hsearch(3)						     Library Functions Manual							hsearch(3)

NAME

       hsearch, hcreate, hdestroy, hsearch_r, hcreate_r, hdestroy_r - Manage hash tables

LIBRARY

       Standard C Library (libc)

SYNOPSIS

       #include <search.h>

       ENTRY *hsearch(	    ENTRY item,      ACTION action);

       int hcreate(	 size_t nel);

       void hdestroy(void);

       int hsearch_r(	   ENTRY item,	    ACTION action,	ENTRY **target,      struct hsearch_data *hsearch_data);

       int hcreate_r(	   size_t nel,	    struct hsearch_data *hsearch_data);

       void hdestroy_r(      struct hsearch_data *hsearch_data);

STANDARDS

       Interfaces documented on this reference page conform to industry standards as follows:

       hsearch(), hcreate(), hdestroy(): XSH4.2

       Refer to the standards(5) reference page for more information about industry standards and associated tags.

PARAMETERS

       Identifies  a  structure  of  the type ENTRY as defined in the search.h header file. It contains two pointers: Points to the comparison key
       string.	Points to any other data associated with the char *key parameter.

	      Pointers to types other than char should be cast as char *.  Specifies a value for an ACTION enum type, which indicates what  is	to
	      be  done with an item key when it cannot be found in the hash table.  The following two actions can be specified for this parameter:
	      Enter the key specified by the item parameter into the hash table at the appropriate place.  When the table is full, a null  pointer
	      is  returned.   Do not enter the item key into the table, but return a null pointer when an item key cannot be found in the hash ta-
	      ble.  Specifies an estimate of the maximum number of entries that the hash table will contain. Under some circumstances,	the  hcre-
	      ate()  function  may  make the hash table larger than specified to obtain mathematically favorable conditions for access to the hash
	      table.  Points to the item actually found.  Consists of data for the hash table.

DESCRIPTION

       The hsearch(), hcreate(), and hdestroy() functions are used to manage hash table operations: The hcreate() function  initializes  the  hash
       table.  You  must  call	the  hcreate()	function before calling the hsearch() function.  The hsearch() function searches a hash table.	It
       returns a pointer into a hash table that indicates where a given entry can be found. The hsearch() function uses  open  addressing  with  a
       hash  function.	 The  hdestroy() function deletes the hash table.  This allows you to start a new hash table because only one table may be
       active at a time. After the call to hdestroy(), the hash table data should no longer be considered accessible.

       [Tru64 UNIX]  The hsearch_r(), hcreate_r(), and hdestroy_r() functions are reentrant versions  of  hsearch(),  hcreate(),  and  hdestroy().
       Upon successful completion, the hsearch_r() function returns 0 (zero).  Upon failure, it returns -1 and sets errno.

       [Tru64  UNIX]  Threads  can share hash tables by using the hcreate_r, hsearch_r, and hdestroy_r functions with a common hsearch_data value.
       To prevent corruption of data when sharing a hash table, locks must be used around calls that use the common hsearch_data value.

RETURN VALUES

       The hsearch() function returns a null pointer when the action parameter is FIND and the key pointed to by item cannot be found or when  the
       specified action is ENTER and the hash table is full.

       Upon  successful completion, the hcreate() function returns a nonzero value. Otherwise, when sufficient space for the table cannot be allo-
       cated, the hcreate() function returns a value of 0 (zero).

ERRORS

       If any of the following conditions occur, the hsearch() function sets errno  to	the  corresponding  value:  The  table	is  full.   [Tru64
       UNIX]  The search failed.

RELATED INFORMATION

       Functions: bsearch(3), lsearch(3), tsearch(3), qsort(3)

       Standards: standards(5) delim off

																	hsearch(3)