src/basic/hash-funcs.h

   1 /* SPDX-License-Identifier: LGPL-2.1+ */
   2 #pragma once
   3
   4 /***
   5   This file is part of systemd.
   6
   7   Copyright 2010 Lennart Poettering
   8   Copyright 2014 Michal Schmidt
   9
  10   systemd is free software; you can redistribute it and/or modify it
  11   under the terms of the GNU Lesser General Public License as published by
  12   the Free Software Foundation; either version 2.1 of the License, or
  13   (at your option) any later version.
  14
  15   systemd is distributed in the hope that it will be useful, but
  16   WITHOUT ANY WARRANTY; without even the implied warranty of
  17   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  18   Lesser General Public License for more details.
  19
  20   You should have received a copy of the GNU Lesser General Public License
  21   along with systemd; If not, see <http://www.gnu.org/licenses/>.
  22 ***/
  23
  24 #include "macro.h"
  25 #include "siphash24.h"
  26
  27 typedef void (*hash_func_t)(const void *p, struct siphash *state);
  28 typedef int (*compare_func_t)(const void *a, const void *b);
  29
  30 struct hash_ops {
  31         hash_func_t hash;
  32         compare_func_t compare;
  33 };
  34
  35 void string_hash_func(const void *p, struct siphash *state);
  36 int string_compare_func(const void *a, const void *b) _pure_;
  37 extern const struct hash_ops string_hash_ops;
  38
  39 /* This will compare the passed pointers directly, and will not
  40  * dereference them. This is hence not useful for strings or
  41  * suchlike. */
  42 void trivial_hash_func(const void *p, struct siphash *state);
  43 int trivial_compare_func(const void *a, const void *b) _const_;
  44 extern const struct hash_ops trivial_hash_ops;
  45
  46 /* 32bit values we can always just embed in the pointer itself, but
  47  * in order to support 32bit archs we need store 64bit values
  48  * indirectly, since they don't fit in a pointer. */
  49 void uint64_hash_func(const void *p, struct siphash *state);
  50 int uint64_compare_func(const void *a, const void *b) _pure_;
  51 extern const struct hash_ops uint64_hash_ops;
  52
  53 /* On some archs dev_t is 32bit, and on others 64bit. And sometimes
  54  * it's 64bit on 32bit archs, and sometimes 32bit on 64bit archs. Yuck! */
  55 #if SIZEOF_DEV_T != 8
  56 void devt_hash_func(const void *p, struct siphash *state) _pure_;
  57 int devt_compare_func(const void *a, const void *b) _pure_;
  58 extern const struct hash_ops devt_hash_ops = {
  59         .hash = devt_hash_func,
  60         .compare = devt_compare_func
  61 };
  62 #else
  63 #define devt_hash_func uint64_hash_func
  64 #define devt_compare_func uint64_compare_func
  65 #define devt_hash_ops uint64_hash_ops
  66 #endif