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LibJS: Implement String.prototype.lastIndexOf with UTF-16 code units

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Timothy Flynn 2021-07-19 15:29:20 -04:00 • committed by Andreas Kling
parent 5ac964d841
commit f920e121b3
2 changed files with 40 additions and 21 deletions
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53
Userland/Libraries/LibJS/Runtime/StringPrototype.cpp
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@ -723,34 +723,45 @@ JS_DEFINE_NATIVE_FUNCTION(StringPrototype::split)
// 22.1.3.9 String.prototype.lastIndexOf ( searchString [ , position ] ), https://tc39.es/ecma262/#sec-string.prototype.lastindexof
JS_DEFINE_NATIVE_FUNCTION(StringPrototype::last_index_of)
{
auto string = ak_string_from(vm, global_object);
if (!string.has_value())
return {};
auto search_string = vm.argument(0).to_string(global_object);
auto string = utf16_string_from(vm, global_object);
if (vm.exception())
return {};
auto search_string = vm.argument(0).to_utf16_string(global_object);
if (vm.exception())
return {};
Utf16View utf16_string_view { string };
auto string_length = utf16_string_view.length_in_code_units();
Utf16View utf16_search_view { search_string };
auto search_length = utf16_search_view.length_in_code_units();
auto position = vm.argument(1).to_number(global_object);
if (vm.exception())
return {};
if (search_string.length() > string->length())
return Value(-1);
auto max_index = string->length() - search_string.length();
auto from_index = max_index;
if (!position.is_nan()) {
// FIXME: from_index should index a UTF-16 code_point view of the string.
auto p = position.to_integer_or_infinity(global_object);
if (vm.exception())
return {};
from_index = clamp(p, static_cast<double>(0), static_cast<double>(max_index));
double pos = position.is_nan() ? static_cast<double>(INFINITY) : position.to_integer_or_infinity(global_object);
if (vm.exception())
return {};
size_t start = clamp(pos, static_cast<double>(0), static_cast<double>(string_length));
Optional<size_t> last_index;
for (size_t k = 0; (k <= start) && (k + search_length <= string_length); ++k) {
bool is_match = true;
for (size_t j = 0; j < search_length; ++j) {
if (utf16_string_view.code_unit_at(k + j) != utf16_search_view.code_unit_at(j)) {
is_match = false;
break;
}
}
if (is_match)
last_index = k;
}
for (i32 i = from_index; i >= 0; --i) {
auto part_view = string->substring_view(i, search_string.length());
if (part_view == search_string)
return Value(i);
}
return Value(-1);
return last_index.has_value() ? Value(*last_index) : Value(-1);
}
// 3.1 String.prototype.at ( index ), https://tc39.es/proposal-relative-indexing-method/#sec-string.prototype.at

8
Userland/Libraries/LibJS/Tests/builtins/String/String.prototype.lastIndexOf.js
View file

@ -20,3 +20,11 @@ test("basic functionality", () => {
expect("hello friends serenity".lastIndexOf("s", 13)).toBe(12);
expect("hello".lastIndexOf("serenity")).toBe(-1);
});
test("UTF-16", () => {
var s = "😀";
expect(s.lastIndexOf("😀")).toBe(0);
expect(s.lastIndexOf("\ud83d")).toBe(0);
expect(s.lastIndexOf("\ude00")).toBe(1);
expect(s.lastIndexOf("a")).toBe(-1);
});