Stub out reading registers and memory

src/gdbserver/request.rs

@@ -1,4 +1,5 @@
 use anyhow::{bail, Result};
+use atoi::FromRadix16;
 use tokio::io::{AsyncRead, AsyncReadExt as _};
 
 #[derive(Clone, Copy, Debug, PartialEq, Eq)]
@@ -6,11 +7,32 @@ pub enum RequestKind {
     Signal,
     Command,
 }
+impl RequestKind {
+    fn name(self) -> &'static str {
+        match self {
+            Self::Signal => "Signal",
+            Self::Command => "Command",
+        }
+    }
+}
 
-#[derive(Debug)]
 pub struct Request<'a> {
     pub kind: RequestKind,
-    body: &'a str,
+    buffer: &'a [u8],
+}
+
+impl std::fmt::Debug for Request<'_> {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        let mut ds = f.debug_tuple(self.kind.name());
+        match self.kind {
+            RequestKind::Signal => ds.field(&self.buffer),
+            RequestKind::Command => match std::str::from_utf8(self.buffer) {
+                Ok(str) => ds.field(&str),
+                Err(_) => ds.field(&self.buffer),
+            },
+        };
+        ds.finish()
+    }
 }
 
 impl<'a> Request<'a> {
@@ -31,10 +53,9 @@ impl<'a> Request<'a> {
         if char == 0x03 {
             // This is how the client "cancels an in-flight request"
             buffer.push(char);
-            let body = std::str::from_utf8(buffer)?;
             return Ok(Self {
                 kind: RequestKind::Signal,
-                body,
+                buffer,
             });
         }
         if char != b'$' {
@@ -61,24 +82,34 @@ impl<'a> Request<'a> {
 
         let mut checksum_bytes = [b'0'; 2];
         reader.read_exact(&mut checksum_bytes).await?;
-        let checksum_str = std::str::from_utf8(&checksum_bytes)?;
-        let real_checksum = u8::from_str_radix(checksum_str, 16)?;
-        if checksum != real_checksum {
+        let (real_checksum, 2) = u8::from_radix_16(&checksum_bytes) else {
             bail!("invalid checksum");
+        };
+        if checksum != real_checksum {
+            bail!("mismatched checksum");
         }
 
-        let body = std::str::from_utf8(buffer)?;
         Ok(Self {
             kind: RequestKind::Command,
-            body,
+            buffer,
         })
     }
 
     pub fn match_str(&mut self, prefix: &str) -> bool {
-        if let Some(new_body) = self.body.strip_prefix(prefix) {
-            self.body = new_body;
+        if let Some(new_buffer) = self.buffer.strip_prefix(prefix.as_bytes()) {
+            self.buffer = new_buffer;
             return true;
         }
         false
     }
+
+    pub fn match_hex<I: FromRadix16>(&mut self) -> Option<I> {
+        match I::from_radix_16(self.buffer) {
+            (_, 0) => None,
+            (val, used) => {
+                self.buffer = self.buffer.split_at(used).1;
+                Some(val)
+            }
+        }
+    }
 }