refactor(estree): use SliceIterExt in string serializer

Author: overlookmotel

crates/oxc_estree/Cargo.toml

@@ -19,7 +19,7 @@ workspace = true
 doctest = false
 
 [dependencies]
-oxc_data_structures = { workspace = true, features = ["code_buffer", "pointer_ext", "stack"], optional = true }
+oxc_data_structures = { workspace = true, features = ["code_buffer", "pointer_ext", "slice_iter_ext", "stack"], optional = true }
 
 itoa = { workspace = true, optional = true }
 ryu-js = { workspace = true, optional = true }

crates/oxc_estree/src/serialize/strings.rs

@@ -1,6 +1,8 @@
 use std::{num::NonZeroU64, slice};
 
-use oxc_data_structures::{code_buffer::CodeBuffer, pointer_ext::PointerExt};
+use oxc_data_structures::{
+    code_buffer::CodeBuffer, pointer_ext::PointerExt, slice_iter_ext::SliceIterExt,
+};
 
 use super::{ESTree, Serializer};
 
@@ -279,13 +281,13 @@ fn write_str<T: EscapeTable>(s: &str, buffer: &mut CodeBuffer) {
                     escape = T::get_escape_for_byte(byte);
                     // Consume bytes before this one.
                     // SAFETY: `found_byte_index < 8` and there are at least 8 bytes remaining in `iter`
-                    unsafe { advance_unchecked(&mut iter, found_byte_index) };
+                    unsafe { iter.advance_unchecked(found_byte_index) };
                     break 'inner;
                 }
 
                 // Consume the whole batch.
                 // SAFETY: There are at least `BATCH_SIZE` bytes remaining in `iter`.
-                unsafe { advance_unchecked(&mut iter, 8) };
+                unsafe { iter.advance_unchecked(8) };
 
                 // Go round `'inner` loop again to continue searching
             } else {
@@ -296,7 +298,7 @@ fn write_str<T: EscapeTable>(s: &str, buffer: &mut CodeBuffer) {
                     if escape != Escape::__ {
                         // Consume bytes before this one.
                         // SAFETY: `i` is an index of `iter`, so cannot be out of bounds.
-                        unsafe { advance_unchecked(&mut iter, i) };
+                        unsafe { iter.advance_unchecked(i) };
                         break 'inner;
                     }
                 }
@@ -334,7 +336,7 @@ fn write_str<T: EscapeTable>(s: &str, buffer: &mut CodeBuffer) {
 
                 // Consume the lossy replacement character.
                 // SAFETY: Lossy replacement character is 3 bytes.
-                unsafe { advance_unchecked(&mut iter, 3) };
+                unsafe { iter.advance_unchecked(3) };
 
                 let hex = iter.as_slice().get(..4).unwrap();
                 if hex == b"fffd" {
@@ -343,7 +345,7 @@ fn write_str<T: EscapeTable>(s: &str, buffer: &mut CodeBuffer) {
 
                     // Consume `fffd`.
                     // SAFETY: We know next 4 bytes are `fffd`.
-                    unsafe { advance_unchecked(&mut iter, 4) };
+                    unsafe { iter.advance_unchecked(4) };
 
                     // Set `chunk_start_ptr` to after `\u{FFFD}fffd`.
                     // That's a complete UTF-8 sequence, so `chunk_start_ptr` is definitely
@@ -366,13 +368,13 @@ fn write_str<T: EscapeTable>(s: &str, buffer: &mut CodeBuffer) {
                     // if there weren't at least 4 bytes remaining in `iter`.
                     // We haven't checked that the 4 following bytes are ASCII, but it doesn't matter
                     // whether `iter` is left on a UTF-8 char boundary or not.
-                    unsafe { advance_unchecked(&mut iter, 4) }
+                    unsafe { iter.advance_unchecked(4) }
                 }
             } else {
                 // Some other unicode character starting with 0xEF.
                 // Consume it and continue the loop.
                 // SAFETY: `0xEF` is always 1st byte in a 3-byte UTF-8 character.
-                unsafe { advance_unchecked(&mut iter, 3) };
+                unsafe { iter.advance_unchecked(3) };
             }
             continue;
         }
@@ -393,7 +395,7 @@ fn write_str<T: EscapeTable>(s: &str, buffer: &mut CodeBuffer) {
         write_char_escape(escape, byte, buffer);
 
         // SAFETY: `'inner` loop above ensures `iter` is not at end of string
-        unsafe { advance_unchecked(&mut iter, 1) };
+        unsafe { iter.advance_unchecked(1) };
 
         // Set `chunk_start_ptr` to be after this character.
         // `escape` is only non-zero for ASCII bytes, except `Escape::LO` which is handled above.
@@ -416,22 +418,6 @@ fn write_str<T: EscapeTable>(s: &str, buffer: &mut CodeBuffer) {
     buffer.print_ascii_byte(b'"');
 }
 
-/// Advance bytes iterator by `count` bytes.
-///
-/// # SAFETY
-/// Caller must ensure there are at least `count` bytes remaining in `iter`.
-#[inline]
-unsafe fn advance_unchecked(iter: &mut slice::Iter<u8>, count: usize) {
-    // Compiler boils this down to just adding `count` to `iter`'s pointer.
-    // SAFETY: Caller guarantees there are at least `count` bytes remaining in `iter`.
-    unsafe {
-        let new_ptr = iter.as_slice().as_ptr().add(count);
-        let new_len = iter.as_slice().len() - count;
-        let slice = slice::from_raw_parts(new_ptr, new_len);
-        *iter = slice.iter();
-    };
-}
-
 /// Write escape sequence to `buffer`.
 fn write_char_escape(escape: Escape, byte: u8, buffer: &mut CodeBuffer) {
     #[expect(clippy::if_not_else)]