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synchronizelists.h
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/*
* Copyright (C) 2013 Jolla Mobile <andrew.den.exter@jollamobile.com>
*
* You may use this file under the terms of the BSD license as follows:
*
* "Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are
* met:
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
* * Neither the name of Nemo Mobile nor the names of its contributors
* may be used to endorse or promote products derived from this
* software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE."
*/
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#ifndef SYNCHRONIZELISTS_H
#define SYNCHRONIZELISTS_H
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// Helper utility to synchronize a cached list with some reference list with correct
// QAbstractItemModel signals and filtering.
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// If the reference list is populated incrementally synchronizeList can be called multiple times with the
// same variables c and r to progressively synchronize the lists. After the final call completeSynchronizeList
// can be called to remove or append any items which remain unsynchronized.
// The Filtered variants allow the reference list to be filtered by a callback function to
// exclude unwanted items from the synchronized list.
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template <typename T>
bool compareIdentity(const T &item, const T &reference)
{
return item == reference;
}
template <typename Agent, typename ReferenceList>
int insertRange(Agent *agent, int index, int count, const ReferenceList &source, int sourceIndex)
{
agent->insertRange(index, count, source, sourceIndex);
return count;
}
template <typename Agent>
int removeRange(Agent *agent, int index, int count)
{
agent->removeRange(index, count);
return 0;
}
template <typename Agent, typename ReferenceList>
int updateRange(Agent *agent, int index, int count, const ReferenceList &source, int sourceIndex)
{
Q_UNUSED(agent);
Q_UNUSED(index);
Q_UNUSED(source);
Q_UNUSED(sourceIndex);
return count;
}
template <typename Agent, typename CacheList, typename ReferenceList>
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class SynchronizeList
{
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typedef typename CacheList::const_reference CacheItem;
typedef typename ReferenceList::const_reference ReferenceItem;
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public:
SynchronizeList(
Agent *agent,
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const CacheList &cache,
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int &c,
const ReferenceList &reference,
int &r)
: agent(agent), cache(cache), c(c), reference(reference), r(r)
{
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int lastEqualC = c;
int lastEqualR = r;
for (; c < cache.count() && r < reference.count(); ++c, ++r) {
if (compareIdentity(cache.at(c), reference.at(r))) {
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continue;
}
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if (c > lastEqualC) {
lastEqualC += updateRange(agent, lastEqualC, c - lastEqualC, reference, lastEqualR);
c = lastEqualC;
lastEqualR = r;
}
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bool match = false;
// Iterate through both the reference and cache lists in parallel looking for first
// point of commonality, when that is found resolve the differences and continue
// looking.
int count = 1;
for (; !match && c + count < cache.count() && r + count < reference.count(); ++count) {
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CacheItem cacheItem = cache.at(c + count);
ReferenceItem referenceItem = reference.at(r + count);
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for (int i = 0; i <= count; ++i) {
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if (cacheMatch(i, count, referenceItem) || referenceMatch(i, count, cacheItem)) {
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match = true;
break;
}
}
}
// Continue scanning the reference list if the cache has been exhausted.
for (int re = r + count; !match && re < reference.count(); ++re) {
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ReferenceItem referenceItem = reference.at(re);
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for (int i = 0; i < count; ++i) {
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if (cacheMatch(i, re - r, referenceItem)) {
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match = true;
break;
}
}
}
// Continue scanning the cache if the reference list has been exhausted.
for (int ce = c + count; !match && ce < cache.count(); ++ce) {
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CacheItem cacheItem = cache.at(ce);
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for (int i = 0; i < count; ++i) {
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if (referenceMatch(i, ce - c, cacheItem)) {
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match = true;
break;
}
}
}
if (!match)
return;
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lastEqualC = c;
lastEqualR = r;
}
if (c > lastEqualC) {
updateRange(agent, lastEqualC, c - lastEqualC, reference, lastEqualR);
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}
}
private:
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// Tests if the cached contact id at i matches a referenceId.
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// If there is a match removes all items traversed in the cache since the previous match
// and inserts any items in the reference set found to to not be in the cache.
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bool cacheMatch(int i, int count, ReferenceItem referenceItem)
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{
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if (compareIdentity(cache.at(c + i), referenceItem)) {
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if (i > 0)
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c += removeRange(agent, c, i);
c += insertRange(agent, c, count, reference, r);
r += count;
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return true;
} else {
return false;
}
}
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// Tests if the reference contact id at i matches a cacheId.
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// If there is a match inserts all items traversed in the reference set since the
// previous match and removes any items from the cache that were not found in the
// reference list.
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bool referenceMatch(int i, int count, CacheItem cacheItem)
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{
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if (compareIdentity(reference.at(r + i), cacheItem)) {
c += removeRange(agent, c, count);
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if (i > 0)
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c += insertRange(agent, c, i, reference, r);
r += i;
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return true;
} else {
return false;
}
}
Agent * const agent;
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const CacheList &cache;
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int &c;
const ReferenceList &reference;
int &r;
};
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template <typename Agent, typename CacheList, typename ReferenceList>
void completeSynchronizeList(
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Agent *agent,
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const CacheList &cache,
int &cacheIndex,
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const ReferenceList &reference,
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int &referenceIndex)
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{
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if (cacheIndex < cache.count()) {
agent->removeRange(cacheIndex, cache.count() - cacheIndex);
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}
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if (referenceIndex < reference.count()) {
agent->insertRange(cache.count(), reference.count() - referenceIndex, reference, referenceIndex);
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}
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cacheIndex = 0;
referenceIndex = 0;
}
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template <typename Agent, typename CacheList, typename ReferenceList>
void synchronizeList(
Agent *agent,
const CacheList &cache,
int &cacheIndex,
const ReferenceList &reference,
int &referenceIndex)
{
SynchronizeList<Agent, CacheList, ReferenceList>(
agent, cache, cacheIndex, reference, referenceIndex);
}
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template <typename Agent, typename CacheList, typename ReferenceList>
void synchronizeList(Agent *agent, const CacheList &cache, const ReferenceList &reference)
{
int cacheIndex = 0;
int referenceIndex = 0;
synchronizeList(agent, cache, cacheIndex, reference, referenceIndex);
completeSynchronizeList(agent, cache, cacheIndex, reference, referenceIndex);
}
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template <typename Agent, typename ReferenceList>
ReferenceList filterList(
Agent *agent,
const ReferenceList &reference)
{
ReferenceList filtered;
filtered.reserve(reference.count());
foreach (const typename ReferenceList::value_type &value, reference)
if (agent->filterValue(value))
filtered.append(value);
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return filtered;
}
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template <typename Agent, typename CacheList, typename ReferenceList>
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void synchronizeFilteredList(
Agent *agent,
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const CacheList &cache,
int &cacheIndex,
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const ReferenceList &reference,
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int &referenceIndex)
{
ReferenceList filtered = filterList(agent, reference);
synchronizeList(agent, cache, cacheIndex, filtered, referenceIndex);
}
template <typename Agent, typename CacheList, typename ReferenceList>
void synchronizeFilteredList(Agent *agent, const CacheList &cache, const ReferenceList &reference)
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{
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int cacheIndex = 0;
int referenceIndex = 0;
ReferenceList filtered = filterList(agent, reference);
synchronizeList(agent, cache, cacheIndex, filtered, referenceIndex);
completeSynchronizeList(agent, cache, cacheIndex, filtered, referenceIndex);
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}
#endif