,
+            mtime: 0,
+            dtime: 0,
+            gid: 0,
+            n_links: 0,
+            n_blocks: 0,
+            flags: 0,
+            direct: [0; DIRECT_NUMBER],
+            single_indirect: 0,
+            double_indirect: 0,
+            triple_indirect: 0,
+            generation: 0,
+            file_acl: 0,
+            dir_acl: 0,
+        }
+    }
+
+    pub fn file() -> Self {
+        Self {
+            mode: InodeMode::IFREG
+                | InodeMode::IRUSR
+                | InodeMode::IWUSR
+                | InodeMode::IXUSR
+                | InodeMode::IRGRP
+                | InodeMode::IXGRP
+                | InodeMode::IROTH
+                | InodeMode::IXOTH,
+            // RegularFile, 755 permissions
+            uid: 0,
+            size: 0,
+            atime: 0,
+            ctime: 0,
+            mtime: 0,
+            dtime: 0,
+            gid: 0,
+            n_links: 0,
+            n_blocks: 0,
+            flags: 0,
+            direct: [0; DIRECT_NUMBER],
+            single_indirect: 0,
+            double_indirect: 0,
+            triple_indirect: 0,
+            generation: 0,
+            file_acl: 0,
+            dir_acl: 0,
+        }
+    }
+}
+
+//
+// #[repr(C)]
+// #[derive(Debug, Default)]
+// pub struct FileInode {
+//     file_size: u32,
+//     direct_blocks: [u32; DIRECT_NUMBER],
+//     indirect_block: u32,
+//     doubly_indirect_block: u32,
+// } // sizeof(FileInode) == 124 bytes
+//
+// #[repr(C)]
+// #[derive(Debug, Default)]
+// pub struct DirectoryInode {
+//     child_number: u32,
+//     direct_blocks: [u32; DIRECT_NUMBER],
+//     indirect_block: u32,
+//     doubly_indirect_block: u32,
+// } // sizeof(FileInode) == 124 bytes
+//
+// #[repr(C)]
+// #[derive(Debug)]
+// pub enum Inode {
+//     File(FileInode),
+//     Directory(DirectoryInode),
+// } // sizeof(Inode) == 128 bytes
+
+pub const INODE_SIZE: usize = std::mem::size_of::<Inode>();
diff --git a/src/disk/mod.rs b/src/disk/mod.rs
new file mode 100644
index 0000000..e4e4216
--- /dev/null
+++ b/src/disk/mod.rs
@@ -0,0 +1,2 @@
+pub mod inode;
+pub mod bitmap;