308 lines
6.5 KiB
COBOL
308 lines
6.5 KiB
COBOL
// This may look like C code, but it is really -*- C++ -*-
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/*
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Copyright (C) 1991 Free Software Foundation
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This file is part of the GNU C++ Library. This library is free
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software; you can redistribute it and/or modify it under the terms of
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the GNU Library General Public License as published by the Free
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Software Foundation; either version 2 of the License, or (at your
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option) any later version. This library is distributed in the hope
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that it will be useful, but WITHOUT ANY WARRANTY; without even the
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implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
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PURPOSE. See the GNU Library General Public License for more details.
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You should have received a copy of the GNU Library General Public
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License along with this library; if not, write to the Free Software
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Foundation, 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
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*/
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#ifdef __GNUG__
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#pragma implementation
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#endif
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#include <stream.h>
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#include <time.h>
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#include "<T>.<C>.SkipMap.h"
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/*
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* Bags implemented via William Pugh SkipList algorithms.
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* CACM, June 1990, p 668-676.
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*
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*/
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MLCG* <T><C>SkipMap::gen = 0;
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int <T><C>SkipMapinit::count = 0;
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static int countbits(long bits)
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{
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int n = 0;
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while(bits>>=1) n++;
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return n;
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}
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<T><C>SkipMap::<T><C>SkipMap(<C&> dflt, long size)
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: <T><C>Map(dflt),
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level(0),
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header(new <T><C>SkipMapNode (countbits(size)+1)),
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max_levels (countbits(size)+1),
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random_bits(gen->asLong()),
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randoms_left(BITS_IN_RANDOM / 2)
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{
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<T><C>SkipMapNodePtr *buffer_start = header->forward;
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<T><C>SkipMapNodePtr *trav = &header->forward[max_levels];
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count = 0;
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while (trav > buffer_start)
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*--trav = (<T><C>SkipMapNodePtr) header;
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}
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<T><C>SkipMap::<T><C>SkipMap(<T><C>SkipMap& b)
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: <T><C>Map(b.def),
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level (0),
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header (new <T><C>SkipMapNode (b.max_levels)),
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max_levels (b.max_levels),
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random_bits (gen->asLong()),
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randoms_left (BITS_IN_RANDOM / 2)
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{
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<T><C>SkipMapNodePtr *buffer_start = header->forward;
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<T><C>SkipMapNodePtr *trav = &header->forward[max_levels];
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count = 0;
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while (trav > buffer_start)
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*--trav = (<T><C>SkipMapNodePtr)header;
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for (<T><C>SkipMapNodePtr t = b.leftmost(); t; t = b.succ(t))
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(*this)[t->item] = t->cont;
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}
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<C>& <T><C>SkipMap::operator [] (<T&> item)
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{
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<T><C>SkipMapNodePtr *update = new <T><C>SkipMapNodePtr[max_levels+1];
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<T><C>SkipMapNodePtr curr =
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(<T><C>SkipMapNodePtr) this->header;
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int l = level;
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<T><C>SkipMapNodePtr temp;
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do
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{
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while ((temp = curr->forward[l])!=header &&
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<T>CMP(temp->item, item) < 0)
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curr = temp;
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update[l] = curr;
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}
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while (--l >= 0);
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if (temp != header && <T>CMP(temp->item, item) == 0)
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{
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delete update;
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return temp->cont;
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}
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if ((l = random_level ()) > level)
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{
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l = ++level;
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update[l] = (<T><C>SkipMapNodePtr)header;
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};
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temp = new <T><C>RealSkipMapNode (item, def, l);
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<T><C>SkipMapNodePtr *temp_forward = temp->forward;
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do
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{
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<T><C>SkipMapNodePtr *curr_forward = update[l]->forward;
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temp_forward[l] = curr_forward[l];
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curr_forward[l] = temp;
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}
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while (--l >= 0);
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count++;
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delete update;
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return temp->cont;
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}
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void <T><C>SkipMap::del(<T&> key)
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{
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int l = level;
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int curr_level = level;
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<T><C>SkipMapNodePtr *update = new <T><C>SkipMapNodePtr[max_levels+1];
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<T><C>SkipMapNodePtr curr = (<T><C>SkipMapNodePtr)header;
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<T><C>SkipMapNodePtr temp;
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do
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{
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while ((temp = curr->forward[l])!=header
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&& <T>CMP(temp->item,key) < 0)
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curr = temp;
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update[l] = curr;
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}
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while (--l >= 0);
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if (<T>CMP(temp->item,key)==0)
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{
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<T><C>SkipMapNodePtr *temp_forward = temp->forward;
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for (l = 0;
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l <= curr_level && (curr = update[l])->forward[l] == temp;
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l++)
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curr->forward[l] = temp_forward[l];
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delete temp;
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<T><C>SkipMapNodePtr *forward = header->forward;
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while (forward[curr_level]==header && curr_level > 0)
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curr_level--;
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level = curr_level;
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count--;
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delete update;
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return;
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}
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}
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<T><C>SkipMapNodePtr <T><C>SkipMap::rightmost()
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{
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<T><C>SkipMapNodePtr temp;
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<T><C>SkipMapNode* curr = header;
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int l = level;
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do
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while ((temp = curr->forward[l])!=header)
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curr = temp;
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while (--l >= 0);
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return temp==header ? 0 : temp;
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}
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<T><C>SkipMapNodePtr <T><C>SkipMap::pred(<T><C>SkipMapNodePtr t)
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{
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<T><C>SkipMapNodePtr temp, curr = (<T><C>SkipMapNodePtr) header;
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int l = level;
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do
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while ((temp = curr->forward[l])!=t)
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curr = temp;
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while (--l >= 0);
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return curr == header ? 0 : curr;
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}
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void <T><C>SkipMap::_kill()
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{
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<T><C>SkipMapNode *p = this->header->forward[0];
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while (p != header)
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{
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<T><C>SkipMapNodePtr q = p->forward[0];
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delete p;
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p = q;
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}
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}
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void <T><C>SkipMap::clear()
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{
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<T><C>SkipMapNodePtr *buffer_start = header->forward;
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<T><C>SkipMapNodePtr *trav = &header->forward[level+1];
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_kill();
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count = 0;
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while (trav > buffer_start)
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*--trav = (<T><C>SkipMapNodePtr)header;
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}
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Pix <T><C>SkipMap::seek(<T&> key)
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{
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<T><C>SkipMapNodePtr temp;
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<T><C>SkipMapNode *curr = header;
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int l = level;
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do
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{
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while ((temp = curr->forward[l])!=header &&
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<T>CMP(temp->item, key) < 0)
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curr = temp;
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}
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while (--l >= 0);
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if (<T>CMP(temp->item, key) != 0)
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return 0;
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else
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{
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return Pix(temp);
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}
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}
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/*
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* random function for probabilistic balancing
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*
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* Hardwired for p = .25. Not too flexible,
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* but fast. Changing this would require a constructor
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* that would accept a different value for p, etc.
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* Perhaps someone else would like to implement this?
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*
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*/
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int <T><C>SkipMap::random_level (void)
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{
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int rlevel = 0;
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int b;
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do
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{
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b = random_bits & 3L;
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if (!b)
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rlevel++;
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random_bits >>= 2;
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if (--randoms_left == 0)
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{
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random_bits = gen->asLong();
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randoms_left = BITS_IN_RANDOM / 2;
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};
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}
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while (!b);
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return rlevel > max_levels ? max_levels : rlevel;
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}
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int <T><C>SkipMap::OK()
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{
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int v = 1;
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if (header == 0)
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v = 0;
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else
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{
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int n = 0;
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<T><C>SkipMapNodePtr trail = leftmost();
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<T><C>SkipMapNodePtr t = 0;
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if (trail) t = succ(trail);
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if (t) n++;
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while (t != 0)
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{
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++n;
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v &= <T>CMP(trail->item, t->item) < 0;
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trail = t;
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t = succ(t);
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}
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v &= n == count;
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}
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if (!v) error("invariant failure");
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return v;
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}
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<T><C>SkipMapinit::<T><C>SkipMapinit()
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{
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if (!count)
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<T><C>SkipMap::gen = new MLCG(time(0));
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count++;
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}
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<T><C>SkipMapinit::~<T><C>SkipMapinit()
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{
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count--;
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if (!count)
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delete <T><C>SkipMap::gen;
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}
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