hash_table.h File Reference

A general purpose hash table. More...

Go to the source code of this file.

Typedefs
typedef unsigned(*	hash_func_t )(const char *key)
	The type signature for a hash function given to hash_table_create. More...

Functions
struct hash_table *	hash_table_create (int buckets, hash_func_t func)
	Create a new hash table. More...
void	hash_table_clear (struct hash_table *h)
	Remove all entries from an hash table. More...
void	hash_table_delete (struct hash_table *h)
	Delete a hash table. More...
int	hash_table_size (struct hash_table *h)
	Count the entries in a hash table. More...
int	hash_table_insert (struct hash_table *h, const char *key, const void *value)
	Insert a key and value. More...
void *	hash_table_lookup (struct hash_table *h, const char *key)
	Look up a value by key. More...
void *	hash_table_remove (struct hash_table *h, const char *key)
	Remove a value by key. More...
void	hash_table_firstkey (struct hash_table *h)
	Begin iteration over all keys. More...
int	hash_table_nextkey (struct hash_table *h, char **key, void **value)
	Continue iteration over all keys. More...
unsigned	hash_string (const char *s)
	A default hash function. More...

Detailed Description

A general purpose hash table.

This hash table module maps C strings to arbitrary objects (void pointers). For example, to store a file object using the pathname as a key:

struct hash_table *h;
h = hash_table_create(0,0);

FILE * file = fopen(pathname,"r");

hash_table_insert(h,pathname,file);
file = hash_table_remove(h,pathname);

To list all of the items in a hash table, use hash_table_firstkey and hash_table_nextkey like this:

char *key;
void *value;

hash_table_firstkey(h);

while(hash_table_nextkey(h,&key,&value)) {
        printf("table contains: %s\n",key);
}

Typedef Documentation

typedef unsigned(* hash_func_t)(const char *key)

The type signature for a hash function given to hash_table_create.

Function Documentation

struct hash_table* hash_table_create	(	int	buckets,
		hash_func_t	func
	)

Create a new hash table.

Parameters

buckets	The number of buckets in the table. If zero, a default value will be used.
func	The default hash function to be used. If zero, hash_string will be used.

Returns

A pointer to a new hash table.

void hash_table_clear

(

struct hash_table *

h

)

Remove all entries from an hash table.

Note that this function will not delete all of the objects contained within the hash table.

Parameters

h	The hash table to delete.

void hash_table_delete

(

struct hash_table *

h

)

Delete a hash table.

Note that this function will not delete all of the objects contained within the hash table.

Parameters

h	The hash table to delete.

int hash_table_size

(

struct hash_table *

h

)

Count the entries in a hash table.

Returns

The number of entries in the table.

Parameters

h	A pointer to a hash table.

int hash_table_insert	(	struct hash_table *	h,
		const char *	key,
		const void *	value
	)

Insert a key and value.

This call will fail if the table already contains the same key. You must call hash_table_remove to remove it. Also note that you cannot insert a null value into the table.

Parameters

h	A pointer to a hash table.
key	A pointer to a string key which will be hashed and duplicated.
value	A pointer to store with the key.

Returns

One if the insert succeeded, failure otherwise

void* hash_table_lookup	(	struct hash_table *	h,
		const char *	key
	)

Look up a value by key.

Parameters

h	A pointer to a hash table.
key	A string key to search for.

Returns

If found, the pointer associated with the key, otherwise null.

void* hash_table_remove	(	struct hash_table *	h,
		const char *	key
	)

Remove a value by key.

Parameters

h	A pointer to a hash table.
key	A string key to remove.

Returns

If found, the pointer associated with the key, otherwise null.

void hash_table_firstkey

(

struct hash_table *

h

)

Begin iteration over all keys.

This function begins a new iteration over a hash table, allowing you to visit every key and value in the table. Next, invoke hash_table_nextkey to retrieve each value in order.

Parameters

h	A pointer to a hash table.

int hash_table_nextkey	(	struct hash_table *	h,
		char **	key,
		void **	value
	)

Continue iteration over all keys.

This function returns the next key and value in the iteration.

Parameters

h	A pointer to a hash table.
key	A pointer to a key pointer.
value	A pointer to a value pointer.

Returns

Zero if there are no more elements to visit, one otherwise.

unsigned hash_string

(

const char *

s

)

A default hash function.

Parameters

s	A string to hash.

Returns

An integer hash of the string.