From d2022d1a6d60edd4e8bb0c02ea7e9f431bd9be00 Mon Sep 17 00:00:00 2001
From: Damien Elmes <gpg@ankiweb.net>
Date: Sat, 19 Aug 2023 08:05:39 +1000
Subject: [PATCH] Avoid allocating in extract_latex() if possible; make public

---
 rslib/src/card_rendering/service.rs |  2 +-
 rslib/src/latex.rs                  | 20 +++++++++++---------
 2 files changed, 12 insertions(+), 10 deletions(-)

diff --git a/rslib/src/card_rendering/service.rs b/rslib/src/card_rendering/service.rs
index c4bde891c..c9cd203f0 100644
--- a/rslib/src/card_rendering/service.rs
+++ b/rslib/src/card_rendering/service.rs
@@ -53,7 +53,7 @@ impl crate::services::CardRenderingService for Collection {
         let (text, extracted) = func(&input.text, input.svg);
 
         Ok(anki_proto::card_rendering::ExtractLatexResponse {
-            text,
+            text: text.into_owned(),
             latex: extracted
                 .into_iter()
                 .map(
diff --git a/rslib/src/latex.rs b/rslib/src/latex.rs
index 833463124..2217bc72d 100644
--- a/rslib/src/latex.rs
+++ b/rslib/src/latex.rs
@@ -46,18 +46,19 @@ pub struct ExtractedLatex {
 pub(crate) fn extract_latex_expanding_clozes(
     text: &str,
     svg: bool,
-) -> (String, Vec<ExtractedLatex>) {
-    let text: Cow<str> = if text.contains("{{c") {
-        expand_clozes_to_reveal_latex(text).into()
+) -> (Cow<str>, Vec<ExtractedLatex>) {
+    if text.contains("{{c") {
+        let expanded = expand_clozes_to_reveal_latex(text);
+        let (text, extracts) = extract_latex(&expanded, svg);
+        (text.into_owned().into(), extracts)
     } else {
-        text.into()
-    };
-    extract_latex(&text, svg)
+        extract_latex(text, svg)
+    }
 }
 
 /// Extract LaTeX from the provided text.
 /// Expects cloze deletions to already be expanded.
-pub(crate) fn extract_latex(text: &str, svg: bool) -> (String, Vec<ExtractedLatex>) {
+pub fn extract_latex(text: &str, svg: bool) -> (Cow<str>, Vec<ExtractedLatex>) {
     let mut extracted = vec![];
 
     let new_text = LATEX.replace_all(text, |caps: &Captures| {
@@ -78,7 +79,7 @@ pub(crate) fn extract_latex(text: &str, svg: bool) -> (String, Vec<ExtractedLate
         img_link
     });
 
-    (new_text.into(), extracted)
+    (new_text, extracted)
 }
 
 fn strip_html_for_latex(html: &str) -> Cow<str> {
@@ -122,7 +123,8 @@ mod test {
                 format!(
                     "a<img class=latex alt=\"one&#x0A;and&#x0A;two\" src=\"{}\">b",
                     fname
-                ),
+                )
+                .into(),
                 vec![ExtractedLatex {
                     fname: fname.into(),
                     latex: "one\nand\ntwo".into()