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AK: Implement FlyString for the new String class

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This implements a FlyString that will de-duplicate String instances. The
FlyString will store the raw encoded data of the String instance: If the
String is a short string, FlyString holds the String::ShortString bytes;
otherwise FlyString holds a pointer to the Detail::StringData.

FlyString itself does not know about String's storage or how to refcount
its Detail::StringData. It defers to String to implement these details.
This commit is contained in:
Timothy Flynn 2023-01-11 08:26:49 -05:00 • committed by Andreas Kling
parent f49a65cb28
commit 1d4f287582
8 changed files with 445 additions and 1 deletions
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73
AK/FlyString.h Normal file
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/*
* Copyright (c) 2023, Tim Flynn <trflynn89@serenityos.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#pragma once
#include <AK/Error.h>
#include <AK/Format.h>
#include <AK/Platform.h>
#include <AK/String.h>
#include <AK/Traits.h>
#include <AK/Types.h>
namespace AK {
class FlyString {
public:
FlyString();
~FlyString();
static ErrorOr<FlyString> from_utf8(StringView);
explicit FlyString(String const&);
FlyString(FlyString const&);
FlyString& operator=(FlyString const&);
FlyString(FlyString&&);
FlyString& operator=(FlyString&&);
[[nodiscard]] bool is_empty() const;
[[nodiscard]] unsigned hash() const;
explicit operator String() const;
String to_string() const;
[[nodiscard]] Utf8View code_points() const;
[[nodiscard]] ReadonlyBytes bytes() const;
[[nodiscard]] StringView bytes_as_string_view() const;
[[nodiscard]] bool operator==(FlyString const& other) const;
[[nodiscard]] bool operator==(String const&) const;
[[nodiscard]] bool operator==(StringView) const;
[[nodiscard]] bool operator==(char const*) const;
static void did_destroy_fly_string_data(Badge<Detail::StringData>, StringView);
[[nodiscard]] uintptr_t data(Badge<String>) const;
// This is primarily interesting to unit tests.
[[nodiscard]] static size_t number_of_fly_strings();
private:
// This will hold either the pointer to the Detail::StringData it represents or the raw bytes of
// an inlined short string.
uintptr_t m_data { 0 };
};
template<>
struct Traits<FlyString> : public GenericTraits<FlyString> {
static unsigned hash(FlyString const&);
};
template<>
struct Formatter<FlyString> : Formatter<StringView> {
ErrorOr<void> format(FormatBuilder&, FlyString const&);
};
}
#if USING_AK_GLOBALLY
using AK::FlyString;
#endif