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LibJS+AK: Make String.prototype.repeat() way faster

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Instead of using a StringBuilder, add a String::repeated(String, N)
overload that takes advantage of knowing it's already all UTF-8.

This makes the following microbenchmark go 4x faster:

    "foo".repeat(100_000_000)

And for single character strings, we can even go 10x faster:

    "x".repeat(100_000_000)
This commit is contained in:
Andreas Kling 2023-12-29 13:20:11 +01:00
parent 9ce267944c
commit a285e36041
3 changed files with 21 additions and 4 deletions
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3
AK/String.h
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@ -92,6 +92,9 @@ public:
// Creates a new String with a single code point repeated N times.
static ErrorOr<String> repeated(u32 code_point, size_t count);
// Creates a new String from another string, repeated N times.
static String repeated(String const&, size_t count);
// Creates a new String by case-transforming this String. Using these methods require linking LibUnicode into your application.
ErrorOr<String> to_lowercase(Optional<StringView> const& locale = {}) const;
ErrorOr<String> to_uppercase(Optional<StringView> const& locale = {}) const;