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HSEARCH
!!!HSEARCH
NAME
SYNOPSIS
DESCRIPTION
RETURN VALUE
CONFORMS TO
BUGS
EXAMPLE
SEE ALSO
----
!!NAME


hcreate, hdestroy, hsearch - hash table management
!!SYNOPSIS


__#include
__ ''item''__, ACTION__ ''action''__);
int hcreate(unsigned__ ''nel''__);
void hdestroy(void);
__
!!DESCRIPTION


These three functions allow the user to create a hash table
which associates a key with any data.


First the table must be created with the function
__hcreate()__. ''nel'' is an estimate of the number of
entries in the table. __hcreate()__ may adjust this value
upward to improve the performance of the resulting hash
table. The GNU implementation of __hsearch()__ will also
enlarge the table if it gets nearly full. malloc(3)
is used to allocate space for the table.


The corresponding function __hdestroy()__ frees the
memory occupied by the hash table so that a new table can be
constructed.


''item'' is of type __ENTRY__, which is a typedef
defined in '''' and includes these
elements:


     typedef struct entry
{
char *''key'';
char *''data'';
} ENTRY;
''key'' points to the zero-terminated ASCII string which is the search key. ''data'' points to the data associated with that key. (A pointer to a type other than character should be cast to pointer-to-character.) __hsearch()__ searches the hash table for an item with the same key as ''item'', and if successful returns a pointer to it. ''action'' determines what __hsearch()__ does after an unsuccessful search. A value of __ENTER__ instructs it to insert the new item, while a value of __FIND__ means to return __NULL__.
!!RETURN VALUE


__hcreate()__ returns __NULL__ if the hash table
cannot be successfully installed.


__hsearch()__ returns __NULL__ if ''action'' is
__ENTER__ and there is insufficient memory to expand the
hash table, or ''action'' is __FIND__ and ''item''
cannot be found in the hash table.
!!CONFORMS TO


SVID, except that in SysV, the hash table cannot
grow.
!!BUGS


The implementation can manage only one hash table at a time.
Individual hash table entries can be added, but not
deleted.
!!EXAMPLE


The following program inserts 24 items in to a hash table,
then prints some of them.


#include
!!SEE ALSO


bsearch(3), lsearch(3), tsearch(3),
malloc(3)
----

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Last edited on Tuesday, June 4, 2002 12:24:24 am by "perry"

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