1.\" $OpenBSD: hcreate.3,v 1.3 2006/01/30 19:50:41 jmc Exp $ 2.\" $NetBSD: hcreate.3,v 1.6 2003/04/16 13:34:46 wiz Exp $ 3.\" 4.\" Copyright (c) 1999 The NetBSD Foundation, Inc. 5.\" All rights reserved. 6.\" 7.\" This code is derived from software contributed to The NetBSD Foundation 8.\" by Klaus Klein. 9.\" 10.\" Redistribution and use in source and binary forms, with or without 11.\" modification, are permitted provided that the following conditions 12.\" are met: 13.\" 1. Redistributions of source code must retain the above copyright 14.\" notice, this list of conditions and the following disclaimer. 15.\" 2. Redistributions in binary form must reproduce the above copyright 16.\" notice, this list of conditions and the following disclaimer in the 17.\" documentation and/or other materials provided with the distribution. 18.\" 3. All advertising materials mentioning features or use of this software 19.\" must display the following acknowledgement: 20.\" This product includes software developed by the NetBSD 21.\" Foundation, Inc. and its contributors. 22.\" 4. Neither the name of The NetBSD Foundation nor the names of its 23.\" contributors may be used to endorse or promote products derived 24.\" from this software without specific prior written permission. 25.\" 26.\" THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS 27.\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 28.\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 29.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 30.\" BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 31.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 32.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 33.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 34.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 35.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 36.\" POSSIBILITY OF SUCH DAMAGE. 37.\" 38.Dd February 13, 2001 39.Dt HCREATE 3 40.Os 41.Sh NAME 42.Nm hcreate , 43.Nm hdestroy , 44.Nm hsearch 45.Nd manage hash search table 46.Sh SYNOPSIS 47.In search.h 48.Ft int 49.Fn hcreate "size_t nel" 50.Ft void 51.Fn hdestroy "void" 52.Ft ENTRY * 53.Fn hsearch "ENTRY item" "ACTION action" 54.Sh DESCRIPTION 55The 56.Fn hcreate , 57.Fn hdestroy , 58and 59.Fn hsearch 60functions manage hash search tables. 61.Pp 62The 63.Fn hcreate 64function allocates and initializes the table. 65The 66.Fa nel 67argument specifies an estimate of the maximum number of entries to be held 68by the table. 69Unless further memory allocation fails, supplying an insufficient 70.Fa nel 71value will not result in functional harm, although a performance degradation 72may occur. 73Initialization using the 74.Fn hcreate 75function is mandatory prior to any access operations using 76.Fn hsearch . 77.Pp 78The 79.Fn hdestroy 80function destroys a table previously created using 81.Fn hcreate . 82After a call to 83.Fn hdestroy , 84the data can no longer be accessed. 85.Pp 86The 87.Fn hsearch 88function is used to search to the hash table. 89It returns a pointer into the 90hash table indicating the address of an item. 91The 92.Fa item 93argument is of type 94.Dv ENTRY , 95a structural type which contains the following members: 96.Pp 97.Bl -tag -compact -offset indent -width voidX*dataXX 98.It Fa char *key 99comparison key. 100.It Fa void *data 101pointer to data associated with 102.Fa key . 103.El 104.Pp 105The key comparison function used by 106.Fn hsearch 107is 108.Xr strcmp 3 . 109.Pp 110The 111.Fa action 112argument is of type 113.Dv ACTION , 114an enumeration type which defines the following values: 115.Bl -tag -offset indent -width ENTERXX 116.It Dv ENTER 117Insert 118.Fa item 119into the hash table. 120If an existing item with the same key is found, it is not replaced. 121Note that the 122.Fa key 123and 124.Fa data 125elements of 126.Fa item 127are used directly by the new table entry. 128The storage for the 129key must not be modified during the lifetime of the hash table. 130.It Dv FIND 131Search the hash table without inserting 132.Fa item . 133.El 134.Sh RETURN VALUES 135If successful, the 136.Fn hcreate 137function returns a non-zero value. 138Otherwise, a value of 0 is returned and 139.Va errno 140is set to indicate the error. 141.Pp 142The 143.Fn hdestroy 144functions 145returns no value. 146.Pp 147If successful, the 148.Fn hsearch 149function returns a pointer to a hash table entry matching 150the provided key. 151If the action is 152.Dv FIND 153and the item was not found, or if the action is 154.Dv ENTER 155and the insertion failed, 156.Dv NULL 157is returned and 158.Va errno 159is set to indicate the error. 160If the action is 161.Dv ENTER 162and an entry already existed in the table matching the given 163key, the existing entry is returned and is not replaced. 164.Sh ERRORS 165The 166.Fn hcreate 167and 168.Fn hsearch 169functions will fail if: 170.Bl -tag -width Er 171.It Bq Er ENOMEM 172Insufficient memory is available. 173.El 174.Sh SEE ALSO 175.Xr bsearch 3 , 176.Xr lsearch 3 , 177.Xr malloc 3 , 178.Xr strcmp 3 179.Sh STANDARDS 180These functions conform to 181.St -p1003.1-2004 . 182.Sh HISTORY 183The 184.Fn hcreate , 185.Fn hdestroy 186and 187.Fn hsearch 188functions first appeared in 189.At V . 190.Sh BUGS 191The interface permits the use of only one hash table at a time. 192