Create example userspace scheme. Remove kernel duplication of syscalls, use syscall crate instead

kernel/scheme/env.rs

@@ -2,8 +2,8 @@ use collections::BTreeMap;
 use core::sync::atomic::{AtomicUsize, Ordering};
 use spin::RwLock;
 
-use syscall::{Error, Result};
-use super::Scheme;
+use syscall::error::*;
+use syscall::scheme::Scheme;
 
 struct Handle {
     data: &'static [u8],
@@ -35,7 +35,7 @@ impl EnvScheme {
 
 impl Scheme for EnvScheme {
     fn open(&self, path: &[u8], _flags: usize) -> Result<usize> {
-        let data = self.files.get(path).ok_or(Error::NoEntry)?;
+        let data = self.files.get(path).ok_or(Error::new(ENOENT))?;
 
         let id = self.next_id.fetch_add(1, Ordering::SeqCst);
         self.handles.write().insert(id, Handle {
@@ -49,7 +49,7 @@ impl Scheme for EnvScheme {
     fn dup(&self, file: usize) -> Result<usize> {
         let (data, seek) = {
             let handles = self.handles.read();
-            let handle = handles.get(&file).ok_or(Error::BadFile)?;
+            let handle = handles.get(&file).ok_or(Error::new(EBADF))?;
             (handle.data, handle.seek)
         };
 
@@ -64,7 +64,7 @@ impl Scheme for EnvScheme {
 
     fn read(&self, file: usize, buffer: &mut [u8]) -> Result<usize> {
         let mut handles = self.handles.write();
-        let mut handle = handles.get_mut(&file).ok_or(Error::BadFile)?;
+        let mut handle = handles.get_mut(&file).ok_or(Error::new(EBADF))?;
 
         let mut i = 0;
         while i < buffer.len() && handle.seek < handle.data.len() {
@@ -76,15 +76,11 @@ impl Scheme for EnvScheme {
         Ok(i)
     }
 
-    fn write(&self, _file: usize, _buffer: &[u8]) -> Result<usize> {
-        Err(Error::NotPermitted)
+    fn fsync(&self, _file: usize) -> Result<usize> {
+        Ok(0)
     }
 
-    fn fsync(&self, _file: usize) -> Result<()> {
-        Ok(())
-    }
-
-    fn close(&self, file: usize) -> Result<()> {
-        self.handles.write().remove(&file).ok_or(Error::BadFile).and(Ok(()))
+    fn close(&self, file: usize) -> Result<usize> {
+        self.handles.write().remove(&file).ok_or(Error::new(EBADF)).and(Ok(0))
     }
 }