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Remove string allocation from try_iter

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This allows to significantly speed up iteration over small collections, where string encoding is the primary overhead.

Related to #1386, but works around only this partial case.
This commit is contained in:
Ingvar Stepanyan 2019-03-26 12:22:47 +00:00
parent b4b3926bb8
commit 11bb8f03c2
1 changed files with 9 additions and 2 deletions
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11
crates/js-sys/src/lib.rs
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@ -1101,6 +1101,14 @@ impl IterState {
/// Create an iterator over `val` using the JS iteration protocol and
/// `Symbol.iterator`.
pub fn try_iter(val: &JsValue) -> Result<Option<IntoIter>, JsValue> {
#[wasm_bindgen]
extern "C" {
type MaybeIterator;
#[wasm_bindgen(method, getter)]
fn next(this: &MaybeIterator) -> JsValue;
}
let iter_sym = Symbol::iterator();
let iter_fn = Reflect::get(val, iter_sym.as_ref())?;
if !iter_fn.is_function() {
@ -1113,8 +1121,7 @@ pub fn try_iter(val: &JsValue) -> Result<Option<IntoIter>, JsValue> {
return Ok(None);
}
let next = JsValue::from("next");
let next = Reflect::get(&it, &next)?;
let next = it.unchecked_ref::<MaybeIterator>().next();
Ok(if next.is_function() {
let it: Iterator = it.unchecked_into();