hilbert-os/kernel/fs/tarfs.cpp

#include <mercury/kernel/fs/tarfs.hpp>

//in fs::tarfs_instance, storage::node_id_t refers to the number
//of bytes into the block device that the info sector is located

namespace mercury::kernel::fs {

  storage::io_result tarfs_mounter(
    storage::block_device *bd, storage::file_system_instance *&fs_out
  ) {
    fs_out = new tarfs_instance(bd);
    return storage::io_result::success;
  }

  tarfs_instance::tarfs_instance(storage::block_device *bd) : bd(bd) {}

  storage::io_result tarfs_instance::next_node(storage::node_id_t &node) {
    uint64_t file_length;
    storage::io_result result = read_num(node + 124, 12, file_length);
    if (result != storage::io_result::success)
      return result;
    node += ((file_length - 1) / 512 + 2) * 512;
    return storage::io_result::success;
  }

  storage::io_result tarfs_instance::read_name(
    storage::node_id_t node, char *name_buf, size_t &name_len_out
  ) {
    name_len_out = 0;
    storage::io_result result = bd->read_bytes(node + 345, 155, name_buf);
    if (result != storage::io_result::success)
      return result;
    while (name_buf[name_len_out] && name_len_out < 155)
      ++name_len_out;
    result = bd->read_bytes(node, 100, name_buf + name_len_out);
    if (result != storage::io_result::success)
      return result;
    size_t new_limit = name_len_out + 100;
    while (name_buf[name_len_out] && name_len_out < new_limit)
      ++name_len_out;
    return storage::io_result::success;
  }

  storage::io_result tarfs_instance::read_num(
    uint64_t offset, size_t len, uint64_t &out
  ) {

    //len <= 12
    char buffer[12];
    storage::io_result result = bd->read_bytes(offset, len, buffer);
    out = 0;

    for (size_t i = 0; i < len; ++i) {
      if (!buffer[i])
        return i == 0 ? storage::io_result::fs_corrupt
                      : storage::io_result::success;
      if (buffer[i] < '0' || buffer[i] > '7')
        return storage::io_result::fs_corrupt;
      out = out * 8 + buffer[i] - '0';
    }

    return storage::io_result::success;

  }

#define RETURN_MAYBE_NOT_FOUND(expr) \
  { \
    storage::io_result _result = expr; \
    if (_result == storage::io_result::out_of_bounds) \
      return storage::io_result::not_found; \
    if (_result != storage::io_result::success) \
      return _result; \
  }

  storage::io_result tarfs_instance::get_root_node(storage::node_id_t &out) {
    out = 0;
    while (true) {
      char name_buf[255];
      size_t name_len;
      RETURN_MAYBE_NOT_FOUND(read_name(out, name_buf, name_len))
      if (name_len == 2 && name_buf[0] == '.' && name_buf[1] == '/')
        return storage::io_result::success;
      RETURN_MAYBE_NOT_FOUND(next_node(out))
    }
  }

  storage::io_result tarfs_instance::get_first_child(storage::node_id_t node,
    storage::node_id_t &out, storage::directory_iter_t &iter_out
  ) {

    out = 0;
    while (true) {

      char name_buf[255];
      size_t name_len;
      RETURN_MAYBE_NOT_FOUND(read_name(out, name_buf, name_len))

      //TODO
      while (1)
        ;

      RETURN_MAYBE_NOT_FOUND(next_node(out))

    }

  }

  storage::io_result tarfs_instance::get_next_child(storage::node_id_t node,
    storage::node_id_t &out, storage::directory_iter_t &iter
  ) {

    out = iter;
    while (true) {

      char name_buf[255];
      size_t name_len;
      RETURN_MAYBE_NOT_FOUND(read_name(out, name_buf, name_len))

      //TODO
      //NOTE: before return, do iter = out.
      while (1)
        ;


      RETURN_MAYBE_NOT_FOUND(next_node(out))

    }

  }

  storage::io_result tarfs_instance::get_child(storage::node_id_t node,
    storage::node_id_t &out, const char *name, size_t name_len
  ) {

    char full_name[255];
    size_t full_name_len;
    RETURN_MAYBE_NOT_FOUND(read_name(out, full_name, full_name_len))

    if (full_name_len + name_len > 255)
      return storage::io_result::not_supported;

    for (size_t i = 0; i < name_len; ++i)
      full_name[full_name_len + i] = name[i];
    full_name_len += name_len;

    out = 0;
    while (true) {

      char cand_name[255];
      size_t cand_name_len;
      RETURN_MAYBE_NOT_FOUND(read_name(out, cand_name, cand_name_len))

      if (cand_name_len != full_name_len)
        goto next_iter;
      for (size_t i = 0; i < full_name_len; ++i)
        if (cand_name[i] != full_name[i])
          goto next_iter;

      return storage::io_result::success;

    next_iter:
      RETURN_MAYBE_NOT_FOUND(next_node(out))

    }

  }

  storage::io_result tarfs_instance::get_name_length(
    storage::node_id_t node, size_t &length_out
  ) {

    //TODO
    while (1)
      ;

  }

  storage::io_result tarfs_instance::get_name(
    storage::node_id_t node, char *buffer, size_t &length_out
  ) {

    //TODO
    while (1)
      ;

  }

  storage::io_result tarfs_instance::get_file_length(
    storage::node_id_t node, uint64_t &length_out
  ) {

    //TODO
    while (1)
      ;

  }

  storage::io_result tarfs_instance::get_file_type(
    storage::node_id_t node, storage::file_type &out
  ) {

    uint64_t ft;
    storage::io_result result = read_num(node + 156, 1, ft);
    if (result != storage::io_result::success)
      return result;

    switch (ft) {
    case 0:
      out = storage::file_type::regular_file;
      return storage::io_result::success;
    case 2:
      out = storage::file_type::symlink;
      return storage::io_result::success;
    case 5:
      out = storage::file_type::directory;
      return storage::io_result::success;
    default:
      return storage::io_result::not_supported;
    }

  }


}