unionfs.hpp

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#pragma once
 
#include <filesystem>
#include <unistd.h>
 
#include "../lib/subprocess.hpp"
#include "../lib/env.hpp"
#include "../lib/fuse.hpp"
#include "../std/filesystem.hpp"
#include "filesystem.hpp"
 
namespace
{
 
namespace fs = std::filesystem;
 
} // namespace

namespace ns_filesystems::ns_unionfs
{
 
class UnionFs final : public ns_filesystem::Filesystem
{
  private:
    fs::path m_path_dir_upper;
    std::vector<fs::path> m_vec_path_dir_layer;
  public:
    UnionFs(pid_t pid_to_die_for
      , fs::path const& path_dir_mount
      , fs::path const& path_dir_upper
      , fs::path const& path_file_log
      , std::vector<fs::path> const& vec_path_dir_layer
    );
    Value<void> mount() override;
};

inline UnionFs::UnionFs(pid_t pid_to_die_for
    , fs::path const& path_dir_mount
    , fs::path const& path_dir_upper
    , fs::path const& path_file_log
    , std::vector<fs::path> const& vec_path_dir_layer
  )
  : ns_filesystem::Filesystem(pid_to_die_for, path_dir_mount, path_file_log)
  , m_path_dir_upper(path_dir_upper)
  , m_vec_path_dir_layer(vec_path_dir_layer)
{
  this->mount().discard("E::Could not mount unionfs filesystem to '{}'", path_dir_mount);
}

inline Value<void> UnionFs::mount()
{
  // Validate directories
  Pop(ns_fs::create_directories(m_path_dir_upper), "E::Could not create upper directory");
  Pop(ns_fs::create_directories(m_path_dir_mount), "E::Could not create lower directory");
  // Find unionfs
  auto path_file_unionfs = Pop(ns_env::search_path("unionfs"), "E::Could not find unionfs in PATH");
  // Create string to represent layers argumnet
  // First layer is the writteable one
  // Layers are overlayed as top_branch:lower_branch:...:lowest_branch
  std::string arg_layers=std::format("{}=RW", m_path_dir_upper.string());
  for (auto&& path_dir_layer : m_vec_path_dir_layer | std::views::reverse)
  {
    arg_layers += std::format(":{}=RO", path_dir_layer.string());
  } // for
  // Include arguments and spawn process
  using enum ns_subprocess::Stream;
  m_child = ns_subprocess::Subprocess(path_file_unionfs)
    .with_args("-f")
    .with_args("-o", "cow")
    .with_args(arg_layers)
    .with_args(m_path_dir_mount)
    .with_die_on_pid(m_pid_to_die_for)
    .with_stdio(ns_subprocess::Stream::Pipe)
    .with_log_file(m_path_file_log)
    .spawn();
  // Wait for mount
  ns_fuse::wait_fuse(m_path_dir_mount);
  return {};
}
 
 
} // namespace ns_filesystems::ns_unionfs
 
/* vim: set expandtab fdm=marker ts=2 sw=2 tw=100 et :*/