--- /dev/null
+#include "nitfol.h"
+
+
+/* Modified and bugfixed for nitfol by Evin Robertson Sept 10, 1999 */
+
+
+/*
+** public domain code by Jerry Coffin, with improvements by HenkJan Wolthuis.
+**
+** Tested with Visual C 1.0 and Borland C 3.1.
+** Compiles without warnings, and seems like it should be pretty
+** portable.
+*/
+
+
+#ifdef HEADER
+/*
+** A hash table consists of an array of these buckets. Each bucket
+** holds a copy of the key, a pointer to the data associated with the
+** key, and a pointer to the next bucket that collided with this one,
+** if there was one.
+*/
+
+typedef struct bucket {
+ char *key;
+ void *data;
+ struct bucket *next;
+} bucket;
+
+/*
+** This is what you actually declare an instance of to create a table.
+** You then call 'construct_table' with the address of this structure,
+** and a guess at the size of the table. Note that more nodes than this
+** can be inserted in the table, but performance degrades as this
+** happens. Performance should still be quite adequate until 2 or 3
+** times as many nodes have been inserted as the table was created with.
+*/
+
+typedef struct hash_table {
+ size_t size;
+ bucket **table;
+} hash_table;
+#endif
+
+
+/*
+** These are used in freeing a table. Perhaps I should code up
+** something a little less grungy, but it works, so what the heck.
+*/
+typedef void (*my_function)(void *);
+static my_function function = NULL;
+static hash_table *the_table = NULL;
+
+/* Initialize the hash_table to the size asked for. Allocates space
+** for the correct number of pointers and sets them to NULL. If it
+** can't allocate sufficient memory, signals error by setting the size
+** of the table to 0.
+*/
+
+hash_table *n_hash_construct_table(hash_table *table, size_t size)
+{
+ size_t i;
+ bucket **temp;
+
+ table -> size = size;
+ table -> table = (bucket * *)n_malloc(sizeof(bucket *) * size);
+ temp = table -> table;
+
+ if ( temp == NULL )
+ {
+ table -> size = 0;
+ return table;
+ }
+
+ for (i=0;i<size;i++)
+ temp[i] = NULL;
+ return table;
+}
+
+
+/*
+** Hashes a string to produce an unsigned short, which should be
+** sufficient for most purposes.
+*/
+
+static unsigned hash(const char *string)
+{
+ unsigned ret_val = 0;
+ int i;
+
+ while (*string)
+ {
+ /* Modified by ecr to fix bug and improve method slightly */
+ ret_val <<= 1;
+ i = string[0] + (string[1] << 8);
+ ret_val ^= i;
+ string ++;
+ }
+ return ret_val;
+}
+
+/*
+** Insert 'key' into hash table.
+** Returns pointer to old data associated with the key, if any, or
+** NULL if the key wasn't in the table previously.
+*/
+
+void *n_hash_insert(const char *key, void *data, hash_table *table)
+{
+ unsigned val = hash(key) % table->size;
+ bucket *ptr;
+
+ /*
+ ** NULL means this bucket hasn't been used yet. We'll simply
+ ** allocate space for our new bucket and put our data there, with
+ ** the table pointing at it.
+ */
+
+ if (NULL == (table->table)[val])
+ {
+ (table->table)[val] = (bucket *)n_malloc(sizeof(bucket));
+ if (NULL==(table->table)[val])
+ return NULL;
+
+ (table->table)[val] -> key = n_strdup(key);
+ (table->table)[val] -> next = NULL;
+ (table->table)[val] -> data = data;
+ return (table->table)[val] -> data;
+ }
+
+ /*
+ ** This spot in the table is already in use. See if the current string
+ ** has already been inserted, and if so, increment its count.
+ */
+
+ for (ptr = (table->table)[val];NULL != ptr; ptr = ptr -> next)
+ if (0 == n_strcmp(key, ptr->key))
+ {
+ void *old_data;
+
+ old_data = ptr->data;
+ ptr -> data = data;
+ return old_data;
+ }
+
+ /*
+ ** This key must not be in the table yet. We'll add it to the head of
+ ** the list at this spot in the hash table. Speed would be
+ ** slightly improved if the list was kept sorted instead. In this case,
+ ** this code would be moved into the loop above, and the insertion would
+ ** take place as soon as it was determined that the present key in the
+ ** list was larger than this one.
+ */
+
+ ptr = (bucket *)n_malloc(sizeof(bucket));
+ if (NULL==ptr)
+ return 0;
+ ptr -> key = n_strdup(key);
+ ptr -> data = data;
+ ptr -> next = (table->table)[val];
+ (table->table)[val] = ptr;
+ return data;
+}
+
+
+/*
+** Look up a key and return the associated data. Returns NULL if
+** the key is not in the table.
+*/
+
+void *n_hash_lookup(const char *key, hash_table *table)
+{
+ unsigned val = hash(key) % table->size;
+ bucket *ptr;
+
+ if (NULL == (table->table)[val])
+ return NULL;
+
+ for ( ptr = (table->table)[val];NULL != ptr; ptr = ptr->next )
+ {
+ if (0 == n_strcmp(key, ptr -> key ) )
+ return ptr->data;
+ }
+ return NULL;
+}
+
+/*
+** Delete a key from the hash table and return associated
+** data, or NULL if not present.
+*/
+
+void *n_hash_del(const char *key, hash_table *table)
+{
+ unsigned val = hash(key) % table->size;
+ void *data;
+ bucket *ptr, *last = NULL;
+
+ if (NULL == (table->table)[val])
+ return NULL;
+
+ /*
+ ** Traverse the list, keeping track of the previous node in the list.
+ ** When we find the node to delete, we set the previous node's next
+ ** pointer to point to the node after ourself instead. We then delete
+ ** the key from the present node, and return a pointer to the data it
+ ** contains.
+ */
+
+ for (last = NULL, ptr = (table->table)[val];
+ NULL != ptr;
+ last = ptr, ptr = ptr->next)
+ {
+ if (0 == n_strcmp(key, ptr -> key))
+ {
+ if (last != NULL )
+ {
+ data = ptr -> data;
+ last -> next = ptr -> next;
+ n_free(ptr->key);
+ n_free(ptr);
+ return data;
+ }
+
+ /*
+ ** If 'last' still equals NULL, it means that we need to
+ ** delete the first node in the list. This simply consists
+ ** of putting our own 'next' pointer in the array holding
+ ** the head of the list. We then dispose of the current
+ ** node as above.
+ */
+
+ else
+ {
+ data = ptr->data;
+ (table->table)[val] = ptr->next;
+ n_free(ptr->key);
+ n_free(ptr);
+ return data;
+ }
+ }
+ }
+
+ /*
+ ** If we get here, it means we didn't find the item in the table.
+ ** Signal this by returning NULL.
+ */
+
+ return NULL;
+}
+
+/*
+** free_table iterates the table, calling this repeatedly to free
+** each individual node. This, in turn, calls one or two other
+** functions - one to free the storage used for the key, the other
+** passes a pointer to the data back to a function defined by the user,
+** process the data as needed.
+*/
+
+static void free_node(const char *key, void *data)
+{
+ (void) data;
+
+ if (function)
+ function(n_hash_del(key,the_table));
+ else n_hash_del(key,the_table);
+}
+
+/*
+** Frees a complete table by iterating over it and freeing each node.
+** the second parameter is the address of a function it will call with a
+** pointer to the data associated with each node. This function is
+** responsible for freeing the data, or doing whatever is needed with
+** it.
+*/
+
+void n_hash_free_table(hash_table *table, void (*func)(void *))
+{
+ function = func;
+ the_table = table;
+
+ n_hash_enumerate( table, free_node);
+ n_free(table->table);
+ table->table = NULL;
+ table->size = 0;
+
+ the_table = NULL;
+ function = (void (*)(void *))NULL;
+}
+
+/*
+** Simply invokes the function given as the second parameter for each
+** node in the table, passing it the key and the associated data.
+*/
+
+void n_hash_enumerate( hash_table *table, void (*func)(const char *, void *))
+{
+ unsigned i;
+ bucket *temp, *next;
+
+ for (i=0; i < table->size; i++)
+ {
+ for (temp = (table->table)[i]; temp; temp=next)
+ {
+ next = temp->next; /* ecr - temp may be deleted by func */
+ func(temp->key, temp->data);
+ }
+ }
+}
projects / rodin / chimara.git / blobdiff