From f91b19c08947aad20e095a4103cf144794baf16d Mon Sep 17 00:00:00 2001
From: Max Brunsfeld <maxbrunsfeld@gmail.com>
Date: Wed, 5 Aug 2020 09:57:45 -0700
Subject: [PATCH] tags, highlight: Avoid completely deallocating buffers when
 shrinking

---
 highlight/src/lib.rs | 16 ++++++++++------
 tags/src/c_lib.rs    | 16 ++++++++++------
 2 files changed, 20 insertions(+), 12 deletions(-)

diff --git a/highlight/src/lib.rs b/highlight/src/lib.rs
index 1cffefa2..e4aebbfb 100644
--- a/highlight/src/lib.rs
+++ b/highlight/src/lib.rs
@@ -900,12 +900,8 @@ impl HtmlRenderer {
     }
 
     pub fn reset(&mut self) {
-        self.html.truncate(BUFFER_HTML_RESERVE_CAPACITY);
-        self.line_offsets.truncate(BUFFER_LINES_RESERVE_CAPACITY);
-        self.html.shrink_to_fit();
-        self.line_offsets.shrink_to_fit();
-        self.html.clear();
-        self.line_offsets.clear();
+        shrink_and_clear(&mut self.html, BUFFER_HTML_RESERVE_CAPACITY);
+        shrink_and_clear(&mut self.line_offsets, BUFFER_LINES_RESERVE_CAPACITY);
         self.line_offsets.push(0);
     }
 
@@ -1069,3 +1065,11 @@ fn injection_for_match<'a>(
 
     (language_name, content_node, include_children)
 }
+
+fn shrink_and_clear<T>(vec: &mut Vec<T>, capacity: usize) {
+    if vec.len() > capacity {
+        vec.truncate(capacity);
+        vec.shrink_to_fit();
+    }
+    vec.clear();
+}
diff --git a/tags/src/c_lib.rs b/tags/src/c_lib.rs
index c2bec6ca..b0786580 100644
--- a/tags/src/c_lib.rs
+++ b/tags/src/c_lib.rs
@@ -119,12 +119,8 @@ pub extern "C" fn ts_tagger_tag(
     let scope_name = unsafe { unwrap(CStr::from_ptr(scope_name).to_str()) };
 
     if let Some(config) = tagger.languages.get(scope_name) {
-        buffer.tags.truncate(BUFFER_TAGS_RESERVE_CAPACITY);
-        buffer.docs.truncate(BUFFER_DOCS_RESERVE_CAPACITY);
-        buffer.tags.shrink_to_fit();
-        buffer.docs.shrink_to_fit();
-        buffer.tags.clear();
-        buffer.docs.clear();
+        shrink_and_clear(&mut buffer.tags, BUFFER_TAGS_RESERVE_CAPACITY);
+        shrink_and_clear(&mut buffer.docs, BUFFER_DOCS_RESERVE_CAPACITY);
 
         let source_code = unsafe { slice::from_raw_parts(source_code, source_code_len as usize) };
         let cancellation_flag = unsafe { cancellation_flag.as_ref() };
@@ -262,3 +258,11 @@ fn unwrap<T, E: fmt::Display>(result: Result<T, E>) -> T {
         abort();
     })
 }
+
+fn shrink_and_clear<T>(vec: &mut Vec<T>, capacity: usize) {
+    if vec.len() > capacity {
+        vec.truncate(capacity);
+        vec.shrink_to_fit();
+    }
+    vec.clear();
+}