feat: Implement the SortBy stream adapter

eyeball-im-util/Cargo.toml

@@ -12,11 +12,11 @@ keywords.workspace = true
 all-features = true
 
 [dependencies]
-arrayvec = "0.7.4"
 eyeball-im = { version = "0.4.2", path = "../eyeball-im" }
 futures-core.workspace = true
 imbl = "2.0.0"
 pin-project-lite = "0.2.9"
+smallvec = { version = "1.11.2", features = ["const_generics", "const_new"] }
 
 [dev-dependencies]
 eyeball = { version = "0.8.6", path = "../eyeball" }

eyeball-im-util/src/vector.rs

@@ -3,6 +3,7 @@
 mod filter;
 mod limit;
 mod ops;
+mod sort;
 mod traits;
 
 use eyeball_im::VectorDiff;
@@ -12,6 +13,7 @@ use self::ops::{VectorDiffContainerFamilyMember, VectorDiffContainerOps};
 pub use self::{
     filter::{Filter, FilterMap},
     limit::{EmptyLimitStream, Limit},
+    sort::SortBy,
     traits::{
         BatchedVectorSubscriber, VectorDiffContainer, VectorObserver, VectorObserverExt,
         VectorSubscriberExt,
@@ -40,5 +42,5 @@ type VectorDiffContainerDiff<S> = VectorDiff<VectorDiffContainerStreamElement<S>
 
 /// Type alias for extracting the buffer type from a stream of
 /// [`VectorDiffContainer`]s.
-type VectorDiffContainerStreamLimitBuf<S> =
+type VectorDiffContainerStreamBuffer<S> =
     <<S as Stream>::Item as VectorDiffContainerOps<VectorDiffContainerStreamElement<S>>>::Buffer;

eyeball-im-util/src/vector/limit.rs

@@ -1,3 +1,4 @@
+use smallvec::SmallVec;
 use std::{
     cmp::{min, Ordering},
     mem,
@@ -6,10 +7,9 @@ use std::{
 };
 
 use super::{
-    VectorDiffContainer, VectorDiffContainerOps, VectorDiffContainerStreamElement,
-    VectorDiffContainerStreamLimitBuf, VectorObserver,
+    VectorDiffContainer, VectorDiffContainerOps, VectorDiffContainerStreamBuffer,
+    VectorDiffContainerStreamElement, VectorObserver,
 };
-use arrayvec::ArrayVec;
 use eyeball_im::VectorDiff;
 use futures_core::Stream;
 use imbl::Vector;
@@ -63,7 +63,7 @@ pin_project! {
         // with a limit of 2 on top: if an item is popped at the front then 10
         // is removed, but 12 has to be pushed back as it "enters" the "view".
         // That second `PushBack` diff is buffered here.
-        ready_values: VectorDiffContainerStreamLimitBuf<S>,
+        ready_values: VectorDiffContainerStreamBuffer<S>,
     }
 }
 
@@ -207,6 +207,7 @@ where
                 update_buffered_vector(&diff, self.buffered_vector);
                 handle_diff(diff, limit, prev_len, self.buffered_vector)
             });
+
             if let Some(diff) = ready {
                 return Poll::Ready(Some(diff));
             }
@@ -318,15 +319,15 @@ fn handle_diff<T: Clone>(
     limit: usize,
     prev_len: usize,
     buffered_vector: &Vector<T>,
-) -> ArrayVec<VectorDiff<T>, 2> {
+) -> SmallVec<[VectorDiff<T>; 2]> {
     // If the limit is zero, we have nothing to do.
     if limit == 0 {
-        return ArrayVec::new();
+        return SmallVec::new();
     }
 
     let is_full = prev_len >= limit;
+    let mut res = SmallVec::new();
 
-    let mut res = ArrayVec::new();
     match diff {
         VectorDiff::Append { mut values } => {
             if is_full {

eyeball-im-util/src/vector/ops.rs

@@ -1,5 +1,5 @@
-use arrayvec::ArrayVec;
 use eyeball_im::VectorDiff;
+use smallvec::SmallVec;
 
 pub trait VectorDiffContainerOps<T>: Sized {
     type Family: VectorDiffContainerFamily;
@@ -15,7 +15,7 @@ pub trait VectorDiffContainerOps<T>: Sized {
     fn push_into_buffer(
         self,
         buffer: &mut Self::Buffer,
-        make_diffs: impl FnMut(VectorDiff<T>) -> ArrayVec<VectorDiff<T>, 2>,
+        make_diffs: impl FnMut(VectorDiff<T>) -> SmallVec<[VectorDiff<T>; 2]>,
     ) -> Option<Self>;
 
     fn pop_from_buffer(buffer: &mut Self::Buffer) -> Option<Self>;
@@ -26,7 +26,7 @@ pub type VectorDiffContainerFamilyMember<F, U> = <F as VectorDiffContainerFamily
 
 impl<T> VectorDiffContainerOps<T> for VectorDiff<T> {
     type Family = VectorDiffFamily;
-    type Buffer = Option<VectorDiff<T>>;
+    type Buffer = SmallVec<[VectorDiff<T>; 2]>;
 
     fn from_item(vector_diff: VectorDiff<T>) -> Self {
         vector_diff
@@ -42,23 +42,28 @@ impl<T> VectorDiffContainerOps<T> for VectorDiff<T> {
     fn push_into_buffer(
         self,
         buffer: &mut Self::Buffer,
-        mut make_diffs: impl FnMut(VectorDiff<T>) -> ArrayVec<VectorDiff<T>, 2>,
+        mut make_diffs: impl FnMut(VectorDiff<T>) -> SmallVec<[VectorDiff<T>; 2]>,
     ) -> Option<Self> {
-        assert!(buffer.is_none(), "buffer must be None when calling push_into_buffer");
+        assert!(buffer.is_empty(), "buffer must be empty when calling `push_into_buffer`");
 
         let mut diffs = make_diffs(self);
 
-        let last = diffs.pop();
-        if let Some(first) = diffs.pop() {
-            *buffer = last;
-            Some(first)
-        } else {
-            last
+        match diffs.len() {
+            0 => None,
+            1 => diffs.pop(),
+            _ => {
+                // We want the first element. We can't “pop front” on a `SmallVec`.
+                // The idea is to reverse the `diffs` and to pop from it.
+                diffs.reverse();
+                *buffer = diffs;
+
+                buffer.pop()
+            }
         }
     }
 
     fn pop_from_buffer(buffer: &mut Self::Buffer) -> Option<Self> {
-        buffer.take()
+        buffer.pop()
     }
 }
 
@@ -75,6 +80,7 @@ impl<T> VectorDiffContainerOps<T> for Vec<VectorDiff<T>> {
         f: impl FnMut(VectorDiff<T>) -> Option<VectorDiff<U>>,
     ) -> Option<VectorDiffContainerFamilyMember<Self::Family, U>> {
         let res: Vec<_> = self.into_iter().filter_map(f).collect();
+
         if res.is_empty() {
             None
         } else {
@@ -85,9 +91,10 @@ impl<T> VectorDiffContainerOps<T> for Vec<VectorDiff<T>> {
     fn push_into_buffer(
         self,
         _buffer: &mut (),
-        make_diffs: impl FnMut(VectorDiff<T>) -> ArrayVec<VectorDiff<T>, 2>,
+        make_diffs: impl FnMut(VectorDiff<T>) -> SmallVec<[VectorDiff<T>; 2]>,
     ) -> Option<Self> {
         let res: Vec<_> = self.into_iter().flat_map(make_diffs).collect();
+
         if res.is_empty() {
             None
         } else {