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/**
* Copyright (C) 2018-present MongoDB, Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the Server Side Public License, version 1,
* as published by MongoDB, Inc.
*
* 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
* Server Side Public License for more details.
*
* You should have received a copy of the Server Side Public License
* along with this program. If not, see
* <http://www.mongodb.com/licensing/server-side-public-license>.
*
* As a special exception, the copyright holders give permission to link the
* code of portions of this program with the OpenSSL library under certain
* conditions as described in each individual source file and distribute
* linked combinations including the program with the OpenSSL library. You
* must comply with the Server Side Public License in all respects for
* all of the code used other than as permitted herein. If you modify file(s)
* with this exception, you may extend this exception to your version of the
* file(s), but you are not obligated to do so. If you do not wish to do so,
* delete this exception statement from your version. If you delete this
* exception statement from all source files in the program, then also delete
* it in the license file.
*/
#include "mongo/platform/basic.h"
#include "mongo/db/query/collation/collation_index_key.h"
#include <memory>
#include <stack>
#include "mongo/bson/bsonobj.h"
#include "mongo/bson/bsonobjbuilder.h"
#include "mongo/bson/util/builder.h"
#include "mongo/db/query/collation/collator_interface.h"
#include "mongo/util/assert_util.h"
namespace mongo {
namespace {
// To implement string translation iteratively, we utilize TranslateContext. A translate context
// holds necessary information for in-progress translations. TranslateContexts are held by a
// TranslateStack, which acts like a heap-allocated call stack.
class TranslateContext {
TranslateContext(const TranslateContext&) = delete;
TranslateContext& operator=(const TranslateContext&) = delete;
public:
TranslateContext(BSONObjIterator&& iter, BufBuilder* buf)
: bob(*buf), _objIterator(std::move(iter)) {}
/**
* Returns true if the underlying iterator has additional elements.
*/
bool more() {
return _objIterator.more();
}
/**
* Access the next element in the underlying iterator, and advance it.
*
* *Precondition*: A call to next() is only valid if a prior call to more() returned true.
*/
BSONElement next() {
return _objIterator.next();
}
BSONObjBuilder& getBuilder() {
return bob;
}
private:
BSONObjBuilder bob;
BSONObjIterator _objIterator;
};
using TranslateStack = std::stack<TranslateContext>;
// Translate a single element, using the provided collator, appending the result to 'out'.
//
// If the element is an object or array, a new context is added to 'ctxStack', and the function
// returns without modifying 'out'.
//
// If ctxStack is null, _translate must *not* be called with an object or array. Additionally,
// an empty string will be used for the field name when appending 'element' to 'out'.
void translateElement(StringData fieldName,
const BSONElement& element,
const CollatorInterface* collator,
BSONObjBuilder* out,
TranslateStack* ctxStack) {
switch (element.type()) {
case BSONType::String: {
out->append(fieldName,
collator->getComparisonKey(element.valueStringData()).getKeyData());
return;
}
case BSONType::Object: {
invariant(ctxStack);
ctxStack->emplace(BSONObjIterator(element.Obj()), &out->subobjStart(fieldName));
return;
}
case BSONType::Array: {
invariant(ctxStack);
ctxStack->emplace(BSONObjIterator(element.Obj()), &out->subarrayStart(fieldName));
return;
}
case BSONType::Symbol: {
uasserted(ErrorCodes::CannotBuildIndexKeys,
str::stream()
<< "Cannot index type Symbol with a collation. Failed to index element: "
<< element
<< ". Index collation: "
<< collator->getSpec().toBSON());
}
default:
out->appendAs(element, fieldName);
}
}
// Translate all strings in 'obj' into comparison keys using 'collator'. The result is
// appended to 'out'.
void translate(BSONObj obj, const CollatorInterface* collator, BufBuilder* out) {
invariant(collator);
TranslateStack ctxStack;
ctxStack.emplace(BSONObjIterator(obj), out);
while (!ctxStack.empty()) {
TranslateContext& ctx = ctxStack.top();
if (!ctx.more()) {
ctxStack.pop();
continue;
}
BSONElement element = ctx.next();
translateElement(
element.fieldNameStringData(), element, collator, &ctx.getBuilder(), &ctxStack);
}
}
}
void CollationIndexKey::collationAwareIndexKeyAppend(BSONElement elt,
const CollatorInterface* collator,
BSONObjBuilder* out) {
invariant(out);
if (!collator) {
out->appendAs(elt, "");
return;
}
if (elt.isABSONObj()) {
translate(elt.Obj(),
collator,
elt.type() == BSONType::Array ? &out->subarrayStart("") : &out->subobjStart(""));
} else {
translateElement("", elt, collator, out, nullptr);
}
}
} // namespace mongo
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