From 1c525fc3df132bd7f4c26ee5439bf4425bd90be3 Mon Sep 17 00:00:00 2001
From: Zhihui Jiao <zhihui.jiao@gmail.com>
Date: Thu, 16 Nov 2023 23:36:04 +0800
Subject: [PATCH] Ensure read offset + data size doesn't exceed the max offset

---
 src/mmap_file.rs | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/src/mmap_file.rs b/src/mmap_file.rs
index 352e6dc..5573652 100644
--- a/src/mmap_file.rs
+++ b/src/mmap_file.rs
@@ -22,7 +22,6 @@ impl MemoryMappedFile {
 
         let mmap = unsafe { MmapMut::map_mut(&file).context(StdIOSnafu)? };
 
-        // TODO max_offset?
         Ok(MemoryMappedFile { mmap, min_offset: start_offset, max_offset: start_offset })
     }
 
@@ -78,9 +77,8 @@ impl MemoryMappedFile {
         let mut buffer = vec![0; data_size];
         let read_pos = offset - self.min_offset;
 
-        // TODO mmap.len should be max_offset?
-        // Ensure the buffer size matches the mapped region.
-        if read_pos + data_size < self.mmap.len() {
+        // Ensure read offset + data size doesn't exceed the max offset.
+        if read_pos + data_size <= self.max_offset {
             buffer.copy_from_slice(&self.mmap[read_pos..read_pos + data_size]);
 
             Ok(buffer)