46e16b347f
This is similar to string_hash_ops but operates one file system paths specifically. It will ensure that "/foo//bar" and "///foo/bar" are considered to be the same path for hashmap purposes. This makes use of the existing path_compare() API, and adds a matching hashing function for it. Note that relative and absolute paths will hash to different values, however whether the path is suffixed with a slash or not is not detected. This matches the existing path_compare() behaviour, and follows the logic that on Linux there can't be two different objects at path /foo/bar and /foo/bar/ either.
135 lines
4.1 KiB
C
135 lines
4.1 KiB
C
/* SPDX-License-Identifier: LGPL-2.1+ */
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/***
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This file is part of systemd.
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Copyright 2010 Lennart Poettering
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Copyright 2014 Michal Schmidt
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systemd is free software; you can redistribute it and/or modify it
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under the terms of the GNU Lesser General Public License as published by
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the Free Software Foundation; either version 2.1 of the License, or
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(at your option) any later version.
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systemd is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with systemd; If not, see <http://www.gnu.org/licenses/>.
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***/
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#include <string.h>
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#include "hash-funcs.h"
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#include "path-util.h"
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void string_hash_func(const void *p, struct siphash *state) {
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siphash24_compress(p, strlen(p) + 1, state);
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}
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int string_compare_func(const void *a, const void *b) {
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return strcmp(a, b);
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}
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const struct hash_ops string_hash_ops = {
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.hash = string_hash_func,
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.compare = string_compare_func
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};
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void path_hash_func(const void *p, struct siphash *state) {
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const char *q = p;
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size_t n;
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assert(q);
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assert(state);
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/* Calculates a hash for a path in a way this duplicate inner slashes don't make a differences, and also
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* whether there's a trailing slash or not. This fits well with the semantics of path_compare(), which does
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* similar checks and also doesn't care for trailing slashes. Note that relative and absolute paths (i.e. those
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* which begin in a slash or not) will hash differently though. */
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n = strspn(q, "/");
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if (n > 0) { /* Eat up initial slashes, and add one "/" to the hash for all of them */
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siphash24_compress(q, 1, state);
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q += n;
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}
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for (;;) {
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/* Determine length of next component */
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n = strcspn(q, "/");
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if (n == 0) /* Reached the end? */
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break;
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/* Add this component to the hash and skip over it */
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siphash24_compress(q, n, state);
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q += n;
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/* How many slashes follow this component? */
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n = strspn(q, "/");
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if (q[n] == 0) /* Is this a trailing slash? If so, we are at the end, and don't care about the slashes anymore */
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break;
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/* We are not add the end yet. Hash exactly one slash for all of the ones we just encountered. */
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siphash24_compress(q, 1, state);
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q += n;
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}
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}
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int path_compare_func(const void *a, const void *b) {
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return path_compare(a, b);
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}
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const struct hash_ops path_hash_ops = {
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.hash = path_hash_func,
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.compare = path_compare_func
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};
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void trivial_hash_func(const void *p, struct siphash *state) {
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siphash24_compress(&p, sizeof(p), state);
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}
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int trivial_compare_func(const void *a, const void *b) {
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return a < b ? -1 : (a > b ? 1 : 0);
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}
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const struct hash_ops trivial_hash_ops = {
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.hash = trivial_hash_func,
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.compare = trivial_compare_func
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};
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void uint64_hash_func(const void *p, struct siphash *state) {
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siphash24_compress(p, sizeof(uint64_t), state);
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}
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int uint64_compare_func(const void *_a, const void *_b) {
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uint64_t a, b;
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a = *(const uint64_t*) _a;
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b = *(const uint64_t*) _b;
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return a < b ? -1 : (a > b ? 1 : 0);
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}
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const struct hash_ops uint64_hash_ops = {
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.hash = uint64_hash_func,
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.compare = uint64_compare_func
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};
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#if SIZEOF_DEV_T != 8
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void devt_hash_func(const void *p, struct siphash *state) {
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siphash24_compress(p, sizeof(dev_t), state);
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}
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int devt_compare_func(const void *_a, const void *_b) {
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dev_t a, b;
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a = *(const dev_t*) _a;
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b = *(const dev_t*) _b;
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return a < b ? -1 : (a > b ? 1 : 0);
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}
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const struct hash_ops devt_hash_ops = {
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.hash = devt_hash_func,
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.compare = devt_compare_func
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};
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#endif
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