overlay.hpp

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#pragma once
 
#include <cstdint>
#include <filesystem>
 
#include "../std/expected.hpp"
#include "../macro.hpp"
#include "../std/enum.hpp"
#include "reserved.hpp"

namespace ns_reserved::ns_overlay
{
 
namespace
{
 
namespace fs = std::filesystem;
 
}
 
ENUM(OverlayType, BWRAP, OVERLAYFS, UNIONFS)
 

inline Value<void> write(fs::path const& path_file_binary, OverlayType const& overlay)
{
  uint8_t mask{};
  switch(overlay)
  {
    case OverlayType::BWRAP: mask = 1 << 1; break;
    case OverlayType::OVERLAYFS: mask = 1 << 2; break;
    case OverlayType::UNIONFS: mask = 1 << 3; break;
    case OverlayType::NONE:
    default: return Error("E::Invalid overlay option");
  }
  uint64_t offset_begin = ns_reserved::FIM_RESERVED_OFFSET_OVERLAY_BEGIN;
  uint64_t offset_end = ns_reserved::FIM_RESERVED_OFFSET_OVERLAY_END;
  uint64_t size = offset_end - offset_begin;
  return_if(size != sizeof(uint8_t), Error("E::Incorrect number of bytes to write overlay mask: {} vs {}", size, sizeof(uint8_t)));
  return ns_reserved::write(path_file_binary, offset_begin, offset_end, reinterpret_cast<char*>(&mask), sizeof(uint8_t));
}

inline Value<OverlayType> read(fs::path const& path_file_binary)
{
  uint64_t offset_begin = ns_reserved::FIM_RESERVED_OFFSET_OVERLAY_BEGIN;
  uint8_t mask;
  ssize_t bytes = Pop(ns_reserved::read(path_file_binary, offset_begin, reinterpret_cast<char*>(&mask), sizeof(uint8_t)));
  log_if(bytes != 1, "E::Possible error to read overlay byte, count is {}", bytes);
  switch(mask)
  {
    case 1 << 1: return OverlayType::BWRAP;
    case 1 << 2: return OverlayType::OVERLAYFS;
    case 1 << 3: return OverlayType::UNIONFS;
    default: return std::unexpected("Invalid overlay option");
  }
}
 
} // namespace ns_reserved::ns_overlay
 
/* vim: set expandtab fdm=marker ts=2 sw=2 tw=100 et :*/