implemented read

fat-bits/src/iter.rs

@@ -22,7 +22,7 @@ impl<'a> ClusterChainReader<'a> {
         }
     }
 
-    fn next_cluster(&mut self) -> bool {
+    fn move_to_next_cluster(&mut self) -> bool {
         let Some(next_cluster) = self.next_cluster else {
             return false;
         };
@@ -37,12 +37,33 @@ impl<'a> ClusterChainReader<'a> {
 
         true
     }
+
+    pub fn skip(&mut self, n: u64) -> u64 {
+        let mut bytes_to_skip = n;
+
+        while bytes_to_skip > self.sub_slice.len() as u64 {
+            bytes_to_skip -= self.sub_slice.len() as u64;
+            if !self.move_to_next_cluster() {
+                // ran out of bytes to seek
+                return n - bytes_to_skip;
+            }
+        }
+
+        if bytes_to_skip != 0 {
+            bytes_to_skip -= self.sub_slice.skip(bytes_to_skip as usize) as u64;
+        }
+
+        // n should absolutely be zero here
+        assert_eq!(bytes_to_skip, 0);
+
+        n
+    }
 }
 
-impl<'a> Read for ClusterChainReader<'a> {
+impl Read for ClusterChainReader<'_> {
     fn read(&mut self, buf: &mut [u8]) -> std::io::Result<usize> {
         if self.sub_slice.is_empty() {
-            if !self.next_cluster() {
+            if !self.move_to_next_cluster() {
                 return Ok(0);
             }
         }

fat-bits/src/lib.rs

@@ -11,7 +11,7 @@ mod datetime;
 pub mod dir;
 pub mod fat;
 pub mod fs_info;
-mod iter;
+pub mod iter;
 mod subslice;
 mod utils;
 
@@ -240,7 +240,7 @@ impl FatFs {
         Ok(data)
     }
 
-    fn chain_reader(&self, first_cluster: u32) -> impl Read {
+    fn chain_reader(&'_ self, first_cluster: u32) -> iter::ClusterChainReader<'_> {
         iter::ClusterChainReader::new(self, first_cluster)
     }
 
@@ -274,4 +274,10 @@ impl FatFs {
 
         DirIter::new(Box::new(cluster_iter))
     }
+
+    pub fn file_reader(&self, first_cluster: u32) -> iter::ClusterChainReader<'_> {
+        assert!(first_cluster >= 2);
+
+        self.chain_reader(first_cluster)
+    }
 }

fat-bits/src/subslice.rs

@@ -104,16 +104,21 @@ impl SubSlice<'_> {
         self.fat_fs
     }
 
-    pub fn fat_fs_mut(&self) -> &FatFs {
-        self.fat_fs
-    }
-
     pub fn is_empty(&self) -> bool {
         self.len() == 0
     }
     pub fn len(&self) -> usize {
         self.len
     }
+
+    pub fn skip(&mut self, n: usize) -> usize {
+        let n = n.min(self.len());
+
+        self.offset += n as u64;
+        self.len -= n;
+
+        n
+    }
 }
 
 impl<'a> SubSlice<'a> {

fat-fuse/src/fuse.rs

@@ -1,11 +1,12 @@
 use std::ffi::c_int;
+use std::io::Read;
 use std::rc::Rc;
 use std::time::Duration;
 
 use fat_bits::dir::DirEntry;
 use fuser::{FileType, Filesystem};
-use libc::{EINVAL, EIO, ENOENT, ENOSYS, ENOTDIR};
-use log::{debug, warn};
+use libc::{EBADF, EINVAL, EIO, EISDIR, ENOENT, ENOSYS, ENOTDIR};
+use log::{debug, error};
 
 use crate::{FatFuse, Inode};
 
@@ -281,6 +282,8 @@ impl Filesystem for FatFuse {
             debug!("fh {} was associated with ino {}, now with ino {}", fh, old_ino, ino);
         }
 
+        debug!("opened inode {}: fh {}", ino, fh);
+
         reply.opened(fh, 0);
     }
 
@@ -291,16 +294,74 @@ impl Filesystem for FatFuse {
         fh: u64,
         offset: i64,
         size: u32,
-        flags: i32,
-        lock_owner: Option<u64>,
+        _flags: i32,
+        _lock_owner: Option<u64>,
         reply: fuser::ReplyData,
     ) {
-        warn!(
-            "[Not Implemented] read(ino: {:#x?}, fh: {}, offset: {}, size: {}, \
-            flags: {:#x?}, lock_owner: {:?})",
-            ino, fh, offset, size, flags, lock_owner
-        );
-        reply.error(ENOSYS);
+        // warn!(
+        //     "[Not Implemented] read(ino: {:#x?}, fh: {}, offset: {}, size: {}, \
+        //     flags: {:#x?}, lock_owner: {:?})",
+        //     ino, fh, offset, size, flags, lock_owner
+        // );
+        // reply.error(ENOSYS);
+
+        if offset < 0 {
+            debug!("tried to read with negative offset {offset}");
+
+            reply.error(EINVAL);
+            return;
+        }
+
+        let offset = offset as u64;
+
+        let Some(inode) = self.get_inode_by_fh(fh) else {
+            debug!("fh {fh} is not associated by any inode");
+
+            reply.error(EBADF);
+            return;
+        };
+
+        if inode.ino() != ino {
+            debug!("fh {fh} is associated with inode {} instead of {ino}", inode.ino());
+
+            reply.error(EIO);
+            return;
+        }
+
+        if !inode.is_file() {
+            debug!("tried to use read on directory {ino}");
+
+            reply.error(EISDIR);
+            return;
+        }
+
+        let mut reader = match inode.file_reader(&self.fat_fs) {
+            Ok(reader) => reader,
+            Err(err) => {
+                reply.error(err);
+                return;
+            }
+        };
+
+        if reader.skip(offset) != offset {
+            // reader is exhausted, bail
+            reply.data(&[]);
+            return;
+        }
+
+        let mut buf = vec![0; size as usize];
+
+        let n = match reader.read(&mut buf) {
+            Ok(n) => n,
+            Err(err) => {
+                error!("error while reading: {err}");
+
+                reply.error(EIO);
+                return;
+            }
+        };
+
+        reply.data(&buf[..n]);
     }
 
     fn write(
@@ -347,13 +408,27 @@ impl Filesystem for FatFuse {
     fn release(
         &mut self,
         _req: &fuser::Request<'_>,
-        _ino: u64,
-        _fh: u64,
+        ino: u64,
+        fh: u64,
         _flags: i32,
         _lock_owner: Option<u64>,
         _flush: bool,
         reply: fuser::ReplyEmpty,
     ) {
+        let Some(found_ino) = self.ino_by_fh.remove(&fh) else {
+            debug!("tried to release fh {fh} with ino {ino}, but no ino was found in mapping");
+
+            reply.error(EINVAL);
+            return;
+        };
+
+        if found_ino != ino {
+            debug!("tried to release fh {fh} with ino {ino}, but found ino is {found_ino} instead");
+
+            reply.error(EIO);
+            return;
+        }
+
         reply.ok();
     }
 

fat-fuse/src/inode.rs

@@ -5,8 +5,9 @@ use std::time::SystemTime;
 use chrono::{NaiveDateTime, NaiveTime};
 use fat_bits::FatFs;
 use fat_bits::dir::DirEntry;
+use fat_bits::iter::ClusterChainReader;
 use fuser::FileAttr;
-use libc::ENOTDIR;
+use libc::{EISDIR, ENOTDIR};
 use log::debug;
 use rand::{Rng, SeedableRng as _};
 
@@ -232,6 +233,14 @@ impl Inode {
         self.kind
     }
 
+    pub fn is_file(&self) -> bool {
+        self.kind == Kind::File
+    }
+
+    pub fn is_dir(&self) -> bool {
+        self.kind == Kind::Dir
+    }
+
     pub fn first_cluster(&self) -> u32 {
         self.first_cluster
     }
@@ -281,4 +290,12 @@ impl Inode {
 
         Ok(fat_fs.dir_iter(self.first_cluster))
     }
+
+    pub fn file_reader<'a>(&'a self, fat_fs: &'a FatFs) -> Result<ClusterChainReader<'a>, i32> {
+        if self.is_dir() {
+            return Err(EISDIR);
+        }
+
+        Ok(fat_fs.file_reader(self.first_cluster()))
+    }
 }

fat-mount/src/main.rs

@@ -30,9 +30,11 @@ fn main() -> anyhow::Result<()> {
     })
     .unwrap();
 
-    let _handle = fuser::spawn_mount2(fat_fuse, mountpoint, &options)?;
+    let handle = fuser::spawn_mount2(fat_fuse, mountpoint, &options)?;
 
     rx.recv().unwrap();
 
+    handle.join();
+
     Ok(())
 }