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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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16
AK/String.h
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@ -73,6 +73,9 @@ public:
[[nodiscard]] bool operator==(String const&) const;
[[nodiscard]] bool operator!=(String const& other) const { return !(*this == other); }
[[nodiscard]] bool operator==(FlyString const&) const;
[[nodiscard]] bool operator!=(FlyString const& other) const { return !(*this == other); }
[[nodiscard]] bool operator==(StringView) const;
[[nodiscard]] bool operator!=(StringView other) const { return !(*this == other); }
@ -102,6 +105,14 @@ public:
// NOTE: This is primarily interesting to unit tests.
[[nodiscard]] bool is_short_string() const;
[[nodiscard]] static String fly_string_data_to_string(Badge<FlyString>, uintptr_t const&);
[[nodiscard]] static StringView fly_string_data_to_string_view(Badge<FlyString>, uintptr_t const&);
[[nodiscard]] uintptr_t to_fly_string_data(Badge<FlyString>) const;
static void ref_fly_string_data(Badge<FlyString>, uintptr_t);
static void unref_fly_string_data(Badge<FlyString>, uintptr_t);
void did_create_fly_string(Badge<FlyString>) const;
// FIXME: Remove these once all code has been ported to String
[[nodiscard]] DeprecatedString to_deprecated_string() const;
static ErrorOr<String> from_deprecated_string(DeprecatedString const&);
@ -110,6 +121,11 @@ private:
// NOTE: If the least significant bit of the pointer is set, this is a short string.
static constexpr uintptr_t SHORT_STRING_FLAG = 1;
static constexpr bool has_short_string_bit(uintptr_t data)
{
return (data & SHORT_STRING_FLAG) != 0;
}
struct ShortString {
ReadonlyBytes bytes() const;
size_t byte_count() const;