sim/arm/bag.c

/*  bag.c -- ARMulator support code:  ARM6 Instruction Emulator.
    Copyright (C) 1994 Advanced RISC Machines Ltd.
 
    This program is free software; 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.
 
    This program 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 program; if not, write to the Free Software
    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */

/********************************************************************/
/* bag.c:                                                           */
/* Offers a data structure for storing and getting pairs of number. */
/* The numbers are stored together, put one can be looked up by     */
/* quoting the other.  If a new pair is entered and one of the      */
/* numbers is a repeat of a previous pair, then the previos pair    */
/* is deleted.                                                      */
/********************************************************************/

#include "bag.h"

#define HASH_TABLE_SIZE 256
#define hash(x) (((x)&0xff)^(((x)>>8)&0xff)^(((x)>>16)&0xff)^(((x)>>24)&0xff))

typedef struct hashentry {
  struct hashentry *next;
  int first;
  int second;
} Hashentry;

Hashentry *lookupbyfirst[HASH_TABLE_SIZE];
Hashentry *lookupbysecond[HASH_TABLE_SIZE];

void addtolist(Hashentry **add, long first, long second) {
  while (*add) add = &((*add)->next);
  /* Malloc will never fail? :o( */
  (*add) = (Hashentry *) malloc(sizeof(Hashentry));
  (*add)->next = (Hashentry *) 0;
  (*add)->first = first;
  (*add)->second = second;
}

void killwholelist(Hashentry *p) {
  Hashentry *q;

  while (p) {
    q = p;
    p = p->next;
    free(q);
  }
}

void removefromlist(Hashentry **p, long first, long second) {
  Hashentry *q;

  while (*p) {
    if ((*p)->first == first) {
      q = (*p)->next;
      free(*p);
      *p = q;
      return;
    }
    p = &((*p)->next);
  }
}

void BAG_putpair(long first, long second) {
  long junk;

  if (BAG_getfirst(&junk, second) != NO_SUCH_PAIR)
    BAG_killpair_bysecond(second);
  addtolist(&lookupbyfirst[hash(first)], first, second);
  addtolist(&lookupbysecond[hash(second)], first, second);
}

Bag_error BAG_getfirst(long *first, long second) {
  Hashentry *look;

  look = lookupbysecond[hash(second)];
  while(look) if (look->second == second) {
    *first = look->first;
    return NO_ERROR;
  }
  return NO_SUCH_PAIR;
}

Bag_error BAG_getsecond(long first, long *second) {
  Hashentry *look;

  look = lookupbyfirst[hash(first)];
  while(look) {
    if (look->first == first) {
      *second = look->second;
      return NO_ERROR;
    }
    look = look->next;
  }
  return NO_SUCH_PAIR;
}

Bag_error BAG_killpair_byfirst(long first) {
  long second;

  if (BAG_getsecond(first, &second) == NO_SUCH_PAIR)
    return NO_SUCH_PAIR;
  removefromlist(&lookupbyfirst[hash(first)], first, second);
  removefromlist(&lookupbysecond[hash(second)], first, second);
  return NO_ERROR;
}

Bag_error BAG_killpair_bysecond(long second) {
  long first;
  
  if (BAG_getfirst(&first, second) == NO_SUCH_PAIR)
    return NO_SUCH_PAIR;
  removefromlist(&lookupbyfirst[hash(first)], first, second);
  removefromlist(&lookupbysecond[hash(second)], first, second);
  return NO_ERROR;
}

void BAG_newbag() {
  int i;

  for (i = 0; i < 256; i++) {
    killwholelist(lookupbyfirst[i]);
    killwholelist(lookupbysecond[i]);
    lookupbyfirst[i] = lookupbysecond[i] = (Hashentry *) 0;
  }
}