1.\" $OpenBSD: ohash_interval.3,v 1.1 2014/05/12 19:09:00 espie Exp $ 2.\" Copyright (c) 2001 Marc Espie <espie@openbsd.org> 3.\" 4.\" Permission to use, copy, modify, and distribute this software for any 5.\" purpose with or without fee is hereby granted, provided that the above 6.\" copyright notice and this permission notice appear in all copies. 7.\" 8.\" THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES 9.\" WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF 10.\" MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR 11.\" ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES 12.\" WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN 13.\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF 14.\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. 15.\" 16.\" $FreeBSD$ 17.\" 18.Dd June 5, 2013 19.Dt OHASH_INTERVAL 3 20.Os 21.Sh NAME 22.Nm ohash_interval , 23.Nm ohash_create_entry , 24.Nm ohash_qlookup , 25.Nm ohash_qlookupi 26.Nd helper functions for open hashing 27.Sh SYNOPSIS 28.In stdint.h 29.In stddef.h 30.In ohash.h 31.Ft uint32_t 32.Fn ohash_interval "const char *start" "const char **pend" 33.Ft "void *" 34.Fn ohash_create_entry "struct ohash_info *info" "const char *start" "const char **pend" 35.Ft "unsigned int" 36.Fn ohash_qlookupi "struct ohash *h" "const char *start" "const char **pend" 37.Ft "unsigned int" 38.Fn ohash_qlookup "struct ohash *h" "const char *start" 39.Sh DESCRIPTION 40These functions are commonly used to simplify open hashing usage, and use 41similar conventions. 42They operate indifferently on NUL-terminated strings 43.Po 44by setting 45.Fa *pend 46= 47.Dv NULL 48.Pc 49or memory ranges 50.Po 51delimited by 52.Fa start 53and 54.Fa *pend 55.Pc . 56For NUL-terminated strings, as a side effect, those functions 57set 58.Fa *pend 59to the terminating NUL byte. 60.Pp 61.Fn ohash_interval 62is a simple hashing function that yields good results on common data sets. 63.Pp 64.Fn ohash_create_entry 65can be used to create a new record with a given key. 66In that case, 67the alloc field of 68.Fa info 69should point to a 70.Xr malloc 3 Ns -like 71function to allocate the storage: 72.Bd -literal -offset indent 73p = (*info->alloc)(sz, info->data); 74.Ed 75.Pp 76.Fn ohash_qlookupi 77is a wrapper function that simply calls 78.Fn ohash_interval 79and 80.Fn ohash_lookup_interval . 81.Pp 82.Fn ohash_qlookup 83is a variation on 84.Fn ohash_qlookupi 85designed for NUL-terminated strings. 86.Sh SEE ALSO 87.Xr ohash_init 3 88.Sh STANDARDS 89Those functions are completely non-standard and should be avoided in 90portable programs. 91.Sh HISTORY 92Those functions were designed and written for 93.Ox 94.Xr make 1 95by Marc Espie in 1999. 96