HSEARCH(3,L)                AIX Technical Reference                HSEARCH(3,L)



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hsearch, hcreate, hdestroy



PURPOSE

Manages hash tables.

LIBRARY

Standard C Library (libc.a)

SYNTAX

#include <search.h>




      ENTRY *hsearch (item, action)       int hcreate (nel)
      ENTRY item;                         unsigned int nel;
      ACTION action;
                                          void hdestroy ( )



DESCRIPTION

The hsearch subroutine is a hash table search routine.  It returns a pointer
into a hash table that indicates the location of a given entry.  The item
parameter is a structure of the type ENTRY as defined in the search.h header
file.  It contains two pointers:

item.key
        Points to the comparison key.
item.data
        Points to any other data be associated with that key.

Pointers to types other than char should be cast to pointer-to-character.  The
action parameter is a value of the ACTION enumeration type that indicates what
is to be done with an entry if it cannot be found in the table:

ENTER   Enters the item into the table at the appropriate point.  If the table
        is full, a NULL pointer is returned.

FIND    Does not enter the item into the table, but returns a NULL pointer if
        the item cannot be found.

The hsearch subroutine uses open addressing with a multiplicative hash
function.




Processed November 7, 1990       HSEARCH(3,L)                                 1

HSEARCH(3,L)                AIX Technical Reference                HSEARCH(3,L)



The hcreate subroutine allocates sufficient space for the table.  You must call
hcreate before calling hsearch.  The nel parameter is an estimate of the
maximum number of entries that the table contains.  Under some circumstances,
hcreate may actually make the table larger than specified.  Upon successful
completion, hcreate returns 1.  hcreate returns 0 if it cannot allocate
sufficient space for the table.

The hdestroy subroutine deletes the hash table.  This allows you to start a new
hash table since only one table can be active at a time.

RELATED INFORMATION

In this book:  "bsearch," "lsearch, lfind," "string," and "tsearch, tdelete,
twalk."









































Processed November 7, 1990       HSEARCH(3,L)                                 2