get and create a FileDescriptor from the fd (#43)

idevice/src/services/afc/file.rs

@@ -1,6 +1,6 @@
 // Jackson Coxson
 
-use std::{io::SeekFrom, pin::Pin};
+use std::{io::SeekFrom, marker::PhantomPinned, pin::Pin};
 
 use tokio::io::{AsyncRead, AsyncSeek, AsyncWrite};
 
@@ -13,8 +13,25 @@ pub struct FileDescriptor<'a> {
 }
 
 impl<'a> FileDescriptor<'a> {
-    pub(crate) fn new(inner: Pin<Box<InnerFileDescriptor<'a>>>) -> Self {
-        Self { inner }
+    /// create a new FileDescriptor from a raw fd
+    ///
+    /// # Safety
+    /// make sure the fd is an opened file, and that you got it from a previous
+    /// FileDescriptor via `as_raw_fd()` method
+    pub unsafe fn new(client: &'a mut super::AfcClient, fd: u64, path: String) -> Self {
+        Self {
+            inner: Box::pin(InnerFileDescriptor {
+                client,
+                fd,
+                path,
+                pending_fut: None,
+                _m: PhantomPinned,
+            }),
+        }
+    }
+
+    pub fn as_raw_fd(&self) -> u64 {
+        self.inner.fd
     }
 }
 impl FileDescriptor<'_> {

idevice/src/services/afc/inner_file.rs

@@ -44,17 +44,6 @@ pub(crate) struct InnerFileDescriptor<'a> {
     pub(crate) _m: std::marker::PhantomPinned,
 }
 
-impl<'a> InnerFileDescriptor<'a> {
-    pub(crate) fn new(client: &'a mut super::AfcClient, fd: u64, path: String) -> Pin<Box<Self>> {
-        Box::pin(Self {
-            client,
-            fd,
-            path,
-            pending_fut: None,
-            _m: std::marker::PhantomPinned,
-        })
-    }
-}
 impl InnerFileDescriptor<'_> {
     /// Generic helper to send an AFC packet and read the response
     pub async fn send_packet(

idevice/src/services/afc/mod.rs

@@ -410,9 +410,9 @@ impl AfcClient {
             return Err(IdeviceError::UnexpectedResponse);
         }
         let fd = u64::from_le_bytes(res.header_payload[..8].try_into().unwrap());
-        Ok(FileDescriptor::new(inner_file::InnerFileDescriptor::new(
-            self, fd, path,
-        )))
+
+        // we know it's a valid fd
+        Ok(unsafe { FileDescriptor::new(self, fd, path) })
     }
 
     /// Creates a hard or symbolic link