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LibJS: Teach String.prototype.concat() to create rope strings

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Defer serialization of the concatenated strings until later. This is
used heavily in SunSpider's string-validate-input subtest, which
sees a small progression.
This commit is contained in:
Andreas Kling 2022-08-06 00:48:22 +02:00 committed by Linus Groh
parent 8ed28890e4
commit e0d7d3c3d5
Notes: sideshowbarker 2024-07-17 08:23:52 +09:00 
Author: https://github.com/awesomekling
Commit: https://github.com/SerenityOS/serenity/commit/e0d7d3c3d5
Pull-request: https://github.com/SerenityOS/serenity/pull/14790
Reviewed-by: https://github.com/linusg ✅
1 changed files with 18 additions and 6 deletions
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24
Userland/Libraries/LibJS/Runtime/StringPrototype.cpp
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@ -525,14 +525,26 @@ JS_DEFINE_NATIVE_FUNCTION(StringPrototype::trim_end)
// 22.1.3.5 String.prototype.concat ( ...args ), https://tc39.es/ecma262/#sec-string.prototype.concat
JS_DEFINE_NATIVE_FUNCTION(StringPrototype::concat)
{
auto string = TRY(ak_string_from(vm, global_object));
StringBuilder builder;
builder.append(string);
// 1. Let O be ? RequireObjectCoercible(this value).
auto object = TRY(require_object_coercible(global_object, vm.this_value(global_object)));
// 2. Let S be ? ToString(O).
auto* string = TRY(object.to_primitive_string(global_object));
// 3. Let R be S.
auto* result = string;
// 4. For each element next of args, do
for (size_t i = 0; i < vm.argument_count(); ++i) {
auto string_argument = TRY(vm.argument(i).to_string(global_object));
builder.append(string_argument);
// a. Let nextString be ? ToString(next).
auto* next_string = TRY(vm.argument(i).to_primitive_string(global_object));
// b. Set R to the string-concatenation of R and nextString.
result = js_rope_string(vm, *result, *next_string);
}
return js_string(vm, builder.to_string());
// 5. Return R.
return result;
}
// 22.1.3.24 String.prototype.substring ( start, end ), https://tc39.es/ecma262/#sec-string.prototype.substring