From 8edcd00b87a6c0200a935b5f8b03d5d9c6cc6d9b Mon Sep 17 00:00:00 2001
From: Jorge Aparicio <jorge.aparicio@ferrous-systems.com>
Date: Tue, 11 Aug 2020 11:19:30 +0200
Subject: [PATCH] implement enum decoder

---
 decoder/src/lib.rs           | 66 +++++++++++++++++++++++++++++++++---
 firmware/qemu/src/bin/log.rs | 17 ++++++++++
 src/impls.rs                 |  2 +-
 3 files changed, 79 insertions(+), 6 deletions(-)

diff --git a/decoder/src/lib.rs b/decoder/src/lib.rs
index 397c6309..7e219681 100644
--- a/decoder/src/lib.rs
+++ b/decoder/src/lib.rs
@@ -355,12 +355,29 @@ fn parse_args<'t>(
             }
             Type::Format => {
                 let format = get_format(format_list, bytes, table)?;
-                let inner_args = parse_args(bytes, format, table, format_list)?;
 
-                args.push(Arg::Format {
-                    format,
-                    args: inner_args,
-                });
+                if format.contains('|') {
+                    // enum
+                    let enum_string = format;
+                    let discriminant = bytes.read_u8().map_err(drop)?;
+                    // NOTE nesting of enums, like "A|B(C|D)" is not possible; indirection is
+                    // required: "A|B({:?})" where "{:?}" -> "C|D"
+                    let variant = enum_string
+                        .split('|')
+                        .nth(usize::from(discriminant))
+                        .ok_or(())?;
+                    let inner_args = parse_args(bytes, variant, table, format_list)?;
+                    args.push(Arg::Format {
+                        format: variant,
+                        args: inner_args,
+                    });
+                } else {
+                    let inner_args = parse_args(bytes, format, table, format_list)?;
+                    args.push(Arg::Format {
+                        format,
+                        args: inner_args,
+                    });
+                }
             }
             Type::I16 => {
                 let data = bytes.read_i16::<LE>().map_err(drop)?;
@@ -937,4 +954,43 @@ mod tests {
             "0.000002 INFO Hello World 125",
         );
     }
+
+    #[test]
+    fn option() {
+        let mut entries = BTreeMap::new();
+        entries.insert(4, "x={:?}".to_owned());
+        entries.insert(3, "None|Some({:?})".to_owned());
+        entries.insert(2, "{:u8}".to_owned());
+
+        let table = Table {
+            entries,
+            debug: 0..0,
+            error: 0..0,
+            info: 4..5,
+            trace: 0..0,
+            warn: 0..0,
+        };
+
+        let bytes = [
+            4,  // string index (INFO)
+            0,  // timestamp
+            3,  // string index (enum)
+            1,  // Some discriminant
+            2,  // string index (u8)
+            42, // Some.0
+        ];
+
+        let frame = super::decode(&bytes, &table).unwrap().0;
+        assert_eq!(frame.display(false).to_string(), "0.000000 INFO x=Some(42)");
+
+        let bytes = [
+            4,  // string index (INFO)
+            1,  // timestamp
+            3,  // string index (enum)
+            0,  // None discriminant
+        ];
+
+        let frame = super::decode(&bytes, &table).unwrap().0;
+        assert_eq!(frame.display(false).to_string(), "0.000001 INFO x=None");
+    }
 }
diff --git a/firmware/qemu/src/bin/log.rs b/firmware/qemu/src/bin/log.rs
index 66a2bbaf..b042aa61 100644
--- a/firmware/qemu/src/bin/log.rs
+++ b/firmware/qemu/src/bin/log.rs
@@ -94,6 +94,23 @@ fn main() -> ! {
     let slices: &[&[u16]] = &[&[256, 257, 258], &[259, 260]];
     binfmt::info!("{:[?]}", slices);
 
+    #[derive(Format)]
+    enum E {
+        A,
+        B,
+    }
+
+    binfmt::info!("e1={:?}", E::A);
+    binfmt::info!("e2={:?}", E::B);
+
+    binfmt::info!("e3={:?}", Some(42u8));
+    binfmt::info!("e4={:?}", None::<u8>);
+
+    binfmt::info!("e5={:?}", Ok::<u8, u16>(42u8));
+    binfmt::info!("e6={:?}", Err::<u8, u16>(256u16));
+
+    binfmt::info!("e7={:?}", Some(X { y: Y { z: 42 } }));
+
     loop {
         debug::exit(debug::EXIT_SUCCESS)
     }
diff --git a/src/impls.rs b/src/impls.rs
index 4a3cbe9e..40f2cd9d 100644
--- a/src/impls.rs
+++ b/src/impls.rs
@@ -194,7 +194,7 @@ where
 {
     fn format(&self, f: &mut Formatter) {
         if f.needs_tag() {
-            let t = internp!("None|Some({})");
+            let t = internp!("None|Some({:?})");
             f.u8(&t);
         }
         match self {