/****************************************************************************** Copyright (c) 1992, 1995, 1996 Xerox Corporation. All rights reserved. Portions of this code were written by Stephen White, aka ghond. Use and copying of this software and preparation of derivative works based upon this software are permitted. Any distribution of this software or derivative works must comply with all applicable United States export control laws. This software is made available AS IS, and Xerox Corporation makes no warranty about the software, its performance or its conformity to any specification. Any person obtaining a copy of this software is requested to send their name and post office or electronic mail address to: Pavel Curtis Xerox PARC 3333 Coyote Hill Rd. Palo Alto, CA 94304 Pavel@Xerox.Com *****************************************************************************/ #include "config.h" #include "exceptions.h" #include "ref_count.h" #include "storage.h" typedef struct reftab_entry { struct reftab_entry *next; const void *p; int count; } reftab_entry; static int table_size; static int table_entries; static int table_power; /* table_power is the power of 2 */ static reftab_entry **ref_table; static int init = 0; static reftab_entry *free_list; static void init_ref_table() { int index; table_size = 1024; table_entries = 0; table_power = 10; ref_table = mymalloc(table_size * sizeof(reftab_entry *), M_REF_TABLE); for (index = 0; index < table_size; index++) ref_table[index] = 0; free_list = 0; init = 1; } static int key(const void *p) { return ((long) p >> 4) & ((1 << table_power) - 1); } static reftab_entry * new_entry() { reftab_entry *ans; table_entries++; if (free_list) { ans = free_list; free_list = free_list->next; } else ans = mymalloc(sizeof(reftab_entry), M_REF_ENTRY); return ans; } static void save_entry(reftab_entry *e) { table_entries--; e->next = free_list; free_list = e; } static void ll_insert_entry(reftab_entry **list, reftab_entry *e) { if ((*list) == 0) { e->next = 0; *list = e; } else if ((*list)->p > e->p) { e->next = *list; *list = e; } else if ((*list)->p == e->p) panic("Error encountered during rehashing"); else ll_insert_entry(&((*list)->next), e); } static void ll_insert_value(reftab_entry **list, const void *p) /* returns 1 if added a new entry */ { reftab_entry *entry; if ((*list == 0) || (*list)->p > p) { entry = new_entry(); entry->p = p; entry->count = 2; entry->next = *list; *list = entry; } else if ((*list)->p == p) { (*list)->count++; } else ll_insert_value(&((*list)->next), p); } static int ll_delete_value(reftab_entry **list, const void *p) /* return number of references to p left */ { reftab_entry **prev = list, *tmp; while ((*list) && (*list)->p < p) { prev = list; list = &((*list)->next); } /* not found, must be last reference */ if (*list == 0 || (*list)->p > p) return 0; else { /* found */ /* not next to last reference */ if ((*list)->count > 2) return --((*list)->count); /* too few references */ else if ((*list)->count < 2) panic ("Error when deleting reference: count too low"); /* next to last reference: remove entry */ else { /* count == 2 */ tmp = *list; (*prev)->next = (*list)->next; if (list == prev) /* head of list */ *prev = (*list)->next; save_entry(tmp); return 1; } } return -1; /* shouldn't reach here */ } static reftab_entry ** rehash(reftab_entry **old, reftab_entry **new) { reftab_entry *link, *next; int loop; for (loop = 0; loop < table_size / 2; loop++) for (link = old[loop]; link; link = next) { int index = key(link->p); next = link->next; ll_insert_entry(&new[index], link); } myfree(old, M_REF_TABLE); return new; } void addref(const void *p) { int index; if (!init) init_ref_table(); if (p == 0) panic ("increasing ref count of 0x0"); index = key(p); ll_insert_value(&(ref_table[index]), p); if (table_entries > table_size) { reftab_entry **new_table; table_power++; table_size *= 2; new_table = mymalloc(table_size * sizeof(reftab_entry *), M_REF_TABLE); for (index = 0; index < table_size; index++) new_table[index] = 0; ref_table = rehash(ref_table, new_table); /* frees old table */ } } unsigned int delref(const void *p) { int index; if (!init) init_ref_table(); if (p == 0) panic ("decreasing ref count of 0x0"); index = key(p); return ll_delete_value(&(ref_table[index]), p); } char rcsid_ref_count[] = "$Id: ref_count.c,v 2.1 1996/02/08 06:53:33 pavel Exp $"; /* $Log: ref_count.c,v $ * Revision 2.1 1996/02/08 06:53:33 pavel * Updated copyright notice for 1996. Release 1.8.0beta1. * * Revision 2.0 1995/11/30 04:31:09 pavel * New baseline version, corresponding to release 1.8.0alpha1. * * Revision 1.6 1992/10/23 23:03:47 pavel * Added copyright notice. * * Revision 1.5 1992/10/23 22:21:58 pavel * Eliminated all uses of the useless macro NULL. * * Revision 1.4 1992/10/21 03:02:35 pavel * Converted to use new automatic configuration system. * * Revision 1.3 1992/09/08 21:54:40 pjames * Fixed #includes. * * Revision 1.2 1992/09/03 16:22:25 pjames * Cleaned up ll_insert code. Changed when table will re-hash. * * Revision 1.1 1992/08/28 16:31:45 pjames * Initial RCS-controlled version. */