Add seek function

src/ext2/file.rs

@@ -11,7 +11,7 @@ use std::io::{self, Read};
 ///
 /// Files are automatically closed when they go out of scope.  Errors detected
 /// on closing are ignored by the implementation of `Drop`.
-#[derive(Debug)]
+#[derive(Debug, Clone)]
 pub struct File {
     inode: Inode,
     block_size: usize,

src/main.rs

@@ -4,17 +4,24 @@ use std::{
     borrow::Cow,
     fs::File,
     os::mikros::{ipc, syscalls},
-    sync::Arc,
+    sync::Arc, usize,
 };
 
 use ext2::Ext2;
 use itertools::Itertools;
 use parking_lot::RwLock;
 
+#[derive(Clone)]
+struct OpenFile {
+    file: ext2::File,
+    pos: u64,
+    mount_id: usize,
+}
+
 #[derive(Clone)]
 struct Serv {
     mounts: Arc<RwLock<Vec<Ext2>>>,
-    files: Arc<RwLock<Vec<(ext2::File, usize)>>>,
+    files: Arc<RwLock<Vec<OpenFile>>>,
     dirs: Arc<RwLock<Vec<(Vec<String>, usize)>>>,
 }
 
@@ -31,7 +38,11 @@ impl fs_rpc::Server for Serv {
         let mounts = self.mounts.read();
         let mount = &mounts[mount_id as usize];
         let file = mount.open(path).map_err(|_| ())?;
-        self.files.write().push((file, mount_id as usize));
+        self.files.write().push(OpenFile {
+            file,
+            pos: 0,
+            mount_id: mount_id as usize
+        });
         let res = Ok((None, (self.files.read().len() - 1) as u64));
         res
     }
@@ -49,18 +60,20 @@ impl fs_rpc::Server for Serv {
 }
 
 impl file_rpc::Server for Serv {
-    fn read(&self, fd: u64, pos: u64, len: usize) -> Result<Cow<'_, [u8]>, ()> {
+    fn read(&self, fd: u64, len: usize) -> Result<Cow<'_, [u8]>, ()> {
         let files = self.files.read();
-        let (file, mount_id) = &files[fd as usize];
+        let file = &files[fd as usize];
         let mounts = self.mounts.read();
-        let mount = &mounts[*mount_id];
+        let mount = &mounts[file.mount_id];
         let mut buf = vec![0; len];
-        let read_len = file.read_at(&mut buf, pos, mount).map_err(|_| ())?;
+        let read_len = file.file.read_at(&mut buf, file.pos, mount).map_err(|_| ())?;
         buf.truncate(read_len);
+        std::mem::drop(files);
+        self.files.write()[fd as usize].pos += read_len as u64;
         Ok(buf.into())
     }
 
-    fn write(&self, _fd: u64, _pos: u64, _data: &[u8]) -> Result<(), ()> {
+    fn write(&self, _fd: u64, _data: &[u8]) -> Result<(), ()> {
         Err(())
     }
 
@@ -68,12 +81,43 @@ impl file_rpc::Server for Serv {
 
     fn size(&self, fd: u64) -> Option<u64> {
         let files = self.files.read();
-        let (file, _mount_id) = &files[fd as usize];
+        let file = &files[fd as usize];
-        Some(file.metadata().len())
+        Some(file.file.metadata().len())
     }
 
     fn dup(&self, fd: u64) -> Option<u64> {
-        Some(fd)
+        let mut files = self.files.write();
+        let file = files[fd as usize].clone();
+        files.push(file);
+        Some((files.len() - 1) as u64)
+    }
+
+    fn seek(&self, fd: u64, pos: file_rpc::SeekFrom) -> u64 {
+        let mut files = self.files.write();
+        let file = &mut files[fd as usize];
+        match pos {
+            file_rpc::SeekFrom::Start(offset) => {
+                file.pos = offset;
+            },
+            file_rpc::SeekFrom::End(offset) => {
+                if offset <= 0 {
+                    file.pos = file.file.metadata().len() - (-offset) as u64;
+                }
+            },
+            file_rpc::SeekFrom::Current(offset) => {
+                if offset > 0 {
+                    file.pos = u64::min(file.pos + offset as u64, file.file.metadata().len());
+                } else {
+                    let offset = (-offset) as u64;
+                    if offset > file.pos {
+                        file.pos = 0;
+                    } else {
+                        file.pos -= offset;
+                    }
+                }
+            },
+        }
+        file.pos
     }
 }