tools/xenstored: hashtable: Constify the parameters of hashfn/eqfn

The parameters of hashfn/eqfn should never be modified. So constify
them and propagate the const to the users.

Take the opportunity to solve some coding style issues around the
code modified.

Signed-off-by: Julien Grall <jgrall@amazon.com>
Reviewed-by: Henry Wang <Henry.Wang@arm.com>
Tested-by: Henry Wang <Henry.Wang@arm.com>
Reviewed-by: Juergen Gross <jgross@suse.com>

tools/xenstore/hashtable.c

@@ -23,8 +23,8 @@ struct hashtable {
     unsigned int entrycount;
     unsigned int loadlimit;
     unsigned int primeindex;
-    unsigned int (*hashfn) (void *k);
-    int (*eqfn) (void *k1, void *k2);
+    unsigned int (*hashfn) (const void *k);
+    int (*eqfn) (const void *k1, const void *k2);
 };
 
 /*
@@ -53,8 +53,8 @@ indexFor(unsigned int tablelength, unsigned int hashvalue) {
 /*****************************************************************************/
 struct hashtable *
 create_hashtable(const void *ctx, unsigned int minsize,
-                 unsigned int (*hashf) (void*),
-                 int (*eqf) (void*,void*),
+                 unsigned int (*hashf) (const void *),
+                 int (*eqf) (const void *, const void *),
                  unsigned int flags)
 {
     struct hashtable *h;
@@ -92,7 +92,7 @@ err0:
 
 /*****************************************************************************/
 unsigned int
-hash(struct hashtable *h, void *k)
+hash(const struct hashtable *h, const void *k)
 {
     /* Aim to protect against poor hash functions by adding logic here
      * - logic taken from java 1.4 hashtable source */
@@ -151,7 +151,7 @@ hashtable_expand(struct hashtable *h)
 
 /*****************************************************************************/
 unsigned int
-hashtable_count(struct hashtable *h)
+hashtable_count(const struct hashtable *h)
 {
     return h->entrycount;
 }
@@ -188,7 +188,7 @@ hashtable_insert(struct hashtable *h, void *k, void *v)
 
 /*****************************************************************************/
 void * /* returns value associated with key */
-hashtable_search(struct hashtable *h, void *k)
+hashtable_search(const struct hashtable *h, const void *k)
 {
     struct entry *e;
     unsigned int hashvalue, index;
@@ -206,7 +206,7 @@ hashtable_search(struct hashtable *h, void *k)
 
 /*****************************************************************************/
 void
-hashtable_remove(struct hashtable *h, void *k)
+hashtable_remove(struct hashtable *h, const void *k)
 {
     /* TODO: consider compacting the table when the load factor drops enough,
      *       or provide a 'compact' method. */

tools/xenstore/hashtable.h

@@ -24,8 +24,8 @@ struct hashtable;
 
 struct hashtable *
 create_hashtable(const void *ctx, unsigned int minsize,
-                 unsigned int (*hashfunction) (void*),
-                 int (*key_eq_fn) (void*,void*),
+                 unsigned int (*hashfunction) (const void *),
+                 int (*key_eq_fn) (const void *, const void *),
                  unsigned int flags
 );
 
@@ -61,7 +61,7 @@ hashtable_insert(struct hashtable *h, void *k, void *v);
  */
 
 void *
-hashtable_search(struct hashtable *h, void *k);
+hashtable_search(const struct hashtable *h, const void *k);
 
 /*****************************************************************************
  * hashtable_remove
@@ -72,7 +72,7 @@ hashtable_search(struct hashtable *h, void *k);
  */
 
 void
-hashtable_remove(struct hashtable *h, void *k);
+hashtable_remove(struct hashtable *h, const void *k);
 
 /*****************************************************************************
  * hashtable_count
@@ -82,7 +82,7 @@ hashtable_remove(struct hashtable *h, void *k);
  * @return      the number of items stored in the hashtable
  */
 unsigned int
-hashtable_count(struct hashtable *h);
+hashtable_count(const struct hashtable *h);
 
 /*****************************************************************************
  * hashtable_iterate

tools/xenstore/xenstored_core.c

@@ -2386,9 +2386,9 @@ void setup_structure(bool live_update)
 	}
 }
 
-static unsigned int hash_from_key_fn(void *k)
+static unsigned int hash_from_key_fn(const void *k)
 {
-	char *str = k;
+	const char *str = k;
 	unsigned int hash = 5381;
 	char c;
 
@@ -2399,9 +2399,9 @@ static unsigned int hash_from_key_fn(void *k)
 }
 
 
-static int keys_equal_fn(void *key1, void *key2)
+static int keys_equal_fn(const void *key1, const void *key2)
 {
-	return 0 == strcmp((char *)key1, (char *)key2);
+	return 0 == strcmp(key1, key2);
 }
 
 int remember_string(struct hashtable *hash, const char *str)

tools/xenstore/xenstored_domain.c

@@ -916,14 +916,14 @@ void dom0_init(void)
 	xenevtchn_notify(xce_handle, dom0->port);
 }
 
-static unsigned int domhash_fn(void *k)
+static unsigned int domhash_fn(const void *k)
 {
-	return *(unsigned int *)k;
+	return *(const unsigned int *)k;
 }
 
-static int domeq_fn(void *key1, void *key2)
+static int domeq_fn(const void *key1, const void *key2)
 {
-	return *(unsigned int *)key1 == *(unsigned int *)key2;
+	return *(const unsigned int *)key1 == *(const unsigned int *)key2;
 }
 
 void domain_init(int evtfd)