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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.
*/
#pragma once
#include <algorithm>
#include <array>
#include "mongo/db/matcher/expression.h"
#include "mongo/stdx/memory.h"
namespace mongo {
/**
* Abstract base class for MatchExpressions that take a fixed 'nargs' number of MatchExpression
* arguments. 'T' is the MatchExpression class that extends this interface.
*/
template <typename T, size_t nargs>
class FixedArityMatchExpression : public MatchExpression {
public:
/**
* The number of arguments accepted by this expression.
*/
static constexpr size_t arity() {
return nargs;
}
virtual ~FixedArityMatchExpression() = default;
void debugString(StringBuilder& debug, int level) const final {
_debugAddSpace(debug, level);
BSONObjBuilder builder;
serialize(&builder);
debug << builder.obj().toString();
}
/**
* The order of arguments is significant when determining equivalence.
*/
bool equivalent(const MatchExpression* expr) const final {
if (matchType() != expr->matchType()) {
return false;
}
auto other = static_cast<const T*>(expr);
const auto& ourChildren = _expressions;
const auto& theirChildren = other->_expressions;
return std::equal(
ourChildren.begin(),
ourChildren.end(),
theirChildren.begin(),
theirChildren.end(),
[](const auto& expr1, const auto& expr2) { return expr1->equivalent(expr2.get()); });
}
std::vector<MatchExpression*>* getChildVector() final {
return nullptr;
}
size_t numChildren() const final {
return nargs;
}
MatchExpression* getChild(size_t i) const final {
invariant(i < nargs);
return _expressions[i].get();
}
/**
* The name of this MatchExpression.
*/
virtual StringData name() const = 0;
/**
* Serializes each subexpression sequentially in a BSONArray.
*/
void serialize(BSONObjBuilder* builder) const final {
BSONArrayBuilder exprArray(builder->subarrayStart(name()));
for (const auto& expr : _expressions) {
BSONObjBuilder exprBuilder(exprArray.subobjStart());
expr->serialize(&exprBuilder);
exprBuilder.doneFast();
}
exprArray.doneFast();
}
/**
* Clones this MatchExpression by recursively cloning each sub-expression.
*/
std::unique_ptr<MatchExpression> shallowClone() const final {
std::array<std::unique_ptr<MatchExpression>, nargs> clonedExpressions;
std::transform(_expressions.begin(),
_expressions.end(),
clonedExpressions.begin(),
[](const auto& orig) {
return orig ? orig->shallowClone()
: std::unique_ptr<MatchExpression>(nullptr);
});
std::unique_ptr<T> clone = stdx::make_unique<T>(std::move(clonedExpressions));
if (getTag()) {
clone->setTag(getTag()->clone());
}
return std::move(clone);
}
protected:
/**
* Takes ownership of the MatchExpressions in 'expressions'.
*/
explicit FixedArityMatchExpression(
MatchType type, std::array<std::unique_ptr<MatchExpression>, nargs> expressions)
: MatchExpression(type), _expressions(std::move(expressions)) {}
const auto& expressions() const {
return _expressions;
}
private:
ExpressionOptimizerFunc getOptimizer() const final {
return [](std::unique_ptr<MatchExpression> expression) {
for (auto& subExpression :
static_cast<FixedArityMatchExpression&>(*expression)._expressions) {
// Since 'subExpression' is a reference to a member of the
// FixedArityMatchExpression's child array, this assignment replaces the original
// child with the optimized child.
subExpression = MatchExpression::optimize(std::move(subExpression));
}
return expression;
};
}
std::array<std::unique_ptr<MatchExpression>, nargs> _expressions;
};
} // namespace mongo
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