Apply suggestions from code review

Co-authored-by: Daniel Prilik <[email protected]>

examples/armv4t/gdb/exec_file.rs

@@ -15,7 +15,7 @@ impl target::ext::exec_file::ExecFile for Emu {
         let filename = b"/test.elf";
         let len = filename.len();
         let data =
-            &filename[(offset as usize).min(len) as usize..((offset + length) as usize).min(len)];
+            &filename[offset.min(len)..(offset + length).min(len)];
         let buf = &mut buf[..data.len()];
         buf.copy_from_slice(data);
         Ok(data.len())

src/protocol/commands/_qXfer_exec_file.rs

@@ -21,7 +21,10 @@ impl<'a> ParseCommand<'a> for qXferExecFileRead<'a> {
         }
 
         let mut body = body.split(|b| *b == b':').skip(1);
-        let pid = decode_hex(body.next()?).ok().and_then(Pid::new);
+        let pid = match body.next()? {
+            [] => None,
+            buf => Some(Pid::new(decode_hex(buf).ok()?)?)
+        }
 
         let mut body = body.next()?.split(|b| *b == b',');
         let offset = decode_hex(body.next()?).ok()?;

src/target/ext/exec_file.rs

@@ -9,11 +9,15 @@ use crate::common::Pid;
 /// I/O Extensions`](crate::target::ext::host_io), which enables the GDB client
 /// to read the executable file directly from the target
 pub trait ExecFile: Target {
-    /// Get full absolute name of the file that was executed to create
-    /// process `pid` running on the remote system, or the filename
-    /// corresponding to the currently executing process if no `pid` is
-    /// provided.
-    /// Store the name into `buf`, and return the length of name.
+    /// Get full absolute path of the file that was executed to create
+    /// process `pid` running on the remote system.
+    ///
+    /// If `pid` is `None`, return the filename corresponding to the 
+    /// currently executing process.
+    ///
+    /// Return the number of bytes written into `buf` (which may be less than `length`).
+    ///
+    /// If `offset` is greater than the length of the underlying data, return `Ok(0)`.
     fn get_exec_file(
         &self,
         pid: Option<Pid>,