2fe8fb192f
There is important information about booting non-ack images in docs/UPDATING. ack/aout-format images can't be built any more, and booting clang/ELF-format ones is a little different. Updating to the new boot monitor is recommended. Changes in this commit: . drop boot monitor -> allowing dropping ack support . facility to copy ELF boot files to /boot so that old boot monitor can still boot fairly easily, see UPDATING . no more ack-format libraries -> single-case libraries . some cleanup of OBJECT_FMT, COMPILER_TYPE, etc cases . drop several ack toolchain commands, but not all support commands (e.g. aal is gone but acksize is not yet). . a few libc files moved to netbsd libc dir . new /bin/date as minix date used code in libc/ . test compile fix . harmonize includes . /usr/lib is no longer special: without ack, /usr/lib plays no kind of special bootstrapping role any more and bootstrapping is done exclusively through packages, so releases depend even less on the state of the machine making them now. . rename nbsd_lib* to lib* . reduce mtree
241 lines
5.3 KiB
Groff
241 lines
5.3 KiB
Groff
.\" $NetBSD: hcreate.3,v 1.8 2010/05/01 06:18:03 jruoho Exp $
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.\"
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.\" Copyright (c) 1999 The NetBSD Foundation, Inc.
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.\" All rights reserved.
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.\"
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.\" This code is derived from software contributed to The NetBSD Foundation
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.\" by Klaus Klein.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
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.\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
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.\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
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.\" BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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.\" POSSIBILITY OF SUCH DAMAGE.
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.\"
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.Dd May 1, 2010
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.Dt HCREATE 3
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.Os
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.Sh NAME
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.Nm hcreate ,
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.Nm hdestroy ,
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.Nm hsearch
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.Nd manage hash search table
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.Sh LIBRARY
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.Lb libc
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.Sh SYNOPSIS
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.In search.h
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.Ft int
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.Fn hcreate "size_t nel"
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.Ft void
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.Fn hdestroy "void"
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.Ft ENTRY *
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.Fn hsearch "ENTRY item" "ACTION action"
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.Sh DESCRIPTION
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The
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.Fn hcreate ,
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.Fn hdestroy
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and
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.Fn hsearch
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functions manage hash search tables.
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.Pp
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The
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.Fn hcreate
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function allocates and initializes the table.
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The
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.Fa nel
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argument specifies an estimate of the maximum number of entries to be held
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by the table.
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Unless further memory allocation fails, supplying an insufficient
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.Fa nel
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value will not result in functional harm, although a performance degradation
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may occur.
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Initialization using the
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.Fn hcreate
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function is mandatory prior to any access operations using
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.Fn hsearch .
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.Pp
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The
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.Fn hdestroy
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function destroys a table previously created using
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.Fn hcreate .
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After a call to
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.Fn hdestroy ,
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the data can no longer be accessed.
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.Pp
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The
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.Fn hsearch
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function is used to search to the hash table.
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It returns a pointer into the
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hash table indicating the address of an item.
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The
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.Fa item
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argument is of type
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.Vt ENTRY ,
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defined in the
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.In search.h
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header.
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This is a structure type that contains two pointers:
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.Pp
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.Bl -tag -compact -offset indent -width "void *data "
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.It Fa char *key
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comparison key
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.It Fa void *data
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pointer to data associated with
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.Fa key
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.El
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.Pp
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The key comparison function used by
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.Fn hsearch
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is
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.Xr strcmp 3 .
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.Pp
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The
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.Fa action
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argument is of type
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.Vt ACTION ,
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an enumeration type which defines the following values:
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.Bl -tag -offset indent -width ENTERXX
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.It Dv ENTER
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Insert
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.Fa item
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into the hash table.
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If an existing item with the same key is found, it is not replaced.
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Note that the
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.Fa key
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and
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.Fa data
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elements of
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.Fa item
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are used directly by the new table entry.
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The storage for the
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key must not be modified during the lifetime of the hash table.
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.It Dv FIND
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Search the hash table without inserting
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.Fa item .
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.El
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.Pp
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Note that the comparison
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.Fa key
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must be allocated using
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.Xr malloc 3
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or
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.Xr calloc 3
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if action is
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.Dv ENTER
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and
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.Fn hdestroy
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will be called.
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This is because
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.Fn hdestroy
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will call
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.Xr free 3
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for each comparison
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.Fa key
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(but not
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.Fa data ) .
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Typically the comparison
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.Fa key
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is allocated by using
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.Xr strdup 3 .
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.Sh RETURN VALUES
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If successful, the
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.Fn hcreate
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function returns a non-zero value.
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Otherwise, a value of 0 is returned and
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.Va errno
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is set to indicate the error.
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.Pp
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The
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.Fn hdestroy
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functions
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returns no value.
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.Pp
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If successful, the
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.Fn hsearch
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function returns a pointer to hash table entry matching
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the provided key.
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If the action is
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.Dv FIND
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and the item was not found, or if the action is
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.Dv ENTER
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and the insertion failed,
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.Dv NULL
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is returned and
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.Va errno
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is set to indicate the error.
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If the action is
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.Dv ENTER
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and an entry already existed in the table matching the given
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key, the existing entry is returned and is not replaced.
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.Sh ERRORS
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The
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.Fn hcreate
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and
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.Fn hsearch
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functions will fail if:
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.Bl -tag -width Er
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.It Bq Er ENOMEM
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Insufficient memory is available.
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.El
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.Sh SEE ALSO
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.Xr bsearch 3 ,
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.Xr lsearch 3 ,
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.Xr malloc 3 ,
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.Xr strcmp 3
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.Sh STANDARDS
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The
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.Fn hcreate ,
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.Fn hdestroy
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and
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.Fn hsearch
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functions conform to
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.St -xpg4.2 .
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.Sh HISTORY
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The
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.Fn hcreate ,
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.Fn hdestroy
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and
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.Fn hsearch
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functions first appeared in
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.At V .
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.Sh CAVEATS
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At least the following limitations can be mentioned:
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.Bl -bullet
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.It
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The interface permits the use of only one hash table at a time.
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.It
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Individual hash table entries can be added, but not deleted.
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.It
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The standard is indecipherable about the
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internal memory usage of the functions,
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mentioning only that
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.Do
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.Fn hcreate
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and
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.Fn hsearch
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functions may use
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.Fn malloc
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to allocate space
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.Dc .
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This limits the portability of the functions,
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given that other implementations may not
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.Xr free 3
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the buffer pointed by
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.Fa key .
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.El
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