feat: upstream ops from WASI-virt

WASI-virt contains functions that are helpful for manipulating modules
and dealing with exports/imports, which would be helpful to an even
wider group if upstreamed here to walrus.

This commit copies and upstreams some operations that were introduced
in WASI-virt for wider use via walrus.

See also: bytecodealliance/WASI-Virt#20

Signed-off-by: Victor Adossi <[email protected]>

src/arena_set.rs

@@ -5,7 +5,7 @@ use std::hash::Hash;
 use std::ops;
 
 /// A set of unique `T`s that are backed by an arena.
-#[derive(Debug)]
+#[derive(Debug, Clone)]
 pub struct ArenaSet<T: Clone + Eq + Hash> {
     arena: TombstoneArena<T>,
     already_in_arena: HashMap<T, Id<T>>,

src/module/exports.rs

@@ -1,5 +1,7 @@
 //! Exported items in a wasm module.
 
+use anyhow::Context;
+
 use crate::emit::{Emit, EmitContext};
 use crate::parse::IndicesToIds;
 use crate::tombstone_arena::{Id, Tombstone, TombstoneArena};
@@ -100,6 +102,16 @@ impl ModuleExports {
         })
     }
 
+    /// Retrieve an exported function by name
+    pub fn get_func_by_name(&self, name: impl AsRef<str>) -> Result<FunctionId> {
+        self.iter()
+            .find_map(|expt| match expt.item {
+                ExportItem::Function(fid) if expt.name == name.as_ref() => Some(fid),
+                _ => None,
+            })
+            .with_context(|| format!("unable to find function export '{}'", name.as_ref()))
+    }
+
     /// Get a reference to a table export given its table id.
     pub fn get_exported_table(&self, t: TableId) -> Option<&Export> {
         self.iter().find(|e| match e.item {
@@ -354,6 +366,16 @@ mod tests {
         assert!(module.exports.get_exported_func(fn_id).is_none());
     }
 
+    #[test]
+    fn get_func_by_name() {
+        let mut module = Module::default();
+        let fn_id: FunctionId = always_the_same_id();
+        let export_id: ExportId = module.exports.add("dummy", fn_id);
+        assert!(module.exports.get_func_by_name("dummy").is_ok());
+        module.exports.delete(export_id);
+        assert!(module.exports.get_func_by_name("dummy").is_err());
+    }
+
     #[test]
     fn iter_mut_can_update_export_item() {
         let mut module = Module::default();