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/*
* Copyright (c) 2018-2021, Andreas Kling <kling@serenityos.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#pragma once
// KBuffer: Memory buffer backed by a kernel region.
//
// The memory is allocated via the global kernel-only page allocator, rather than via
// kmalloc() which is what ByteBuffer/Vector/etc will use.
//
// This makes KBuffer a little heavier to allocate, but much better for large and/or
// long-lived allocations, since they don't put all that weight and pressure on the
// severely limited kmalloc heap.
#include <AK/Assertions.h>
#include <AK/StringView.h>
#include <Kernel/Library/StdLib.h> // For memcpy. FIXME: Make memcpy less expensive to access a declaration of in the Kernel.
#include <Kernel/Memory/MemoryManager.h>
namespace Kernel {
class [[nodiscard]] KBuffer {
public:
static ErrorOr<NonnullOwnPtr<KBuffer>> try_create_with_size(StringView name, size_t size, Memory::Region::Access access = Memory::Region::Access::ReadWrite, AllocationStrategy strategy = AllocationStrategy::Reserve)
{
auto rounded_size = TRY(Memory::page_round_up(size));
auto region = TRY(MM.allocate_kernel_region(rounded_size, name, access, strategy));
return TRY(adopt_nonnull_own_or_enomem(new (nothrow) KBuffer { size, move(region) }));
}
static ErrorOr<NonnullOwnPtr<KBuffer>> try_create_with_bytes(StringView name, ReadonlyBytes bytes, Memory::Region::Access access = Memory::Region::Access::ReadWrite, AllocationStrategy strategy = AllocationStrategy::Reserve)
{
auto buffer = TRY(try_create_with_size(name, bytes.size(), access, strategy));
memcpy(buffer->data(), bytes.data(), bytes.size());
return buffer;
}
[[nodiscard]] u8* data() { return m_region->vaddr().as_ptr(); }
[[nodiscard]] u8 const* data() const { return m_region->vaddr().as_ptr(); }
[[nodiscard]] size_t size() const { return m_size; }
[[nodiscard]] size_t capacity() const { return m_region->size(); }
[[nodiscard]] ReadonlyBytes bytes() const { return { data(), size() }; }
[[nodiscard]] Bytes bytes() { return { data(), size() }; }
void set_size(size_t size)
{
VERIFY(size <= capacity());
m_size = size;
}
private:
explicit KBuffer(size_t size, NonnullOwnPtr<Memory::Region> region)
: m_size(size)
, m_region(move(region))
{
}
size_t m_size { 0 };
NonnullOwnPtr<Memory::Region> m_region;
};
}
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