basic: split hash functions into their own header files

The hash operations are not really that specific to hashmaps, hence split them into a .c module of their own.

src/basic/hash-funcs.c

@@ -0,0 +1,83 @@
+/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
+
+/***
+  This file is part of systemd.
+
+  Copyright 2010 Lennart Poettering
+  Copyright 2014 Michal Schmidt
+
+  systemd is free software; you can redistribute it and/or modify it
+  under the terms of the GNU Lesser General Public License as published by
+  the Free Software Foundation; either version 2.1 of the License, or
+  (at your option) any later version.
+
+  systemd is distributed in the hope that it will be useful, but
+  WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+  Lesser General Public License for more details.
+
+  You should have received a copy of the GNU Lesser General Public License
+  along with systemd; If not, see <http://www.gnu.org/licenses/>.
+***/
+
+#include "hash-funcs.h"
+
+void string_hash_func(const void *p, struct siphash *state) {
+        siphash24_compress(p, strlen(p) + 1, state);
+}
+
+int string_compare_func(const void *a, const void *b) {
+        return strcmp(a, b);
+}
+
+const struct hash_ops string_hash_ops = {
+        .hash = string_hash_func,
+        .compare = string_compare_func
+};
+
+void trivial_hash_func(const void *p, struct siphash *state) {
+        siphash24_compress(&p, sizeof(p), state);
+}
+
+int trivial_compare_func(const void *a, const void *b) {
+        return a < b ? -1 : (a > b ? 1 : 0);
+}
+
+const struct hash_ops trivial_hash_ops = {
+        .hash = trivial_hash_func,
+        .compare = trivial_compare_func
+};
+
+void uint64_hash_func(const void *p, struct siphash *state) {
+        siphash24_compress(p, sizeof(uint64_t), state);
+}
+
+int uint64_compare_func(const void *_a, const void *_b) {
+        uint64_t a, b;
+        a = *(const uint64_t*) _a;
+        b = *(const uint64_t*) _b;
+        return a < b ? -1 : (a > b ? 1 : 0);
+}
+
+const struct hash_ops uint64_hash_ops = {
+        .hash = uint64_hash_func,
+        .compare = uint64_compare_func
+};
+
+#if SIZEOF_DEV_T != 8
+void devt_hash_func(const void *p, struct siphash *state) {
+        siphash24_compress(p, sizeof(dev_t), state);
+}
+
+int devt_compare_func(const void *_a, const void *_b) {
+        dev_t a, b;
+        a = *(const dev_t*) _a;
+        b = *(const dev_t*) _b;
+        return a < b ? -1 : (a > b ? 1 : 0);
+}
+
+const struct hash_ops devt_hash_ops = {
+        .hash = devt_hash_func,
+        .compare = devt_compare_func
+};
+#endif