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 June 6, 2012 35.Dt HASHINIT 9 36.Os 37.Sh NAME 38.Nm hashinit , 39.Nm hashinit_ext , 40.Nm hashdestroy , 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 hashdestroy "void *hashtbl" "struct malloc_type *type" "u_long hashmask" 54.Ft void * 55.Fn phashinit "int count" "struct malloc_type *type" "u_long *nentries" 56.Ft void * 57.Fn phashinit_ext "int count" "size_t size" "struct malloc_type *type" "u_long *nentries" 58.Sh DESCRIPTION 59The kernel hash functions are used for creating a generic hash table. 60.Pp 61The 62.Fn hashinit 63function returns a pointer to a hash table which is sized a 64.Dq "power of two" 65greater or equal to the element 66.Fa count 67requested. 68The masking value is stored in 69.Fa hashmask . 70.Pp 71The 72.Fn phashinit 73function returns a pointer to a prime number sized hash table. 74The element 75.Fa count 76requested is used to dictate an upper-bound for the size of the 77hash table. 78The final size of the hash table is stored by the function in 79.Fa nentries . 80.Pp 81The 82.Fa type 83argument to both of the above functions is used for keeping track 84of memory allocated for the hash table. 85See the 86.Xr kmalloc 9 87manual page for more information on memory statistics. 88.Pp 89The 90.Fn hashinit_ext 91and 92.Fn phashinit_ext 93functions are extended versions of 94.Fn hashinit 95and 96.Fn phashinit 97which take the 98.Fa size 99of the structure as an additional argument and will zero the array instead 100of assuming that it is an array of 101.Dv LIST_HEAD Ns s . 102.Pp 103The 104.Fn hashdestroy 105function frees the space occupied by the hash table pointed to by argument 106.Fa hashtbl . 107Argument 108.Fa type 109determines the malloc arena to use when freeing space. 110The argument 111.Fa hashmask 112should be the bit mask returned by the call to 113.Fn hashinit 114that allocated the hash table. 115The argument 116.Fa flags 117must be used with one of the following values. 118.Sh SEE ALSO 119.Xr tcp 4 , 120.Xr udp 4 , 121.Xr kmalloc 9 , 122.Xr nlookup 9 123.Sh AUTHORS 124This manual page was written by 125.An Hiten Pandya Aq Mt hmp@backplane.com . 126.Sh BUGS 127There is no 128.Fn phashdestroy 129function, and using 130.Fn hashdestroy 131to free a hash table allocated by 132.Fn phashinit 133usually has grave consequences. 134