ladybird/AK/StringBase.cpp
Andreas Kling a88799c032 AK: Remove excessive hashing caused by FlyString table
Before this change, the global FlyString table looked like this:

    HashMap<StringView, Detail::StringBase>

After this change, we have:

    HashTable<Detail::StringData const*, FlyStringTableHashTraits>

The custom hash traits are used to extract the stored hash from
StringData which avoids having to rehash the StringView repeatedly like
we did before.

This necessitated a handful of smaller changes to make it work.
2024-03-24 13:28:24 +01:00

125 lines
3.0 KiB
C++

/*
* Copyright (c) 2023, Dan Klishch <danilklishch@gmail.com>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#include <AK/Badge.h>
#include <AK/FlyString.h>
#include <AK/StringBase.h>
#include <AK/StringData.h>
namespace AK::Detail {
ReadonlyBytes ShortString::bytes() const
{
return { storage, byte_count() };
}
size_t ShortString::byte_count() const
{
return byte_count_and_short_string_flag >> 1;
}
StringBase::StringBase(NonnullRefPtr<Detail::StringData const> data)
: m_data(&data.leak_ref())
{
}
StringBase::StringBase(StringBase const& other)
: m_data(other.m_data)
{
if (!is_short_string())
m_data->ref();
}
StringBase& StringBase::operator=(StringBase&& other)
{
if (!is_short_string())
m_data->unref();
m_data = exchange(other.m_data, nullptr);
other.m_short_string.byte_count_and_short_string_flag = SHORT_STRING_FLAG;
return *this;
}
StringBase& StringBase::operator=(StringBase const& other)
{
if (&other != this) {
if (!is_short_string())
m_data->unref();
m_data = other.m_data;
if (!is_short_string())
m_data->ref();
}
return *this;
}
ReadonlyBytes StringBase::bytes() const
{
if (is_short_string())
return m_short_string.bytes();
return m_data->bytes();
}
u32 StringBase::hash() const
{
if (is_short_string()) {
auto bytes = this->bytes();
return string_hash(reinterpret_cast<char const*>(bytes.data()), bytes.size());
}
return m_data->hash();
}
size_t StringBase::byte_count() const
{
if (is_short_string())
return m_short_string.byte_count_and_short_string_flag >> 1;
return m_data->byte_count();
}
bool StringBase::operator==(StringBase const& other) const
{
if (is_short_string())
return m_data == other.m_data;
if (other.is_short_string())
return false;
if (m_data->is_fly_string() && other.m_data->is_fly_string())
return m_data == other.m_data;
return bytes() == other.bytes();
}
ErrorOr<Bytes> StringBase::replace_with_uninitialized_buffer(size_t byte_count)
{
if (byte_count <= MAX_SHORT_STRING_BYTE_COUNT)
return replace_with_uninitialized_short_string(byte_count);
u8* buffer = nullptr;
destroy_string();
m_data = &TRY(StringData::create_uninitialized(byte_count, buffer)).leak_ref();
return Bytes { buffer, byte_count };
}
ErrorOr<StringBase> StringBase::substring_from_byte_offset_with_shared_superstring(size_t start, size_t length) const
{
VERIFY(start + length <= byte_count());
if (length == 0)
return StringBase {};
if (length <= MAX_SHORT_STRING_BYTE_COUNT) {
StringBase result;
bytes().slice(start, length).copy_to(result.replace_with_uninitialized_short_string(length));
return result;
}
return StringBase { TRY(Detail::StringData::create_substring(*m_data, start, length)) };
}
void StringBase::destroy_string()
{
if (!is_short_string())
m_data->unref();
}
}