Refactor HashMap handling in typed.rs to use lower_map_iter for improved iteration and memory management. Introduce new implementations for ComponentType, Lower, and Lift traits for std::collections::HashMap, enhancing support for map types in the component model.

Author: yordis

crates/wasmtime/src/runtime/component/func/typed.rs

@@ -2138,7 +2138,7 @@ where
             }
             _ => bad_type_info(),
         };
-        let (ptr, len) = lower_map(cx, key_ty, value_ty, self)?;
+        let (ptr, len) = lower_map_iter(cx, key_ty, value_ty, self.len(), self.iter())?;
         // See "WRITEPTR64" above for why this is always storing a 64-bit
         // integer.
         map_maybe_uninit!(dst[0]).write(ValRaw::i64(ptr as i64));
@@ -2160,36 +2160,36 @@ where
             _ => bad_type_info(),
         };
         debug_assert!(offset % (Self::ALIGN32 as usize) == 0);
-        let (ptr, len) = lower_map(cx, key_ty, value_ty, self)?;
+        let (ptr, len) = lower_map_iter(cx, key_ty, value_ty, self.len(), self.iter())?;
         *cx.get(offset + 0) = u32::try_from(ptr).unwrap().to_le_bytes();
         *cx.get(offset + 4) = u32::try_from(len).unwrap().to_le_bytes();
         Ok(())
     }
 }
 
-fn lower_map<K, V, U>(
+fn lower_map_iter<'a, K, V, U>(
     cx: &mut LowerContext<'_, U>,
     key_ty: InterfaceType,
     value_ty: InterfaceType,
-    map: &HashMap<K, V>,
+    len: usize,
+    iter: impl Iterator<Item = (&'a K, &'a V)>,
 ) -> Result<(usize, usize)>
 where
-    K: Lower,
-    V: Lower,
+    K: Lower + 'a,
+    V: Lower + 'a,
 {
     // Calculate the tuple layout: each entry is a (key, value) record.
     let tuple_abi = CanonicalAbiInfo::record_static(&[K::ABI, V::ABI]);
     let tuple_size = tuple_abi.size32 as usize;
     let tuple_align = tuple_abi.align32;
 
-    let size = map
-        .len()
+    let size = len
         .checked_mul(tuple_size)
         .ok_or_else(|| format_err!("size overflow copying a map"))?;
     let ptr = cx.realloc(0, 0, tuple_align, size)?;
 
     let mut entry_offset = ptr;
-    for (key, value) in map.iter() {
+    for (key, value) in iter {
         // Lower key at the start of the tuple
         let mut field_offset = 0usize;
         let key_field = K::ABI.next_field32_size(&mut field_offset);
@@ -2200,7 +2200,7 @@ where
         entry_offset += tuple_size;
     }
 
-    Ok((ptr, map.len()))
+    Ok((ptr, len))
 }
 
 unsafe impl<K, V> Lift for HashMap<K, V>
@@ -2293,6 +2293,176 @@ where
     Ok(result)
 }
 
+// =============================================================================
+// std::collections::HashMap<K, V> support for component model `map<K, V>`
+//
+// This mirrors the wasmtime_environ::collections::HashMap implementation above
+// but works with the standard library HashMap type, which is what users will
+// naturally reach for.
+
+#[cfg(feature = "std")]
+unsafe impl<K, V> ComponentType for std::collections::HashMap<K, V>
+where
+    K: ComponentType,
+    V: ComponentType,
+{
+    type Lower = [ValRaw; 2];
+
+    const ABI: CanonicalAbiInfo = CanonicalAbiInfo::POINTER_PAIR;
+
+    fn typecheck(ty: &InterfaceType, types: &InstanceType<'_>) -> Result<()> {
+        match ty {
+            InterfaceType::Map(t) => {
+                let map_ty = &types.types[*t];
+                K::typecheck(&map_ty.key, types)?;
+                V::typecheck(&map_ty.value, types)?;
+                Ok(())
+            }
+            other => bail!("expected `map` found `{}`", desc(other)),
+        }
+    }
+}
+
+#[cfg(feature = "std")]
+unsafe impl<K, V> Lower for std::collections::HashMap<K, V>
+where
+    K: Lower,
+    V: Lower,
+{
+    fn linear_lower_to_flat<U>(
+        &self,
+        cx: &mut LowerContext<'_, U>,
+        ty: InterfaceType,
+        dst: &mut MaybeUninit<[ValRaw; 2]>,
+    ) -> Result<()> {
+        let (key_ty, value_ty) = match ty {
+            InterfaceType::Map(i) => {
+                let m = &cx.types[i];
+                (m.key, m.value)
+            }
+            _ => bad_type_info(),
+        };
+        let (ptr, len) = lower_map_iter(cx, key_ty, value_ty, self.len(), self.iter())?;
+        // See "WRITEPTR64" above for why this is always storing a 64-bit
+        // integer.
+        map_maybe_uninit!(dst[0]).write(ValRaw::i64(ptr as i64));
+        map_maybe_uninit!(dst[1]).write(ValRaw::i64(len as i64));
+        Ok(())
+    }
+
+    fn linear_lower_to_memory<U>(
+        &self,
+        cx: &mut LowerContext<'_, U>,
+        ty: InterfaceType,
+        offset: usize,
+    ) -> Result<()> {
+        let (key_ty, value_ty) = match ty {
+            InterfaceType::Map(i) => {
+                let m = &cx.types[i];
+                (m.key, m.value)
+            }
+            _ => bad_type_info(),
+        };
+        debug_assert!(offset % (Self::ALIGN32 as usize) == 0);
+        let (ptr, len) = lower_map_iter(cx, key_ty, value_ty, self.len(), self.iter())?;
+        *cx.get(offset + 0) = u32::try_from(ptr).unwrap().to_le_bytes();
+        *cx.get(offset + 4) = u32::try_from(len).unwrap().to_le_bytes();
+        Ok(())
+    }
+}
+
+#[cfg(feature = "std")]
+unsafe impl<K, V> Lift for std::collections::HashMap<K, V>
+where
+    K: Lift + Eq + Hash,
+    V: Lift,
+{
+    fn linear_lift_from_flat(
+        cx: &mut LiftContext<'_>,
+        ty: InterfaceType,
+        src: &Self::Lower,
+    ) -> Result<Self> {
+        let (key_ty, value_ty) = match ty {
+            InterfaceType::Map(i) => {
+                let m = &cx.types[i];
+                (m.key, m.value)
+            }
+            _ => bad_type_info(),
+        };
+        // FIXME(#4311): needs memory64 treatment
+        let ptr = src[0].get_u32();
+        let len = src[1].get_u32();
+        let (ptr, len) = (usize::try_from(ptr)?, usize::try_from(len)?);
+        lift_std_map(cx, key_ty, value_ty, ptr, len)
+    }
+
+    fn linear_lift_from_memory(
+        cx: &mut LiftContext<'_>,
+        ty: InterfaceType,
+        bytes: &[u8],
+    ) -> Result<Self> {
+        let (key_ty, value_ty) = match ty {
+            InterfaceType::Map(i) => {
+                let m = &cx.types[i];
+                (m.key, m.value)
+            }
+            _ => bad_type_info(),
+        };
+        debug_assert!((bytes.as_ptr() as usize) % (Self::ALIGN32 as usize) == 0);
+        // FIXME(#4311): needs memory64 treatment
+        let ptr = u32::from_le_bytes(bytes[..4].try_into().unwrap());
+        let len = u32::from_le_bytes(bytes[4..].try_into().unwrap());
+        let (ptr, len) = (usize::try_from(ptr)?, usize::try_from(len)?);
+        lift_std_map(cx, key_ty, value_ty, ptr, len)
+    }
+}
+
+#[cfg(feature = "std")]
+fn lift_std_map<K, V>(
+    cx: &mut LiftContext<'_>,
+    key_ty: InterfaceType,
+    value_ty: InterfaceType,
+    ptr: usize,
+    len: usize,
+) -> Result<std::collections::HashMap<K, V>>
+where
+    K: Lift + Eq + Hash,
+    V: Lift,
+{
+    let tuple_abi = CanonicalAbiInfo::record_static(&[K::ABI, V::ABI]);
+    let tuple_size = tuple_abi.size32 as usize;
+    let tuple_align = tuple_abi.align32 as usize;
+
+    match len
+        .checked_mul(tuple_size)
+        .and_then(|total| ptr.checked_add(total))
+    {
+        Some(n) if n <= cx.memory().len() => {}
+        _ => bail!("map pointer/length out of bounds of memory"),
+    }
+    if ptr % tuple_align != 0 {
+        bail!("map pointer is not aligned");
+    }
+
+    let mut result = std::collections::HashMap::with_capacity(len);
+    for i in 0..len {
+        let entry_base = ptr + (i * tuple_size);
+
+        let mut field_offset = 0usize;
+        let key_field = K::ABI.next_field32_size(&mut field_offset);
+        let key_bytes = &cx.memory()[entry_base + key_field..][..K::SIZE32];
+        let key = K::linear_lift_from_memory(cx, key_ty, key_bytes)?;
+
+        let value_field = V::ABI.next_field32_size(&mut field_offset);
+        let value_bytes = &cx.memory()[entry_base + value_field..][..V::SIZE32];
+        let value = V::linear_lift_from_memory(cx, value_ty, value_bytes)?;
+
+        result.insert(key, value);
+    }
+
+    Ok(result)
+}
+
 /// Verify that the given wasm type is a tuple with the expected fields in the right order.
 fn typecheck_tuple(
     ty: &InterfaceType,