137 lines
3.8 KiB
C
137 lines
3.8 KiB
C
/* Copyright (c) 2014 Anton Titov.
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* Copyright (c) 2014 pCloud Ltd.
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are met:
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* * Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* * Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* * Neither the name of pCloud Ltd nor the
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* names of its contributors may be used to endorse or promote products
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* derived from this software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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* DISCLAIMED. IN NO EVENT SHALL pCloud Ltd BE LIABLE FOR ANY
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* DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
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* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
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* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
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* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#include "pcompat.h"
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#include "plist.h"
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/* Fairly simple in-place merge sort with constant storage requirements.
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*
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* Recursive approach might would use O(log N) storage on the stack but may
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* have better cache locality for lists that do not fit in processor cache,
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* may benefit from precise in-half splitting and can go without needless
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* iterating of the list to reach the half of it.
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*/
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void psync_list_sort(psync_list *l, psync_list_compare cmp){
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psync_list *ls, *l1, *l2, **tail;
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psync_uint_t depth, cnt, i, l1len, l2len;
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if (psync_list_isempty(l))
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return;
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ls=l->next;
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l->prev->next=NULL;
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depth=1;
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while (1){
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l1=ls;
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tail=&ls;
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cnt=0;
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while (l1){
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cnt++;
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l2=l1;
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for (i=0; i<depth && l2; i++)
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l2=l2->next;
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if (!l2){
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*tail=l1;
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goto nol2;
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}
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l1len=i;
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l2len=depth;
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while (1){
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if (cmp(l1, l2)<=0){
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l1len--;
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*tail=l1;
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tail=&l1->next;
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if (!l1len)
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goto l1fin;
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l1=l1->next;
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}
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else{
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l2len--;
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*tail=l2;
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tail=&l2->next;
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l2=l2->next;
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if (!l2len || !l2)
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goto l2fin;
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}
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}
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l2fin:
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*tail=l1;
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for (i=0; i<l1len-1; i++)
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l1=l1->next;
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tail=&l1->next;
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l1=l2;
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continue;
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l1fin:
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*tail=l2;
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for (i=0; l2->next && i<l2len-1; i++)
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l2=l2->next;
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tail=&l2->next;
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l1=l2->next;
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}
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*tail=NULL;
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nol2:
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if (cnt<=1)
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break;
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depth*=2;
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}
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l->next=ls;
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l1=l;
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while (ls){
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ls->prev=l1;
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l1=ls;
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ls=ls->next;
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}
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l1->next=l;
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l->prev=l1;
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}
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void psync_list_extract_repeating(psync_list *l1, psync_list *l2, psync_list *extracted1, psync_list *extracted2, psync_list_compare cmp){
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psync_list *li1, *li2, *ln1, *ln2;
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int cr;
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psync_list_sort(l1, cmp);
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psync_list_sort(l2, cmp);
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li1=l1->next;
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li2=l2->next;
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while (li1!=l1 && li2!=l2){
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cr=cmp(li1, li2);
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if (cr<0)
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li1=li1->next;
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else if (cr>0)
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li2=li2->next;
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else{
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ln1=li1->next;
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ln2=li2->next;
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psync_list_del(li1);
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psync_list_add_tail(extracted1, li1);
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psync_list_del(li2);
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psync_list_add_tail(extracted2, li2);
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li1=ln1;
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li2=ln2;
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}
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}
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}
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