1 files changed, 77 insertions, 0 deletions
diff --git a/Kernel/FileSystem/File.h b/Kernel/FileSystem/File.h
new file mode 100644
index 0000000000..0f26eb6ec1
--- /dev/null
+++ b/Kernel/FileSystem/File.h
@@ -0,0 +1,77 @@
+#pragma once
+
+#include <AK/AKString.h>
+#include <AK/RefCounted.h>
+#include <AK/NonnullRefPtr.h>
+#include <AK/Types.h>
+#include <Kernel/KResult.h>
+#include <Kernel/UnixTypes.h>
+#include <Kernel/VirtualAddress.h>
+
+class FileDescription;
+class Process;
+class Region;
+
+// File is the base class for anything that can be referenced by a FileDescription.
+//
+// The most important functions in File are:
+//
+// read() and write()
+//   - Implement reading and writing.
+//   - Return the number of bytes read/written, OR a negative error code.
+//
+// can_read() and can_write()
+//
+//   - Used to implement blocking I/O, and the select() and poll() syscalls.
+//   - Return true if read() or write() would succeed, respectively.
+//   - Note that can_read() should return true in EOF conditions,
+//     and a subsequent call to read() should return 0.
+//
+// ioctl()
+//
+//   - Optional. If unimplemented, ioctl() on this File will fail with -ENOTTY.
+//   - Can be overridden in subclasses to implement arbitrary functionality.
+//   - Subclasses should take care to validate incoming addresses before dereferencing.
+//
+// mmap()
+//
+//   - Optional. If unimplemented, mmap() on this File will fail with -ENODEV.
+//   - Called by mmap() when userspace wants to memory-map this File somewhere.
+//   - Should create a Region in the Process and return it if successful.
+
+class File : public RefCounted<File> {
+public:
+    virtual ~File();
+
+    virtual KResultOr<NonnullRefPtr<FileDescription>> open(int options);
+    virtual void close();
+
+    virtual bool can_read(FileDescription&) const = 0;
+    virtual bool can_write(FileDescription&) const = 0;
+
+    virtual ssize_t read(FileDescription&, u8*, ssize_t) = 0;
+    virtual ssize_t write(FileDescription&, const u8*, ssize_t) = 0;
+    virtual int ioctl(FileDescription&, unsigned request, unsigned arg);
+    virtual KResultOr<Region*> mmap(Process&, FileDescription&, VirtualAddress preferred_vaddr, size_t offset, size_t size, int prot);
+
+    virtual String absolute_path(const FileDescription&) const = 0;
+
+    virtual KResult truncate(off_t) { return KResult(-EINVAL); }
+
+    virtual const char* class_name() const = 0;
+
+    virtual bool is_seekable() const { return false; }
+
+    virtual bool is_inode() const { return false; }
+    virtual bool is_shared_memory() const { return false; }
+    virtual bool is_fifo() const { return false; }
+    virtual bool is_device() const { return false; }
+    virtual bool is_tty() const { return false; }
+    virtual bool is_master_pty() const { return false; }
+    virtual bool is_block_device() const { return false; }
+    virtual bool is_character_device() const { return false; }
+    virtual bool is_socket() const { return false; }
+
+protected:
+    File();
+};