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NAME    [Toc]    [Back]

     hcreate, hdestroy, hsearch - manage hash search table

SYNOPSIS    [Toc]    [Back]

     #include <search.h>

     hcreate(size_t nel);


     ENTRY *
     hsearch(ENTRY item, ACTION action);

DESCRIPTION    [Toc]    [Back]

     The hcreate(), hdestroy()  and  hsearch()  functions  manage
hash search tables.

     The  hcreate() function allocates and initializes the table.
The nel argument
 specifies an estimate of the maximum  number  of  entries to be held
     by  the table.  Unless further memory allocation fails, supplying an insufficient
 nel value will not result in functional harm, although a performance
  degradation  may  occur.  Initialization using the
hcreate() function
 is mandatory  prior  to  any  access  operations  using

     The  hdestroy() function destroys a table previously created
     hcreate().  After a call to  hdestroy(),  the  data  can  no
longer be accessed.

     The  hsearch() function is used to search to the hash table.
It returns a
     pointer into the hash table indicating  the  address  of  an
item.  The item
     argument  is of type ENTRY, a structural type which contains
the following
           char *key     comparison key.
           void *data    pointer to data associated with key.

     The key comparison function used by hsearch() is  strcmp(3).

     The  action  argument is of type ACTION, an enumeration type
which defines
     the following values:
           ENTER    Insert item into the hash table.  If  an  existing item with
                    the  same  key  is found, it is not replaced.
Note that the
                    key and data elements of item  are  used  directly by the new
                    table  entry.   The  storage for the key must
not be modified
                    during the lifetime of the hash table.
           FIND     Search the hash table without inserting item.

RETURN VALUES    [Toc]    [Back]

     If  successful,  the  hcreate()  function returns a non-zero
value.  Otherwise,
 a value of 0 is returned and errno is set to  indicate
the error.

     The hdestroy() functions returns no value.

     If  successful,  the hsearch() function returns a pointer to
hash table entry
 matching the provided key.  If the action  is  FIND  and
the item was
     not  found,  or  if  the  action  is ENTER and the insertion
failed, NULL is
     returned and errno is set to indicate the error.  If the action is ENTER
     and an entry already existed in the table matching the given
key, the existing
 entry is returned and is not replaced.

ERRORS    [Toc]    [Back]

     The hcreate() and hsearch() functions will fail if:

     [ENOMEM]      Insufficient memory is available.

SEE ALSO    [Toc]    [Back]

     bsearch(3), lsearch(3), malloc(3), strcmp(3)

STANDARDS    [Toc]    [Back]

     The hcreate(), hdestroy() and hsearch() functions conform to
     Portability Guide Issue 4.2 (``XPG4.2'').

HISTORY    [Toc]    [Back]

     The  hcreate(), hdestroy() and hsearch() functions first appeared in AT&T
     System V UNIX.

BUGS    [Toc]    [Back]

     The interface permits the use of only one hash  table  at  a

OpenBSD      3.6                        February     13,     2001
[ Back ]
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