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/**
* Copyright (C) 2019-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 <boost/intrusive_ptr.hpp>
#include "mongo/db/query/projection_ast.h"
namespace mongo::projection_ast_walker {
/**
* Provided with a Walker and an ASTNode*, walk() calls each of the following:
* * walker.preVisit() once before walking to each child.
* * walker.inVisit() between walking to each child. It is called multiple times, once between each
* pair of children. walker.inVisit() is skipped if the ASTNode has fewer than two children.
* * walker.postVisit() once after walking to each child.
* Each of the ASTNode's child ASTNode is recursively walked and the same three methods are
* called for it.
*
* If the caller doesn't intend to modify the AST, then the template argument 'IsConst' should be
* set to 'true'. In this case the 'node' pointer will be qualified with 'const'.
*/
template <typename Walker, bool IsConst = true>
void walk(Walker* walker, projection_ast::MaybeConstPtr<IsConst, projection_ast::ASTNode> node) {
if (node) {
walker->preVisit(node);
auto count = 0ull;
for (auto&& child : node->children()) {
if (count)
walker->inVisit(count, node);
++count;
walk<Walker, IsConst>(walker, child.get());
}
walker->postVisit(node);
}
}
} // namespace mongo::projection_ast_walker
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