hashtable: Make key arguments const

This allows using const strings etc. for lookups without cast. And keys
are not modifiable anyway.

src/libstrongswan/collections/hashtable.h

@@ -31,7 +31,7 @@ typedef struct hashtable_t hashtable_t;
  * @param key			key to hash
  * @return				hash code
  */
-typedef u_int (*hashtable_hash_t)(void *key);
+typedef u_int (*hashtable_hash_t)(const void *key);
 
 /**
  * Hashtable hash function calculation the hash solely based on the key pointer.
@@ -39,7 +39,7 @@ typedef u_int (*hashtable_hash_t)(void *key);
  * @param key			key to hash
  * @return				hash of key
  */
-u_int hashtable_hash_ptr(void *key);
+u_int hashtable_hash_ptr(const void *key);
 
 /**
  * Hashtable hash function calculation the hash for char* keys.
@@ -47,7 +47,7 @@ u_int hashtable_hash_ptr(void *key);
  * @param key			key to hash, a char*
  * @return				hash of key
  */
-u_int hashtable_hash_str(void *key);
+u_int hashtable_hash_str(const void *key);
 
 /**
  * Prototype for a function that compares the two keys for equality.
@@ -56,7 +56,7 @@ u_int hashtable_hash_str(void *key);
  * @param other_key		second key
  * @return				TRUE if the keys are equal
  */
-typedef bool (*hashtable_equals_t)(void *key, void *other_key);
+typedef bool (*hashtable_equals_t)(const void *key, const void *other_key);
 
 /**
  * Hashtable equals function comparing pointers.
@@ -65,7 +65,7 @@ typedef bool (*hashtable_equals_t)(void *key, void *other_key);
  * @param other_key		other key to compare
  * @return				TRUE if key == other_key
  */
-bool hashtable_equals_ptr(void *key, void *other_key);
+bool hashtable_equals_ptr(const void *key, const void *other_key);
 
 /**
  * Hashtable equals function comparing char* keys.
@@ -74,7 +74,7 @@ bool hashtable_equals_ptr(void *key, void *other_key);
  * @param other_key		other key to compare
  * @return				TRUE if streq(key, other_key)
  */
-bool hashtable_equals_str(void *key, void *other_key);
+bool hashtable_equals_str(const void *key, const void *other_key);
 
 /**
  * Class implementing a hash table.
@@ -100,7 +100,7 @@ struct hashtable_t {
 	 * @param value		the value to store
 	 * @return			NULL if no item was replaced, the old value otherwise
 	 */
-	void *(*put) (hashtable_t *this, void *key, void *value);
+	void *(*put) (hashtable_t *this, const void *key, void *value);
 
 	/**
 	 * Returns the value with the given key, if the hash table contains such an
@@ -109,7 +109,7 @@ struct hashtable_t {
 	 * @param key		the key of the requested value
 	 * @return			the value, NULL if not found
 	 */
-	void *(*get) (hashtable_t *this, void *key);
+	void *(*get) (hashtable_t *this, const void *key);
 
 	/**
 	 * Returns the value with a matching key, if the hash table contains such an
@@ -125,7 +125,8 @@ struct hashtable_t {
 	 * @param match		match function to be used when comparing keys
 	 * @return			the value, NULL if not found
 	 */
-	void *(*get_match) (hashtable_t *this, void *key, hashtable_equals_t match);
+	void *(*get_match) (hashtable_t *this, const void *key,
+						hashtable_equals_t match);
 
 	/**
 	 * Removes the value with the given key from the hash table and returns the
@@ -134,7 +135,7 @@ struct hashtable_t {
 	 * @param key		the key of the value to remove
 	 * @return			the removed value, NULL if not found
 	 */
-	void *(*remove) (hashtable_t *this, void *key);
+	void *(*remove) (hashtable_t *this, const void *key);
 
 	/**
 	 * Removes the key and value pair from the hash table at which the given