474 lines
9.8 KiB
C
474 lines
9.8 KiB
C
/* Part of SWI-Prolog
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Author: Jan Wielemaker
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E-mail: J.Wielemaker@vu.nl
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WWW: http://www.swi-prolog.org
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Copyright (C): 1985-2012, University of Amsterdam
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VU University Amsterdam
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This 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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This 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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You should have received a copy of the GNU Lesser General Public
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License along with this library; if not, write to the Free Software
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Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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/*#define O_DEBUG 1*/
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#include "pl-incl.h"
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#ifdef O_PLMT
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#define LOCK_TABLE(t) if ( t->mutex ) simpleMutexLock(t->mutex)
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#define UNLOCK_TABLE(t) if ( t->mutex ) simpleMutexUnlock(t->mutex)
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#else
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#define LOCK_TABLE(t) (void)0
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#define UNLOCK_TABLE(t) (void)0
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#endif
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static inline Symbol rawAdvanceTableEnum(TableEnum e);
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/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
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This file provides generic hash-tables. Most of the implementation is
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rather straightforward. Special are the *TableEnum() functions to
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create, advance over and destroy enumerator objects. These objects are
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used to enumerate the symbols of these tables, used primarily for the
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pl_current_* predicates.
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The enumerators cause two things: (1) as long as enumerators are
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associated, the table will not be rehashed and (2) if symbols are
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deleted that are referenced by an enumerator, the enumerator is
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automatically advanced to the next free symbol. This, in general, makes
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the enumeration of hash-tables safe.
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TBD: Resizing hash-tables causes major headaches for concurrent access.
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We can avoid this by using a dynamic array for the list of hash-entries.
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Ongoing work in the RDF store shows hash-tables that can handle
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concurrent lock-free access.
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- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
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static Symbol *
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allocHTableEntries(int buckets)
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{ size_t bytes = buckets * sizeof(Symbol);
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Symbol *p;
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p = allocHeapOrHalt(bytes);
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memset(p, 0, bytes);
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return p;
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}
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Table
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newHTable(int buckets)
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{ Table ht;
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ht = allocHeapOrHalt(sizeof(struct table));
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ht->buckets = (buckets & ~TABLE_MASK);
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ht->size = 0;
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ht->enumerators = NULL;
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ht->free_symbol = NULL;
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ht->copy_symbol = NULL;
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#ifdef O_PLMT
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if ( (buckets & TABLE_UNLOCKED) )
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ht->mutex = NULL;
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else
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{ ht->mutex = allocHeapOrHalt(sizeof(simpleMutex));
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simpleMutexInit(ht->mutex);
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}
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#endif
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ht->entries = allocHTableEntries(ht->buckets);
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return ht;
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}
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void
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destroyHTable(Table ht)
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{
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#ifdef O_PLMT
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if ( ht->mutex )
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{ simpleMutexDelete(ht->mutex);
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freeHeap(ht->mutex, sizeof(*ht->mutex));
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ht->mutex = NULL;
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}
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#endif
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clearHTable(ht);
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freeHeap(ht->entries, ht->buckets * sizeof(Symbol));
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freeHeap(ht, sizeof(struct table));
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}
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#if O_DEBUG
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static int lookups;
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static int cmps;
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int
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exitTables(int status, void *arg)
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{ (void)status;
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(void)arg;
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Sdprintf("hashstat: Anonymous tables: %d lookups using %d compares\n",
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lookups, cmps);
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return 0;
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}
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#endif
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void
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initTables(void)
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{ static int done = FALSE;
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if ( !done )
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{ done = TRUE;
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DEBUG(MSG_HASH_STAT, PL_on_halt(exitTables, NULL));
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}
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}
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Symbol
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lookupHTable(Table ht, void *name)
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{ Symbol s = ht->entries[pointerHashValue(name, ht->buckets)];
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DEBUG(MSG_HASH_STAT, lookups++);
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for( ; s; s = s->next)
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{ DEBUG(MSG_HASH_STAT, cmps++);
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if ( s->name == name )
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return s;
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}
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return NULL;
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}
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#ifdef O_DEBUG
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void
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checkHTable(Table ht)
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{ int i;
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int n = 0;
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for(i=0; i<ht->buckets; i++)
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{ Symbol s;
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for(s=ht->entries[i]; s; s=s->next)
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{ assert(lookupHTable(ht, s->name) == s);
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n++;
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}
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}
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assert(n == ht->size);
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}
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#endif
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/* MT: Locked by calling addHTable()
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*/
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static Symbol
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rehashHTable(Table ht, Symbol map)
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{ Symbol *newentries, *oldentries;
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int newbuckets, oldbuckets;
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int i;
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#if P_PLMT
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int safe_copy = (ht->mutex != NULL);
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#else
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int safe_copy = TRUE;
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#endif
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newbuckets = ht->buckets*2;
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newentries = allocHTableEntries(newbuckets);
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DEBUG(MSG_HASH_STAT,
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Sdprintf("Rehashing table %p to %d entries\n", ht, ht->buckets));
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for(i=0; i<ht->buckets; i++)
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{ Symbol s, n;
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if ( safe_copy )
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{ for(s=ht->entries[i]; s; s = n)
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{ int v = (int)pointerHashValue(s->name, newbuckets);
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Symbol s2 = allocHeapOrHalt(sizeof(*s2));
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n = s->next;
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if ( s == map )
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map = s2;
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*s2 = *s;
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s2->next = newentries[v];
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newentries[v] = s2;
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}
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} else
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{ for(s=ht->entries[i]; s; s = n)
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{ int v = (int)pointerHashValue(s->name, newbuckets);
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n = s->next;
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s->next = newentries[v];
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newentries[v] = s;
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}
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}
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}
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oldentries = ht->entries;
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oldbuckets = ht->buckets;
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ht->entries = newentries;
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ht->buckets = newbuckets;
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if ( safe_copy )
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{ /* Here we should be waiting until */
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/* active lookup are finished */
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for(i=0; i<oldbuckets; i++)
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{ Symbol s, n;
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for(s=oldentries[i]; s; s = n)
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{ n = s->next;
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s->next = NULL; /* that causes old readers to stop */
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freeHeap(s, sizeof(*s));
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}
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}
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}
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freeHeap(oldentries, oldbuckets * sizeof(Symbol));
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DEBUG(CHK_SECURE, checkHTable(ht));
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return map;
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}
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Symbol
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addHTable(Table ht, void *name, void *value)
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{ Symbol s;
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int v;
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LOCK_TABLE(ht);
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v = (int)pointerHashValue(name, ht->buckets);
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if ( lookupHTable(ht, name) )
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{ UNLOCK_TABLE(ht);
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return NULL;
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}
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s = allocHeapOrHalt(sizeof(struct symbol));
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s->name = name;
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s->value = value;
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s->next = ht->entries[v];
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ht->entries[v] = s;
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ht->size++;
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DEBUG(9, Sdprintf("addHTable(0x%x, 0x%x, 0x%x) --> size = %d\n",
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ht, name, value, ht->size));
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if ( ht->buckets * 2 < ht->size && !ht->enumerators )
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s = rehashHTable(ht, s);
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UNLOCK_TABLE(ht);
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DEBUG(1, checkHTable(ht));
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return s;
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}
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/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
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Note: s must be in the table!
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- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
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void
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deleteSymbolHTable(Table ht, Symbol s)
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{ int v;
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Symbol *h;
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TableEnum e;
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LOCK_TABLE(ht);
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v = (int)pointerHashValue(s->name, ht->buckets);
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h = &ht->entries[v];
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for( e=ht->enumerators; e; e = e->next )
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{ if ( e->current == s )
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rawAdvanceTableEnum(e);
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}
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for( ; *h; h = &(*h)->next )
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{ if ( *h == s )
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{ *h = (*h)->next;
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s->next = NULL; /* force crash */
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s->name = NULL;
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s->value = NULL;
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freeHeap(s, sizeof(struct symbol));
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ht->size--;
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break;
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}
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}
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UNLOCK_TABLE(ht);
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}
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void
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clearHTable(Table ht)
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{ int n;
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TableEnum e;
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LOCK_TABLE(ht);
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for( e=ht->enumerators; e; e = e->next )
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{ e->current = NULL;
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e->key = ht->buckets;
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}
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for(n=0; n < ht->buckets; n++)
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{ Symbol s, q;
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for(s = ht->entries[n]; s; s = q)
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{ q = s->next;
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if ( ht->free_symbol )
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(*ht->free_symbol)(s);
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freeHeap(s, sizeof(struct symbol));
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}
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ht->entries[n] = NULL;
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}
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ht->size = 0;
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UNLOCK_TABLE(ht);
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}
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/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
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Table copyHTable(Table org)
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Make a copy of a hash-table. This is used to realise the copy-on-write
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as defined by SharedTable. The table is copied to have exactly the
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same dimensions as the original. If the copy_symbol function is
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provided, it is called to allow duplicating the symbols name or value
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fields.
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- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
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Table
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copyHTable(Table org)
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{ Table ht;
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int n;
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ht = allocHeapOrHalt(sizeof(struct table));
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LOCK_TABLE(org);
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*ht = *org; /* copy all attributes */
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#ifdef O_PLMT
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ht->mutex = NULL;
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#endif
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ht->entries = allocHTableEntries(ht->buckets);
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for(n=0; n < ht->buckets; n++)
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{ Symbol s, *q;
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q = &ht->entries[n];
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for(s = org->entries[n]; s; s = s->next)
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{ Symbol s2 = allocHeapOrHalt(sizeof(*s2));
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*q = s2;
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q = &s2->next;
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s2->name = s->name;
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s2->value = s->value;
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if ( ht->copy_symbol )
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(*ht->copy_symbol)(s2);
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}
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*q = NULL;
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}
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#ifdef O_PLMT
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if ( org->mutex )
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{ ht->mutex = allocHeapOrHalt(sizeof(simpleMutex));
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simpleMutexInit(ht->mutex);
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}
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#endif
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UNLOCK_TABLE(org);
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return ht;
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}
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/*******************************
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* ENUMERATING *
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*******************************/
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TableEnum
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newTableEnum(Table ht)
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{ TableEnum e = allocHeapOrHalt(sizeof(struct table_enum));
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Symbol n;
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LOCK_TABLE(ht);
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e->table = ht;
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e->key = 0;
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e->next = ht->enumerators;
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ht->enumerators = e;
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n = ht->entries[0];
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while(!n && ++e->key < ht->buckets)
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n=ht->entries[e->key];
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e->current = n;
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UNLOCK_TABLE(ht);
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return e;
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}
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void
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freeTableEnum(TableEnum e)
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{ TableEnum *ep;
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Table ht;
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if ( !e )
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return;
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ht = e->table;
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LOCK_TABLE(ht);
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for( ep=&ht->enumerators; *ep ; ep = &(*ep)->next )
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{ if ( *ep == e )
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{ *ep = (*ep)->next;
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freeHeap(e, sizeof(*e));
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break;
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}
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}
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UNLOCK_TABLE(ht);
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}
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static inline Symbol
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rawAdvanceTableEnum(TableEnum e)
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{ Symbol s, n;
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Table ht = e->table;
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if ( !(s = e->current) )
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return s;
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n = s->next;
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while(!n)
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{ if ( ++e->key >= ht->buckets )
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{ e->current = NULL;
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return s;
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}
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n=ht->entries[e->key];
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}
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e->current = n;
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return s;
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}
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Symbol
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advanceTableEnum(TableEnum e)
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{ Symbol s;
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#ifdef O_PLMT
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Table ht = e->table;
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#endif
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LOCK_TABLE(ht);
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s = rawAdvanceTableEnum(e);
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UNLOCK_TABLE(ht);
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return s;
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}
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