Make as many variables const as possible.

include/ht.h

@@ -45,21 +45,21 @@ struct ht_s {
    * @param input the data being hashed.
    * @return the data's hash.
    */
-  unsigned long (*hash_func)(void* input);
+  unsigned long (*hash_func)(const void* input);
   /**
    * Function to compare two keys.
    * @param given_key the key being used to retrieve data
    * @param current_key the key of a hash table node
    * @return nonzero value if the keys match.
    */
-  int (*cmp_func)(void* given_key, void* current_key);
+  int (*cmp_func)(const void* given_key, const void* current_key);
   /**
    * Function used to duplicate the given key and
    * store it in a node.
    * @param key the key to copy
    * @return pointer to a new key.
    */
-  void* (*copy_func)(void* key);
+  void* (*copy_func)(const void* key);
   /**
    * Function used to free a previously copied key.
    * @param key the key to free.
@@ -76,7 +76,7 @@ typedef struct ht_s ht;
  * @param key the data to hash.
  * @return the produced hashed integer.
  */
-unsigned long ht_default_hash_func(void* key);
+unsigned long ht_default_hash_func(const void* key);
 /**
  * The default key comparison function.
  * Assumes both keys are strings and uses strcmp.
@@ -84,13 +84,13 @@ unsigned long ht_default_hash_func(void* key);
  * @param b the key compared against
  * @return true if the keys represent the same string.
  */
-int ht_default_cmp_func(void* a, void* b);
+int ht_default_cmp_func(const void* a, const void* b);
 /**
  * The default key copy function.
  * @param key the key being copied
  * @return a pointer to the copy of the key.
  */
-void* ht_default_copy_func(void* key);
+void* ht_default_copy_func(const void* key);
 /**
  * The default key free function. Simply calls free()
  * @param key the key to free.
@@ -117,20 +117,20 @@ void ht_free(ht* ht);
  * @param value the value to store.
  * @return LIBDS_SUCCESS if all goes well, LIBDS_MALLOC if an allocation fails.
  */
-libds_result ht_put(ht* ht, void* key, void* value);
+libds_result ht_put(ht* ht, const void* key, void* value);
 /**
  * Retrieves a value from the hash table.
  * @param ht the hash table to retrieve a value from.
  * @param key the key to use to find the data.
  * @return the data, or NULL if it is not found.
  */
-void* ht_get(ht* ht, void* key);
+void* ht_get(ht* ht, const void* key);
 /**
  * Removes a value from the hash table.
  * @param ht the hash table to remove a value from.
  * @param key the key to use to find the data.
  */
-void ht_remove(ht* ht, void* key);
+void ht_remove(ht* ht, const void* key);
 
 /**
  * Runs through every element in the hash table, and compares it against the

include/libds.h

@@ -15,7 +15,7 @@ typedef enum libds_result_e libds_result;
  * The function should take two elements, and, if they match, return 1. Otherwise, it should
  * return 0.
  */
-typedef int (*compare_func)(void*, void*);
+typedef int (*compare_func)(const void*, const void*);
 /**
  * Foreach function type.
  * Foreach functions are passed to _foreach calls.
@@ -29,13 +29,13 @@ typedef int (*foreach_func)(void*, va_list);
  * @param b The second piece of data being compared
  * @return always true, i.e 1
  */
-int compare_always(void* a, void* b);
+int compare_always(const void* a, const void* b);
 /**
  * A compare_func implementation that compares two pointers using ==.
  * @param a the first piece of data being compared
  * @param b the second piece of data being compared
  * @return true if a and b are the same value.
  */
-int compare_pointer(void* a, void* b);
+int compare_pointer(const void* a, const void* b);
 
 #endif