/*
 * spiffs_check.c
 *
 * Contains functionality for checking file system consistency
 * and mending problems.
 * Three levels of consistency checks are implemented:
 *
 * Look up consistency
 *   Checks if indices in lookup pages are coherent with page headers
 * Object index consistency
 *   Checks if there are any orphaned object indices (missing object index headers).
 *   If an object index is found but not its header, the object index is deleted.
 *   This is critical for the following page consistency check.
 * Page consistency
 *   Checks for pages that ought to be indexed, ought not to be indexed, are multiple indexed
 *
 *
 *  Created on: Jul 7, 2013
 *      Author: petera
 */

#include "spiffs.h"
#include "spiffs_nucleus.h"

//---------------------------------------
// Look up consistency

// searches in the object indices and returns the referenced page index given
// the object id and the data span index
// destroys fs->lu_work
static s32_t spiffs_object_get_data_page_index_reference(
  spiffs *fs,
  spiffs_obj_id obj_id,
  spiffs_span_ix data_spix,
  spiffs_page_ix *pix,
  spiffs_page_ix *objix_pix) {
  s32_t res;

  // calculate object index span index for given data page span index
  spiffs_span_ix objix_spix = SPIFFS_OBJ_IX_ENTRY_SPAN_IX(fs, data_spix);

  // find obj index for obj id and span index
  res = spiffs_obj_lu_find_id_and_span(fs, obj_id | SPIFFS_OBJ_ID_IX_FLAG, objix_spix, 0, objix_pix);
  SPIFFS_CHECK_RES(res);

  // load obj index entry
  u32_t addr = SPIFFS_PAGE_TO_PADDR(fs, *objix_pix);
  if (objix_spix == 0) {
    // get referenced page from object index header
    addr += sizeof(spiffs_page_object_ix_header) + data_spix * sizeof(spiffs_page_ix);
  } else {
    // get referenced page from object index
    addr += sizeof(spiffs_page_object_ix) + SPIFFS_OBJ_IX_ENTRY(fs, data_spix) * sizeof(spiffs_page_ix);
  }

  res = _spiffs_rd(fs, SPIFFS_OP_T_OBJ_LU2 | SPIFFS_OP_C_READ, 0, addr, sizeof(spiffs_page_ix), (u8_t *)pix);

  return res;
}

// copies page contents to a new page
static s32_t spiffs_rewrite_page(spiffs *fs, spiffs_page_ix cur_pix, spiffs_page_header *p_hdr, spiffs_page_ix *new_pix) {
  s32_t res;
  res = spiffs_page_allocate_data(fs, p_hdr->obj_id, p_hdr, 0,0,0,0, new_pix);
  SPIFFS_CHECK_RES(res);
  res = spiffs_phys_cpy(fs, 0,
      SPIFFS_PAGE_TO_PADDR(fs, *new_pix) + sizeof(spiffs_page_header),
      SPIFFS_PAGE_TO_PADDR(fs, cur_pix) + sizeof(spiffs_page_header),
      SPIFFS_DATA_PAGE_SIZE(fs));
  SPIFFS_CHECK_RES(res);
  return res;
}

// rewrites the object index for given object id and replaces the
// data page index to a new page index
static s32_t spiffs_rewrite_index(spiffs *fs, spiffs_obj_id obj_id, spiffs_span_ix data_spix, spiffs_page_ix new_data_pix, spiffs_page_ix objix_pix) {
  s32_t res;
  spiffs_block_ix bix;
  int entry;
  spiffs_page_ix free_pix;
  obj_id |= SPIFFS_OBJ_ID_IX_FLAG;

  // find free entry
  res = spiffs_obj_lu_find_free(fs, fs->free_cursor_block_ix, fs->free_cursor_obj_lu_entry, &bix, &entry);
  SPIFFS_CHECK_RES(res);
  free_pix = SPIFFS_OBJ_LOOKUP_ENTRY_TO_PIX(fs, bix, entry);

  // calculate object index span index for given data page span index
  spiffs_span_ix objix_spix = SPIFFS_OBJ_IX_ENTRY_SPAN_IX(fs, data_spix);
  if (objix_spix == 0) {
    // calc index in index header
    entry = data_spix;
  } else {
    // calc entry in index
    entry = SPIFFS_OBJ_IX_ENTRY(fs, data_spix);
  }
  // load index
  res = _spiffs_rd(fs, SPIFFS_OP_T_OBJ_LU2 | SPIFFS_OP_C_READ,
      0, SPIFFS_PAGE_TO_PADDR(fs, objix_pix), SPIFFS_CFG_LOG_PAGE_SZ(fs), fs->lu_work);
  SPIFFS_CHECK_RES(res);
  spiffs_page_header *objix_p_hdr = (spiffs_page_header *)fs->lu_work;

  // be ultra safe, double check header against provided data
  if (objix_p_hdr->obj_id != obj_id) {
    spiffs_page_delete(fs, free_pix);
    return SPIFFS_ERR_CHECK_OBJ_ID_MISM;
  }
  if (objix_p_hdr->span_ix != objix_spix) {
    spiffs_page_delete(fs, free_pix);
    return SPIFFS_ERR_CHECK_SPIX_MISM;
  }
  if ((objix_p_hdr->flags & (SPIFFS_PH_FLAG_USED | SPIFFS_PH_FLAG_IXDELE | SPIFFS_PH_FLAG_INDEX |
                            SPIFFS_PH_FLAG_FINAL | SPIFFS_PH_FLAG_DELET)) !=
                                (SPIFFS_PH_FLAG_IXDELE | SPIFFS_PH_FLAG_DELET)) {
    spiffs_page_delete(fs, free_pix);
    return SPIFFS_ERR_CHECK_FLAGS_BAD;
  }

  // rewrite in mem
  if (objix_spix == 0) {
    ((spiffs_page_ix*)((u8_t *)fs->lu_work + sizeof(spiffs_page_object_ix_header)))[data_spix] = new_data_pix;
  } else {
    ((spiffs_page_ix*)((u8_t *)fs->lu_work + sizeof(spiffs_page_object_ix)))[SPIFFS_OBJ_IX_ENTRY(fs, data_spix)] = new_data_pix;
  }

  res = _spiffs_wr(fs, SPIFFS_OP_T_OBJ_DA | SPIFFS_OP_C_UPDT,
      0, SPIFFS_PAGE_TO_PADDR(fs, free_pix), SPIFFS_CFG_LOG_PAGE_SZ(fs), fs->lu_work);
  SPIFFS_CHECK_RES(res);
  res = _spiffs_wr(fs, SPIFFS_OP_T_OBJ_LU | SPIFFS_OP_C_UPDT,
      0, SPIFFS_BLOCK_TO_PADDR(fs, SPIFFS_BLOCK_FOR_PAGE(fs, free_pix)) + SPIFFS_OBJ_LOOKUP_ENTRY_FOR_PAGE(fs, free_pix) * sizeof(spiffs_page_ix),
      sizeof(spiffs_obj_id),
      (u8_t *)&obj_id);
  SPIFFS_CHECK_RES(res);
  res = spiffs_page_delete(fs, objix_pix);

  return res;
}

// deletes an object just by marking object index header as deleted
static s32_t spiffs_delete_obj_lazy(spiffs *fs, spiffs_obj_id obj_id) {
  spiffs_page_ix objix_hdr_pix;
  s32_t res;
  res = spiffs_obj_lu_find_id_and_span(fs, obj_id, 0, 0, &objix_hdr_pix);
  if (res == SPIFFS_ERR_NOT_FOUND) {
    return SPIFFS_OK;
  }
  SPIFFS_CHECK_RES(res);
  u8_t flags = 0xff & ~SPIFFS_PH_FLAG_IXDELE;
  res = _spiffs_wr(fs, SPIFFS_OP_T_OBJ_LU | SPIFFS_OP_C_UPDT,
      0, SPIFFS_PAGE_TO_PADDR(fs, objix_hdr_pix) + offsetof(spiffs_page_header, flags),
      sizeof(u8_t),
      (u8_t *)&flags);
  return res;
}

// validates the given look up entry
static s32_t spiffs_lookup_check_validate(spiffs *fs, spiffs_obj_id lu_obj_id, spiffs_page_header *p_hdr,
    spiffs_page_ix cur_pix, spiffs_block_ix cur_block, int cur_entry, int *reload_lu) {
  u8_t delete_page = 0;
  s32_t res = SPIFFS_OK;
  spiffs_page_ix objix_pix;
  spiffs_page_ix ref_pix;
  // check validity, take actions
  if (((lu_obj_id == SPIFFS_OBJ_ID_DELETED) && (p_hdr->flags & SPIFFS_PH_FLAG_DELET)) ||
      ((lu_obj_id == SPIFFS_OBJ_ID_FREE) && (p_hdr->flags & SPIFFS_PH_FLAG_USED) == 0)) {
    // look up entry deleted / free but used in page header
    SPIFFS_CHECK_DBG("LU: pix %04x deleted/free in lu but not on page\n", cur_pix);
    *reload_lu = 1;
    delete_page = 1;
    if (p_hdr->flags & SPIFFS_PH_FLAG_INDEX) {
      // header says data page
      // data page can be removed if not referenced by some object index
      res = spiffs_object_get_data_page_index_reference(fs, p_hdr->obj_id, p_hdr->span_ix, &ref_pix, &objix_pix);
      if (res == SPIFFS_ERR_NOT_FOUND) {
        // no object with this id, so remove page safely
        res = SPIFFS_OK;
      } else {
        SPIFFS_CHECK_RES(res);
        if (ref_pix == cur_pix) {
          // data page referenced by object index but deleted in lu
          // copy page to new place and re-write the object index to new place
          spiffs_page_ix new_pix;
          res = spiffs_rewrite_page(fs, cur_pix, p_hdr, &new_pix);
          SPIFFS_CHECK_DBG("LU: FIXUP: data page not found elsewhere, rewriting %04x to new page %04x\n", cur_pix, new_pix);
          SPIFFS_CHECK_RES(res);
          *reload_lu = 1;
          SPIFFS_CHECK_DBG("LU: FIXUP: %04x rewritten to %04x, affected objix_pix %04x\n", cur_pix, new_pix, objix_pix);
          res = spiffs_rewrite_index(fs, p_hdr->obj_id, p_hdr->span_ix, new_pix, objix_pix);
          if (res <= _SPIFFS_ERR_CHECK_FIRST && res > _SPIFFS_ERR_CHECK_LAST) {
            // index bad also, cannot mend this file
            SPIFFS_CHECK_DBG("LU: FIXUP: index bad %i, cannot mend!\n", res);
            res = spiffs_page_delete(fs, new_pix);
            SPIFFS_CHECK_RES(res);
            res = spiffs_delete_obj_lazy(fs, p_hdr->obj_id);
            if (fs->check_cb_f) fs->check_cb_f(SPIFFS_CHECK_LOOKUP, SPIFFS_CHECK_DELETE_BAD_FILE, p_hdr->obj_id, 0);
          } else {
            if (fs->check_cb_f) fs->check_cb_f(SPIFFS_CHECK_LOOKUP, SPIFFS_CHECK_FIX_INDEX, p_hdr->obj_id, p_hdr->span_ix);
          }
          SPIFFS_CHECK_RES(res);
        }
      }
    } else {
      // header says index page
      // index page can be removed if other index with same obj_id and spanix is found
      res = spiffs_obj_lu_find_id_and_span(fs, p_hdr->obj_id | SPIFFS_OBJ_ID_IX_FLAG, p_hdr->span_ix, cur_pix, 0);
      if (res == SPIFFS_ERR_NOT_FOUND) {
        // no such index page found, check for a data page amongst page headers
        // lu cannot be trusted
        res = spiffs_obj_lu_find_id_and_span_by_phdr(fs, p_hdr->obj_id | SPIFFS_OBJ_ID_IX_FLAG, 0, 0, 0);
        if (res == SPIFFS_OK) { // ignore other errors
          // got a data page also, assume lu corruption only, rewrite to new page
          spiffs_page_ix new_pix;
          res = spiffs_rewrite_page(fs, cur_pix, p_hdr, &new_pix);
          SPIFFS_CHECK_DBG("LU: FIXUP: ix page with data not found elsewhere, rewriting %04x to new page %04x\n", cur_pix, new_pix);
          SPIFFS_CHECK_RES(res);
          *reload_lu = 1;
          if (fs->check_cb_f) fs->check_cb_f(SPIFFS_CHECK_LOOKUP, SPIFFS_CHECK_FIX_LOOKUP, p_hdr->obj_id, p_hdr->span_ix);
        }
      } else {
        SPIFFS_CHECK_RES(res);
      }
    }
  }
  if (lu_obj_id != SPIFFS_OBJ_ID_FREE && lu_obj_id != SPIFFS_OBJ_ID_DELETED) {
    // look up entry used
    if ((p_hdr->obj_id | SPIFFS_OBJ_ID_IX_FLAG) != (lu_obj_id | SPIFFS_OBJ_ID_IX_FLAG)) {
      SPIFFS_CHECK_DBG("LU: pix %04x differ in obj_id lu:%04x ph:%04x\n", cur_pix, lu_obj_id, p_hdr->obj_id);
      delete_page = 1;
      if ((p_hdr->flags & SPIFFS_PH_FLAG_DELET) == 0 ||
          (p_hdr->flags & SPIFFS_PH_FLAG_FINAL) ||
          (p_hdr->flags & (SPIFFS_PH_FLAG_INDEX | SPIFFS_PH_FLAG_IXDELE)) == 0) {
        // page deleted or not finalized, just remove it
      } else {
        if (p_hdr->flags & SPIFFS_PH_FLAG_INDEX) {
          // if data page, check for reference to this page
          res = spiffs_object_get_data_page_index_reference(fs, p_hdr->obj_id, p_hdr->span_ix, &ref_pix, &objix_pix);
          if (res == SPIFFS_ERR_NOT_FOUND) {
            // no object with this id, so remove page safely
            res = SPIFFS_OK;
          } else {
            SPIFFS_CHECK_RES(res);
            //   if found, rewrite page with object id, update index, and delete current
            if (ref_pix == cur_pix) {
              spiffs_page_ix new_pix;
              res = spiffs_rewrite_page(fs, cur_pix, p_hdr, &new_pix);
              SPIFFS_CHECK_RES(res);
              res = spiffs_rewrite_index(fs, p_hdr->obj_id, p_hdr->span_ix, new_pix, objix_pix);
              if (res <= _SPIFFS_ERR_CHECK_FIRST && res > _SPIFFS_ERR_CHECK_LAST) {
                // index bad also, cannot mend this file
                SPIFFS_CHECK_DBG("LU: FIXUP: index bad %i, cannot mend!\n", res);
                res = spiffs_page_delete(fs, new_pix);
                SPIFFS_CHECK_RES(res);
                res = spiffs_delete_obj_lazy(fs, p_hdr->obj_id);
                *reload_lu = 1;
                if (fs->check_cb_f) fs->check_cb_f(SPIFFS_CHECK_LOOKUP, SPIFFS_CHECK_DELETE_BAD_FILE, p_hdr->obj_id, 0);
              }
              SPIFFS_CHECK_RES(res);
            }
          }
        } else {
          // else if index, check for other pages with both obj_id's and spanix
          spiffs_page_ix objix_pix_lu, objix_pix_ph;
          // see if other object index page exists for lookup obj id and span index
          res = spiffs_obj_lu_find_id_and_span(fs, lu_obj_id | SPIFFS_OBJ_ID_IX_FLAG, p_hdr->span_ix, 0, &objix_pix_lu);
          if (res == SPIFFS_ERR_NOT_FOUND) {
            res = SPIFFS_OK;
            objix_pix_lu = 0;
          }
          SPIFFS_CHECK_RES(res);
          // see if other object index exists for page header obj id and span index
          res = spiffs_obj_lu_find_id_and_span(fs, p_hdr->obj_id | SPIFFS_OBJ_ID_IX_FLAG, p_hdr->span_ix, 0, &objix_pix_ph);
          if (res == SPIFFS_ERR_NOT_FOUND) {
            res = SPIFFS_OK;
            objix_pix_ph = 0;
          }
          SPIFFS_CHECK_RES(res);
          //   if both obj_id's found, just delete current
          if (objix_pix_ph == 0 || objix_pix_lu == 0) {
            // otherwise try finding first corresponding data pages
            spiffs_page_ix data_pix_lu, data_pix_ph;
            // see if other data page exists for look up obj id and span index
            res = spiffs_obj_lu_find_id_and_span(fs, lu_obj_id & ~SPIFFS_OBJ_ID_IX_FLAG, 0, 0, &data_pix_lu);
            if (res == SPIFFS_ERR_NOT_FOUND) {
              res = SPIFFS_OK;
              objix_pix_lu = 0;
            }
            SPIFFS_CHECK_RES(res);
            // see if other data page exists for page header obj id and span index
            res = spiffs_obj_lu_find_id_and_span(fs, p_hdr->obj_id & ~SPIFFS_OBJ_ID_IX_FLAG, 0, 0, &data_pix_ph);
            if (res == SPIFFS_ERR_NOT_FOUND) {
              res = SPIFFS_OK;
              objix_pix_ph = 0;
            }
            SPIFFS_CHECK_RES(res);

            spiffs_page_header new_ph;
            new_ph.flags = 0xff & ~(SPIFFS_PH_FLAG_USED | SPIFFS_PH_FLAG_INDEX | SPIFFS_PH_FLAG_FINAL);
            new_ph.span_ix = p_hdr->span_ix;
            spiffs_page_ix new_pix;
            if ((objix_pix_lu && data_pix_lu && data_pix_ph && objix_pix_ph == 0) ||
                (objix_pix_lu == 0 && data_pix_ph && objix_pix_ph == 0)) {
              //   got a data page for page header obj id
              //   rewrite as obj_id_ph
              new_ph.obj_id = p_hdr->obj_id | SPIFFS_OBJ_ID_IX_FLAG;
              res = spiffs_rewrite_page(fs, cur_pix, &new_ph, &new_pix);
              SPIFFS_CHECK_DBG("LU: FIXUP: rewrite page %04x as %04x to pix %04x\n", cur_pix, new_ph.obj_id, new_pix);
              if (fs->check_cb_f) fs->check_cb_f(SPIFFS_CHECK_LOOKUP, SPIFFS_CHECK_FIX_LOOKUP, p_hdr->obj_id, p_hdr->span_ix);
              SPIFFS_CHECK_RES(res);
              *reload_lu = 1;
            } else if ((objix_pix_ph && data_pix_ph && data_pix_lu && objix_pix_lu == 0) ||
                (objix_pix_ph == 0 && data_pix_lu && objix_pix_lu == 0)) {
              //   got a data page for look up obj id
              //   rewrite as obj_id_lu
              new_ph.obj_id =  lu_obj_id | SPIFFS_OBJ_ID_IX_FLAG;
              SPIFFS_CHECK_DBG("LU: FIXUP: rewrite page %04x as %04x\n", cur_pix, new_ph.obj_id);
              if (fs->check_cb_f) fs->check_cb_f(SPIFFS_CHECK_LOOKUP, SPIFFS_CHECK_FIX_LOOKUP, p_hdr->obj_id, p_hdr->span_ix);
              res = spiffs_rewrite_page(fs, cur_pix, &new_ph, &new_pix);
              SPIFFS_CHECK_RES(res);
              *reload_lu = 1;
            } else {
              // cannot safely do anything
              SPIFFS_CHECK_DBG("LU: FIXUP: nothing to do, just delete\n");
            }
          }
        }
      }
    } else if (((lu_obj_id & SPIFFS_OBJ_ID_IX_FLAG) && (p_hdr->flags & SPIFFS_PH_FLAG_INDEX)) ||
        ((lu_obj_id & SPIFFS_OBJ_ID_IX_FLAG) == 0 && (p_hdr->flags & SPIFFS_PH_FLAG_INDEX) == 0)) {
      SPIFFS_CHECK_DBG("LU: %04x lu/page index marking differ\n", cur_pix);
      spiffs_page_ix data_pix, objix_pix;
      // see if other data page exists for given obj id and span index
      res = spiffs_obj_lu_find_id_and_span(fs, lu_obj_id & ~SPIFFS_OBJ_ID_IX_FLAG, p_hdr->span_ix, cur_pix, &data_pix);
      if (res == SPIFFS_ERR_NOT_FOUND) {
        res = SPIFFS_OK;
        data_pix = 0;
      }
      SPIFFS_CHECK_RES(res);
      // see if other object index exists for given obj id and span index
      res = spiffs_obj_lu_find_id_and_span(fs, lu_obj_id | SPIFFS_OBJ_ID_IX_FLAG, p_hdr->span_ix, cur_pix, &objix_pix);
      if (res == SPIFFS_ERR_NOT_FOUND) {
        res = SPIFFS_OK;
        objix_pix = 0;
      }
      SPIFFS_CHECK_RES(res);

      delete_page = 1;
      // if other data page exists and object index exists, just delete page
      if (data_pix && objix_pix) {
        SPIFFS_CHECK_DBG("LU: FIXUP: other index and data page exists, simply remove\n");
      } else
      // if only data page exists, make this page index
      if (data_pix && objix_pix == 0) {
        SPIFFS_CHECK_DBG("LU: FIXUP: other data page exists, make this index\n");
        if (fs->check_cb_f) fs->check_cb_f(SPIFFS_CHECK_LOOKUP, SPIFFS_CHECK_FIX_INDEX, lu_obj_id, p_hdr->span_ix);
        spiffs_page_header new_ph;
        spiffs_page_ix new_pix;
        new_ph.flags = 0xff & ~(SPIFFS_PH_FLAG_USED | SPIFFS_PH_FLAG_FINAL | SPIFFS_PH_FLAG_INDEX);
        new_ph.obj_id = lu_obj_id | SPIFFS_OBJ_ID_IX_FLAG;
        new_ph.span_ix = p_hdr->span_ix;
        res = spiffs_page_allocate_data(fs, new_ph.obj_id, &new_ph, 0, 0, 0, 1, &new_pix);
        SPIFFS_CHECK_RES(res);
        res = spiffs_phys_cpy(fs, 0, SPIFFS_PAGE_TO_PADDR(fs, new_pix) + sizeof(spiffs_page_header),
            SPIFFS_PAGE_TO_PADDR(fs, cur_pix) + sizeof(spiffs_page_header),
            SPIFFS_CFG_LOG_PAGE_SZ(fs) - sizeof(spiffs_page_header));
        SPIFFS_CHECK_RES(res);
      } else
      // if only index exists, make data page
      if (data_pix == 0 && objix_pix) {
        SPIFFS_CHECK_DBG("LU: FIXUP: other index page exists, make this data\n");
        if (fs->check_cb_f) fs->check_cb_f(SPIFFS_CHECK_LOOKUP, SPIFFS_CHECK_FIX_LOOKUP, lu_obj_id, p_hdr->span_ix);
        spiffs_page_header new_ph;
        spiffs_page_ix new_pix;
        new_ph.flags = 0xff & ~(SPIFFS_PH_FLAG_USED | SPIFFS_PH_FLAG_FINAL);
        new_ph.obj_id = lu_obj_id & ~SPIFFS_OBJ_ID_IX_FLAG;
        new_ph.span_ix = p_hdr->span_ix;
        res = spiffs_page_allocate_data(fs, new_ph.obj_id, &new_ph, 0, 0, 0, 1, &new_pix);
        SPIFFS_CHECK_RES(res);
        res = spiffs_phys_cpy(fs, 0, SPIFFS_PAGE_TO_PADDR(fs, new_pix) + sizeof(spiffs_page_header),
            SPIFFS_PAGE_TO_PADDR(fs, cur_pix) + sizeof(spiffs_page_header),
            SPIFFS_CFG_LOG_PAGE_SZ(fs) - sizeof(spiffs_page_header));
        SPIFFS_CHECK_RES(res);
      } else {
        // if nothing exists, we cannot safely make a decision - delete
      }
    }
    else if ((p_hdr->flags & SPIFFS_PH_FLAG_DELET) == 0) {
      SPIFFS_CHECK_DBG("LU: pix %04x busy in lu but deleted on page\n", cur_pix);
      delete_page = 1;
    } else if ((p_hdr->flags & SPIFFS_PH_FLAG_FINAL)) {
      SPIFFS_CHECK_DBG("LU: pix %04x busy but not final\n", cur_pix);
      // page can be removed if not referenced by object index
      *reload_lu = 1;
      res = spiffs_object_get_data_page_index_reference(fs, lu_obj_id, p_hdr->span_ix, &ref_pix, &objix_pix);
      if (res == SPIFFS_ERR_NOT_FOUND) {
        // no object with this id, so remove page safely
        res = SPIFFS_OK;
        delete_page = 1;
      } else {
        SPIFFS_CHECK_RES(res);
        if (ref_pix != cur_pix) {
          SPIFFS_CHECK_DBG("LU: FIXUP: other finalized page is referred, just delete\n");
          delete_page = 1;
        } else {
          // page referenced by object index but not final
          // just finalize
          SPIFFS_CHECK_DBG("LU: FIXUP: unfinalized page is referred, finalizing\n");
          if (fs->check_cb_f) fs->check_cb_f(SPIFFS_CHECK_LOOKUP, SPIFFS_CHECK_FIX_LOOKUP, p_hdr->obj_id, p_hdr->span_ix);
          u8_t flags = 0xff & ~SPIFFS_PH_FLAG_FINAL;
          res = _spiffs_wr(fs, SPIFFS_OP_T_OBJ_DA | SPIFFS_OP_C_UPDT,
              0, SPIFFS_PAGE_TO_PADDR(fs, cur_pix) + offsetof(spiffs_page_header, flags),
              sizeof(u8_t), (u8_t*)&flags);
        }
      }
    }
  }

  if (delete_page) {
    SPIFFS_CHECK_DBG("LU: FIXUP: deleting page %04x\n", cur_pix);
    if (fs->check_cb_f) fs->check_cb_f(SPIFFS_CHECK_LOOKUP, SPIFFS_CHECK_DELETE_PAGE, cur_pix, 0);
    res = spiffs_page_delete(fs, cur_pix);
    SPIFFS_CHECK_RES(res);
  }

  return res;
}

static s32_t spiffs_lookup_check_v(spiffs *fs, spiffs_obj_id obj_id, spiffs_block_ix cur_block, int cur_entry,
    u32_t user_data, void *user_p) {
  s32_t res = SPIFFS_OK;
  spiffs_page_header p_hdr;
  spiffs_page_ix cur_pix = SPIFFS_OBJ_LOOKUP_ENTRY_TO_PIX(fs, cur_block, cur_entry);

  if (fs->check_cb_f) fs->check_cb_f(SPIFFS_CHECK_LOOKUP, SPIFFS_CHECK_PROGRESS,
      (cur_block * 256)/fs->block_count, 0);

  // load header
  res = _spiffs_rd(fs, SPIFFS_OP_T_OBJ_LU2 | SPIFFS_OP_C_READ,
      0, SPIFFS_PAGE_TO_PADDR(fs, cur_pix), sizeof(spiffs_page_header), (u8_t*)&p_hdr);
  SPIFFS_CHECK_RES(res);

  int reload_lu = 0;

  res = spiffs_lookup_check_validate(fs, obj_id, &p_hdr, cur_pix, cur_block, cur_entry, &reload_lu);
  SPIFFS_CHECK_RES(res);

  if (res == SPIFFS_OK) {
    return reload_lu ? SPIFFS_VIS_COUNTINUE_RELOAD : SPIFFS_VIS_COUNTINUE;
  }
  return res;
}


// Scans all object look up. For each entry, corresponding page header is checked for validity.
// If an object index header page is found, this is also checked
s32_t spiffs_lookup_consistency_check(spiffs *fs, u8_t check_all_objects) {
  s32_t res = SPIFFS_OK;

  if (fs->check_cb_f) fs->check_cb_f(SPIFFS_CHECK_LOOKUP, SPIFFS_CHECK_PROGRESS, 0, 0);

  res = spiffs_obj_lu_find_entry_visitor(fs, 0, 0, 0, 0, spiffs_lookup_check_v, 0, 0, 0, 0);

  if (res == SPIFFS_VIS_END) {
    res = SPIFFS_OK;
  }

  if (res != SPIFFS_OK) {
    if (fs->check_cb_f) fs->check_cb_f(SPIFFS_CHECK_LOOKUP, SPIFFS_CHECK_ERROR, res, 0);
  }

  if (fs->check_cb_f) fs->check_cb_f(SPIFFS_CHECK_LOOKUP, SPIFFS_CHECK_PROGRESS, 256, 0);

  return res;
}

//---------------------------------------
// Page consistency

// Scans all pages (except lu pages), reserves 4 bits in working memory for each page
// bit 0: 0 == FREE|DELETED, 1 == USED
// bit 1: 0 == UNREFERENCED, 1 == REFERENCED
// bit 2: 0 == NOT_INDEX,    1 == INDEX
// bit 3: unused
// A consistent file system will have only pages being
//  * x000 free, unreferenced, not index
//  * x011 used, referenced only once, not index
//  * x101 used, unreferenced, index
// The working memory might not fit all pages so several scans might be needed
static s32_t spiffs_page_consistency_check_i(spiffs *fs) {
  const u32_t bits = 4;
  const spiffs_page_ix pages_per_scan = SPIFFS_CFG_LOG_PAGE_SZ(fs) * 8 / bits;

  s32_t res = SPIFFS_OK;
  spiffs_page_ix pix_offset = 0;

  // for each range of pages fitting into work memory
  while (pix_offset < SPIFFS_PAGES_PER_BLOCK(fs) * fs->block_count) {
    // set this flag to abort all checks and rescan the page range
    u8_t restart = 0;
    c_memset(fs->work, 0, SPIFFS_CFG_LOG_PAGE_SZ(fs));

    spiffs_block_ix cur_block = 0;
    // build consistency bitmap for id range traversing all blocks
    while (!restart && cur_block < fs->block_count) {
      if (fs->check_cb_f) fs->check_cb_f(SPIFFS_CHECK_PAGE, SPIFFS_CHECK_PROGRESS,
          (pix_offset*256)/(SPIFFS_PAGES_PER_BLOCK(fs) * fs->block_count) +
          ((((cur_block * pages_per_scan * 256)/ (SPIFFS_PAGES_PER_BLOCK(fs) * fs->block_count))) / fs->block_count),
          0);

      // traverse each page except for lookup pages
      spiffs_page_ix cur_pix = SPIFFS_OBJ_LOOKUP_PAGES(fs) + SPIFFS_PAGES_PER_BLOCK(fs) * cur_block;
      while (!restart && cur_pix < SPIFFS_PAGES_PER_BLOCK(fs) * (cur_block+1)) {
        // read header
        spiffs_page_header p_hdr;
        res = _spiffs_rd(fs, SPIFFS_OP_T_OBJ_LU2 | SPIFFS_OP_C_READ,
            0, SPIFFS_PAGE_TO_PADDR(fs, cur_pix), sizeof(spiffs_page_header), (u8_t*)&p_hdr);
        SPIFFS_CHECK_RES(res);

        u8_t within_range = (cur_pix >= pix_offset && cur_pix < pix_offset + pages_per_scan);
        const u32_t pix_byte_ix = (cur_pix - pix_offset) / (8/bits);
        const u8_t pix_bit_ix = (cur_pix & ((8/bits)-1)) * bits;

        if (within_range &&
            (p_hdr.flags & SPIFFS_PH_FLAG_DELET) && (p_hdr.flags & SPIFFS_PH_FLAG_USED) == 0) {
          // used
          fs->work[pix_byte_ix] |= (1<<(pix_bit_ix + 0));
        }
        if ((p_hdr.flags & SPIFFS_PH_FLAG_DELET) &&
            (p_hdr.flags & SPIFFS_PH_FLAG_IXDELE) &&
            (p_hdr.flags & (SPIFFS_PH_FLAG_INDEX | SPIFFS_PH_FLAG_USED)) == 0) {
          // found non-deleted index
          if (within_range) {
            fs->work[pix_byte_ix] |= (1<<(pix_bit_ix + 2));
          }

          // load non-deleted index
          res = _spiffs_rd(fs, SPIFFS_OP_T_OBJ_LU2 | SPIFFS_OP_C_READ,
              0, SPIFFS_PAGE_TO_PADDR(fs, cur_pix), SPIFFS_CFG_LOG_PAGE_SZ(fs), fs->lu_work);
          SPIFFS_CHECK_RES(res);

          // traverse index for referenced pages
          spiffs_page_ix *object_page_index;
          spiffs_page_header *objix_p_hdr = (spiffs_page_header *)fs->lu_work;

          int entries;
          int i;
          spiffs_span_ix data_spix_offset;
          if (p_hdr.span_ix == 0) {
            // object header page index
            entries = SPIFFS_OBJ_HDR_IX_LEN(fs);
            data_spix_offset = 0;
            object_page_index = (spiffs_page_ix *)((u8_t *)fs->lu_work + sizeof(spiffs_page_object_ix_header));
          } else {
            // object page index
            entries = SPIFFS_OBJ_IX_LEN(fs);
            data_spix_offset = SPIFFS_OBJ_HDR_IX_LEN(fs) + SPIFFS_OBJ_IX_LEN(fs) * (p_hdr.span_ix - 1);
            object_page_index = (spiffs_page_ix *)((u8_t *)fs->lu_work + sizeof(spiffs_page_object_ix));
          }

          // for all entries in index
          for (i = 0; !restart && i < entries; i++) {
            spiffs_page_ix rpix = object_page_index[i];
            u8_t rpix_within_range = rpix >= pix_offset && rpix < pix_offset + pages_per_scan;

            if ((rpix != (spiffs_page_ix)-1 && rpix > SPIFFS_MAX_PAGES(fs))
                || (rpix_within_range && SPIFFS_IS_LOOKUP_PAGE(fs, rpix))) {

              // bad reference
              SPIFFS_CHECK_DBG("PA: pix %04x bad pix / LU referenced from page %04x\n",
                  rpix, cur_pix);
              // check for data page elsewhere
              spiffs_page_ix data_pix;
              res = spiffs_obj_lu_find_id_and_span(fs, objix_p_hdr->obj_id & ~SPIFFS_OBJ_ID_IX_FLAG,
                  data_spix_offset + i, 0, &data_pix);
              if (res == SPIFFS_ERR_NOT_FOUND) {
                res = SPIFFS_OK;
                data_pix = 0;
              }
              SPIFFS_CHECK_RES(res);
              if (data_pix == 0) {
                // if not, allocate free page
                spiffs_page_header new_ph;
                new_ph.flags = 0xff & ~(SPIFFS_PH_FLAG_USED | SPIFFS_PH_FLAG_FINAL);
                new_ph.obj_id = objix_p_hdr->obj_id & ~SPIFFS_OBJ_ID_IX_FLAG;
                new_ph.span_ix = data_spix_offset + i;
                res = spiffs_page_allocate_data(fs, new_ph.obj_id, &new_ph, 0, 0, 0, 1, &data_pix);
                SPIFFS_CHECK_RES(res);
                SPIFFS_CHECK_DBG("PA: FIXUP: found no existing data page, created new @ %04x\n", data_pix);
              }
              // remap index
              SPIFFS_CHECK_DBG("PA: FIXUP: rewriting index pix %04x\n", cur_pix);
              res = spiffs_rewrite_index(fs, objix_p_hdr->obj_id | SPIFFS_OBJ_ID_IX_FLAG,
                  data_spix_offset + i, data_pix, cur_pix);
              if (res <= _SPIFFS_ERR_CHECK_FIRST && res > _SPIFFS_ERR_CHECK_LAST) {
                // index bad also, cannot mend this file
                SPIFFS_CHECK_DBG("PA: FIXUP: index bad %i, cannot mend - delete object\n", res);
                if (fs->check_cb_f) fs->check_cb_f(SPIFFS_CHECK_PAGE, SPIFFS_CHECK_DELETE_BAD_FILE, objix_p_hdr->obj_id, 0);
                // delete file
                res = spiffs_page_delete(fs, cur_pix);
              } else {
                if (fs->check_cb_f) fs->check_cb_f(SPIFFS_CHECK_PAGE, SPIFFS_CHECK_FIX_INDEX, objix_p_hdr->obj_id, objix_p_hdr->span_ix);
              }
              SPIFFS_CHECK_RES(res);
              restart = 1;

            } else if (rpix_within_range) {

              // valid reference
              // read referenced page header
              spiffs_page_header rp_hdr;
              res = _spiffs_rd(fs, SPIFFS_OP_T_OBJ_LU2 | SPIFFS_OP_C_READ,
                  0, SPIFFS_PAGE_TO_PADDR(fs, rpix), sizeof(spiffs_page_header), (u8_t*)&rp_hdr);
              SPIFFS_CHECK_RES(res);

              // cross reference page header check
              if (rp_hdr.obj_id != (p_hdr.obj_id & ~SPIFFS_OBJ_ID_IX_FLAG) ||
                  rp_hdr.span_ix != data_spix_offset + i ||
                  (rp_hdr.flags & (SPIFFS_PH_FLAG_DELET | SPIFFS_PH_FLAG_INDEX | SPIFFS_PH_FLAG_USED)) !=
                      (SPIFFS_PH_FLAG_DELET | SPIFFS_PH_FLAG_INDEX)) {
               SPIFFS_CHECK_DBG("PA: pix %04x has inconsistent page header ix id/span:%04x/%04x, ref id/span:%04x/%04x flags:%02x\n",
                    rpix, p_hdr.obj_id & ~SPIFFS_OBJ_ID_IX_FLAG, data_spix_offset + i,
                    rp_hdr.obj_id, rp_hdr.span_ix, rp_hdr.flags);
               // try finding correct page
               spiffs_page_ix data_pix;
               res = spiffs_obj_lu_find_id_and_span(fs, p_hdr.obj_id & ~SPIFFS_OBJ_ID_IX_FLAG,
                   data_spix_offset + i, rpix, &data_pix);
               if (res == SPIFFS_ERR_NOT_FOUND) {
                 res = SPIFFS_OK;
                 data_pix = 0;
               }
               SPIFFS_CHECK_RES(res);
               if (data_pix == 0) {
                 // not found, this index is badly borked
                 SPIFFS_CHECK_DBG("PA: FIXUP: index bad, delete object id %04x\n", p_hdr.obj_id);
                 if (fs->check_cb_f) fs->check_cb_f(SPIFFS_CHECK_PAGE, SPIFFS_CHECK_DELETE_BAD_FILE, p_hdr.obj_id, 0);
                 res = spiffs_delete_obj_lazy(fs, p_hdr.obj_id);
                 SPIFFS_CHECK_RES(res);
                 break;
               } else {
                 // found it, so rewrite index
                 SPIFFS_CHECK_DBG("PA: FIXUP: found correct data pix %04x, rewrite ix pix %04x id %04x\n",
                     data_pix, cur_pix, p_hdr.obj_id);
                 res = spiffs_rewrite_index(fs, p_hdr.obj_id, data_spix_offset + i, data_pix, cur_pix);
                 if (res <= _SPIFFS_ERR_CHECK_FIRST && res > _SPIFFS_ERR_CHECK_LAST) {
                   // index bad also, cannot mend this file
                   SPIFFS_CHECK_DBG("PA: FIXUP: index bad %i, cannot mend!\n", res);
                   if (fs->check_cb_f) fs->check_cb_f(SPIFFS_CHECK_PAGE, SPIFFS_CHECK_DELETE_BAD_FILE, p_hdr.obj_id, 0);
                   res = spiffs_delete_obj_lazy(fs, p_hdr.obj_id);
                 } else {
                   if (fs->check_cb_f) fs->check_cb_f(SPIFFS_CHECK_PAGE, SPIFFS_CHECK_FIX_INDEX, p_hdr.obj_id, p_hdr.span_ix);
                 }
                 SPIFFS_CHECK_RES(res);
                 restart = 1;
               }
              }
              else {
                // mark rpix as referenced
                const u32_t rpix_byte_ix = (rpix - pix_offset) / (8/bits);
                const u8_t rpix_bit_ix = (rpix & ((8/bits)-1)) * bits;
                if (fs->work[rpix_byte_ix] & (1<<(rpix_bit_ix + 1))) {
                  SPIFFS_CHECK_DBG("PA: pix %04x multiple referenced from page %04x\n",
                      rpix, cur_pix);
                  // Here, we should have fixed all broken references - getting this means there
                  // must be multiple files with same object id. Only solution is to delete
                  // the object which is referring to this page
                  SPIFFS_CHECK_DBG("PA: FIXUP: removing object %04x and page %04x\n",
                      p_hdr.obj_id, cur_pix);
                  if (fs->check_cb_f) fs->check_cb_f(SPIFFS_CHECK_PAGE, SPIFFS_CHECK_DELETE_BAD_FILE, p_hdr.obj_id, 0);
                  res = spiffs_delete_obj_lazy(fs, p_hdr.obj_id);
                  SPIFFS_CHECK_RES(res);
                  // extra precaution, delete this page also
                  res = spiffs_page_delete(fs, cur_pix);
                  SPIFFS_CHECK_RES(res);
                  restart = 1;
                }
                fs->work[rpix_byte_ix] |= (1<<(rpix_bit_ix + 1));
              }
            }
          } // for all index entries
        } // found index

        // next page
        cur_pix++;
      }
      // next block
      cur_block++;
    }
    // check consistency bitmap
    if (!restart) {
      spiffs_page_ix objix_pix;
      spiffs_page_ix rpix;

      int byte_ix;
      int bit_ix;
      for (byte_ix = 0; !restart && byte_ix < SPIFFS_CFG_LOG_PAGE_SZ(fs); byte_ix++) {
        for (bit_ix = 0; !restart && bit_ix < 8/bits; bit_ix ++) {
          u8_t bitmask = (fs->work[byte_ix] >> (bit_ix * bits)) & 0x7;
          spiffs_page_ix cur_pix = pix_offset + byte_ix * (8/bits) + bit_ix;

          // 000 ok - free, unreferenced, not index

          if (bitmask == 0x1) {

            // 001
            SPIFFS_CHECK_DBG("PA: pix %04x USED, UNREFERENCED, not index\n", cur_pix);

            u8_t rewrite_ix_to_this = 0;
            u8_t delete_page = 0;
            // check corresponding object index entry
            spiffs_page_header p_hdr;
            res = _spiffs_rd(fs, SPIFFS_OP_T_OBJ_LU2 | SPIFFS_OP_C_READ,
                0, SPIFFS_PAGE_TO_PADDR(fs, cur_pix), sizeof(spiffs_page_header), (u8_t*)&p_hdr);
            SPIFFS_CHECK_RES(res);

            res = spiffs_object_get_data_page_index_reference(fs, p_hdr.obj_id, p_hdr.span_ix,
                &rpix, &objix_pix);
            if (res == SPIFFS_OK) {
              if (((rpix == (spiffs_page_ix)-1 || rpix > SPIFFS_MAX_PAGES(fs)) || (SPIFFS_IS_LOOKUP_PAGE(fs, rpix)))) {
                // pointing to a bad page altogether, rewrite index to this
                rewrite_ix_to_this = 1;
                SPIFFS_CHECK_DBG("PA: corresponding ref is bad: %04x, rewrite to this %04x\n", rpix, cur_pix);
              } else {
                // pointing to something else, check what
                spiffs_page_header rp_hdr;
                res = _spiffs_rd(fs, SPIFFS_OP_T_OBJ_LU2 | SPIFFS_OP_C_READ,
                    0, SPIFFS_PAGE_TO_PADDR(fs, rpix), sizeof(spiffs_page_header), (u8_t*)&rp_hdr);
                SPIFFS_CHECK_RES(res);
                if (((p_hdr.obj_id & ~SPIFFS_OBJ_ID_IX_FLAG) == rp_hdr.obj_id) &&
                    ((rp_hdr.flags & (SPIFFS_PH_FLAG_INDEX | SPIFFS_PH_FLAG_DELET | SPIFFS_PH_FLAG_USED | SPIFFS_PH_FLAG_FINAL)) ==
                        (SPIFFS_PH_FLAG_INDEX | SPIFFS_PH_FLAG_DELET))) {
                  // pointing to something else valid, just delete this page then
                  SPIFFS_CHECK_DBG("PA: corresponding ref is good but different: %04x, delete this %04x\n", rpix, cur_pix);
                  delete_page = 1;
                } else {
                  // pointing to something weird, update index to point to this page instead
                  if (rpix != cur_pix) {
                    SPIFFS_CHECK_DBG("PA: corresponding ref is weird: %04x %s%s%s%s, rewrite this %04x\n", rpix,
                        (rp_hdr.flags & SPIFFS_PH_FLAG_INDEX) ? "" : "INDEX ",
                            (rp_hdr.flags & SPIFFS_PH_FLAG_DELET) ? "" : "DELETED ",
                                (rp_hdr.flags & SPIFFS_PH_FLAG_USED) ? "NOTUSED " : "",
                                    (rp_hdr.flags & SPIFFS_PH_FLAG_FINAL) ? "NOTFINAL " : "",
                        cur_pix);
                    rewrite_ix_to_this = 1;
                  } else {
                    // should not happen, destined for fubar
                  }
                }
              }
            } else if (res == SPIFFS_ERR_NOT_FOUND) {
              SPIFFS_CHECK_DBG("PA: corresponding ref not found, delete %04x\n", cur_pix);
              delete_page = 1;
              res = SPIFFS_OK;
            }

            if (rewrite_ix_to_this) {
              // if pointing to invalid page, redirect index to this page
              SPIFFS_CHECK_DBG("PA: FIXUP: rewrite index id %04x data spix %04x to point to this pix: %04x\n",
                  p_hdr.obj_id, p_hdr.span_ix, cur_pix);
              res = spiffs_rewrite_index(fs, p_hdr.obj_id, p_hdr.span_ix, cur_pix, objix_pix);
              if (res <= _SPIFFS_ERR_CHECK_FIRST && res > _SPIFFS_ERR_CHECK_LAST) {
                // index bad also, cannot mend this file
                SPIFFS_CHECK_DBG("PA: FIXUP: index bad %i, cannot mend!\n", res);
                if (fs->check_cb_f) fs->check_cb_f(SPIFFS_CHECK_PAGE, SPIFFS_CHECK_DELETE_BAD_FILE, p_hdr.obj_id, 0);
                res = spiffs_page_delete(fs, cur_pix);
                SPIFFS_CHECK_RES(res);
                res = spiffs_delete_obj_lazy(fs, p_hdr.obj_id);
              } else {
                if (fs->check_cb_f) fs->check_cb_f(SPIFFS_CHECK_PAGE, SPIFFS_CHECK_FIX_INDEX, p_hdr.obj_id, p_hdr.span_ix);
              }
              SPIFFS_CHECK_RES(res);
              restart = 1;
              continue;
            } else if (delete_page) {
              SPIFFS_CHECK_DBG("PA: FIXUP: deleting page %04x\n", cur_pix);
              if (fs->check_cb_f) fs->check_cb_f(SPIFFS_CHECK_PAGE, SPIFFS_CHECK_DELETE_PAGE, cur_pix, 0);
              res = spiffs_page_delete(fs, cur_pix);
            }
            SPIFFS_CHECK_RES(res);
          }
          if (bitmask == 0x2) {

            // 010
            SPIFFS_CHECK_DBG("PA: pix %04x FREE, REFERENCED, not index\n", cur_pix);

            // no op, this should be taken care of when checking valid references
          }

          // 011 ok - busy, referenced, not index

          if (bitmask == 0x4) {

            // 100
            SPIFFS_CHECK_DBG("PA: pix %04x FREE, unreferenced, INDEX\n", cur_pix);

            // this should never happen, major fubar
          }

          // 101 ok - busy, unreferenced, index

          if (bitmask == 0x6) {

            // 110
            SPIFFS_CHECK_DBG("PA: pix %04x FREE, REFERENCED, INDEX\n", cur_pix);

            // no op, this should be taken care of when checking valid references
          }
          if (bitmask == 0x7) {

            // 111
            SPIFFS_CHECK_DBG("PA: pix %04x USED, REFERENCED, INDEX\n", cur_pix);

            // no op, this should be taken care of when checking valid references
          }
        }
      }
    }
    // next page range
    if (!restart) {
      pix_offset += pages_per_scan;
    }
  } // while page range not reached end
  return res;
}

// Checks consistency amongst all pages and fixes irregularities
s32_t spiffs_page_consistency_check(spiffs *fs) {
  if (fs->check_cb_f) fs->check_cb_f(SPIFFS_CHECK_PAGE, SPIFFS_CHECK_PROGRESS, 0, 0);
  s32_t res = spiffs_page_consistency_check_i(fs);
  if (res != SPIFFS_OK) {
    if (fs->check_cb_f) fs->check_cb_f(SPIFFS_CHECK_PAGE, SPIFFS_CHECK_ERROR, res, 0);
  }
  if (fs->check_cb_f) fs->check_cb_f(SPIFFS_CHECK_PAGE, SPIFFS_CHECK_PROGRESS, 256, 0);
  return res;
}

//---------------------------------------
// Object index consistency

// searches for given object id in temporary object id index,
// returns the index or -1
static int spiffs_object_index_search(spiffs *fs, spiffs_obj_id obj_id) {
  int i;
  spiffs_obj_id *obj_table = (spiffs_obj_id *)fs->work;
  obj_id &= ~SPIFFS_OBJ_ID_IX_FLAG;
  for (i = 0; i < SPIFFS_CFG_LOG_PAGE_SZ(fs) / sizeof(spiffs_obj_id); i++) {
    if ((obj_table[i] & ~SPIFFS_OBJ_ID_IX_FLAG) == obj_id) {
      return i;
    }
  }
  return -1;
}

s32_t spiffs_object_index_consistency_check_v(spiffs *fs, spiffs_obj_id obj_id, spiffs_block_ix cur_block,
    int cur_entry, u32_t user_data, void *user_p) {
  s32_t res_c = SPIFFS_VIS_COUNTINUE;
  s32_t res = SPIFFS_OK;
  u32_t *log_ix = (u32_t *)user_p;
  spiffs_obj_id *obj_table = (spiffs_obj_id *)fs->work;

  if (fs->check_cb_f) fs->check_cb_f(SPIFFS_CHECK_INDEX, SPIFFS_CHECK_PROGRESS,
      (cur_block * 256)/fs->block_count, 0);

  if (obj_id != SPIFFS_OBJ_ID_FREE && obj_id != SPIFFS_OBJ_ID_DELETED && (obj_id & SPIFFS_OBJ_ID_IX_FLAG)) {
    spiffs_page_header p_hdr;
    spiffs_page_ix cur_pix = SPIFFS_OBJ_LOOKUP_ENTRY_TO_PIX(fs, cur_block, cur_entry);

    // load header
    res = _spiffs_rd(fs, SPIFFS_OP_T_OBJ_LU2 | SPIFFS_OP_C_READ,
        0, SPIFFS_PAGE_TO_PADDR(fs, cur_pix), sizeof(spiffs_page_header), (u8_t*)&p_hdr);
    SPIFFS_CHECK_RES(res);

    if (p_hdr.span_ix == 0 &&
        (p_hdr.flags & (SPIFFS_PH_FLAG_INDEX | SPIFFS_PH_FLAG_FINAL | SPIFFS_PH_FLAG_DELET | SPIFFS_PH_FLAG_IXDELE)) ==
        (SPIFFS_PH_FLAG_DELET)) {
      SPIFFS_CHECK_DBG("IX: pix %04x, obj id:%04x spix:%04x header not fully deleted - deleting\n",
          cur_pix, obj_id, p_hdr.span_ix);
      if (fs->check_cb_f) fs->check_cb_f(SPIFFS_CHECK_INDEX, SPIFFS_CHECK_DELETE_PAGE, cur_pix, obj_id);
      res = spiffs_page_delete(fs, cur_pix);
      SPIFFS_CHECK_RES(res);
      return res_c;
    }

    if ((p_hdr.flags & (SPIFFS_PH_FLAG_INDEX | SPIFFS_PH_FLAG_FINAL | SPIFFS_PH_FLAG_DELET | SPIFFS_PH_FLAG_IXDELE)) ==
        (SPIFFS_PH_FLAG_DELET | SPIFFS_PH_FLAG_IXDELE)) {
      return res_c;
    }

    if (p_hdr.span_ix == 0) {
      // objix header page, register objid as reachable
      int r = spiffs_object_index_search(fs, obj_id);
      if (r == -1) {
        // not registered, do it
        obj_table[*log_ix] = obj_id & ~SPIFFS_OBJ_ID_IX_FLAG;
        (*log_ix)++;
        if (*log_ix >= SPIFFS_CFG_LOG_PAGE_SZ(fs) / sizeof(spiffs_obj_id)) {
          *log_ix = 0;
        }
      }
    } else { // span index
      // objix page, see if header can be found
      int r = spiffs_object_index_search(fs, obj_id);
      u8_t delete = 0;
      if (r == -1) {
        // not in temporary index, try finding it
        spiffs_page_ix objix_hdr_pix;
        res = spiffs_obj_lu_find_id_and_span(fs, obj_id | SPIFFS_OBJ_ID_IX_FLAG, 0, 0, &objix_hdr_pix);
        res_c = SPIFFS_VIS_COUNTINUE_RELOAD;
        if (res == SPIFFS_OK) {
          // found, register as reachable
          obj_table[*log_ix] = obj_id & ~SPIFFS_OBJ_ID_IX_FLAG;
        } else if (res == SPIFFS_ERR_NOT_FOUND) {
          // not found, register as unreachable
          delete = 1;
          obj_table[*log_ix] = obj_id | SPIFFS_OBJ_ID_IX_FLAG;
        } else {
          SPIFFS_CHECK_RES(res);
        }
        (*log_ix)++;
        if (*log_ix >= SPIFFS_CFG_LOG_PAGE_SZ(fs) / sizeof(spiffs_obj_id)) {
          *log_ix = 0;
        }
      } else {
        // in temporary index, check reachable flag
        if ((obj_table[r] & SPIFFS_OBJ_ID_IX_FLAG)) {
          // registered as unreachable
          delete = 1;
        }
      }

      if (delete) {
        SPIFFS_CHECK_DBG("IX: FIXUP: pix %04x, obj id:%04x spix:%04x is orphan index - deleting\n",
            cur_pix, obj_id, p_hdr.span_ix);
        if (fs->check_cb_f) fs->check_cb_f(SPIFFS_CHECK_INDEX, SPIFFS_CHECK_DELETE_ORPHANED_INDEX, cur_pix, obj_id);
        res = spiffs_page_delete(fs, cur_pix);
        SPIFFS_CHECK_RES(res);
      }
    } // span index
  } // valid object index id

  return res_c;
}

// Removes orphaned and partially deleted index pages.
// Scans for index pages. When an index page is found, corresponding index header is searched for.
// If no such page exists, the index page cannot be reached as no index header exists and must be
// deleted.
s32_t spiffs_object_index_consistency_check(spiffs *fs) {
  s32_t res = SPIFFS_OK;
  // impl note:
  // fs->work is used for a temporary object index memory, listing found object ids and
  // indicating whether they can be reached or not. Acting as a fifo if object ids cannot fit.
  // In the temporary object index memory, SPIFFS_OBJ_ID_IX_FLAG bit is used to indicate
  // a reachable/unreachable object id.
  c_memset(fs->work, 0, SPIFFS_CFG_LOG_PAGE_SZ(fs));
  u32_t obj_id_log_ix = 0;
  if (fs->check_cb_f) fs->check_cb_f(SPIFFS_CHECK_INDEX, SPIFFS_CHECK_PROGRESS, 0, 0);
  res = spiffs_obj_lu_find_entry_visitor(fs, 0, 0, 0, 0, spiffs_object_index_consistency_check_v, 0, &obj_id_log_ix,
      0, 0);
  if (res == SPIFFS_VIS_END) {
    res = SPIFFS_OK;
  }
  if (res != SPIFFS_OK) {
    if (fs->check_cb_f) fs->check_cb_f(SPIFFS_CHECK_INDEX, SPIFFS_CHECK_ERROR, res, 0);
  }
  if (fs->check_cb_f) fs->check_cb_f(SPIFFS_CHECK_INDEX, SPIFFS_CHECK_PROGRESS, 256, 0);
  return res;
}

