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94 lines
2.5 KiB
Groff
94 lines
2.5 KiB
Groff
.\" $OpenBSD: ohash_interval.3,v 1.1 2014/05/12 19:09:00 espie Exp $
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.\" Copyright (c) 2001 Marc Espie <espie@openbsd.org>
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.\"
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.\" Permission to use, copy, modify, and distribute this software for any
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.\" purpose with or without fee is hereby granted, provided that the above
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.\" copyright notice and this permission notice appear in all copies.
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.\"
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.\" THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
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.\" WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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.\" MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
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.\" ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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.\" WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
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.\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
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.\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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.\"
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.Dd June 5, 2013
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.Dt OHASH_INTERVAL 3
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.Os
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.Sh NAME
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.Nm ohash_interval ,
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.Nm ohash_create_entry ,
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.Nm ohash_qlookup ,
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.Nm ohash_qlookupi
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.Nd helper functions for open hashing
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.Sh SYNOPSIS
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.In stdint.h
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.In stddef.h
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.In ohash.h
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.Ft uint32_t
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.Fn ohash_interval "const char *start" "const char **pend"
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.Ft "void *"
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.Fn ohash_create_entry "struct ohash_info *info" "const char *start" "const char **pend"
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.Ft "unsigned int"
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.Fn ohash_qlookupi "struct ohash *h" "const char *start" "const char **pend"
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.Ft "unsigned int"
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.Fn ohash_qlookup "struct ohash *h" "const char *start"
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.Sh DESCRIPTION
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These functions are commonly used to simplify open hashing usage, and use
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similar conventions.
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They operate indifferently on NUL-terminated strings
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.Po
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by setting
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.Fa *pend
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=
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.Dv NULL
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.Pc
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or memory ranges
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.Po
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delimited by
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.Fa start
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and
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.Fa *pend
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.Pc .
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For NUL-terminated strings, as a side effect, those functions
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set
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.Fa *pend
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to the terminating NUL byte.
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.Pp
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.Fn ohash_interval
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is a simple hashing function that yields good results on common data sets.
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.Pp
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.Fn ohash_create_entry
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can be used to create a new record with a given key.
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In that case,
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the alloc field of
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.Fa info
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should point to a
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.Xr malloc 3 Ns -like
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function to allocate the storage:
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.Bd -literal -offset indent
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p = (*info->alloc)(sz, info->data);
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.Ed
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.Pp
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.Fn ohash_qlookupi
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is a wrapper function that simply calls
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.Fn ohash_interval
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and
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.Fn ohash_lookup_interval .
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.Pp
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.Fn ohash_qlookup
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is a variation on
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.Fn ohash_qlookupi
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designed for NUL-terminated strings.
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.Sh SEE ALSO
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.Xr ohash_init 3
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.Sh STANDARDS
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Those functions are completely non-standard and should be avoided in
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portable programs.
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.Sh HISTORY
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Those functions were designed and written for
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.Ox
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.Xr make 1
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by Marc Espie in 1999.
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