Load dynamic programs using FAT32

src/fs.rs

@@ -0,0 +1,42 @@
+use bffs::io::{IoBase, Read, Seek};
+
+const DISK_ADDR: *const u8 = 0x9000_0000 as *const _;
+
+#[derive(Debug)]
+pub struct Disk {
+    pos: u64,
+    size: u64,
+}
+
+impl Disk {
+    pub fn new(size: u64) -> Self {
+        Self { pos: 0, size }
+    }
+}
+
+impl IoBase for Disk {
+    type Error = ();
+}
+
+impl Seek for Disk {
+    fn seek(&mut self, pos: bffs::io::SeekFrom) -> Result<u64, bffs::error::Error<Self::Error>> {
+        match pos {
+            bffs::io::SeekFrom::Start(pos) => self.pos = pos,
+            bffs::io::SeekFrom::End(_) => unimplemented!(),
+            bffs::io::SeekFrom::Current(pos) => self.pos = (self.pos as i64 + pos) as u64,
+        }
+        Ok(self.pos)
+    }
+}
+
+impl Read for Disk {
+    fn read(&mut self, buf: &mut [u8]) -> Result<usize, bffs::error::Error<Self::Error>> {
+        if self.pos >= self.size {
+            return Ok(0);
+        }
+        let size = usize::min(buf.len(), (self.size - self.pos) as usize);
+        (0..size).for_each(|i| buf[i] = unsafe { *DISK_ADDR.byte_add(i + self.pos as usize) });
+        self.pos += size as u64;
+        Ok(size)
+    }
+}