libluna: Add a very simple Buffer class, to help implement tmpfs files

libluna/CMakeLists.txt

@@ -10,6 +10,7 @@ set(FREESTANDING_SOURCES
     src/Units.cpp
     src/SystemError.cpp
     src/Bitmap.cpp
+    src/Buffer.cpp
     src/Stack.cpp
     src/OwnedStringView.cpp
     src/Utf8.cpp

libluna/include/luna/Buffer.h

@@ -0,0 +1,40 @@
+#pragma once
+#include <luna/Result.h>
+#include <luna/Types.h>
+
+class Buffer
+{
+  public:
+    Buffer();
+    ~Buffer();
+
+    Buffer(Buffer&& other);
+    Buffer(const Buffer& other) = delete; // For now.
+
+    static Result<Buffer> create_sized(usize size);
+
+    Result<void> try_resize(usize new_size);
+
+    Result<u8*> create_slice_at_end(usize size);
+
+    u8* data()
+    {
+        return m_data;
+    }
+
+    const u8* data() const
+    {
+        return m_data;
+    }
+
+    usize size() const
+    {
+        return m_size;
+    }
+
+  private:
+    Buffer(u8* data, usize size);
+
+    u8* m_data { nullptr };
+    usize m_size { 0 };
+};

libluna/src/Buffer.cpp

@@ -0,0 +1,40 @@
+#include <luna/Buffer.h>
+#include <luna/Heap.h>
+
+Buffer::Buffer()
+{
+}
+
+Buffer::Buffer(u8* data, usize size) : m_data(data), m_size(size)
+{
+}
+
+Buffer::Buffer(Buffer&& other) : m_data(other.data()), m_size(other.size())
+{
+    other.m_data = nullptr;
+}
+
+Buffer::~Buffer()
+{
+    if (m_data) free_impl(m_data);
+}
+
+Result<Buffer> Buffer::create_sized(usize size)
+{
+    u8* data = (u8*)TRY(malloc_impl(size));
+    return Buffer { data, size };
+}
+
+Result<void> Buffer::try_resize(usize new_size)
+{
+    m_data = (u8*)TRY(realloc_impl(m_data, new_size));
+    m_size = new_size;
+    return {};
+}
+
+Result<u8*> Buffer::create_slice_at_end(usize size)
+{
+    usize old_size = m_size;
+    TRY(try_resize(m_size + size));
+    return m_data + old_size;
+}