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/**
* Copyright (C) 2013 10gen Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License, version 3,
* as published by the Free Software Foundation.
*
* 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 Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include "mongo/db/field_ref_set.h"
#include "mongo/util/assert_util.h"
namespace mongo {
namespace {
// For legacy purposes, we must handle empty fieldnames, which FieldRef clearly
// prohibits. It is preferrable to have FieldRef keep that constraint and relax it here
// -- stricly in update code. The rationale is that, if we want to ban data with no
// field names, we must allow that data to be updated.
StringData safeFirstPart(const FieldRef* fieldRef) {
if (fieldRef->numParts() == 0) {
return StringData();
}
else {
return fieldRef->getPart(0);
}
}
}
bool FieldRefSet::FieldRefPtrLessThan::operator()(const FieldRef* l, const FieldRef* r) const {
return *l < *r;
}
FieldRefSet::FieldRefSet() {
}
bool FieldRefSet::insert(const FieldRef* toInsert, const FieldRef** conflict) {
// We can determine if two fields conflict by checking their common prefix.
//
// If each field is exactly of the size of the common prefix, this means the fields are
// the same. If one of the fields is greater than the common prefix and the other
// isn't, the latter is a prefix of the former. And vice-versa.
//
// Example:
//
// inserted > | a a.c
// exiting v | (0) (+1)
// ----------------|------------------------
// a (0) | equal prefix <
// a.b (+1) | prefix ^ *
//
// * Disjoint sub-trees
// At each insertion, we only need to bother checking the fields in the set that have
// at least some common prefix with the 'toInsert' field.
StringData prefixStr = safeFirstPart(toInsert);
FieldRef prefixField;
prefixField.parse(prefixStr);
FieldSet::iterator it = _fieldSet.lower_bound(&prefixField);
// Now, iterate over all the present fields in the set that have the same prefix.
while (it != _fieldSet.end() && safeFirstPart(*it) == prefixStr) {
size_t common = (*it)->commonPrefixSize(*toInsert);
if ((*it)->numParts() == common || toInsert->numParts() == common) {
*conflict = *it;
return false;
}
++it;
}
_fieldSet.insert(it, toInsert);
*conflict = NULL;
return true;
}
} // namespace mongo
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