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+/* Copyright (C) 1993, 1995, 1996, 1997, 2002 Free Software Foundation, Inc.
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+ This file is part of the GNU C Library.
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+ Contributed by Ulrich Drepper <drepper@gnu.ai.mit.edu>, 1993.
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+
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+ The GNU C Library is free software; you can redistribute it and/or
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+ modify it under the terms of the GNU Lesser General Public
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+ License as published by the Free Software Foundation; either
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+ version 2.1 of the License, or (at your option) any later version.
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+
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+ The GNU C Library is distributed in the hope that it will be useful,
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+ but WITHOUT ANY WARRANTY; without even the implied warranty of
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+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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+ Lesser General Public License for more details.
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+
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+ You should have received a copy of the GNU Lesser General Public
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+ License along with the GNU C Library; if not, write to the Free
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+ Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
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+ 02111-1307 USA. */
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+
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+#ifndef _GNU_SOURCE
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+#define _GNU_SOURCE
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+#endif
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+
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+#include <errno.h>
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+#include <malloc.h>
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+#include <string.h>
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+
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+#include <search.h>
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+
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+/* [Aho,Sethi,Ullman] Compilers: Principles, Techniques and Tools, 1986
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+ [Knuth] The Art of Computer Programming, part 3 (6.4) */
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+
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+
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+/* The reentrant version has no static variables to maintain the state.
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+ Instead the interface of all functions is extended to take an argument
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+ which describes the current status. */
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+typedef struct _ENTRY
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+{
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+ unsigned int used;
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+ ENTRY entry;
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+}
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+_ENTRY;
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+
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+
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+#ifdef L_hcreate_r
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+
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+/* For the used double hash method the table size has to be a prime. To
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+ correct the user given table size we need a prime test. This trivial
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+ algorithm is adequate because
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+ a) the code is (most probably) called a few times per program run and
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+ b) the number is small because the table must fit in the core */
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+static int isprime (unsigned int number)
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+{
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+ /* no even number will be passed */
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+ unsigned int div = 3;
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+
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+ while (div * div < number && number % div != 0)
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+ div += 2;
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+
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+ return number % div != 0;
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+}
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+
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+
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+/* Before using the hash table we must allocate memory for it.
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+ Test for an existing table are done. We allocate one element
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+ more as the found prime number says. This is done for more effective
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+ indexing as explained in the comment for the hsearch function.
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+ The contents of the table is zeroed, especially the field used
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+ becomes zero. */
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+int hcreate_r (size_t nel, struct hsearch_data *htab)
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+{
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+ /* Test for correct arguments. */
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+ if (htab == NULL)
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+ {
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+ __set_errno (EINVAL);
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+ return 0;
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+ }
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+
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+ /* There is still another table active. Return with error. */
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+ if (htab->table != NULL)
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+ return 0;
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+
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+ /* Change nel to the first prime number not smaller as nel. */
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+ nel |= 1; /* make odd */
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+ while (!isprime (nel))
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+ nel += 2;
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+
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+ htab->size = nel;
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+ htab->filled = 0;
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+
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+ /* allocate memory and zero out */
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+ htab->table = (_ENTRY *) calloc (htab->size + 1, sizeof (_ENTRY));
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+ if (htab->table == NULL)
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+ return 0;
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+
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+ /* everything went alright */
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+ return 1;
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+}
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+/* libc_hidden_def (hcreate_r) */
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+#endif
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+
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+#ifdef L_hdestroy_r
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+/* After using the hash table it has to be destroyed. The used memory can
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+ be freed and the local static variable can be marked as not used. */
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+void hdestroy_r (struct hsearch_data *htab)
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+{
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+ /* Test for correct arguments. */
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+ if (htab == NULL)
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+ {
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+ __set_errno (EINVAL);
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+ return;
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+ }
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+
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+ if (htab->table != NULL)
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+ /* free used memory */
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+ free (htab->table);
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+
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+ /* the sign for an existing table is an value != NULL in htable */
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+ htab->table = NULL;
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+}
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+/* libc_hidden_def (hdestroy_r) */
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+#endif
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+
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+#ifdef L_hsearch_r
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+/* This is the search function. It uses double hashing with open addressing.
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+ The argument item.key has to be a pointer to an zero terminated, most
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+ probably strings of chars. The function for generating a number of the
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+ strings is simple but fast. It can be replaced by a more complex function
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+ like ajw (see [Aho,Sethi,Ullman]) if the needs are shown.
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+
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+ We use an trick to speed up the lookup. The table is created by hcreate
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+ with one more element available. This enables us to use the index zero
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+ special. This index will never be used because we store the first hash
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+ index in the field used where zero means not used. Every other value
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+ means used. The used field can be used as a first fast comparison for
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+ equality of the stored and the parameter value. This helps to prevent
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+ unnecessary expensive calls of strcmp. */
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+int hsearch_r (ENTRY item, ACTION action, ENTRY **retval,
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+ struct hsearch_data *htab)
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+{
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+ unsigned int hval;
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+ unsigned int count;
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+ unsigned int len = strlen (item.key);
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+ unsigned int idx;
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+
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+ /* Compute an value for the given string. Perhaps use a better method. */
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+ hval = len;
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+ count = len;
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+ while (count-- > 0)
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+ {
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+ hval <<= 4;
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+ hval += item.key[count];
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+ }
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+
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+ /* First hash function: simply take the modul but prevent zero. */
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+ hval %= htab->size;
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+ if (hval == 0)
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+ ++hval;
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+
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+ /* The first index tried. */
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+ idx = hval;
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+
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+ if (htab->table[idx].used)
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+ {
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+ /* Further action might be required according to the action value. */
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+ unsigned hval2;
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+
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+ if (htab->table[idx].used == hval
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+ && strcmp (item.key, htab->table[idx].entry.key) == 0)
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+ {
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+ *retval = &htab->table[idx].entry;
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+ return 1;
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+ }
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+
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+ /* Second hash function, as suggested in [Knuth] */
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+ hval2 = 1 + hval % (htab->size - 2);
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+
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+ do
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+ {
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+ /* Because SIZE is prime this guarantees to step through all
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+ available indeces. */
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+ if (idx <= hval2)
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+ idx = htab->size + idx - hval2;
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+ else
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+ idx -= hval2;
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+
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+ /* If we visited all entries leave the loop unsuccessfully. */
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+ if (idx == hval)
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+ break;
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+
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+ /* If entry is found use it. */
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+ if (htab->table[idx].used == hval
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+ && strcmp (item.key, htab->table[idx].entry.key) == 0)
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+ {
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+ *retval = &htab->table[idx].entry;
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+ return 1;
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+ }
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+ }
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+ while (htab->table[idx].used);
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+ }
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+
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+ /* An empty bucket has been found. */
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+ if (action == ENTER)
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+ {
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+ /* If table is full and another entry should be entered return
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+ with error. */
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+ if (action == ENTER && htab->filled == htab->size)
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+ {
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+ __set_errno (ENOMEM);
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+ *retval = NULL;
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+ return 0;
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+ }
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+
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+ htab->table[idx].used = hval;
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+ htab->table[idx].entry = item;
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+
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+ ++htab->filled;
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+
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+ *retval = &htab->table[idx].entry;
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+ return 1;
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+ }
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+
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+ __set_errno (ESRCH);
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+ *retval = NULL;
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+ return 0;
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+}
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+/* libc_hidden_def (hsearch_r) */
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+#endif
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