From: Lennart Poettering <lennart@poettering.net>
Date: Mon, 18 Aug 2014 22:04:46 +0000 (+0200)
Subject: hashmap: try to use the existing 64bit hash functions for dev_t if it is 64bit
X-Git-Tag: v216~40
X-Git-Url: http://www.chiark.greenend.org.uk/ucgi/~ianmdlvl/git?p=elogind.git;a=commitdiff_plain;h=de99c9dcbaf6e474551266d8f0b519bf2d8d0522;ds=inline

hashmap: try to use the existing 64bit hash functions for dev_t if it is 64bit
---

diff --git a/configure.ac b/configure.ac
index d95a34894..83ba33d76 100644
--- a/configure.ac
+++ b/configure.ac
@@ -225,6 +225,7 @@ AC_CHECK_SIZEOF(pid_t)
 AC_CHECK_SIZEOF(uid_t)
 AC_CHECK_SIZEOF(gid_t)
 AC_CHECK_SIZEOF(time_t)
+AC_CHECK_SIZEOF(dev_t)
 AC_CHECK_SIZEOF(rlim_t,,[
        #include <sys/time.h>
        #include <sys/resource.h>
diff --git a/src/login/logind-session.c b/src/login/logind-session.c
index 9d05faf47..136bbce78 100644
--- a/src/login/logind-session.c
+++ b/src/login/logind-session.c
@@ -44,21 +44,6 @@
 
 static void session_remove_fifo(Session *s);
 
-static unsigned long devt_hash_func(const void *p, const uint8_t hash_key[HASH_KEY_SIZE]) {
-        uint64_t u = *(const dev_t*)p;
-
-        return uint64_hash_func(&u, hash_key);
-}
-
-static 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);
-}
-
 Session* session_new(Manager *m, const char *id) {
         Session *s;
 
diff --git a/src/shared/hashmap.c b/src/shared/hashmap.c
index 5c3efa8dd..dbf91c439 100644
--- a/src/shared/hashmap.c
+++ b/src/shared/hashmap.c
@@ -164,6 +164,21 @@ int uint64_compare_func(const void *_a, const void *_b) {
         return a < b ? -1 : (a > b ? 1 : 0);
 }
 
+#if SIZEOF_DEV_T != 8
+unsigned long devt_hash_func(const void *p, const uint8_t hash_key[HASH_KEY_SIZE]) {
+        uint64_t u;
+        siphash24((uint8_t*) &u, p, sizeof(dev_t), hash_key);
+        return (unsigned long) u;
+}
+
+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);
+}
+#endif
+
 static unsigned bucket_hash(Hashmap *h, const void *p) {
         return (unsigned) (h->hash_func(p, h->hash_key) % h->n_buckets);
 }
diff --git a/src/shared/hashmap.h b/src/shared/hashmap.h
index bfad97007..f89e7e8fb 100644
--- a/src/shared/hashmap.h
+++ b/src/shared/hashmap.h
@@ -52,9 +52,23 @@ int string_compare_func(const void *a, const void *b) _pure_;
 unsigned long trivial_hash_func(const void *p, const uint8_t hash_key[HASH_KEY_SIZE]) _pure_;
 int trivial_compare_func(const void *a, const void *b) _const_;
 
+/* 32bit values we can always just embedd in the pointer itself, but
+ * in order to support 32bit archs we need store 64bit values
+ * indirectly, since they don't fit in a pointer. */
 unsigned long uint64_hash_func(const void *p, const uint8_t hash_key[HASH_KEY_SIZE]) _pure_;
 int uint64_compare_func(const void *a, const void *b) _pure_;
 
+/* On some archs dev_t is 32bit, and on others 64bit. And sometimes
+ * it's 64bit on 32bit archs, and sometimes 32bit on 64bit archs. Yuck! */
+#if SIZEOF_DEV_T != 8
+unsigned long devt_hash_func(const void *p, const uint8_t hash_key[HASH_KEY_SIZE]) _pure_;
+int devt_compare_func(const void *a, const void *b) _pure_;
+#else
+/* No need to define a second version of this... */
+#define devt_hash_func uint64_hash_func
+#define devt_compare_func uint64_compare_func
+#endif
+
 Hashmap *hashmap_new(hash_func_t hash_func, compare_func_t compare_func);
 void hashmap_free(Hashmap *h);
 void hashmap_free_free(Hashmap *h);