src/fs/rock/RockDbCell.h

   1 /*
   2  * Copyright (C) 1996-2020 The Squid Software Foundation and contributors
   3  *
   4  * Squid software is distributed under GPLv2+ license and includes
   5  * contributions from numerous individuals and organizations.
   6  * Please see the COPYING and CONTRIBUTORS files for details.
   7  */
   8
   9 #ifndef SQUID_FS_ROCK_DB_CELL_H
  10 #define SQUID_FS_ROCK_DB_CELL_H
  11
  12 #include "store/forward.h"
  13
  14 namespace Rock
  15 {
  16
  17 /** \ingroup Rock
  18  * Meta-information at the beginning of every db cell.
  19  * Links multiple map slots belonging to the same entry into an entry chain.
  20  * Stored on disk and used as sizeof() argument so it must remain POD.
  21  */
  22 class DbCellHeader
  23 {
  24 public:
  25     DbCellHeader();
  26
  27     /// true iff no entry occupies this slot
  28     bool empty() const { return !firstSlot && !nextSlot && !payloadSize; }
  29
  30     /* members below are not meaningful if empty() */
  31
  32     /// whether this slot is not corrupted
  33     bool sane(const size_t slotSize, int slotLimit) const {
  34         return
  35             0 <= firstSlot && firstSlot < slotLimit &&
  36             -1 <= nextSlot && nextSlot < slotLimit &&
  37             version > 0 &&
  38             0 < payloadSize && payloadSize <= slotSize - sizeof(DbCellHeader);
  39     }
  40
  41     uint64_t key[2]; ///< StoreEntry key
  42     uint64_t entrySize; ///< total entry content size or zero if still unknown
  43     uint32_t payloadSize; ///< slot contents size, always positive
  44     uint32_t version;  ///< detects conflicts among same-key entries
  45     sfileno firstSlot; ///< slot ID of the first slot occupied by the entry
  46     sfileno nextSlot; ///< slot ID of the next slot occupied by the entry
  47 };
  48
  49 } // namespace Rock
  50
  51 #endif /* SQUID_FS_ROCK_DB_CELL_H */
  52