file_descriptor.hpp

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#pragma once
 
#include <array>
#include <cstddef>
#include <cstdint>
 
#include "expected.hpp"
#include "spinlock.hpp"
#include "vfs.hpp"
 
namespace filesystem {
 
class FileDescriptorTable {
 public:
  static constexpr int kMaxFd = 64;
 
  static constexpr int kStdinFd = 0;
  static constexpr int kStdoutFd = 1;
  static constexpr int kStderrFd = 2;
 
  FileDescriptorTable();
  FileDescriptorTable(const FileDescriptorTable&) = delete;
  FileDescriptorTable(FileDescriptorTable&& other);
  auto operator=(const FileDescriptorTable&) -> FileDescriptorTable& = delete;
  auto operator=(FileDescriptorTable&& other) -> FileDescriptorTable&;
  ~FileDescriptorTable();
 
  [[nodiscard]] auto Alloc(vfs::File* file) -> Expected<int>;
 
  [[nodiscard]] auto Get(int fd) -> vfs::File*;
 
  [[nodiscard]] auto Free(int fd) -> Expected<void>;
  [[nodiscard]] auto Dup(int old_fd, int new_fd = -1) -> Expected<int>;
  [[nodiscard]] auto CloseAll() -> Expected<void>;
 
  [[nodiscard]] auto SetupStandardFiles(vfs::File* stdin_file,
                                        vfs::File* stdout_file,
                                        vfs::File* stderr_file)
      -> Expected<void>;
  [[nodiscard]] auto GetOpenCount() const -> int;
 
 private:
  std::array<vfs::File*, kMaxFd> table_;
  int open_count_{0};
  SpinLock lock_{"fd_table"};
};
 
}  // namespace filesystem