From f0999d7ac0c2a96a493cee91ce7dff78d34dcaf9 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Tu=E1=BA=A5n-Anh=20Nguy=E1=BB=85n?= <ubolonton@gmail.com>
Date: Wed, 28 Aug 2019 23:28:47 +0700
Subject: [PATCH] Make Rust functions return ExactSizeIterator instead of just
 Iterator  (#438)

* Add CBufferIter::size_hint

* Make Rust functions return ExactSizeIterator instead of just Iterator

* Fix wrong CBufferIter::size_hint
---
 lib/binding_rust/lib.rs  | 4 ++--
 lib/binding_rust/util.rs | 9 ++++++++-
 2 files changed, 10 insertions(+), 3 deletions(-)

diff --git a/lib/binding_rust/lib.rs b/lib/binding_rust/lib.rs
index 23315ea4..0ee168da 100644
--- a/lib/binding_rust/lib.rs
+++ b/lib/binding_rust/lib.rs
@@ -448,7 +448,7 @@ impl Tree {
         TreePropertyCursor::new(self, property_sheet, source)
     }
 
-    pub fn changed_ranges(&self, other: &Tree) -> impl Iterator<Item = Range> {
+    pub fn changed_ranges(&self, other: &Tree) -> impl ExactSizeIterator<Item = Range> {
         let mut count = 0;
         unsafe {
             let ptr = ffi::ts_tree_get_changed_ranges(self.0, other.0, &mut count as *mut _ as *mut u32);
@@ -570,7 +570,7 @@ impl<'tree> Node<'tree> {
         unsafe { ffi::ts_node_child_count(self.0) as usize }
     }
 
-    pub fn children(&self) -> impl Iterator<Item = Node<'tree>> {
+    pub fn children(&self) -> impl ExactSizeIterator<Item = Node<'tree>> {
         let me = self.clone();
         (0..self.child_count())
             .into_iter()
diff --git a/lib/binding_rust/util.rs b/lib/binding_rust/util.rs
index df73f830..e62e371f 100644
--- a/lib/binding_rust/util.rs
+++ b/lib/binding_rust/util.rs
@@ -22,15 +22,22 @@ impl<T: Copy> Iterator for CBufferIter<T> {
 
     fn next(&mut self) -> Option<Self::Item> {
         let i = self.i;
-        self.i += 1;
         if i >= self.count {
             None
         } else {
+            self.i += 1;
             Some(unsafe { *self.ptr.offset(i as isize) })
         }
     }
+
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        let remaining = self.count - self.i;
+        (remaining, Some(remaining))
+    }
 }
 
+impl<T: Copy> ExactSizeIterator for CBufferIter<T> {}
+
 impl<T> Drop for CBufferIter<T> {
     fn drop(&mut self) {
         unsafe { free_ptr(self.ptr as *mut c_void); }