hashtable: update documentation

Some of the existing documentation was incorrect or insufficient. Also,
add new documentation to describe the design "feature" of this table:
that 0/NULL is not a valid key.

diff --git a/hashtable.h b/hashtable.h
index 71b05cea015d939d7b2b039c4cea8f81afec8170..2802eabead5af4f48ec49196a21ad34edfe1fa1a 100644 (file)
--- a/hashtable.h
+++ b/hashtable.h
@@ -2,8 +2,8 @@
  *  @brief Hashtable.  Standard chained bucket variety.
  */
 
-#ifndef HASHTABLE_H
-#define HASHTABLE_H
+#ifndef __HASHTABLE_H__
+#define __HASHTABLE_H__
 
 #include <stdlib.h>
 #include <stdio.h>
@@ -12,22 +12,12 @@
 #include "common.h"
 
 /**
- * @brief HashTable linked node class, for chained storage of hash table conflicts
- *
- * By default it is snapshotting, but you can pass in your own allocation
- * functions.
+ * @brief HashTable node
  *
  * @tparam _Key    Type name for the key
  * @tparam _Val    Type name for the values to be stored
- * @tparam _malloc Provide your own 'malloc' for the table, or default to
- *                 snapshotting.
- * @tparam _calloc Provide your own 'calloc' for the table, or default to
- *                 snapshotting.
- * @tparam _free   Provide your own 'free' for the table, or default to
- *                 snapshotting.
  */
 template<typename _Key, typename _Val>
-
 struct hashlistnode {
        _Key key;
        _Val val;
@@ -37,8 +27,9 @@ struct hashlistnode {
  * @brief A simple, custom hash table
  *
  * By default it is snapshotting, but you can pass in your own allocation
- * functions. Note that this table does not support 0 (NULL) keys and is
- * designed primarily with pointer-based keys in mind.
+ * functions. Note that this table does not support the value 0 (NULL) used as
+ * a key and is designed primarily with pointer-based keys in mind. Other
+ * primitive key types are supported only for non-zero values.
  *
  * @tparam _Key    Type name for the key
  * @tparam _Val    Type name for the values to be stored
@@ -53,10 +44,10 @@ struct hashlistnode {
  *                 snapshotting.
  */
 template<typename _Key, typename _Val, typename _KeyInt, int _Shift = 0, void * (* _malloc)(size_t) = snapshot_malloc, void * (* _calloc)(size_t, size_t) = snapshot_calloc, void (*_free)(void *) = snapshot_free>
-       class HashTable {
+class HashTable {
  public:
        /**
-        * Constructor
+        * @brief Hash table constructor
         * @param initialcapacity Sets the initial capacity of the hash table.
         * Default size 1024.
         * @param factor Sets the percentage full before the hashtable is
@@ -73,7 +64,7 @@ template<typename _Key, typename _Val, typename _KeyInt, int _Shift = 0, void *
                size = 0; // Initial number of elements in the hash
        }
 
-       /** Destructor */
+       /** @brief Hash table destructor */
        ~HashTable() {
                _free(table);
        }
@@ -98,13 +89,17 @@ template<typename _Key, typename _Val, typename _KeyInt, int _Shift = 0, void *
                _free(p);
        }
 
-       /** Reset the table to its initial state. */
+       /** @brief Reset the table to its initial state. */
        void reset() {
                memset(table, 0, capacity * sizeof(struct hashlistnode<_Key, _Val>));
                size = 0;
        }
 
-       /** Put a key value pair into the table. */
+       /**
+        * @brief Put a key/value pair into the table
+        * @param key The key for the new value; must not be 0 or NULL
+        * @param val The value to store in the table
+        */
        void put(_Key key, _Val val) {
                /* HashTable cannot handle 0 as a key */
                ASSERT(key);
@@ -130,7 +125,11 @@ template<typename _Key, typename _Val, typename _KeyInt, int _Shift = 0, void *
                size++;
        }
 
-       /** Lookup the corresponding value for the given key. */
+       /**
+        * @brief Lookup the corresponding value for the given key
+        * @param key The key for finding the value; must not be 0 or NULL
+        * @return The value in the table, if the key is found; otherwise 0
+        */
        _Val get(_Key key) const {
                struct hashlistnode<_Key, _Val> *search;
 
@@ -148,7 +147,11 @@ template<typename _Key, typename _Val, typename _KeyInt, int _Shift = 0, void *
                return (_Val)0;
        }
 
-       /** Check whether the table contains a value for the given key. */
+       /**
+        * @brief Check whether the table contains a value for the given key
+        * @param key The key for finding the value; must not be 0 or NULL
+        * @return True, if the key is found; false otherwise
+        */
        bool contains(_Key key) const {
                struct hashlistnode<_Key, _Val> *search;
 
@@ -166,7 +169,10 @@ template<typename _Key, typename _Val, typename _KeyInt, int _Shift = 0, void *
                return false;
        }
 
-       /** Resize the table. */
+       /**
+        * @brief Resize the table
+        * @param newsize The new size of the table
+        */
        void resize(unsigned int newsize) {
                struct hashlistnode<_Key, _Val> *oldtable = table;
                struct hashlistnode<_Key, _Val> *newtable;
@@ -212,4 +218,5 @@ template<typename _Key, typename _Val, typename _KeyInt, int _Shift = 0, void *
        unsigned int threshold;
        double loadfactor;
 };
-#endif
+
+#endif /* __HASHTABLE_H__ */