hsearch(3)hsearch(3)Name
hsearch, hcreate, hdestroy - manage hash search tables
Syntax
#include <search.h>
ENTRY ∗hsearch (item, action)
ENTRY item;
ACTION action;
int hcreate (nel)
unsigned nel;
void hdestroy ( )
Description
The subroutine is a hash-table search routine generalized from Knuth
(6.4) Algorithm D. It returns a pointer into a hash table indicating
the location at which an entry can be found. The item is a structure
of type ENTRY (defined in the <search.h> header file) containing two
pointers: item.key points to the comparison key, and item.data points
to any other data to be associated with that key. (Pointers to types
other than character should be cast to pointer-to-character.) The
action is a member of an enumeration type ACTION indicating the dispo‐
sition of the entry if it cannot be found in the table. ENTER indi‐
cates that the item should be inserted in the table at an appropriate
point. FIND indicates that no entry should be made. Unsuccessful res‐
olution is indicated by the return of a NULL pointer.
The subroutine allocates sufficient space for the table, and must be
called before is used. The nel is an estimate of the maximum number of
entries that the table will contain. This number may be adjusted
upward by the algorithm in order to obtain certain mathematically
favorable circumstances.
The subroutine destroys the search table, and may be followed by
another call to
Restrictions
Only one hash search table may be active at any given time.
Diagnostics
The subroutine returns a NULL pointer if either the action is FIND and
the item could not be found or the action is ENTER and the table is
full.
The subroutine returns zero if it cannot allocate sufficient space for
the table.
See Alsobsearch(3), lsearch(3), string(3), tsearch(3)hsearch(3)
