hash_lookup(3pub) [debian man page]

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

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 unsigned 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 argument 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 elements 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
       install 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(3pub)

Check Out this Related Man Page

lsearch(3C)															       lsearch(3C)

NAME

       lsearch(), lfind() - linear search and update

SYNOPSIS

DESCRIPTION

       is a linear search routine generalized from Knuth (6.1) Algorithm S.
		      It  returns  a  pointer into a table indicating where a datum may be found.  If the datum does not occur, it is added at the
		      end of the table.

			   key		  Points to the datum to be sought in the table.

			   base 	  Points to the first element in the table.

			   nelp 	  Points to an integer containing the current number of elements in the table.	The integer is incremented
					  if the datum is added to the table.

			   compar	  Name	of  the  comparison function which the user must supply for example).  It is called with two argu-
					  ments that point to the elements being compared.  The function must return  zero  if	the  elements  are
					  equal and non-zero otherwise.

       Same as	      except that if the datum is not found, it is not added to the table.  Instead, a NULL pointer is returned.

   Notes
       The  pointers to the key and the element at the base of the table should be of type pointer-to-element, and cast to type pointer-to-charac-
       ter.

       The comparison function need not compare every byte, so arbitrary data may be contained in the elements in addition  to	the  values  being
       compared.

       Although declared as type pointer-to-character, the value returned should be cast into type pointer-to-element.

EXAMPLES

       This code fragment reads in <= strings of length <= and stores them in a table, eliminating duplicates.

		    ...
		    ...

RETURN VALUE

       If the searched-for datum is found, both and return a pointer to it.  Otherwise, returns NULL and returns a pointer to the newly added ele-
       ment.

WARNINGS

       Undefined results can occur if there is not enough room in the table to add a new item.

SEE ALSO

       bsearch(3C), hsearch(3C), tsearch(3C), thread_safety(5).

STANDARDS CONFORMANCE

																       lsearch(3C)

Linux and UNIX Man Pages

hash_lookup(3pub) [debian man page]

Check Out this Related Man Page