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HASH(3)			     C Programmer's Manual		       HASH(3)

NAME
       hash_create,  hash_destroy,  hash_install, hash_lookup, hash_uninstall,
       hash_iter - generic hash	tables

SYNOPSIS
       #include	<publib.h>

       Hashtab *hash_create(unsigned long (*fun)(void *),
		int (*cmp)(const void *, const void *));
       void hash_destroy(Hashtab *ht);
       void *hash_install(Hashtab *ht, void *data, size_t size);
       void *hash_lookup(Hashtab *ht, void *data);
       int hash_uninstall(Hashtab *ht, void *data);
       int hash_iter(Hashtab *ht, int (*doit)(void *, void *), void *param);

DESCRIPTION
       These functions implement generic hash tables.  The table is created by
       hash_create  and	 destroyed  by	hash_destroy.	The  fun argument is a
       pointer to the hashing function,	which must convert a datum to  an  un-
       signed  long,  which is then converted to an index into the hashing ta-
       ble.  cmp is a qsort(3)-like comparison functions, used to  compare  to
       (wannabe) hash table elements.

       hash_install  installs  a  new  datum into the table.  A	pointer	to the
       data and	the size of the	data are given as the arguments.  If the  size
       is  0, only the pointer value is	copied to the table.  Otherwise	a copy
       of the data is made into	dynamically allocated memory.

       hash_lookup attempts to find a datum in the hash	table.	A  pointer  to
       another datum is	given as the argument.	The comparison function	should
       compare equal (return 0)	the desired datum and this datum (but the  ar-
       gument needn't be a fully initialized datum, although that is up	to the
       writer of the comparison	function).  There cannot be  two  elements  in
       the  hash  table	 that are equal	(the comparison	function returns 0 for
       them).  It is up	to the user to handle collisions.

       hash_uninstall removes an element from a	 table.	  The  argument	 is  a
       pointer to a datum that identifies the element.

       hash_iter  goes	through	 every element in the hash table and calls the
       doit function for each.	The first argument it provides to doit is  the
       element	in  question, the second is whatever was given to hash_iter as
       param.  If doit returns -1 or 0 for any	element	 in  the  hash	table,
       hash_iter  immediately returns without going through the	remaining ele-
       ments in	the hash table.	 Any other return value	from doit is ignored.

RETURNS
       hash_create returns a pointer to	the new	hash  table,  or  NULL	if  it
       fails.

       hash_install  returns  a	pointer	to an element in the table (either the
       installed one, or one that was already installed, if one	tries  to  in-
       stall the same datum twice).

       hash_uninstall returns 0	if it found the	element	in the array, or -1 if
       it didn't.

       hash_lookup return a pointer to the element it finds,  or  NULL	if  it
       doesn't find anything beautiful.

       hash_iter returns -1, 0,	or 1.  If hash_iter receives a return value of
       -1 or 0 for some	element	from doit, hash_iter immediately returns -1 or
       0, respectively.	 In all	other cases hash_iter returns 1.

SEE ALSO
       publib(3), qsort(3), bsearch(3)

AUTHOR
       Lars Wirzenius (lars.wirzenius@helsinki.fi)

Publib			     C Programmer's Manual		       HASH(3)

NAME | SYNOPSIS | DESCRIPTION | RETURNS | SEE ALSO | AUTHOR

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