implement computing message layout

src/bag.rs

@@ -1,9 +1,9 @@
 use std::{fs::File, path::Path};
 
 use eyre::Context;
-use log::{error, trace};
+use log::debug;
 
-use crate::{Result, index::BagIndex, info::BagInfo, message::parse_msgs, reader::MmapReader};
+use crate::{index::BagIndex, info::BagInfo, message::compute_layout, reader::MmapReader, Result};
 
 pub struct Bag {
     reader: MmapReader,
@@ -20,21 +20,8 @@ impl Bag {
 
     pub fn compute_message_layouts(&mut self) -> Result<()> {
         for conn in &self.index.connections {
-            match parse_msgs(conn) {
+            let layout = compute_layout(conn)?;
-                Ok(msgs) => {
+            debug!("message layout: {:#?}", layout);
-                    for msg in &msgs {
-                        trace!(
-                            "message definition parsed: {:#?}",
-                            msg.fields()
-                                .iter()
-                                .filter(|field| !field.is_constant())
-                                .map(ToString::to_string)
-                                .collect::<Vec<_>>()
-                        );
-                    }
-                }
-                Err(err) => error!("could not parse message definition: {}", err),
-            }
         }
         Ok(())
     }
@@ -43,4 +30,3 @@ impl Bag {
         BagInfo::compute(&mut self.reader, &self.index)
     }
 }
-

src/layout.rs

@@ -1,6 +1,39 @@
-use ros_message::I8Variant;
+use std::collections::HashMap;
 
-use crate::SmallStr;
+use eyre::{bail, eyre};
+use ros_message::{DataType, FieldCase, FieldInfo, I8Variant, MessagePath, Msg, U8Variant};
+use thiserror::Error;
+
+use crate::{Result, SmallStr};
+
+type Dependencies = HashMap<MessagePath, MessageLayoutRef>;
+
+#[derive(Clone, Debug, Error)]
+#[error("missing dependent message definition: {0}")]
+pub struct MissingDependency(MessagePath);
+
+#[derive(Clone, Debug, Error)]
+#[error("dependency cycle involving: {0:?}")]
+pub struct DependencyCycle(Vec<String>);
+
+struct Resolver<'a> {
+    dependencies: &'a HashMap<MessagePath, MessageLayoutRef>,
+    current_path: &'a MessagePath,
+}
+
+impl<'a> Resolver<'a> {
+    fn get_dep(&self, path: &MessagePath) -> Result<MessageLayoutRef> {
+        self.dependencies
+            .get(path)
+            .cloned()
+            .ok_or_else(|| eyre!(MissingDependency(path.clone())))
+    }
+
+    fn get_local_dep(&self, name: &str) -> Result<MessageLayoutRef> {
+        let full_path = self.current_path.peer(name);
+        self.get_dep(&full_path)
+    }
+}
 
 #[derive(Clone, Debug)]
 pub enum FieldType {
@@ -15,7 +48,7 @@ pub enum FieldType {
     /// Represents `int64`.
     I64,
     /// Represents `uint8` or `char`.
-    U8(I8Variant),
+    U8(U8Variant),
     /// Represents `uint16`.
     U16,
     /// Represents `uint32`.
@@ -36,6 +69,29 @@ pub enum FieldType {
     Message(MessageLayoutRef),
 }
 
+impl FieldType {
+    fn from_datatype_and_resolver(datatype: &DataType, resolver: &Resolver) -> Result<Self> {
+        Ok(match datatype {
+            DataType::Bool => FieldType::Bool,
+            DataType::I8(v) => FieldType::I8(v.clone()),
+            DataType::I16 => FieldType::I16,
+            DataType::I32 => FieldType::I32,
+            DataType::I64 => FieldType::I64,
+            DataType::U8(v) => FieldType::U8(v.clone()),
+            DataType::U16 => FieldType::U16,
+            DataType::U32 => FieldType::U32,
+            DataType::U64 => FieldType::U64,
+            DataType::F32 => FieldType::F32,
+            DataType::F64 => FieldType::F64,
+            DataType::String => FieldType::String,
+            DataType::Time => FieldType::Time,
+            DataType::Duration => FieldType::Duration,
+            DataType::LocalMessage(path) => FieldType::Message(resolver.get_local_dep(path)?),
+            DataType::GlobalMessage(path) => FieldType::Message(resolver.get_dep(path)?),
+        })
+    }
+}
+
 #[derive(Clone, Debug)]
 pub struct FieldLayout {
     pub typ: FieldType,
@@ -43,6 +99,21 @@ pub struct FieldLayout {
     pub multiplicity: Multiplicity,
 }
 
+impl FieldLayout {
+    fn from_info_and_resolver(info: &FieldInfo, resolver: &Resolver) -> Result<Self> {
+        Ok(Self {
+            typ: FieldType::from_datatype_and_resolver(info.datatype(), resolver)?,
+            name: info.name().into(),
+            multiplicity: match info.case() {
+                FieldCase::Unit => Multiplicity::Unit,
+                FieldCase::Vector => Multiplicity::Dynamic,
+                FieldCase::Array(n) => Multiplicity::Fixed(*n),
+                FieldCase::Const(_) => unreachable!(),
+            },
+        })
+    }
+}
+
 #[derive(Clone, Debug, PartialEq, Eq)]
 pub enum Multiplicity {
     Unit,
@@ -56,3 +127,62 @@ pub struct MessageLayout {
 }
 
 pub type MessageLayoutRef = std::sync::Arc<MessageLayout>;
+
+impl MessageLayout {
+    pub fn from_msgs<'a, M, I>(msgs: M) -> Result<MessageLayout>
+    where
+        M: IntoIterator<IntoIter = I>,
+        I: Iterator<Item = &'a Msg> + DoubleEndedIterator,
+    {
+        let mut dependencies: Dependencies = Default::default();
+        let mut msgs = msgs.into_iter();
+        let main = msgs
+            .next()
+            .ok_or_else(|| eyre!("at least one msg required"))?;
+
+        let mut deps: Vec<_> = msgs.collect();
+
+        while !deps.is_empty() {
+            let mut remaining = Vec::new();
+            let orig_length = deps.len();
+            for msg in deps.drain(..) {
+                let layout = match MessageLayout::from_msg_and_deps(msg, &dependencies) {
+                    Ok(layout) => layout,
+                    Err(err) => {
+                        if err.root_cause().is::<MissingDependency>() {
+                            // Has a missing dependency, resovle it on the next iteration
+                            remaining.push(msg);
+                            continue;
+                        } else {
+                            return Err(err);
+                        }
+                    }
+                };
+                dependencies.insert(msg.path().clone(), MessageLayoutRef::from(layout));
+            }
+            if remaining.len() == orig_length {
+                // Made no progress, there is a dependency cycle
+                bail!(DependencyCycle(
+                    remaining.iter().map(|msg| msg.path().to_string()).collect()
+                ));
+            }
+            deps = remaining;
+        }
+
+        MessageLayout::from_msg_and_deps(main, &dependencies)
+    }
+
+    fn from_msg_and_deps(msg: &Msg, dependencies: &Dependencies) -> Result<MessageLayout> {
+        let resolver = Resolver {
+            dependencies,
+            current_path: msg.path(),
+        };
+        let fields = msg
+            .fields()
+            .iter()
+            .filter(|field| !field.is_constant())
+            .map(|field| FieldLayout::from_info_and_resolver(field, &resolver))
+            .collect::<Result<Vec<_>, _>>()?;
+        Ok(MessageLayout { fields })
+    }
+}

src/message.rs

@@ -5,10 +5,10 @@ use log::trace;
 use regex::Regex;
 use ros_message::{MessagePath, Msg};
 
-use crate::{index::ConnInfo, Result};
+use crate::{index::ConnInfo, layout::MessageLayout, Result};
 
 fn parse_msg(message_name: &str, msgdef: &str) -> Result<Msg> {
-    trace!("message definition: {}", msgdef);
+    trace!("message definition {}: {}", message_name, msgdef);
     let path = MessagePath::try_from(message_name)?;
     let msgtype = Msg::new(path, msgdef)?;
     Ok(msgtype)
@@ -18,7 +18,7 @@ lazy_static! {
     static ref BOUNDARY_RE: Regex = Regex::new(r"\r?\n==+\r?\nMSG: ([^\r\n]+)\r?\n").unwrap();
 }
 
-pub fn parse_msgs(conn: &ConnInfo) -> Result<Vec<Msg>> {
+fn parse_msgs(conn: &ConnInfo) -> Result<Vec<Msg>> {
     let msgdefs = &conn.message_definition;
     let mut name = conn.datatype.clone();
     let mut begin = 0usize;
@@ -43,3 +43,8 @@ pub fn parse_msgs(conn: &ConnInfo) -> Result<Vec<Msg>> {
 
     Ok(msgs)
 }
+
+pub fn compute_layout(conn: &ConnInfo) -> Result<MessageLayout> {
+    let msgs = parse_msgs(conn)?;
+    MessageLayout::from_msgs(&msgs)
+}

src/parse.rs

@@ -13,4 +13,4 @@ pub type IResult<'a, T> = nom::IResult<Input<'a>, T, Error<Input<'a>>>;
 pub type InputStr<'a> = &'a str;
 pub type IResultStr<'a, T> = nom::IResult<InputStr<'a>, T, Error<InputStr<'a>>>;
 
-pub type SmallStr = String;
+pub type SmallStr = crate::SmallStr;