1.\" 2.\" Copyright (c) 2003, 2004 The DragonFly Project. All rights reserved. 3.\" 4.\" This code is derived from software contributed to The DragonFly Project 5.\" by Hiten Pandya <hmp@backplane.com>. 6.\" 7.\" Redistribution and use in source and binary forms, with or without 8.\" modification, are permitted provided that the following conditions 9.\" are met: 10.\" 11.\" 1. Redistributions of source code must retain the above copyright 12.\" notice, this list of conditions and the following disclaimer. 13.\" 2. Redistributions in binary form must reproduce the above copyright 14.\" notice, this list of conditions and the following disclaimer in 15.\" the documentation and/or other materials provided with the 16.\" distribution. 17.\" 3. Neither the name of The DragonFly Project nor the names of its 18.\" contributors may be used to endorse or promote products derived 19.\" from this software without specific, prior written permission. 20.\" 21.\" THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 22.\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 23.\" LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS 24.\" FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE 25.\" COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, 26.\" INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING, 27.\" BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 28.\" LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED 29.\" AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, 30.\" OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT 31.\" OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32.\" SUCH DAMAGE. 33.\" 34.Dd December 20, 2009 35.Dt HASH 9 36.Os 37.Sh NAME 38.Nm hash , 39.Nm hashinit , 40.Nm hashinit_ext , 41.Nm phashinit , 42.Nm phashinit_ext 43.Nd generic hash table functions for the kernel 44.Sh SYNOPSIS 45.In sys/param.h 46.In sys/systm.h 47.In sys/malloc.h 48.Ft void * 49.Fn hashinit "int count" "struct malloc_type *type" "u_long *hashmask" 50.Ft void * 51.Fn hashinit_ext "int count" "size_t size" "struct malloc_type *type" "u_long *hashmask" 52.Ft void * 53.Fn phashinit "int count" "struct malloc_type *type" "u_long *nentries" 54.Ft void * 55.Fn phashinit_ext "int count" "size_t size" "struct malloc_type *type" "u_long *nentries" 56.Sh DESCRIPTION 57The kernel hash functions are used for creating a generic hash table. 58.Pp 59The 60.Fn hashinit 61function returns a pointer to a hash table which is sized a 62.Dq "power of two" 63greater or equal to the element 64.Fa count 65requested. 66The masking value is stored in 67.Fa hashmask . 68.Pp 69The 70.Fn phashinit 71function returns a pointer to a prime number sized hash table. 72The element 73.Fa count 74requested is used to dictate an upper-bound for the size of the 75hash table. 76The final size of the hash table is stored by the function in 77.Fa nentries . 78.Pp 79The 80.Fa type 81argument to both of the above functions is used for keeping track 82of memory allocated for the hash table. 83See the 84.Xr kmalloc 9 85manual page for more information on memory statistics. 86.Pp 87The 88.Fn hashinit_ext 89and 90.Fn phashinit_ext 91functions are extended versions of 92.Fn hashinit 93and 94.Fn phashinit 95which take the 96.Fa size 97of the structure as an additional argument and will zero the array instead 98of assuming that it is an array of 99.Dv LIST_HEAD Ns s . 100.Sh SEE ALSO 101.Xr tcp 4 , 102.Xr udp 4 , 103.Xr kmalloc 9 , 104.Xr nlookup 9 105.Sh AUTHORS 106This manual page was written by 107.An Hiten Pandya Aq hmp@backplane.com . 108