Switch to encoding_rs::mem

Signed-off-by: Narfinger <Narfinger@users.noreply.github.com>

Author: Narfinger

mozjs/Cargo.toml

@@ -17,6 +17,7 @@ profilemozjs = ['mozjs_sys/profilemozjs']
 crown = ['mozjs_sys/crown']
 
 [dependencies]
+encoding_rs = "0.8.35"
 libc.workspace = true
 log = "0.4"
 mozjs_sys = { path = "../mozjs-sys" }

mozjs/src/conversions.rs

@@ -48,6 +48,7 @@ use log::debug;
 use mozjs_sys::jsgc::Rooted;
 use std::borrow::Cow;
 use std::mem;
+use std::mem::MaybeUninit;
 use std::rc::Rc;
 use std::{ptr, slice};
 
@@ -525,12 +526,6 @@ impl FromJSValConvertible for f64 {
     }
 }
 
-/// A simple wrapper for ascii compatible chars. This and the mem::transmute call
-/// in latin1_to_string should be replaced when the `ascii_char` feature is stable.
-/// See: <https://github.com/rust-lang/rust/issues/110998>.
-#[repr(transparent)]
-struct AsciiChar(u8);
-
 /// Converts a `JSString`, encoded in "Latin1" (i.e. U+0000-U+00FF encoded as 0x00-0xFF) into a
 /// `String`.
 pub unsafe fn latin1_to_string(cx: *mut JSContext, s: *mut JSString) -> String {
@@ -541,16 +536,12 @@ pub unsafe fn latin1_to_string(cx: *mut JSContext, s: *mut JSString) -> String {
     assert!(!chars.is_null());
 
     let chars = slice::from_raw_parts(chars, length as usize);
-    let mut s = String::with_capacity(length as usize);
-
-    let v = s.as_mut_vec();
-    for c in chars {
-        // This is safe as we are ensured that we only have "Latin1" strings which have the upper
-        // code word 00.
-        v.push(*c);
-    }
+    let mut v = Vec::with_capacity(length * 2);
+    v.set_len(length * 2);
 
-    s
+    let real_size = encoding_rs::mem::convert_latin1_to_utf8(chars, v.as_mut_slice());
+    v.truncate(real_size);
+    String::from_utf8_unchecked(v)
 }
 
 /// Converts a `JSString` into a `String`, regardless of used encoding.