[linuxjm/LDP_man-pages.git] / draft / man3 / hsearch.3

.\" Hey Emacs! This file is -*- nroff -*- source.
.\" Copyright 1993 Ulrich Drepper (drepper@karlsruhe.gmd.de)
.\" and Copyright 2008, Linux Foundation, written by Michael Kerrisk
.\"     <mtk.manpages@gmail.com>
.\"
.\" This is free documentation; you can redistribute it and/or
.\" modify it under the terms of the GNU General Public License as
.\" published by the Free Software Foundation; either version 2 of
.\" the License, or (at your option) any later version.
.\"
.\" The GNU General Public License's references to "object code"
.\" and "executables" are to be interpreted as the output of any
.\" document formatting or typesetting system, including
.\" intermediate and printed output.
.\"
.\" This manual is distributed in the hope that it will be useful,
.\" but WITHOUT ANY WARRANTY; without even the implied warranty of
.\" MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
.\" GNU General Public License for more details.
.\"
.\" You should have received a copy of the GNU General Public
.\" License along with this manual; if not, write to the Free
.\" Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111,
.\" USA.
.\"
.\" References consulted:
.\"     SunOS 4.1.1 man pages
.\" Modified Sat Sep 30 21:52:01 1995 by Jim Van Zandt <jrv@vanzandt.mv.com>
.\" Remarks from dhw@gamgee.acad.emich.edu Fri Jun 19 06:46:31 1998
.\" Modified 2001-12-26, 2003-11-28, 2004-05-20, aeb
.\" 2008-09-02, mtk: various additions and rewrites
.\" 2008-09-03, mtk, restructured somewhat, in part after suggestions from
.\"     Timothy S. Nelson <wayland@wayland.id.au>
.\"
.\" Japanese Version Copyright (c) 1998 George Momma,
.\"     Copyright (c) 2001-2005 Yuichi SATO,
.\"     and Copyright (c) 2008 Akihiro MOTOKI
.\" Translated 1998-05-23, George Momma <momma@wakhok.ac.jp>
.\" Updated & Modified 2001-10-15, Yuichi SATO <ysato@h4.dion.ne.jp>
.\" Updated & Modified 2002-01-03, Yuichi SATO
.\" Updated & Modified 2004-01-17, Yuichi SATO <ysato444@yahoo.co.jp>
.\" Updated & Modified 2005-01-10, Yuichi SATO
.\" Updated 2008-09-20, Akihiro MOTOKI <amotoki@dd.iij4u.or.jp>
.\"
.\"WORD:        hash table              ¥Ï¥Ã¥·¥å¥Æ¡¼¥Ö¥ë
.\"WORD:        entry                   ¥¨¥ó¥È¥ê¡¼
.\"WORD:        allocate                ³ä¤êÅö¤Æ
.\"WORD:        NUL-terminated          ¥Ì¥ëʸ»ú \0 ¤Ç½ªÃ¼¤µ¤ì¤¿
.\"WORD:        pointer                 ¥Ý¥¤¥ó¥¿
.\"WORD:        character               ʸ»ú·¿
.\"WORD:        item                    ¹àÌÜ
.\"
.TH HSEARCH 3 2008-10-06 "GNU" "Linux Programmer's Manual"
.\"O .SH NAME
.SH ̾Á°
.\"O hcreate, hdestroy, hsearch, hcreate_r, hdestroy_r,
.\"O hsearch_r \- hash table management
hcreate, hdestroy, hsearch, hcreate_r, hdestroy_r,
hsearch_r \- ¥Ï¥Ã¥·¥å¥Æ¡¼¥Ö¥ë¤Î´ÉÍý
.\"O .SH SYNOPSIS
.SH ½ñ¼°
.nf
.B #include <search.h>
.sp
.BI "int hcreate(size_t " nel );
.sp
.BI "ENTRY *hsearch(ENTRY " item ", ACTION " action );
.sp
.B "void hdestroy(void);"
.sp
.B #define _GNU_SOURCE
.br
.B #include <search.h>
.sp
.BI "int hcreate_r(size_t " nel ", struct hsearch_data *" htab );
.sp
.BI "int hsearch_r(ENTRY " item ", ACTION " action ", ENTRY **" retval ,
.BI "              struct hsearch_data *" htab );
.sp
.BI "void hdestroy_r(struct hsearch_data *" htab );
.fi
.\"O .SH DESCRIPTION
.SH ÀâÌÀ
.\"O The three functions
.\"O .BR hcreate (),
.\"O .BR hsearch (),
.\"O and
.\"O .BR hdestroy ()
.\"O allow the caller to create and manage a hash search table
.\"O containing entries consisting of a key (a string) and associated data.
.\"O Using these functions, only one hash table can be used at a time.
.BR hcreate (),
.BR hsearch (),
.BR hdestroy ()
¤Î 3 ¤Ä¤Î´Ø¿ô¤òÍøÍѤ¹¤ë¤È¡¢¥­¡¼ (ʸ»úÎó) ¤ÈÂбþ¤¹¤ë¥Ç¡¼¥¿¤«¤é¹½À®¤µ¤ì¤ë
¥¨¥ó¥È¥ê¤ò³ÊǼ¤Ç¤­¤ë¥Ï¥Ã¥·¥å¸¡º÷¥Æ¡¼¥Ö¥ë¤òºîÀ®¡¢´ÉÍý¤¹¤ë¤³¤È¤¬¤Ç¤­¤ë¡£
¤³¤ì¤é¤Î´Ø¿ô¤ò»È¤Ã¤Æ¡¢°ìÅ٤˻ÈÍѤǤ­¤ë¤Î¤Ï°ì¤Ä¤Î¥Ï¥Ã¥·¥å¥Æ¡¼¥Ö¥ë¤À¤±¤Ç¤¢¤ë¡£

.\"O The three functions
.\"O .BR hcreate_r (),
.\"O .BR hsearch_r (),
.\"O .BR hdestroy_r ()
.\"O are reentrant versions that allow a program to use
.\"O more than one hash search table at the same time.
.\"O The last argument,
.\"O .IR htab ,
.\"O points to a structure that describes the table
.\"O on which the function is to operate.
.\"O The programmer should treat this structure as opaque
.\"O (i.e., do not attempt to directly access or modify
.\"O the fields in this structure).
.BR hcreate_r (),
.BR hsearch_r (),
.BR hdestroy_r ()
¤Î 3 ¤Ä¤Î´Ø¿ô¤Ï¥ê¥¨¥ó¥È¥é¥ó¥ÈÈǤǡ¢¤³¤ì¤é¤òÍøÍѤ¹¤ë¤È¡¢
°ì¤Ä¤Î¥×¥í¥°¥é¥à¤ÇƱ»þ¤ËÊ£¿ô¤Î¥Ï¥Ã¥·¥å¥Æ¡¼¥Ö¥ë¤ò»È¤¦¤³¤È¤¬¤Ç¤­¤ë¡£
ºÇ¸å¤Î°ú¤­¿ô
.I htab
¤Ï´Ø¿ô¤ÎÁàºîÂоݤȤʤë¥Æ¡¼¥Ö¥ë¤ò¼¨¤¹¹½Â¤ÂΤؤΥݥ¤¥ó¥¿¤Ç¤¢¤ë¡£
¥×¥í¥°¥é¥Þ¤Ï¤³¤Î¹½Â¤ÂΤò¥Ö¥é¥Ã¥¯¥Ü¥Ã¥¯¥¹¤È¤·¤Æ°·¤¦¤Ù¤­¤Ç¤¢¤ë
(¤Ä¤Þ¤ê¡¢¤³¤Î¹½Â¤ÂΤΥե£¡¼¥ë¥É¤ËľÀÜ¥¢¥¯¥»¥¹¤·¤¿¤êÊѹ¹¤·¤¿¤ê
¤·¤Ê¤¤¤³¤È)¡£

.\"O First a hash table must be created using
.\"O .BR hcreate ().
.\"O The argument \fInel\fP specifies the maximum number of entries
.\"O in the table.
.\"O (This maximum cannot be changed later, so choose it wisely.)
.\"O The implementation may adjust this value upward to improve the
.\"O performance of the resulting hash table.
ºÇ½é¤Ë¡¢
.BR hcreate ()
´Ø¿ô¤Ë¤è¤Ã¤Æ¥Ï¥Ã¥·¥å¥Æ¡¼¥Ö¥ë¤òºîÀ®¤·¤Ê¤±¤ì¤Ð¤Ê¤é¤Ê¤¤¡£
°ú¤­¿ô \fInel\fP ¤Ç¥Æ¡¼¥Ö¥ë¤ÎºÇÂ票¥ó¥È¥ê¿ô¤ò»ØÄꤹ¤ë
(¤³¤ÎºÇÂçÃͤϸå¤ÇÊѹ¹¤¹¤ë¤³¤È¤Ï¤Ç¤­¤Ê¤¤¤Î¤Ç¡¢¤è¤¯¹Í¤¨¤ÆÁªÂò¤¹¤ë¤³¤È)¡£
ºîÀ®¤µ¤ì¤ë¥Ï¥Ã¥·¥å¥Æ¡¼¥Ö¥ë¤ÎÀ­Ç½¤ò¸þ¾å¤µ¤»¤ë¤¿¤á¤Ë¡¢
´Ø¿ôÆâÉô¤Î¼ÂÁõ¤Ë¤è¤ê¤³¤ÎÃͤÏÁý¤ä¤µ¤ì¤ë¾ì¹ç¤â¤¢¤ë¡£
.\" e.g., in glibc it is raised to the next higher prime number

.\"O The
.\"O .BR hcreate_r ()
.\"O function performs the same task as
.\"O .BR hcreate (),
.\"O but for the table described by the structure
.\"O .IR *htab .
.\"O The structure pointed to by
.\"O .I htab
.\"O must be zeroed before the first call to
.\"O .BR hcreate_r ().
.BR hcreate_r ()
´Ø¿ô¤Ï
.BR hcreate ()
¤ÈƱ¤¸Æ°ºî¤ò¤¹¤ë¤¬¡¢¹½Â¤ÂÎ
.I *htab
¤Ç¼¨¤µ¤ì¤ë¥Æ¡¼¥Ö¥ë¤òÂоݤȤ·¤ÆÆ°ºî¤¹¤ë¡£
.I htab
¤¬»Ø¤·¼¨¤¹¹½Â¤ÂΤϡ¢
.BR hcreate_r ()
¤ò½é¤á¤Æ¸Æ¤Ó½Ð¤¹Á°¤Ë 0 ¤ÇËä¤á¤Æ¤ª¤«¤Ê¤±¤ì¤Ð¤Ê¤é¤Ê¤¤¡£

.\"O The function
.\"O .BR hdestroy ()
.\"O frees the memory occupied by the hash table that was created by
.\"O .BR hcreate ().
.\"O After calling
.\"O .BR hdestroy ()
.\"O a new hash table can be created using
.\"O .BR hcreate ().
.\"O The
.\"O .BR hdestroy_r ()
.\"O function performs the analogous task for a hash table described by
.\"O .IR *htab ,
.\"O which was previously created using
.\"O .BR hcreate_r ().
.BR hdestroy ()
´Ø¿ô¤Ï¡¢
.BR hcreate ()
¤ÇºîÀ®¤µ¤ì¤¿¥Ï¥Ã¥·¥å¥Æ¡¼¥Ö¥ë¤¬ÀêÍ­¤·¤Æ¤¤¤¿¥á¥â¥ê¤ò²òÊü¤¹¤ë¡£
¥Ï¥Ã¥·¥å¥Æ¡¼¥Ö¥ë¤Ë¤è¤Ã¤ÆÀêÍ­¤µ¤ì¤Æ¤¤¤¿¥á¥â¥ê¤ò²òÊü¤·¡¢
¿·¤·¤¤¥Æ¡¼¥Ö¥ë¤òºîÀ®¤Ç¤­¤ë¤è¤¦¤Ë¤¹¤ë¡£
.BR hdestroy ()
¤ò¸Æ¤Ó½Ð¤¹¤È¡¢¤½¤Î¸å¤Ï
.BR hcreate ()
¤ò»È¤Ã¤Æ¿·¤·¤¤¥Ï¥Ã¥·¥å¥Æ¡¼¥Ö¥ë¤òºîÀ®¤¹¤ë¤³¤È¤¬¤Ç¤­¤ë¡£
.BR hdestroy_r ()
´Ø¿ô¤Ï¡¢Æ±ÍͤνèÍý¤ò¡¢¤½¤ì°ÊÁ°¤Ë
.BR hcreate_r ()
¤ò»È¤Ã¤ÆºîÀ®¤·¤¿
.I *htab
¤Ç¼¨¤µ¤ì¤ë¥Ï¥Ã¥·¥å¥Æ¡¼¥Ö¥ë¤ËÂФ·¤Æ¼Â¹Ô¤¹¤ë¡£

.\"O The
.\"O .BR hsearch ()
.\"O function searches the hash table for an
.\"O item with the same key as \fIitem\fP (where "the same" is determined using
.\"O .BR strcmp (3)),
.\"O and if successful returns a pointer to it.
.BR hsearch ()
´Ø¿ô¤Ï¡¢\fIitem\fP ¤ÈƱ¤¸¥­¡¼¤ò»ý¤Ä¹àÌܤò¥Ï¥Ã¥·¥å¥Æ¡¼¥Ö¥ë¤«¤é
¸¡º÷¤·¡¢¹àÌܤ¬¸«¤Ä¤«¤Ã¤¿¾ì¹ç¤Ë¤Ï¤½¤Î¹àÌܤؤΥݥ¤¥ó¥¿¤òÊÖ¤¹
(¡ÖƱ¤¸¡×¤«¤É¤¦¤«¤Ï
.BR strcmp (3)
¤ò»È¤Ã¤ÆȽÄꤹ¤ë)¡£

.\"O The argument \fIitem\fP is of type \fIENTRY\fP, which is defined in
.\"O \fI<search.h>\fP as follows:
°ú¤­¿ô \fIitem\fP ¤Ï \fBENTRY\fP ·¿¤Ç¤¢¤ê¡¢\fI<search.h>\fP ¤ÎÃæ¤Ç
°Ê²¼¤Î¤è¤¦¤ËÄêµÁ¤µ¤ì¤Æ¤¤¤ë¡£
.in +4n
.sp
.nf
typedef struct entry {
    char *key;
    void *data;
} ENTRY;
.in
.fi
.sp
.\"O The field \fIkey\fP points to a null-terminated string which is the
.\"O search key.
.\"O The field \fIdata\fP points to data that is associated with that key.
¥Õ¥£¡¼¥ë¥É \fIkey\fP ¤Ï¸¡º÷¥­¡¼¤È¤Ê¤ë NULL ½ªÃ¼¤µ¤ì¤¿Ê¸»úÎó¤ò»Ø¤¹¡£
¥Õ¥£¡¼¥ë¥É \fIdata\fP ¤Ï¡¢¤³¤Î¥­¡¼¤ËÂбþ¤¹¤ë¥Ç¡¼¥¿¤ò»Ø¤¹¡£

.\"O The argument \fIaction\fP determines what
.\"O .BR hsearch ()
.\"O does after an unsuccessful search.
¸¡º÷¤¬¼ºÇÔ¤·¤¿¸å¤ÎÆ°ºî¤Ï¡¢°ú¤­¿ô \fIaction\fP ¤Ë¤è¤ê·è¤Þ¤ë¡£
.\"O This argument must either have the value
.\"O .BR ENTER ,
.\"O meaning insert a copy of
.\"O .IR item
.\"O (and return a pointer to the new hash table entry as the function result),
.\"O or the value
.\"O .BR FIND ,
.\"O meaning that NULL should be returned.
.\"O (If
.\"O .I action
.\"O is
.\"O .BR FIND ,
.\"O then
.\"O .I data
.\"O is ignored.)
¤³¤Î°ú¤­¿ô¤Ë¤Ï
.B ENTER
¤«
.B FIND
¤Î¤¤¤º¤ì¤«¤ÎÃͤò»ØÄꤷ¤Ê¤±¤ì¤Ð¤Ê¤é¤Ê¤¤¡£
.B ENTER
¤Ï
.I item
¤Î¥³¥Ô¡¼¤òÁÞÆþ¤¹¤ë¤³¤È¤ò
(´Ø¿ô¤Î·ë²Ì¤È¤·¤Æ¿·¤·¤¤¥Ï¥Ã¥·¥å¥Æ¡¼¥Ö¥ë¥¨¥ó¥È¥ê¤Ø¤Î¥Ý¥¤¥ó¥¿¤òÊÖ¤¹)¡¢
.B FIND
¤Ï NULL ¤òÊÖ¤¹¤³¤È¤ò°ÕÌ£¤¹¤ë
.RI ( action
¤¬
.B FIND
¤Î¾ì¹ç¡¢
.I data
¤Ï̵»ë¤µ¤ì¤ë)¡£

.\"O The
.\"O .BR hsearch_r ()
.\"O function is like
.\"O .BR hsearch ()
.\"O but operates on the hash table described by
.\"O .IR *htab .
.\"O The
.\"O .BR hsearch_r ()
.\"O function differs from
.\"O .BR hsearch ()
.\"O in that a pointer to the found item is returned in
.\"O .IR *retval ,
.\"O rather than as the function result.
.BR hsearch_r ()
´Ø¿ô¤Ï
.BR hsearch ()
¤ÈƱÍͤÀ¤¬¡¢
.I *htab
¤Ç¼¨¤µ¤ì¤ë¥Ï¥Ã¥·¥å¥Æ¡¼¥Ö¥ë¤ËÂФ·¤Æ½èÍý¤ò¹Ô¤¦¡£
.BR hsearch_r ()
´Ø¿ô¤¬
.BR hsearch ()
¤È°Û¤Ê¤ë¤Î¤Ï¡¢¸«¤Ä¤«¤Ã¤¿¹àÌܤؤΥݥ¤¥ó¥¿¤ò¡¢
´Ø¿ô¤Î·ë²Ì¤È¤·¤Æ¤Ç¤Ï¤Ê¤¯¡¢
.I *retval
¤Ë³ÊǼ¤·¤ÆÊÖ¤¹ÅÀ¤Ç¤¢¤ë¡£
.\"O .SH "RETURN VALUE"
.SH ÊÖ¤êÃÍ
.\"O .BR hcreate ()
.\"O and
.\"O .BR hcreate_r ()
.\"O return nonzero on success.
.\"O They return 0 on error.
.BR hcreate ()
¤È
.BR hcreate_r ()
¤Ï¡¢À®¸ù¤·¤¿¾ì¹ç 0 °Ê³°¤ÎÃͤòÊÖ¤·¡¢
¥¨¥é¡¼¤Î¾ì¹ç 0 ¤òÊÖ¤¹¡£

.\"O On success,
.\"O .BR hsearch ()
.\"O returns a pointer to an entry in the hash table.
.\"O .BR hsearch ()
.\"O returns NULL on error, that is,
.\"O if \fIaction\fP is \fBENTER\fP and
.\"O the hash table is full, or \fIaction\fP is \fBFIND\fP and \fIitem\fP
.\"O cannot be found in the hash table.
À®¸ù¤¹¤ë¤È¡¢
.BR hsearch ()
¤Ï¡¢¥Ï¥Ã¥·¥å¥Æ¡¼¥Ö¥ëÆâ¤Î¥¨¥ó¥È¥ê¤Ø¤Î¥Ý¥¤¥ó¥¿¤òÊÖ¤¹¡£
¥¨¥é¡¼¤Î¾ì¹ç¡¢
.BR hsearch ()
¤Ï NULL ¤òÊÖ¤¹¡£
¥¨¥é¡¼¤È¤Ê¤ë¤Î¤Ï¡¢
\fIaction\fP ¤¬ \fBENTER\fP ¤Ç¥Ï¥Ã¥·¥å¥Æ¡¼¥Ö¥ë¤¬¤¤¤Ã¤Ñ¤¤¤Î¾ì¹ç¤«¡¢
\fIaction\fP ¤¬ \fBFIND\fP ¤Ç \fIitem\fP ¤¬¥Ï¥Ã¥·¥å¥Æ¡¼¥Ö¥ëÆâ¤Ë
¸«¤Ä¤«¤é¤Ê¤¤¾ì¹ç¤Ç¤¢¤ë¡£
.\"O .BR hsearch_r ()
.\"O returns nonzero on success, and 0 on error.
.BR hsearch_r ()
¤Ï¡¢À®¸ù¤¹¤ë¤È 0 °Ê³°¤òÊÖ¤·¡¢¥¨¥é¡¼¤Î¾ì¹ç 0 ¤òÊÖ¤¹¡£
.\"O .SH ERRORS
.SH ¥¨¥é¡¼
.LP
.\"O .BR hcreate ()
.\"O and
.\"O .BR hcreate_r ()
.\"O can fail for the following reasons:
.BR hcreate ()
¤È
.BR hcreate_r ()
¤Ï°Ê²¼¤ÎÍýͳ¤Ç¼ºÇÔ¤¹¤ë²ÄǽÀ­¤¬¤¢¤ë¡£
.TP
.B EINVAL
.\"O .RB ( hcreate_r ())
.\"O .I htab
.\"O is NULL.
.RB ( hcreate_r ())
.I htab
¤¬ NULL ¤Ç¤¢¤ë¡£
.TP
.B ENOMEM
.\"O Table full with \fIaction\fP set to \fBENTER\fP.
\fBENTER\fP ¤ËÀßÄꤵ¤ì¤¿ \fIaction\fP ¤Ç¡¢
¥Æ¡¼¥Ö¥ë¤¬¤¤¤Ã¤Ñ¤¤¤Ë¤Ê¤Ã¤¿¡£
.TP
.B ESRCH
.\"O The \fIaction\fP argument is \fBFIND\fP and no corresponding element
.\"O is found in the table.
\fIaction\fP °ú¤­¿ô¤¬ \fBFIND\fP ¤Ç¡¢
¤«¤ÄÂбþ¤¹¤ëÍ×ÁǤ¬¥Æ¡¼¥Ö¥ë¤Ë¸«¤Ä¤«¤é¤Ê¤«¤Ã¤¿¡£
.\"O .\" hdestroy_r() can set errno to EINVAL if 'tab' is NULL.
.\" hdestroy_r() ¤Ï 'tab' ¤¬ NULL ¤Î¾ì¹ç errno ¤Ë EINVAL ¤òÀßÄꤹ¤ë¾ì¹ç¤¬¤¢¤ë¡£
.PP
.\"O .BR hsearch ()
.\"O and
.\"O .BR hsearch_r ()
.\"O can fail for the following reasons:
.BR hsearch ()
¤È
.BR hsearch_r ()
¤Ï°Ê²¼¤ÎÍýͳ¤Ç¼ºÇÔ¤¹¤ë²ÄǽÀ­¤¬¤¢¤ë¡£
.TP
.B ENOMEM
.\"O .I action
.\"O was
.\"O .BR ENTER ,
.\"O .I key
.\"O was not found in the table,
.\"O and there was no room in the table to add a new entry.
.I action
¤¬
.B ENTER
¤Ç¡¢
.I key
¤¬¥Æ¡¼¥Ö¥ëÆâ¤Ë¸«¤Ä¤«¤é¤º¡¢
¥Æ¡¼¥Ö¥ë¤Ë¿·¤·¤¤¥¨¥ó¥È¥ê¤òÄɲ乤ë;ÃϤ¬¤Ê¤«¤Ã¤¿¡£
.TP
.B ESRCH
.\"O .I action
.\"O was
.\"O .BR FIND ,
.\"O and
.\"O .I key
.\"O was not found in the table.
.I action
¤¬
.B FIND
¤Ç¡¢
.I key
¤¬¥Æ¡¼¥Ö¥ëÆâ¤Ë¸«¤Ä¤«¤é¤Ê¤«¤Ã¤¿¡£
.PP
.\"O POSIX.1-2001 only specifies the
.\"O .B ENOMEM
.\"O error.
POSIX.1-2001 ¤¬µ¬Äꤷ¤Æ¤¤¤ë¤Î¤Ï¡¢¥¨¥é¡¼
.B ENOMEM
¤À¤±¤Ç¤¢¤ë¡£
.\"O .SH "CONFORMING TO"
.SH ½àµò
.\"O The functions
.\"O .BR hcreate (),
.\"O .BR hsearch (),
.\"O and
.\"O .BR hdestroy ()
.\"O are from SVr4, and are described in POSIX.1-2001.
´Ø¿ô
.BR hcreate (),
.BR hsearch (),
.BR hdestroy ()
¤Ï SVr4 ¤«¤éƳÆþ¤µ¤ì¤¿¤â¤Î¤Ç¡¢POSIX.1-2001 ¤Ëµ­½Ò¤µ¤ì¤Æ¤¤¤ë¡£
.\"O The functions
.\"O .BR hcreate_r ,
.\"O .BR hsearch_r ,
.\"O and
.\"O .BR hdestroy_r
.\"O are GNU extensions.
´Ø¿ô
.BR hcreate_r ,
.BR hsearch_r ,
.B hdestroy_r
¤Ï GNU ¤Î³ÈÄ¥¤Ç¤¢¤ë¡£
.\"O .SH NOTES
.SH Ãí°Õ
.\"O Hash table implementations are usually more efficient when the
.\"O table contains enough free space to minimize collisions.
.\"O Typically, this means that
.\"O .I nel
.\"O should be at least 25% larger than the maximum number of elements
.\"O that the caller expects to store in the table.
Ä̾¥Ï¥Ã¥·¥å¥Æ¡¼¥Ö¥ë¤Î¼ÂÁõ¤Ï¡¢¾×ÆͤòºÇ¾®¸Â¤Ë¤¹¤ë¤¿¤á¤Ë
¥Æ¡¼¥Ö¥ë¤Ë½½Ê¬¤Ê¶õ¤­Îΰ褬¤¢¤ë¾ì¹ç¤Ë¸úΨ¤¬¤è¤¯¤Ê¤ë¡£
¤³¤Î¤¿¤á¡¢ÉáÄ̤ϡ¢
.I nel
¤ò¡¢¸Æ¤Ó½Ð¤·Â¦¤¬¥Æ¡¼¥Ö¥ë¤Ë³ÊǼ¤·¤è¤¦¤È»×¤Ã¤Æ¤¤¤ë
¥¨¥ó¥È¥ê¤ÎºÇÂç¿ô¤è¤ê¾¯¤Ê¤¯¤È¤â 25% ¤ÏÂ礭¤ÊÃͤˤ¹¤Ù¤­¤Ç¤¢¤ë¡£

.\"O The
.\"O .BR hdestroy ()
.\"O and
.\"O .BR hdestroy _r()
.\"O functions do not free the buffers pointed to by the
.\"O .I key
.\"O and
.\"O .I data
.\"O elements of the hash table entries.
.\"O (It can't do this because it doesn't know
.\"O whether these buffers were allocated dynamically.)
.BR hdestroy ()
¤È
.BR hdestroy_r ()
¤Ï¡¢¥Ï¥Ã¥·¥å¥Æ¡¼¥Ö¥ë¤Î¥¨¥ó¥È¥ê¤ÎÍ×ÁǤǤ¢¤ë
.I key
¤È
.I data
¤¬»Ø¤¹¥Ð¥Ã¥Õ¥¡¤ò²òÊü¤·¤Ê¤¤
(¤³¤ì¤¬¤Ç¤­¤Ê¤¤¤Î¤Ï¡¢¤³¤ì¤é¤Î¥Ð¥Ã¥Õ¥¡¤¬Æ°Åª¤Ë³ä¤êÅö¤Æ¤é¤ì¤¿¤Î¤«¤ò
ÃΤ뤳¤È¤¬¤Ç¤­¤Ê¤¤¤«¤é¤Ç¤¢¤ë)¡£
.\"O If these buffers need to be freed (perhaps because the program
.\"O is repeatedly creating and destroying hash tables,
.\"O rather than creating a single table whose lifetime
.\"O matches that of the program),
.\"O then the program must maintain bookkeeping data structures that
.\"O allow it to free them.
¤³¤ì¤é¤Î¥Ð¥Ã¥Õ¥¡¤ò²òÊü¤¹¤ëɬÍפ¬¤¢¤ë¾ì¹ç¡¢
¥×¥í¥°¥é¥à¤Ç¤Ï¡¢¤³¤ì¤é¤Î¥Ð¥Ã¥Õ¥¡¤ò²òÊü¤Ç¤­¤ë¤è¤¦¤Ë´ÉÍýÍѤΥǡ¼¥¿¹½Â¤¤ò
Àߤ±¤Æ¡¢¤³¤ì¤ò´ÉÍý¤·¤Ê¤±¤ì¤Ð¤Ê¤é¤Ê¤¤
(²òÊü¤¬É¬ÍפȤʤëÍýͳ¤Ï¡¢¤¿¤¤¤Æ¤¤¤Ï¡¢¥×¥í¥°¥é¥à¼«¿È¤ÈÀ¸Â¸´ü´Ö¤¬Æ±¤¸
¥Ï¥Ã¥·¥å¥Æ¡¼¥Ö¥ë¤ò°ì¤Ä¤À¤±ºîÀ®¤¹¤ë¤Î¤Ç¤Ï¤Ê¤¯¡¢¤½¤Î¥×¥í¥°¥é¥à¤Ç¤ÏÊ£¿ô¤Î
¥Ï¥Ã¥·¥å¥Æ¡¼¥Ö¥ë¤ò·«¤êÊÖ¤·¤ÆºîÀ®¤·¤¿¤êÇË´þ¤·¤¿¤ê¤¹¤ë¤«¤é¤Ç¤¢¤í¤¦)¡£
.\"O .SH BUGS
.SH ¥Ð¥°
.\"O SVr4 and POSIX.1-2001 specify that \fIaction\fP
.\"O is significant only for unsuccessful searches, so that an \fBENTER\fP
.\"O should not do anything for a successful search.
.\"O In libc and glibc (before version 2.3), the
.\"O implementation violates the specification,
.\"O updating the \fIdata\fP for the given \fIkey\fP in this case.
SVr4 ¤È POSIX.1-2001 ¤Îµ¬Äê¤Ç¤Ï¡¢
\fIaction\fP ¤Ï¸¡º÷¤¬¼ºÇÔ¤·¤¿¤È¤­¤Ë¤À¤±°ÕÌ£¤ò»ý¤Ä¤È¤Ê¤Ã¤Æ¤¤¤ë¡£
¤è¤Ã¤Æ¡¢¸¡º÷¤¬À®¸ù¤·¤¿¾ì¹ç¡¢\fIaction\fP ¤ÎÃͤ¬ \fBENTER\fP ¤Ç¤â
²¿¤â¤¹¤Ù¤­¤Ç¤Ï¤Ê¤¤¡£
(¥Ð¡¼¥¸¥ç¥ó 2.3 ¤è¤êÁ°¤Î) libc ¤È glibc ¤Î¼ÂÁõ¤Ï¤³¤Îµ¬³Ê¤Ë°ãÈ¿¤·¤Æ¤ª¤ê¡¢
¤³¤Î¾õ¶·¤Ç¡¢»ØÄꤵ¤ì¤¿ \fIkey\fP ¤ËÂбþ¤¹¤ë \fIdata\fP ¤¬¹¹¿·¤µ¤ì¤ë¡£

.\"O Individual hash table entries can be added, but not deleted.
¥Ï¥Ã¥·¥å¥Æ¡¼¥Ö¥ë¥¨¥ó¥È¥ê¡¼¤ÎÄɲäϤǤ­¤ë¤¬¡¢ºï½ü¤¬¤Ç¤­¤Ê¤¤¡£
.\"O .SH EXAMPLE
.SH Îã
.PP
.\"O The following program inserts 24 items into a hash table, then prints
.\"O some of them.
¼¡¤Î¥×¥í¥°¥é¥à¤Ï¡¢¥Ï¥Ã¥·¥å¥Æ¡¼¥Ö¥ë¤Ë 24 ¸Ä¤Î¹àÌܤòÁÞÆþ¤·¡¢
¤½¤ì¤«¤é¤½¤Î¤¦¤Á¤Î¤¤¤¯¤Ä¤«¤òɽ¼¨¤¹¤ë¡£
.nf

#include <stdio.h>
#include <stdlib.h>
#include <search.h>

char *data[] = { "alpha", "bravo", "charlie", "delta",
     "echo", "foxtrot", "golf", "hotel", "india", "juliet",
     "kilo", "lima", "mike", "november", "oscar", "papa",
     "quebec", "romeo", "sierra", "tango", "uniform",
     "victor", "whisky", "x\-ray", "yankee", "zulu"
};

int main()
{
    ENTRY e, *ep;
    int i;

    hcreate(30);

    for (i = 0; i < 24; i++) {
        e.key = data[i];
.\"O         /* data is just an integer, instead of a
.\"O            pointer to something */
        /* ¥Ç¡¼¥¿¤Ï¡¢¥Ý¥¤¥ó¥¿¤Ç¤Ï¤Ê¤¯¡¢Ã±¤Ê¤ëÀ°¿ôÃͤǤ¢¤ë¡£ */
        e.data = (void *) i;
        ep = hsearch(e, ENTER);
.\"O         /* there should be no failures */
        /* ¥¨¥é¡¼¤Ïµ¯¤³¤é¤Ê¤¤¤Ï¤º¤Ç¤¢¤ë¡£ */
        if (ep == NULL) {
            fprintf(stderr, "entry failed\\n");
            exit(EXIT_FAILURE);
        }
    }

    for (i = 22; i < 26; i++) {
.\"O         /* print two entries from the table, and
.\"O            show that two are not in the table */
        /* ¥Æ¡¼¥Ö¥ë¤Ë¤¢¤ë 2 ¤Ä¤Î¥¨¥ó¥È¥ê¤òɽ¼¨¤·¡¢
           ¤¢¤È¤Î 2 ¤Ä¤¬¥Æ¡¼¥Ö¥ë¤Ë¤Ê¤¤¤³¤È¤ò¼¨¤¹¡£ */
        e.key = data[i];
        ep = hsearch(e, FIND);
        printf("%9.9s \-> %9.9s:%d\\n", e.key,
               ep ? ep\->key : "NULL", ep ? (int)(ep\->data) : 0);
    }
    hdestroy();
    exit(EXIT_SUCCESS);
}
.fi
.\"O .SH "SEE ALSO"
.SH ´ØÏ¢¹àÌÜ
.BR bsearch (3),
.BR lsearch (3),
.BR malloc (3),
.BR tsearch (3),
.BR feature_test_macros (7)