1 files changed, 135 insertions, 0 deletions
diff --git a/storage/variant/src/bag.rs b/storage/variant/src/bag.rs
new file mode 100644
index 0000000000..91653ba226
--- /dev/null
+++ b/storage/variant/src/bag.rs
@@ -0,0 +1,135 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use nserror::{nsresult, NS_ERROR_CANNOT_CONVERT_DATA, NS_OK};
+use nsstring::nsString;
+use xpcom::{
+    getter_addrefs,
+    interfaces::{nsIProperty, nsIPropertyBag, nsIWritablePropertyBag},
+    RefPtr, XpCom,
+};
+
+use crate::{NsIVariantExt, VariantType};
+
+extern "C" {
+    fn NS_NewHashPropertyBag(bag: *mut *const nsIWritablePropertyBag);
+}
+
+/// A hash property bag backed by storage variant values.
+pub struct HashPropertyBag(RefPtr<nsIWritablePropertyBag>);
+
+// This is safe as long as our `nsIWritablePropertyBag` is an instance of
+// `mozilla::nsHashPropertyBag`, which is atomically reference counted, and
+// all properties are backed by `Storage*Variant`s, all of which are
+// thread-safe.
+unsafe impl Send for HashPropertyBag {}
+unsafe impl Sync for HashPropertyBag {}
+
+impl Default for HashPropertyBag {
+    fn default() -> HashPropertyBag {
+        // This is safe to unwrap because `NS_NewHashPropertyBag` is infallible.
+        let bag = getter_addrefs(|p| {
+            unsafe { NS_NewHashPropertyBag(p) };
+            NS_OK
+        })
+        .unwrap();
+        HashPropertyBag(bag)
+    }
+}
+
+impl HashPropertyBag {
+    /// Creates an empty property bag.
+    #[inline]
+    pub fn new() -> Self {
+        Self::default()
+    }
+
+    /// Creates a property bag from an instance of `nsIPropertyBag`, cloning its
+    /// contents. The `source` bag can only contain primitive values for which
+    /// the `VariantType` trait is implemented. Attempting to clone a bag with
+    /// unsupported types, such as arrays, interface pointers, and `jsval`s,
+    /// fails with `NS_ERROR_CANNOT_CONVERT_DATA`.
+    ///
+    /// `clone_from_bag` can be used to clone a thread-unsafe `nsIPropertyBag`,
+    /// like one passed from JavaScript via XPConnect, into one that can be
+    /// shared across threads.
+    pub fn clone_from_bag(source: &nsIPropertyBag) -> Result<Self, nsresult> {
+        let enumerator = getter_addrefs(|p| unsafe { source.GetEnumerator(p) })?;
+        let b = HashPropertyBag::new();
+        while {
+            let mut has_more = false;
+            unsafe { enumerator.HasMoreElements(&mut has_more) }.to_result()?;
+            has_more
+        } {
+            let element = getter_addrefs(|p| unsafe { enumerator.GetNext(p) })?;
+            let property = element
+                .query_interface::<nsIProperty>()
+                .ok_or(NS_ERROR_CANNOT_CONVERT_DATA)?;
+            let mut name = nsString::new();
+            unsafe { property.GetName(&mut *name) }.to_result()?;
+            let value = getter_addrefs(|p| unsafe { property.GetValue(p) })?;
+            unsafe { b.0.SetProperty(&*name, value.try_clone()?.coerce()) }.to_result()?;
+        }
+        Ok(b)
+    }
+
+    /// Returns the value for a property name. Fails with `NS_ERROR_FAILURE`
+    /// if the property doesn't exist, or `NS_ERROR_CANNOT_CONVERT_DATA` if the
+    /// property exists, but is not of the value type `V`.
+    pub fn get<K, V>(&self, name: K) -> Result<V, nsresult>
+    where
+        K: AsRef<str>,
+        V: VariantType,
+    {
+        getter_addrefs(|p| unsafe { self.0.GetProperty(&*nsString::from(name.as_ref()), p) })
+            .and_then(|v| V::from_variant(v.coerce()))
+    }
+
+    /// Returns the value for a property name, or the default if not set or
+    /// not of the value type `V`.
+    #[inline]
+    pub fn get_or_default<K, V>(&self, name: K) -> V
+    where
+        K: AsRef<str>,
+        V: VariantType + Default,
+    {
+        self.get(name).unwrap_or_default()
+    }
+
+    /// Sets a property with the name to the value, overwriting any previous
+    /// value.
+    pub fn set<K, V>(&mut self, name: K, value: V)
+    where
+        K: AsRef<str>,
+        V: VariantType,
+    {
+        let v = value.into_variant();
+        unsafe {
+            // This is safe to unwrap because
+            // `nsHashPropertyBagBase::SetProperty` only returns an error if `v`
+            // is a null pointer.
+            self.0
+                .SetProperty(&*nsString::from(name.as_ref()), v.coerce())
+                .to_result()
+                .unwrap()
+        }
+    }
+
+    /// Deletes a property with the name. Returns `true` if the property
+    /// was previously in the bag, `false` if not.
+    pub fn delete(&mut self, name: impl AsRef<str>) -> bool {
+        unsafe {
+            self.0
+                .DeleteProperty(&*nsString::from(name.as_ref()))
+                .to_result()
+                .is_ok()
+        }
+    }
+
+    /// Returns a reference to the backing `nsIWritablePropertyBag`.
+    #[inline]
+    pub fn bag(&self) -> &nsIWritablePropertyBag {
+        &self.0
+    }
+}