perf: ReplaceSourceChunks by unsafe

Author: SyMind

src/replace_source.rs

@@ -422,6 +422,7 @@ impl<'a> ReplaceSourceChunks<'a> {
 }
 
 impl Chunks for ReplaceSourceChunks<'_> {
+  #[allow(unsafe_code)]
   fn stream<'a>(
     &'a self,
     object_pool: &'a ObjectPool,
@@ -541,14 +542,16 @@ impl Chunks for ReplaceSourceChunks<'_> {
               original.source_index,
               original.original_line,
               original.original_column,
-              &chunk[0..chunk_pos as usize],
+              unsafe { chunk.get_unchecked(..chunk_pos as usize) },
             )
           }) {
             original.original_column += chunk_pos;
           }
           pos += chunk_pos;
           let chunk_utf16_pos =
-            chunk[..chunk_pos as usize].encode_utf16().count();
+            unsafe { chunk.get_unchecked(..chunk_pos as usize) }
+              .encode_utf16()
+              .count();
           let line = mapping.generated_line as i64 + generated_line_offset;
           if generated_column_offset_line == line {
             generated_column_offset -= chunk_utf16_pos as i64;
@@ -567,8 +570,11 @@ impl Chunks for ReplaceSourceChunks<'_> {
           if next_replacement_pos > pos {
             // Emit chunk until replacement
             let offset = next_replacement_pos - pos;
-            let chunk_slice =
-              &chunk[chunk_pos as usize..(chunk_pos + offset) as usize];
+            let chunk_slice = unsafe {
+              chunk.get_unchecked(
+                chunk_pos as usize..(chunk_pos + offset) as usize,
+              )
+            };
             let utf8_offset = chunk_slice.encode_utf16().count() as u32;
             on_chunk(
               Some(chunk_slice),
@@ -610,9 +616,7 @@ impl Chunks for ReplaceSourceChunks<'_> {
             }
           }
           // Insert replacement content split into chunks by lines
-          #[allow(unsafe_code)]
-          // SAFETY: The safety of this operation relies on the fact that the `ReplaceSource` type will not delete the `replacements` during its entire lifetime.
-          let repl = &repls[i];
+          let repl = unsafe { repls.get_unchecked(i) };
 
           let lines =
             split_into_lines(repl.content.as_str()).collect::<Vec<_>>();
@@ -683,11 +687,7 @@ impl Chunks for ReplaceSourceChunks<'_> {
 
           // Move to next replacement
           i += 1;
-          next_replacement = if i < repls.len() {
-            Some(repls[i].start)
-          } else {
-            None
-          };
+          next_replacement = self.replacements.get(i).map(|repl| repl.start);
 
           // Skip over when it has been replaced
           let offset = chunk.len() as i64 - end_pos as i64
@@ -707,11 +707,15 @@ impl Chunks for ReplaceSourceChunks<'_> {
                 }
               } else if generated_column_offset_line == line {
                 let remaining_chunk_utf16_len =
-                  chunk[chunk_pos as usize..].encode_utf16().count() as i64;
+                  unsafe { chunk.get_unchecked(chunk_pos as usize..) }
+                    .encode_utf16()
+                    .count() as i64;
                 generated_column_offset -= remaining_chunk_utf16_len;
               } else {
                 generated_column_offset =
-                  -(chunk[chunk_pos as usize..].encode_utf16().count() as i64);
+                  -(unsafe { chunk.get_unchecked(chunk_pos as usize..) }
+                    .encode_utf16()
+                    .count() as i64);
                 generated_column_offset_line = line;
               }
               pos = end_pos;
@@ -726,18 +730,24 @@ impl Chunks for ReplaceSourceChunks<'_> {
                   original.source_index,
                   original.original_line,
                   original.original_column,
-                  &chunk
-                    [chunk_pos as usize..(chunk_pos + offset as u32) as usize],
+                  unsafe {
+                    chunk.get_unchecked(
+                      chunk_pos as usize..(chunk_pos + offset as u32) as usize,
+                    )
+                  },
                 )
               })
             {
               original.original_column += offset as u32;
             }
 
-            let utf16_offset = chunk
-              [chunk_pos as usize..(chunk_pos + offset as u32) as usize]
-              .encode_utf16()
-              .count() as i64;
+            let utf16_offset = unsafe {
+              chunk.get_unchecked(
+                chunk_pos as usize..(chunk_pos + offset as u32) as usize,
+              )
+            }
+            .encode_utf16()
+            .count() as i64;
             chunk_pos += offset as u32;
             pos += offset as u32;
 
@@ -809,7 +819,7 @@ impl Chunks for ReplaceSourceChunks<'_> {
     // Handle remaining replacements one by one
     let mut line = result.generated_line as i64 + generated_line_offset;
     while i < repls.len() {
-      let content = &repls[i].content;
+      let content = &unsafe { repls.get_unchecked(i) }.content;
       let lines: Vec<&str> = split_into_lines(content).collect();
 
       for (line_idx, content_line) in lines.iter().enumerate() {