Kernel: Simplify KBuffer by removing KBufferImpl

This patch moves everything from KBufferImpl into KBuffer instead.
One layer of indirection is removed, and the whole thing is massively
simplified. :^)

Kernel/KBuffer.h

@@ -1,14 +1,13 @@
 /*
- * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
+ * Copyright (c) 2018-2021, Andreas Kling <kling@serenityos.org>
  *
  * SPDX-License-Identifier: BSD-2-Clause
  */
 
 #pragma once
 
-// KBuffer: Statically sized kernel-only memory buffer.
+// KBuffer: Memory buffer backed by a kernel region.
 //
-// A KBuffer is a value-type convenience class that wraps a NonnullRefPtr<KBufferImpl>.
 // The memory is allocated via the global kernel-only page allocator, rather than via
 // kmalloc() which is what ByteBuffer/Vector/etc will use.
 //
@@ -17,51 +16,34 @@
 // severely limited kmalloc heap.
 
 #include <AK/Assertions.h>
-#include <AK/ByteBuffer.h>
 #include <AK/Memory.h>
 #include <AK/StringView.h>
 #include <Kernel/Memory/MemoryManager.h>
-#include <Kernel/Memory/Region.h>
 
 namespace Kernel {
 
-class KBufferImpl : public RefCounted<KBufferImpl> {
+class [[nodiscard]] KBuffer {
 public:
-    static RefPtr<KBufferImpl> try_create_with_size(size_t size, Memory::Region::Access access, StringView name = "KBuffer", AllocationStrategy strategy = AllocationStrategy::Reserve)
+    static KResultOr<NonnullOwnPtr<KBuffer>> try_create_with_size(size_t size, Memory::Region::Access access = Memory::Region::Access::ReadWrite, StringView name = "KBuffer", AllocationStrategy strategy = AllocationStrategy::Reserve)
     {
-        auto region_or_error = MM.allocate_kernel_region(Memory::page_round_up(size), name, access, strategy);
-        if (region_or_error.is_error())
-            return nullptr;
-        return adopt_ref_if_nonnull(new (nothrow) KBufferImpl(region_or_error.release_value(), size, strategy));
+        auto region = TRY(MM.allocate_kernel_region(Memory::page_round_up(size), name, access, strategy));
+        return TRY(adopt_nonnull_own_or_enomem(new (nothrow) KBuffer { size, move(region) }));
     }
 
-    static RefPtr<KBufferImpl> try_create_with_bytes(ReadonlyBytes bytes, Memory::Region::Access access, StringView name = "KBuffer", AllocationStrategy strategy = AllocationStrategy::Reserve)
+    static KResultOr<NonnullOwnPtr<KBuffer>> try_create_with_bytes(ReadonlyBytes bytes, Memory::Region::Access access = Memory::Region::Access::ReadWrite, StringView name = "KBuffer", AllocationStrategy strategy = AllocationStrategy::Reserve)
     {
-        auto region_or_error = MM.allocate_kernel_region(Memory::page_round_up(bytes.size()), name, access, strategy);
-        if (region_or_error.is_error())
-            return nullptr;
-        auto region = region_or_error.release_value();
-        memcpy(region->vaddr().as_ptr(), bytes.data(), bytes.size());
-
-        return adopt_ref_if_nonnull(new (nothrow) KBufferImpl(move(region), bytes.size(), strategy));
+        auto buffer = TRY(try_create_with_size(bytes.size(), access, name, strategy));
+        memcpy(buffer->data(), bytes.data(), bytes.size());
+        return buffer;
     }
 
-    static RefPtr<KBufferImpl> create_with_size(size_t size, Memory::Region::Access access, StringView name, AllocationStrategy strategy = AllocationStrategy::Reserve)
+    static KResultOr<NonnullOwnPtr<KBuffer>> try_copy(const void* data, size_t size, Memory::Region::Access access = Memory::Region::Access::ReadWrite, StringView name = "KBuffer")
     {
-        return try_create_with_size(size, access, name, strategy);
-    }
-
-    static RefPtr<KBufferImpl> copy(const void* data, size_t size, Memory::Region::Access access, StringView name)
-    {
-        auto buffer = create_with_size(size, access, name, AllocationStrategy::AllocateNow);
-        if (!buffer)
-            return {};
-        memcpy(buffer->data(), data, size);
-        return buffer;
+        return try_create_with_bytes(ReadonlyBytes { data, size }, access, name);
     }
 
     [[nodiscard]] u8* data() { return m_region->vaddr().as_ptr(); }
-    [[nodiscard]] const u8* data() const { 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(); }
 
@@ -71,62 +53,15 @@ public:
         m_size = size;
     }
 
-    [[nodiscard]] Memory::Region const& region() const { return *m_region; }
-    [[nodiscard]] Memory::Region& region() { return *m_region; }
-
 private:
-    explicit KBufferImpl(NonnullOwnPtr<Memory::Region>&& region, size_t size, AllocationStrategy strategy)
+    explicit KBuffer(size_t size, NonnullOwnPtr<Memory::Region> region)
         : m_size(size)
-        , m_allocation_strategy(strategy)
         , m_region(move(region))
     {
     }
 
     size_t m_size { 0 };
-    AllocationStrategy m_allocation_strategy { AllocationStrategy::Reserve };
     NonnullOwnPtr<Memory::Region> m_region;
 };
 
-class [[nodiscard]] KBuffer {
-public:
-    static KResultOr<NonnullOwnPtr<KBuffer>> try_create_with_size(size_t size, Memory::Region::Access access = Memory::Region::Access::ReadWrite, StringView name = "KBuffer", AllocationStrategy strategy = AllocationStrategy::Reserve)
-    {
-        auto impl = KBufferImpl::try_create_with_size(size, access, name, strategy);
-        if (!impl)
-            return ENOMEM;
-        return adopt_nonnull_own_or_enomem(new (nothrow) KBuffer(impl.release_nonnull()));
-    }
-
-    static KResultOr<NonnullOwnPtr<KBuffer>> try_create_with_bytes(ReadonlyBytes bytes, Memory::Region::Access access = Memory::Region::Access::ReadWrite, StringView name = "KBuffer", AllocationStrategy strategy = AllocationStrategy::Reserve)
-    {
-        auto impl = KBufferImpl::try_create_with_bytes(bytes, access, name, strategy);
-        if (!impl)
-            return ENOMEM;
-        return adopt_nonnull_own_or_enomem(new (nothrow) KBuffer(impl.release_nonnull()));
-    }
-
-    static KResultOr<NonnullOwnPtr<KBuffer>> try_copy(const void* data, size_t size, Memory::Region::Access access = Memory::Region::Access::ReadWrite, StringView name = "KBuffer")
-    {
-        auto impl = KBufferImpl::copy(data, size, access, name);
-        if (!impl)
-            return ENOMEM;
-        return adopt_nonnull_own_or_enomem(new (nothrow) KBuffer(impl.release_nonnull()));
-    }
-
-    [[nodiscard]] u8* data() { return m_impl->data(); }
-    [[nodiscard]] const u8* data() const { return m_impl->data(); }
-    [[nodiscard]] size_t size() const { return m_impl->size(); }
-    [[nodiscard]] size_t capacity() const { return m_impl->capacity(); }
-
-    void set_size(size_t size) { m_impl->set_size(size); }
-
-private:
-    explicit KBuffer(NonnullRefPtr<KBufferImpl> impl)
-        : m_impl(move(impl))
-    {
-    }
-
-    NonnullRefPtr<KBufferImpl> m_impl;
-};
-
 }