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a3e82eaad3
DeprecatedString (formerly String) has been with us since the start, and it has served us well. However, it has a number of shortcomings that I'd like to address. Some of these issues are hard if not impossible to solve incrementally inside of DeprecatedString, so instead of doing that, let's build a new String class and then incrementally move over to it instead. Problems in DeprecatedString: - It assumes string allocation never fails. This makes it impossible to use in allocation-sensitive contexts, and is the reason we had to ban DeprecatedString from the kernel entirely. - The awkward null state. DeprecatedString can be null. It's different from the empty state, although null strings are considered empty. All code is immediately nicer when using Optional<DeprecatedString> but DeprecatedString came before Optional, which is how we ended up like this. - The encoding of the underlying data is ambiguous. For the most part, we use it as if it's always UTF-8, but there have been cases where we pass around strings in other encodings (e.g ISO8859-1) - operator[] and length() are used to iterate over DeprecatedString one byte at a time. This is done all over the codebase, and will *not* give the right results unless the string is all ASCII. How we solve these issues in the new String: - Functions that may allocate now return ErrorOr<String> so that ENOMEM errors can be passed to the caller. - String has no null state. Use Optional<String> when needed. - String is always UTF-8. This is validated when constructing a String. We may need to add a bypass for this in the future, for cases where you have a known-good string, but for now: validate all the things! - There is no operator[] or length(). You can get the underlying data with bytes(), but for iterating over code points, you should be using an UTF-8 iterator. Furthermore, it has two nifty new features: - String implements a small string optimization (SSO) for strings that can fit entirely within a pointer. This means up to 3 bytes on 32-bit platforms, and 7 bytes on 64-bit platforms. Such small strings will not be heap-allocated. - String can create substrings without making a deep copy of the substring. Instead, the superstring gets +1 refcount from the substring, and it acts like a view into the superstring. To make substrings like this, use the substring_with_shared_superstring() API. One caveat: - String does not guarantee that the underlying data is null-terminated like DeprecatedString does today. While this was nifty in a handful of places where we were calling C functions, it did stand in the way of shared-superstring substrings.
212 lines
4.1 KiB
C++
212 lines
4.1 KiB
C++
/*
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* Copyright (c) 2020, Andreas Kling <kling@serenityos.org>
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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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#pragma once
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#include <AK/Types.h>
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namespace AK {
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namespace Detail {
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template<size_t inline_capacity>
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class ByteBuffer;
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}
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class Bitmap;
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using ByteBuffer = AK::Detail::ByteBuffer<32>;
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class Error;
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class GenericLexer;
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class IPv4Address;
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class JsonArray;
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class JsonObject;
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class JsonValue;
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class StackInfo;
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class DeprecatedString;
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class StringBuilder;
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class StringImpl;
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class StringView;
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class Time;
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class URL;
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class FlyString;
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class String;
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class Utf16View;
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class Utf32View;
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class Utf8CodePointIterator;
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class Utf8View;
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class InputStream;
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class InputMemoryStream;
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class DuplexMemoryStream;
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class OutputStream;
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class InputBitStream;
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class OutputBitStream;
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class OutputMemoryStream;
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template<size_t Capacity>
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class CircularDuplexStream;
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template<typename T>
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class Span;
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template<typename T, size_t Size>
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struct Array;
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template<typename Container, typename ValueType>
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class SimpleIterator;
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using ReadonlyBytes = Span<u8 const>;
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using Bytes = Span<u8>;
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template<typename T, AK::MemoryOrder DefaultMemoryOrder>
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class Atomic;
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template<typename T>
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class SinglyLinkedList;
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template<typename T>
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class DoublyLinkedList;
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template<typename T, size_t capacity>
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class CircularQueue;
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template<typename T>
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struct Traits;
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template<typename T, typename TraitsForT = Traits<T>, bool IsOrdered = false>
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class HashTable;
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template<typename T, typename TraitsForT = Traits<T>>
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using OrderedHashTable = HashTable<T, TraitsForT, true>;
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template<typename K, typename V, typename KeyTraits = Traits<K>, bool IsOrdered = false>
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class HashMap;
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template<typename K, typename V, typename KeyTraits = Traits<K>>
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using OrderedHashMap = HashMap<K, V, KeyTraits, true>;
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template<typename T>
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class Badge;
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template<typename T>
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class FixedArray;
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template<size_t precision, typename Underlying = i32>
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class FixedPoint;
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template<typename>
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class Function;
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template<typename Out, typename... In>
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class Function<Out(In...)>;
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template<typename T>
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class NonnullRefPtr;
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template<typename T>
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class NonnullOwnPtr;
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template<typename T, size_t inline_capacity = 0>
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class NonnullOwnPtrVector;
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template<typename T, size_t inline_capacity = 0>
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class NonnullRefPtrVector;
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template<typename T>
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class Optional;
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#ifdef KERNEL
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template<typename T>
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class NonnullLockRefPtr;
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template<typename T, size_t inline_capacity = 0>
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class NonnullLockRefPtrVector;
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template<typename T>
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struct LockRefPtrTraits;
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template<typename T, typename PtrTraits = LockRefPtrTraits<T>>
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class LockRefPtr;
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#endif
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template<typename T>
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class RefPtr;
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template<typename T>
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class OwnPtr;
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template<typename T>
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class WeakPtr;
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template<typename T, size_t inline_capacity = 0>
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requires(!IsRvalueReference<T>) class Vector;
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template<typename T, typename ErrorType = Error>
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class [[nodiscard]] ErrorOr;
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}
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#if USING_AK_GLOBALLY
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using AK::Array;
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using AK::Atomic;
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using AK::Badge;
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using AK::Bitmap;
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using AK::ByteBuffer;
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using AK::Bytes;
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using AK::CircularDuplexStream;
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using AK::CircularQueue;
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using AK::DeprecatedString;
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using AK::DoublyLinkedList;
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using AK::DuplexMemoryStream;
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using AK::Error;
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using AK::ErrorOr;
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using AK::FixedArray;
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using AK::FixedPoint;
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using AK::FlyString;
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using AK::Function;
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using AK::GenericLexer;
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using AK::HashMap;
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using AK::HashTable;
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using AK::InputBitStream;
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using AK::InputMemoryStream;
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using AK::InputStream;
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using AK::IPv4Address;
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using AK::JsonArray;
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using AK::JsonObject;
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using AK::JsonValue;
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using AK::NonnullOwnPtr;
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using AK::NonnullOwnPtrVector;
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using AK::NonnullRefPtr;
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using AK::NonnullRefPtrVector;
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using AK::Optional;
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using AK::OutputBitStream;
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using AK::OutputMemoryStream;
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using AK::OutputStream;
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using AK::OwnPtr;
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using AK::ReadonlyBytes;
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using AK::RefPtr;
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using AK::SinglyLinkedList;
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using AK::Span;
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using AK::StackInfo;
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using AK::String;
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using AK::StringBuilder;
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using AK::StringImpl;
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using AK::StringView;
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using AK::Time;
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using AK::Traits;
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using AK::URL;
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using AK::Utf16View;
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using AK::Utf32View;
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using AK::Utf8CodePointIterator;
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using AK::Utf8View;
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using AK::Vector;
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# ifdef KERNEL
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using AK::LockRefPtr;
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using AK::LockRefPtrTraits;
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using AK::NonnullLockRefPtr;
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using AK::NonnullLockRefPtrVector;
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# endif
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#endif
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