From d96ba093915598b35cb097e34edee5cae9cef3df Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Tu=E1=BA=A5n-Anh=20Nguy=E1=BB=85n?= <ubolonton@gmail.com>
Date: Tue, 27 Aug 2019 09:36:16 +0700
Subject: [PATCH] Make Tree::changed_ranges return an Iterator instead of a Vec
 (#437)

* Make Tree::changed_ranges return an Iterator instead of a Vec

* Remove CBufferIter.free parameter
---
 cli/src/tests/corpus_test.rs |  2 +-
 cli/src/tests/parser_test.rs |  4 ++--
 cli/src/tests/tree_test.rs   |  2 +-
 lib/binding_rust/lib.rs      | 22 +++++++--------------
 lib/binding_rust/util.rs     | 38 ++++++++++++++++++++++++++++++++++++
 5 files changed, 49 insertions(+), 19 deletions(-)
 create mode 100644 lib/binding_rust/util.rs

diff --git a/cli/src/tests/corpus_test.rs b/cli/src/tests/corpus_test.rs
index 19c90e19..a8adce5f 100644
--- a/cli/src/tests/corpus_test.rs
+++ b/cli/src/tests/corpus_test.rs
@@ -337,7 +337,7 @@ fn check_consistent_sizes(tree: &Tree, input: &Vec<u8>) {
 }
 
 fn check_changed_ranges(old_tree: &Tree, new_tree: &Tree, input: &Vec<u8>) -> Result<(), String> {
-    let changed_ranges = old_tree.changed_ranges(new_tree);
+    let changed_ranges = old_tree.changed_ranges(new_tree).collect();
     let old_scope_sequence = ScopeSequence::new(old_tree);
     let new_scope_sequence = ScopeSequence::new(new_tree);
     old_scope_sequence.check_changes(&new_scope_sequence, &input, &changed_ranges)
diff --git a/cli/src/tests/parser_test.rs b/cli/src/tests/parser_test.rs
index 184afd04..96b08af0 100644
--- a/cli/src/tests/parser_test.rs
+++ b/cli/src/tests/parser_test.rs
@@ -767,7 +767,7 @@ fn test_parsing_with_a_newly_excluded_range() {
     );
 
     assert_eq!(
-        tree.changed_ranges(&first_tree),
+        tree.changed_ranges(&first_tree).collect::<Vec<_>>(),
         vec![
             // The first range that has changed syntax is the range of the newly-inserted text.
             Range {
@@ -837,7 +837,7 @@ fn test_parsing_with_a_newly_included_range() {
     );
 
     assert_eq!(
-        tree.changed_ranges(&first_tree),
+        tree.changed_ranges(&first_tree).collect::<Vec<_>>(),
         vec![Range {
             start_byte: first_code_end_index + 1,
             end_byte: second_code_end_index + 1,
diff --git a/cli/src/tests/tree_test.rs b/cli/src/tests/tree_test.rs
index e22ce18e..b4e8ce7c 100644
--- a/cli/src/tests/tree_test.rs
+++ b/cli/src/tests/tree_test.rs
@@ -370,7 +370,7 @@ fn get_changed_ranges(
 ) -> Vec<Range> {
     perform_edit(tree, source_code, &edit);
     let new_tree = parser.parse(&source_code, Some(tree)).unwrap();
-    let result = tree.changed_ranges(&new_tree);
+    let result = tree.changed_ranges(&new_tree).collect();
     *tree = new_tree;
     result
 }
diff --git a/lib/binding_rust/lib.rs b/lib/binding_rust/lib.rs
index 208c45e3..23315ea4 100644
--- a/lib/binding_rust/lib.rs
+++ b/lib/binding_rust/lib.rs
@@ -1,4 +1,5 @@
 mod ffi;
+mod util;
 
 #[macro_use]
 extern crate serde_derive;
@@ -16,7 +17,7 @@ use std::ffi::CStr;
 use std::marker::PhantomData;
 use std::os::raw::{c_char, c_void};
 use std::sync::atomic::AtomicUsize;
-use std::{fmt, ptr, slice, str, u16};
+use std::{fmt, ptr, str, u16};
 
 pub const LANGUAGE_VERSION: usize = ffi::TREE_SITTER_LANGUAGE_VERSION;
 pub const PARSER_HEADER: &'static str = include_str!("../include/tree_sitter/parser.h");
@@ -447,15 +448,11 @@ impl Tree {
         TreePropertyCursor::new(self, property_sheet, source)
     }
 
-    pub fn changed_ranges(&self, other: &Tree) -> Vec<Range> {
+    pub fn changed_ranges(&self, other: &Tree) -> impl Iterator<Item = Range> {
+        let mut count = 0;
         unsafe {
-            let mut count = 0;
-            let ptr =
-                ffi::ts_tree_get_changed_ranges(self.0, other.0, &mut count as *mut _ as *mut u32);
-            let ranges = slice::from_raw_parts(ptr, count);
-            let result = ranges.into_iter().map(|r| r.clone().into()).collect();
-            free_ptr(ptr as *mut c_void);
-            result
+            let ptr = ffi::ts_tree_get_changed_ranges(self.0, other.0, &mut count as *mut _ as *mut u32);
+            util::CBufferIter::new(ptr, count).map(|r| r.into())
         }
     }
 }
@@ -638,7 +635,7 @@ impl<'tree> Node<'tree> {
             .to_str()
             .unwrap()
             .to_string();
-        unsafe { free_ptr(c_string as *mut c_void) };
+        unsafe { util::free_ptr(c_string as *mut c_void) };
         result
     }
 
@@ -1072,8 +1069,3 @@ impl std::error::Error for PropertySheetError {
         }
     }
 }
-
-extern "C" {
-    #[link_name = "rust_tree_sitter_free"]
-    fn free_ptr(ptr: *mut c_void);
-}
diff --git a/lib/binding_rust/util.rs b/lib/binding_rust/util.rs
new file mode 100644
index 00000000..df73f830
--- /dev/null
+++ b/lib/binding_rust/util.rs
@@ -0,0 +1,38 @@
+use std::os::raw::c_void;
+
+extern "C" {
+    #[link_name = "rust_tree_sitter_free"]
+    pub fn free_ptr(ptr: *mut c_void);
+}
+
+pub struct CBufferIter<T> {
+    ptr: *mut T,
+    count: usize,
+    i: usize,
+}
+
+impl<T> CBufferIter<T> {
+    pub unsafe fn new(ptr: *mut T, count: usize) -> Self {
+        Self { ptr, count, i: 0 }
+    }
+}
+
+impl<T: Copy> Iterator for CBufferIter<T> {
+    type Item = T;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        let i = self.i;
+        self.i += 1;
+        if i >= self.count {
+            None
+        } else {
+            Some(unsafe { *self.ptr.offset(i as isize) })
+        }
+    }
+}
+
+impl<T> Drop for CBufferIter<T> {
+    fn drop(&mut self) {
+        unsafe { free_ptr(self.ptr as *mut c_void); }
+    }
+}