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/* $Id: pl-table.c,v 1.21 1999/12/08 08:53:57 jan Exp $
Copyright (c) 1990 Jan Wielemaker. All rights reserved.
See ../LICENCE to find out about your rights.
jan@swi.psy.uva.nl
Purpose: generic support for (numeric) hashTables
*/
/*#define O_DEBUG 1*/
#include "pl-incl.h"
#define LOCK() PL_LOCK(L_TABLE)
#define UNLOCK() PL_UNLOCK(L_TABLE)
static inline Symbol rawAdvanceTableEnum(TableEnum e);
/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
This file provides generic hash-tables. Most of the implementation is
rather straightforward. Special are the *TableEnum() functions to
create, advance over and destroy enumerator objects. These objects are
used to enumerate the symbols of these tables, used primarily for the
pl_current_* predicates.
The enumerators cause two things: (1) as long enumerators are
associated, the table will not be rehashed and (2) if symbols are
deleted that are referenced by an enumerator, the enumerator is
automatically advanced to the next free symbol. This, in general, makes
the enumeration of hash-tables safe.
TODO: abort should delete any pending enumerators. This should be
thread-local, as thread_exit/1 should do the same.
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
static void
allocHTableEntries(Table ht)
{ int n;
Symbol *p;
ht->entries = allocHeap(ht->buckets * sizeof(Symbol));
for(n=0, p = &ht->entries[0]; n < ht->buckets; n++, p++)
*p = NULL;
}
Table
newHTable(int buckets)
{ Table ht;
ht = allocHeap(sizeof(struct table));
ht->buckets = buckets;
ht->size = 0;
ht->enumerators = NULL;
ht->free_symbol = NULL;
ht->copy_symbol = NULL;
allocHTableEntries(ht);
return ht;
}
void
destroyHTable(Table ht)
{ clearHTable(ht);
freeHeap(ht->entries, ht->buckets * sizeof(Symbol));
freeHeap(ht, sizeof(struct table));
}
#if O_DEBUG || O_HASHSTAT
#define HASHSTAT(c) c
static int lookups;
static int cmps;
void
exitTables(int status, void *arg)
{ Sdprintf("hashstat: Anonymous tables: %d lookups using %d compares\n",
lookups, cmps);
}
#else
#define HASHSTAT(c)
#endif /*O_DEBUG*/
void
initTables()
{ static int done = FALSE;
LOCK();
if ( !done )
{ done = TRUE;
initMemAlloc();
HASHSTAT(PL_on_halt(exitTables, NULL));
}
UNLOCK();
}
Symbol
lookupHTable(Table ht, void *name)
{ Symbol s = ht->entries[pointerHashValue(name, ht->buckets)];
HASHSTAT(lookups++);
for( ; s; s = s->next)
{ HASHSTAT(cmps++);
if ( s->name == name )
return s;
}
return NULL;
}
#ifdef O_DEBUG
void
checkHTable(Table ht)
{ int i;
int n = 0;
for(i=0; i<ht->buckets; i++)
{ Symbol s;
for(s=ht->entries[i]; s; s=s->next)
{ assert(lookupHTable(ht, s->name) == s);
n++;
}
}
assert(n == ht->size);
}
#endif
/* MT: Locked by calling addHTable()
*/
static void
rehashHTable(Table ht)
{ Symbol *oldtab;
int oldbucks;
int i;
oldtab = ht->entries;
oldbucks = ht->buckets;
ht->buckets *= 2;
allocHTableEntries(ht);
DEBUG(1, Sdprintf("Rehashing table %p to %d entries\n", ht, ht->buckets));
for(i=0; i<oldbucks; i++)
{ Symbol s, n;
for(s=oldtab[i]; s; s = n)
{ int v = pointerHashValue(s->name, ht->buckets);
n = s->next;
s->next = ht->entries[v];
ht->entries[v] = s;
}
}
freeHeap(oldtab, oldbucks * sizeof(Symbol));
DEBUG(0, checkHTable(ht));
}
bool
addHTable(Table ht, void *name, void *value)
{ Symbol s;
int v;
LOCK();
v = pointerHashValue(name, ht->buckets);
if ( lookupHTable(ht, name) )
{ UNLOCK();
fail;
}
s = allocHeap(sizeof(struct symbol));
s->name = name;
s->value = value;
s->next = ht->entries[v];
ht->entries[v] = s;
ht->size++;
DEBUG(9, Sdprintf("addHTable(0x%x, 0x%x, 0x%x) --> size = %d\n",
ht, name, value, ht->size));
if ( ht->buckets * 2 < ht->size && !ht->enumerators )
rehashHTable(ht);
UNLOCK();
DEBUG(1, checkHTable(ht));
succeed;
}
/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Note: s must be in the table!
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
void
deleteSymbolHTable(Table ht, Symbol s)
{ int v;
Symbol *h;
TableEnum e;
LOCK();
v = pointerHashValue(s->name, ht->buckets);
h = &ht->entries[v];
for( e=ht->enumerators; e; e = e->next )
{ if ( e->current == s )
rawAdvanceTableEnum(e);
}
for( ; *h; h = &(*h)->next )
{ if ( *h == s )
{ *h = (*h)->next;
freeHeap(s, sizeof(struct symbol));
ht->size--;
break;
}
}
UNLOCK();
}
void
clearHTable(Table ht)
{ int n;
TableEnum e;
LOCK();
for( e=ht->enumerators; e; e = e->next )
{ e->current = NULL;
e->key = ht->buckets;
}
for(n=0; n < ht->buckets; n++)
{ Symbol s, q;
for(s = ht->entries[n]; s; s = q)
{ q = s->next;
if ( ht->free_symbol )
(*ht->free_symbol)(s);
freeHeap(s, sizeof(struct symbol));
}
ht->entries[n] = NULL;
}
ht->size = 0;
UNLOCK();
}
/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Table copyHTable(Table org)
Make a copy of a hash-table. This is used to realise the copy-on-write
as defined by SharedTable. The table is copied to have exactly the
same dimensions as the original. If the copy_symbol function is
provided, it is called to allow duplicating the symbols name or value
fields.
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
Table
copyHTable(Table org)
{ Table ht;
int n;
LOCK();
ht = allocHeap(sizeof(struct table));
*ht = *org; /* copy all attributes */
allocHTableEntries(ht);
for(n=0; n < ht->buckets; n++)
{ Symbol s, *q;
q = &ht->entries[n];
for(s = org->entries[n]; s; s = s->next)
{ Symbol s2 = allocHeap(sizeof(*s2));
*q = s2;
q = &s2->next;
s2->name = s->name;
s2->value = s->value;
if ( ht->copy_symbol )
(*ht->copy_symbol)(s2);
}
*q = NULL;
}
UNLOCK();
return ht;
}
/*******************************
* ENUMERATING *
*******************************/
TableEnum
newTableEnum(Table ht)
{ TableEnum e = allocHeap(sizeof(struct table_enum));
Symbol n;
LOCK();
e->table = ht;
e->key = 0;
e->next = ht->enumerators;
ht->enumerators = e;
n = ht->entries[0];
while(!n && ++e->key < ht->buckets)
n=ht->entries[e->key];
e->current = n;
UNLOCK();
return e;
}
void
freeTableEnum(TableEnum e)
{ TableEnum *ep;
Table ht;
if ( !e )
return;
LOCK();
ht = e->table;
for( ep=&ht->enumerators; *ep ; ep = &(*ep)->next )
{ if ( *ep == e )
{ *ep = (*ep)->next;
freeHeap(e, sizeof(*e));
break;
}
}
UNLOCK();
}
static inline Symbol
rawAdvanceTableEnum(TableEnum e)
{ Symbol s, n;
Table ht = e->table;
if ( !(s = e->current) )
return s;
n = s->next;
while(!n)
{ if ( ++e->key >= ht->buckets )
{ e->current = NULL;
return s;
}
n=ht->entries[e->key];
}
e->current = n;
return s;
}
Symbol
advanceTableEnum(TableEnum e)
{ Symbol s;
LOCK();
s = rawAdvanceTableEnum(e);
UNLOCK();
return s;
}
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