added superblock, group descriptors, and mmp structured

src/lib.rs

@@ -1 +1,94 @@
+use std::io::SeekFrom;
 
+pub use crate::superblock::{SUPERBLOCK_SIZE, Superblock};
+pub use crate::utils::group_has_superblock;
+
+mod group_descriptor;
+mod mmp;
+mod superblock;
+mod utils;
+
+pub trait FileLike {
+    fn read_at_offset(&mut self, offset: u64, buf: &mut [u8]) -> anyhow::Result<()>;
+
+    fn write_at_offset(&mut self, offset: u64, bytes: &[u8]) -> anyhow::Result<()>;
+
+    fn read_at_offset_const<const N: usize>(&mut self, offset: u64) -> anyhow::Result<[u8; N]> {
+        let mut buf = [0; N];
+
+        self.read_at_offset(offset, &mut buf)?;
+
+        Ok(buf)
+    }
+}
+
+impl<F: std::io::Read + std::io::Write + std::io::Seek> FileLike for F {
+    fn read_at_offset(&mut self, offset: u64, buf: &mut [u8]) -> anyhow::Result<()> {
+        self.seek(SeekFrom::Start(offset))?;
+
+        self.read_exact(buf)?;
+
+        Ok(())
+    }
+
+    fn write_at_offset(&mut self, offset: u64, bytes: &[u8]) -> anyhow::Result<()> {
+        self.seek(SeekFrom::Start(offset))?;
+
+        self.write_all(bytes)?;
+
+        Ok(())
+    }
+}
+
+// impl FileLike for &mut [u8] {
+// fn read_at_offset(&mut self, offset: u64, buf: &mut [u8]) -> anyhow::Result<()> {
+// anyhow::ensure!(
+// offset as usize + buf.len() <= self.len(),
+// "reading {} bytes at offset {} is out of bounds for slice of len {}",
+// buf.len(),
+// offset,
+// self.len()
+// );
+//
+// buf.copy_from_slice(&self[offset as usize..][..buf.len()]);
+//
+// Ok(())
+// }
+//
+// fn write_at_offset(&mut self, offset: u64, bytes: &[u8]) -> anyhow::Result<()> {
+// anyhow::ensure!(
+// offset as usize + bytes.len() <= self.len(),
+// "writing {} bytes at offset {} is out of bounds for slice of len {}",
+// bytes.len(),
+// offset,
+// self.len()
+// );
+//
+// self[offset as usize..][..bytes.len()].copy_from_slice(bytes);
+//
+// Ok(())
+// }
+// }
+
+pub struct Ext4Fs<F: FileLike> {
+    #[allow(dead_code)]
+    file: F,
+
+    superblock: superblock::Superblock,
+}
+
+impl<F: FileLike> Ext4Fs<F> {
+    pub fn load(file: F) -> Result<Ext4Fs<F>, anyhow::Error> {
+        let mut file = file;
+
+        let superblock_bytes = file.read_at_offset_const::<SUPERBLOCK_SIZE>(1024)?;
+
+        let superblock = Superblock::from_bytes(&superblock_bytes)?;
+
+        Ok(Ext4Fs { file, superblock })
+    }
+
+    pub fn super_block(&self) -> &Superblock {
+        &self.superblock
+    }
+}