1.\" $NetBSD: hash.9,v 1.2 2002/02/13 08:18:42 ross Exp $ 2.\" 3.\" Copyright (c) 2001 The NetBSD Foundation, Inc. 4.\" All rights reserved. 5.\" 6.\" This code is derived from software contributed to The NetBSD Foundation 7.\" by Luke Mewburn of Wasabi Systems, Inc. 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 December 5, 2001 38.Dt HASH 9 39.Os 40.Sh NAME 41.Nm hash , 42.Nm hash32_buf , 43.Nm hash32_str , 44.Nm hash32_strn 45.Nd kernel hash functions 46.Sh SYNOPSIS 47.Fd #include \*[Lt]sys/types.h\*[Gt] 48.Fd #include \*[Lt]sys/hash.h\*[Gt] 49.Ft uint32_t 50.Fn hash32_buf "const void *buf" "size_t len" "uint32_t ihash" 51.Ft uint32_t 52.Fn hash32_str "const void *buf" "uint32_t ihash" 53.Ft uint32_t 54.Fn hash32_strn "const void *buf" "size_t len" "uint32_t ihash" 55.Sh DESCRIPTION 56The 57.Nm 58functions returns a hash of the given buffer. 59.Pp 60The 61.Fn hash32_buf 62function returns a 32 bit hash of 63.Fa buf , 64which is 65.Fa len 66bytes long, 67seeded with an initial hash of 68.Fa ihash 69(which is usually 70.Dv HASH32_BUF_INIT ) . 71This function may use a different algorithm to 72.Fn hash32_str 73and 74.Fn hash32_strn . 75.Pp 76The 77.Fn hash32_str 78function returns a 32 bit hash of 79.Fa buf , 80which is 81a 82.Dv NUL 83terminated 84.Tn ASCII 85string, 86seeded with an initial hash of 87.Fa ihash 88(which is usually 89.Dv HASH32_STR_INIT ) . 90This function must use the same algorithm as 91.Fn hash32_strn , 92so that the same data returns the same hash. 93.Pp 94The 95.Fn hash32_strn 96function returns a 32 bit hash of 97.Fa buf , 98which is 99a 100.Dv NUL 101terminated 102.Tn ASCII 103string, 104up to a maximum of 105.Fa len 106bytes, 107seeded with an initial hash of 108.Fa ihash 109(which is usually 110.Dv HASH32_STR_INIT ) . 111This function must use the same algorithm as 112.Fn hash32_str , 113so that the same data returns the same hash. 114.Pp 115The 116.Fa ihash 117parameter is provided to allow for incremental hashing by allowing 118successive calls to use a previous hash value. 119.Sh RETURN VALUES 120The 121.Fa hash32_* 122functions return a 32 bit hash of the provided buffer. 123.Sh HISTORY 124The kernel hashing API first appeared in 125.Nx 1.6 . 126