f14fb60209
* Updating common/lib * Updating lib/csu * Updating lib/libc * Updating libexec/ld.elf_so * Corrected test on __minix in featuretest to actually follow the meaning of the comment. * Cleaned up _REENTRANT-related defintions. * Disabled -D_REENTRANT for libfetch * Removing some unneeded __NBSD_LIBC defines and tests Change-Id: Ic1394baef74d11b9f86b312f5ff4bbc3cbf72ce2
321 lines
6.6 KiB
Groff
321 lines
6.6 KiB
Groff
.\" $NetBSD: hcreate.3,v 1.10 2011/09/15 09:14:54 wiz Exp $
|
|
.\"
|
|
.\" Copyright (c) 1999 The NetBSD Foundation, Inc.
|
|
.\" All rights reserved.
|
|
.\"
|
|
.\" This code is derived from software contributed to The NetBSD Foundation
|
|
.\" by Klaus Klein.
|
|
.\"
|
|
.\" Redistribution and use in source and binary forms, with or without
|
|
.\" modification, are permitted provided that the following conditions
|
|
.\" are met:
|
|
.\" 1. Redistributions of source code must retain the above copyright
|
|
.\" notice, this list of conditions and the following disclaimer.
|
|
.\" 2. Redistributions in binary form must reproduce the above copyright
|
|
.\" notice, this list of conditions and the following disclaimer in the
|
|
.\" documentation and/or other materials provided with the distribution.
|
|
.\"
|
|
.\" THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
|
|
.\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
|
|
.\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
|
|
.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
|
|
.\" BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
|
|
.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
|
|
.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
|
|
.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
|
|
.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
|
|
.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
|
|
.\" POSSIBILITY OF SUCH DAMAGE.
|
|
.\"
|
|
.Dd September 14, 2011
|
|
.Dt HCREATE 3
|
|
.Os
|
|
.Sh NAME
|
|
.Nm hcreate ,
|
|
.Nm hcreate_r ,
|
|
.Nm hdestroy ,
|
|
.Nm hdestroy_r ,
|
|
.Nm hsearch ,
|
|
.Nm hsearch_r
|
|
.Nd manage hash search table
|
|
.Sh LIBRARY
|
|
.Lb libc
|
|
.Sh SYNOPSIS
|
|
.In search.h
|
|
.Ft int
|
|
.Fn hcreate "size_t nel"
|
|
.Ft int
|
|
.Fn hcreate_r "size_t nel" "struct hsearch_data *table"
|
|
.Ft void
|
|
.Fn hdestroy "void"
|
|
.Ft void
|
|
.Fn hdestroy_r "struct hsearch_data *table"
|
|
.Ft ENTRY *
|
|
.Fn hsearch "ENTRY item" "ACTION action"
|
|
.Ft int
|
|
.Fn hsearch_r "ENTRY item" "ACTION action" "ENTRY ** itemp" "struct hsearch_data *table"
|
|
.Sh DESCRIPTION
|
|
The
|
|
.Fn hcreate ,
|
|
.Fn hcreate_r ,
|
|
.Fn hdestroy ,
|
|
.Fn hdestroy_r
|
|
.Fn hsearch ,
|
|
and
|
|
.Fn hsearch_r
|
|
functions manage hash search tables.
|
|
.Pp
|
|
The
|
|
.Fn hcreate
|
|
function allocates and initializes the table.
|
|
The
|
|
.Fa nel
|
|
argument specifies an estimate of the maximum number of entries to be held
|
|
by the table.
|
|
Unless further memory allocation fails, supplying an insufficient
|
|
.Fa nel
|
|
value will not result in functional harm, although a performance degradation
|
|
may occur.
|
|
Initialization using the
|
|
.Fn hcreate
|
|
function is mandatory prior to any access operations using
|
|
.Fn hsearch .
|
|
.Pp
|
|
The
|
|
.Fn hdestroy
|
|
function destroys a table previously created using
|
|
.Fn hcreate .
|
|
After a call to
|
|
.Fn hdestroy ,
|
|
the data can no longer be accessed.
|
|
.Pp
|
|
The
|
|
.Fn hsearch
|
|
function is used to search to the hash table.
|
|
It returns a pointer into the
|
|
hash table indicating the address of an item.
|
|
The
|
|
.Fa item
|
|
argument is of type
|
|
.Vt ENTRY ,
|
|
defined in the
|
|
.In search.h
|
|
header.
|
|
This is a structure type that contains two pointers:
|
|
.Pp
|
|
.Bl -tag -compact -offset indent -width "void *data "
|
|
.It Fa char *key
|
|
comparison key
|
|
.It Fa void *data
|
|
pointer to data associated with
|
|
.Fa key
|
|
.El
|
|
.Pp
|
|
The key comparison function used by
|
|
.Fn hsearch
|
|
is
|
|
.Xr strcmp 3 .
|
|
.Pp
|
|
The
|
|
.Fa action
|
|
argument is of type
|
|
.Vt ACTION ,
|
|
an enumeration type which defines the following values:
|
|
.Bl -tag -offset indent -width ENTERXX
|
|
.It Dv ENTER
|
|
Insert
|
|
.Fa item
|
|
into the hash table.
|
|
If an existing item with the same key is found, it is not replaced.
|
|
Note that the
|
|
.Fa key
|
|
and
|
|
.Fa data
|
|
elements of
|
|
.Fa item
|
|
are used directly by the new table entry.
|
|
The storage for the
|
|
key must not be modified during the lifetime of the hash table.
|
|
.It Dv FIND
|
|
Search the hash table without inserting
|
|
.Fa item .
|
|
.El
|
|
.Pp
|
|
Note that the comparison
|
|
.Fa key
|
|
must be allocated using
|
|
.Xr malloc 3
|
|
or
|
|
.Xr calloc 3
|
|
if action is
|
|
.Dv ENTER
|
|
and
|
|
.Fn hdestroy
|
|
will be called.
|
|
This is because
|
|
.Fn hdestroy
|
|
will call
|
|
.Xr free 3
|
|
for each comparison
|
|
.Fa key
|
|
(but not
|
|
.Fa data ) .
|
|
Typically the comparison
|
|
.Fa key
|
|
is allocated by using
|
|
.Xr strdup 3 .
|
|
.Pp
|
|
The
|
|
.Fn hcreate_r ,
|
|
.Fn hdestroy_r ,
|
|
and
|
|
.Fn hsearch_r
|
|
functions are re-entrant versions of the above functions that can
|
|
operate on a table supplied by the user.
|
|
The
|
|
.Fn hsearch_r
|
|
function returns
|
|
.Dv 0
|
|
if the action is
|
|
.Dv ENTER
|
|
and the element cannot be created,
|
|
.Dv 1
|
|
otherwise.
|
|
If the element exists or can be created, it will be placed in
|
|
.Fa itemp ,
|
|
otherwise
|
|
.Fa itemp
|
|
will be set to
|
|
.Dv NULL .
|
|
.Sh RETURN VALUES
|
|
If successful, the
|
|
.Fn hcreate
|
|
and
|
|
.Fn hcreate_r
|
|
functions return a non-zero value.
|
|
Otherwise, a value of
|
|
.Dv 0
|
|
is returned and
|
|
.Va errno
|
|
is set to indicate the error.
|
|
.Pp
|
|
The
|
|
.Fn hdestroy
|
|
and
|
|
.Fn hdestroy_r
|
|
functions return no value.
|
|
.Pp
|
|
If successful, the
|
|
.Fn hsearch
|
|
function returns a pointer to hash table entry matching
|
|
the provided key.
|
|
If the action is
|
|
.Dv FIND
|
|
and the item was not found, or if the action is
|
|
.Dv ENTER
|
|
and the insertion failed,
|
|
.Dv NULL
|
|
is returned and
|
|
.Va errno
|
|
is set to indicate the error.
|
|
If the action is
|
|
.Dv ENTER
|
|
and an entry already existed in the table matching the given
|
|
key, the existing entry is returned and is not replaced.
|
|
.Pp
|
|
The
|
|
.Fn hsearch_r
|
|
function returns
|
|
.Dv 1
|
|
unless the table is full, when it returns
|
|
.Dv 0 .
|
|
If
|
|
.Fn hsearch
|
|
returns
|
|
.Dv 0
|
|
or the element is not found,
|
|
.Va errno
|
|
is set to indicate the error.
|
|
.Sh ERRORS
|
|
The
|
|
.Fn hcreate ,
|
|
.Fn hcreate_r ,
|
|
.Fn hsearch
|
|
and
|
|
.Fn hsearch_r
|
|
functions will fail if:
|
|
.Bl -tag -width Er
|
|
.It Bq Er ENOMEM
|
|
Insufficient memory is available.
|
|
.El
|
|
.Pp
|
|
The
|
|
.Fn hsearch
|
|
and
|
|
.Fn hsearch_r
|
|
functions will also fail if the action is
|
|
.Dv SEARCH
|
|
and the element is not found:
|
|
.Bl -tag -width Er
|
|
.It Bq Er ESRCH
|
|
The
|
|
.Fa item
|
|
given is not found.
|
|
.El
|
|
.Sh SEE ALSO
|
|
.Xr bsearch 3 ,
|
|
.Xr lsearch 3 ,
|
|
.Xr malloc 3 ,
|
|
.Xr strcmp 3
|
|
.Sh STANDARDS
|
|
The
|
|
.Fn hcreate ,
|
|
.Fn hdestroy
|
|
and
|
|
.Fn hsearch
|
|
functions conform to
|
|
.St -xpg4.2 .
|
|
.Sh HISTORY
|
|
The
|
|
.Fn hcreate ,
|
|
.Fn hdestroy
|
|
and
|
|
.Fn hsearch
|
|
functions first appeared in
|
|
.At V .
|
|
The
|
|
.Fn hcreate_r ,
|
|
.Fn hdestroy_r
|
|
and
|
|
.Fn hsearch_r
|
|
functions are
|
|
.Tn GNU
|
|
extensions.
|
|
.Sh CAVEATS
|
|
At least the following limitations can be mentioned:
|
|
.Bl -bullet
|
|
.It
|
|
The original,
|
|
.Pf non- Tn GNU
|
|
interface permits the use of only one hash table at a time.
|
|
.It
|
|
Individual hash table entries can be added, but not deleted.
|
|
.It
|
|
The standard is indecipherable about the
|
|
internal memory usage of the functions,
|
|
mentioning only that
|
|
.Do
|
|
.Fn hcreate
|
|
and
|
|
.Fn hsearch
|
|
functions may use
|
|
.Fn malloc
|
|
to allocate space
|
|
.Dc .
|
|
This limits the portability of the functions,
|
|
given that other implementations may not
|
|
.Xr free 3
|
|
the buffer pointed by
|
|
.Fa key .
|
|
.El
|