1.\" $NetBSD: hcreate.3,v 1.2 2001/02/14 05:59:56 cgd Exp $ 2.\" 3.\" Copyright (c) 1999 The NetBSD Foundation, Inc. 4.\" All rights reserved. 5.\" 6.\" This code is derived from software contributed to The NetBSD Foundation 7.\" by Klaus Klein. 8.\" 9.\" Redistribution and use in source and binary forms, with or without 10.\" modification, are permitted provided that the following conditions 11.\" are met: 12.\" 1. Redistributions of source code must retain the above copyright 13.\" notice, this list of conditions and the following disclaimer. 14.\" 2. Redistributions in binary form must reproduce the above copyright 15.\" notice, this list of conditions and the following disclaimer in the 16.\" documentation and/or other materials provided with the distribution. 17.\" 3. All advertising materials mentioning features or use of this software 18.\" must display the following acknowledgement: 19.\" This product includes software developed by the NetBSD 20.\" Foundation, Inc. and its contributors. 21.\" 4. Neither the name of The NetBSD Foundation nor the names of its 22.\" contributors may be used to endorse or promote products derived 23.\" from this software without specific prior written permission. 24.\" 25.\" THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS 26.\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 27.\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 28.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 29.\" BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 30.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 31.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 32.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 33.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 34.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 35.\" POSSIBILITY OF SUCH DAMAGE. 36.\" 37.Dd February 13, 2001 38.Dt HCREATE 3 39.Os 40.Sh NAME 41.Nm hcreate , 42.Nm hdestroy , 43.Nm hsearch 44.Nd manage hash search table 45.Sh LIBRARY 46.Lb libc 47.Sh SYNOPSIS 48.Fd #include <search.h> 49.Ft int 50.Fn hcreate "size_t nel" 51.Ft void 52.Fn hdestroy "void" 53.Ft ENTRY * 54.Fn hsearch "ENTRY item" "ACTION action" 55.Sh DESCRIPTION 56The 57.Fn hcreate , 58.Fn hdestroy 59and 60.Fn hsearch 61functions manage hash search tables. 62.Pp 63The 64.Fn hcreate 65function allocates and initializes the table. 66The 67.Fa nel 68argument specifies an estimate of the maximum number of entries to be held 69by the table. Unless further memory allocation fails, supplying an 70insufficient 71.Fa nel 72value will not result in functional harm, although a performance degradation 73may occur. 74Initialization using the 75.Fn hcreate 76function is mandatory prior to any access operations using 77.Fn hsearch . 78.Pp 79The 80.Fn hdestroy 81function destroys a table previously created using 82.Fn hcreate . 83After a call to 84.Fn hdestroy , 85the data can no longer be accessed. 86.Pp 87The 88.Fn hsearch 89function is used to search to the hash table. It returns a pointer into the 90hash table indicating the address of an item. The 91.Fa item 92argument is of type 93.Dv ENTRY , 94a structural type which contains the following members: 95.Bl -tag -compact -offset indent -width voidX*dataXX 96.It Fa char *key 97comparison key. 98.It Fa void *data 99pointer to data associated with 100.Fa key . 101.El 102.Pp 103The key comparison function used by 104.Fn hsearch 105is 106.Xr strcmp 3 . 107.Pp 108The 109.Fa action 110argument is of type 111.Dv ACTION , 112an enumeration type which defines the following values: 113.Bl -tag -compact -offset indent -width ENTERXX 114.It Dv ENTER 115Insert 116.Fa item 117into the hash table. 118If an existing item with the same key is found, it is not replaced. 119Note that the 120.Fa key 121and 122.Fa data 123elements of 124.Fa item 125are used directly by the new table entry. The storage for the 126key must not be modified during the lifetime of the hash table. 127.It Dv FIND 128Search the hash table without inserting 129.Fa item . 130.El 131.Pp 132.Sh RETURN VALUES 133If successful, the 134.Fn hcreate 135function returns a non-zero value. Otherwise, a value of 0 is returned and 136.Va errno 137is set to indicate the error. 138.Pp 139The 140.Fn hdestroy 141functions 142returns no value. 143.Pp 144If successful, the 145.Fn hsearch 146function returns a pointer to hash table entry matching 147the provided key. 148If the action is 149.Dv FIND 150and the item was not found, or if the action is 151.Dv ENTER 152and the insertion failed, 153.Dv NULL 154is returned and 155.Va errno 156is set to indicate the error. 157If the action is 158.Dv ENTER 159and an entry already existed in the table matching the given 160key, the existing entry is returned and is not replaced. 161.Sh ERRORS 162The 163.Fn hcreate 164and 165.Fn hsearch 166functions will fail if: 167.Bl -tag -width Er 168.It Bq Er ENOMEM 169Insufficient memory is available. 170.El 171.Sh SEE ALSO 172.Xr bsearch 3 , 173.Xr lsearch 3 , 174.Xr malloc 3 , 175.Xr strcmp 3 176.Sh STANDARDS 177The 178.Fn hcreate , 179.Fn hdestroy 180and 181.Fn hsearch 182functions conform to 183.St -xpg4.2 . 184.Sh BUGS 185.Pp 186The interface permits the use of only one hash table at a time. 187.Sh HISTORY 188The 189.Fn hcreate , 190.Fn hdestroy 191and 192.Fn hsearch 193functions first appeared in 194.At V . 195