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Kernel: Add KString, a single-owner string with OOM failure exposion

This is a simple string class for use in the kernel. It encapsulates
a length + character array in a single-allocation object.

Main differences from AK::String:

- Single-owner (no reference counting.)
- Allocation failures are exposed, not hidden.

The basic idea is to allow better and more precise string management
in the kernel.
This commit is contained in:
Andreas Kling 2021-05-28 09:25:02 +02:00
parent 377b06c8ac
commit 279383a8f3
3 changed files with 89 additions and 0 deletions

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@ -112,6 +112,7 @@ set(KERNEL_SOURCES
Interrupts/SpuriousInterruptHandler.cpp Interrupts/SpuriousInterruptHandler.cpp
Interrupts/UnhandledInterruptHandler.cpp Interrupts/UnhandledInterruptHandler.cpp
KBufferBuilder.cpp KBufferBuilder.cpp
KString.cpp
KSyms.cpp KSyms.cpp
Lock.cpp Lock.cpp
Net/E1000NetworkAdapter.cpp Net/E1000NetworkAdapter.cpp

40
Kernel/KString.cpp Normal file
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@ -0,0 +1,40 @@
/*
* Copyright (c) 2021, Andreas Kling <kling@serenityos.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#include <Kernel/KString.h>
namespace Kernel {
OwnPtr<KString> KString::try_create(StringView const& string)
{
char* characters = nullptr;
size_t length = string.length();
auto new_string = KString::try_create_uninitialized(length, characters);
if (!new_string)
return {};
if (!string.is_empty())
__builtin_memcpy(characters, string.characters_without_null_termination(), length);
characters[length] = '\0';
return new_string;
}
OwnPtr<KString> KString::try_create_uninitialized(size_t length, char*& characters)
{
size_t allocation_size = sizeof(KString) + (sizeof(char) * length) + sizeof(char);
auto* slot = kmalloc(allocation_size);
if (!slot)
return {};
auto* new_string = new (slot) KString(length);
characters = new_string->m_characters;
return adopt_own(*new_string);
}
OwnPtr<KString> KString::try_clone() const
{
return try_create(view());
}
}

48
Kernel/KString.h Normal file
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@ -0,0 +1,48 @@
/*
* Copyright (c) 2021, Andreas Kling <kling@serenityos.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#pragma once
#include <AK/Format.h>
#include <AK/OwnPtr.h>
namespace Kernel {
class KString {
public:
static OwnPtr<KString> try_create_uninitialized(size_t, char*&);
static OwnPtr<KString> try_create(StringView const&);
OwnPtr<KString> try_clone() const;
bool is_empty() const { return m_length == 0; }
size_t length() const { return m_length; }
char const* characters() const { return m_characters; }
StringView view() const { return { characters(), length() }; }
private:
explicit KString(size_t length)
: m_length(length)
{
}
size_t m_length { 0 };
char m_characters[0];
};
}
namespace AK {
template<>
struct Formatter<Kernel::KString> : Formatter<StringView> {
void format(FormatBuilder& builder, Kernel::KString const& value)
{
Formatter<StringView>::format(builder, value.characters());
}
};
}