From cbb87720d2a32eefdb0a7e18184deab2727d6d2e Mon Sep 17 00:00:00 2001
From: cardigan1008 <yunboni@smail.nju.edu.cn>
Date: Sun, 28 Jul 2024 17:46:57 +0800
Subject: [PATCH 1/2] fix: arithmetic overflow

---
 src/grapheme.rs | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/src/grapheme.rs b/src/grapheme.rs
index 97f53a8..45d72bb 100644
--- a/src/grapheme.rs
+++ b/src/grapheme.rs
@@ -412,7 +412,7 @@ impl GraphemeCursor {
     /// ```
     pub fn provide_context(&mut self, chunk: &str, chunk_start: usize) {
         use crate::tables::grapheme as gr;
-        assert!(chunk_start + chunk.len() == self.pre_context_offset.unwrap());
+        assert!(chunk_start.saturating_add(chunk.len()) == self.pre_context_offset.unwrap());
         self.pre_context_offset = None;
         if self.is_extended && chunk_start + chunk.len() == self.offset {
             let ch = chunk.chars().next_back().unwrap();
@@ -598,15 +598,15 @@ impl GraphemeCursor {
         if self.state == GraphemeState::NotBreak {
             return Ok(false);
         }
-        if (self.offset < chunk_start || self.offset >= chunk_start + chunk.len())
-            && (self.offset > chunk_start + chunk.len() || self.cat_after.is_none())
+        if (self.offset < chunk_start || self.offset >= chunk_start.saturating_add(chunk.len()))
+            && (self.offset > chunk_start.saturating_add(chunk.len()) || self.cat_after.is_none())
         {
             return Err(GraphemeIncomplete::InvalidOffset);
         }
         if let Some(pre_context_offset) = self.pre_context_offset {
             return Err(GraphemeIncomplete::PreContext(pre_context_offset));
         }
-        let offset_in_chunk = self.offset - chunk_start;
+        let offset_in_chunk = self.offset.saturating_sub(chunk_start);
         if self.cat_after.is_none() {
             let ch = chunk[offset_in_chunk..].chars().next().unwrap();
             self.cat_after = Some(self.grapheme_category(ch));
@@ -702,7 +702,7 @@ impl GraphemeCursor {
                     self.cat_after = Some(self.grapheme_category(ch));
                 }
             } else {
-                self.offset += ch.len_utf8();
+                self.offset = self.offset.saturating_add(ch.len_utf8());
                 self.state = GraphemeState::Unknown;
                 self.cat_before = self.cat_after.take();
                 if self.cat_before.is_none() {
@@ -781,7 +781,7 @@ impl GraphemeCursor {
         if self.offset == chunk_start {
             return Err(GraphemeIncomplete::PrevChunk);
         }
-        let mut iter = chunk[..self.offset - chunk_start].chars().rev();
+        let mut iter = chunk[..self.offset.saturating_sub(chunk_start)].chars().rev();
         let mut ch = iter.next().unwrap();
         loop {
             if self.offset == chunk_start {

From 164f787b72d044562103cd4edb2027f321d032b8 Mon Sep 17 00:00:00 2001
From: Manish Goregaokar <manishsmail@gmail.com>
Date: Mon, 29 Jul 2024 03:45:12 -0700
Subject: [PATCH 2/2] fmt

---
 src/grapheme.rs | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/src/grapheme.rs b/src/grapheme.rs
index 45d72bb..be88b48 100644
--- a/src/grapheme.rs
+++ b/src/grapheme.rs
@@ -781,7 +781,9 @@ impl GraphemeCursor {
         if self.offset == chunk_start {
             return Err(GraphemeIncomplete::PrevChunk);
         }
-        let mut iter = chunk[..self.offset.saturating_sub(chunk_start)].chars().rev();
+        let mut iter = chunk[..self.offset.saturating_sub(chunk_start)]
+            .chars()
+            .rev();
         let mut ch = iter.next().unwrap();
         loop {
             if self.offset == chunk_start {