ladybird/AK/StringBase.cpp
Dan Klishch 870a947040 AK: Remove StringInternals.h
Since we do not expose memory layout anymore in StringBase, there is no
need to keep StringData public.
2024-01-21 16:16:15 -07:00

255 lines
6.8 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>
namespace AK::Detail {
class StringData final : public RefCounted<StringData> {
public:
static ErrorOr<NonnullRefPtr<StringData>> create_uninitialized(size_t byte_count, u8*& buffer)
{
VERIFY(byte_count);
void* slot = malloc(allocation_size_for_string_data(byte_count));
if (!slot) {
return Error::from_errno(ENOMEM);
}
auto new_string_data = adopt_ref(*new (slot) StringData(byte_count));
buffer = const_cast<u8*>(new_string_data->bytes().data());
return new_string_data;
}
static ErrorOr<NonnullRefPtr<StringData>> create_substring(StringData const& superstring, size_t start, size_t byte_count)
{
// Strings of MAX_SHORT_STRING_BYTE_COUNT bytes or less should be handled by the String short string optimization.
VERIFY(byte_count > MAX_SHORT_STRING_BYTE_COUNT);
void* slot = malloc(sizeof(StringData) + sizeof(StringData::SubstringData));
if (!slot) {
return Error::from_errno(ENOMEM);
}
return adopt_ref(*new (slot) StringData(superstring, start, byte_count));
}
struct SubstringData {
StringData const* superstring { nullptr };
u32 start_offset { 0 };
};
void operator delete(void* ptr)
{
free(ptr);
}
void unref() const
{
if (m_is_fly_string && m_ref_count == 2) {
m_is_fly_string = false; // Otherwise unref from did_destory_fly_string_data will cause infinite recursion.
FlyString::did_destroy_fly_string_data({}, bytes_as_string_view());
}
RefCounted::unref();
}
~StringData()
{
if (m_substring)
substring_data().superstring->unref();
}
SubstringData const& substring_data() const
{
return *reinterpret_cast<SubstringData const*>(m_bytes_or_substring_data);
}
// NOTE: There is no guarantee about null-termination.
ReadonlyBytes bytes() const
{
if (m_substring) {
auto const& data = substring_data();
return data.superstring->bytes().slice(data.start_offset, m_byte_count);
}
return { &m_bytes_or_substring_data[0], m_byte_count };
}
StringView bytes_as_string_view() const { return { bytes() }; }
bool operator==(StringData const& other) const
{
return bytes_as_string_view() == other.bytes_as_string_view();
}
unsigned hash() const
{
if (!m_has_hash)
compute_hash();
return m_hash;
}
bool is_fly_string() const { return m_is_fly_string; }
void set_fly_string(bool is_fly_string) const { m_is_fly_string = is_fly_string; }
size_t byte_count() const { return m_byte_count; }
private:
static constexpr size_t allocation_size_for_string_data(size_t length)
{
return sizeof(StringData) + (sizeof(char) * length);
}
explicit StringData(size_t byte_count)
: m_byte_count(byte_count)
{
}
StringData(StringData const& superstring, size_t start, size_t byte_count)
: m_byte_count(byte_count)
, m_substring(true)
{
auto& data = const_cast<SubstringData&>(substring_data());
data.start_offset = start;
data.superstring = &superstring;
superstring.ref();
}
void compute_hash() const
{
auto bytes = this->bytes();
if (bytes.size() == 0)
m_hash = 0;
else
m_hash = string_hash(reinterpret_cast<char const*>(bytes.data()), bytes.size());
m_has_hash = true;
}
u32 m_byte_count { 0 };
mutable unsigned m_hash { 0 };
mutable bool m_has_hash { false };
bool m_substring { false };
mutable bool m_is_fly_string { false };
alignas(SubstringData) u8 m_bytes_or_substring_data[0];
};
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();
}
void StringBase::did_create_fly_string(Badge<FlyString>) const
{
VERIFY(!is_short_string());
m_data->set_fly_string(true);
}
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();
}
}