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/**
* Copyright (C) 2017 MongoDB 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/>.
*
* 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 GNU Affero General 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 "mongo/db/pipeline/document.h"
#include "mongo/stdx/memory.h"
#include "mongo/stdx/unordered_map.h"
#include "mongo/util/string_map.h"
namespace mongo {
/// The state used as input and working space for Expressions.
class Variables {
MONGO_DISALLOW_COPYING(Variables);
public:
// Each unique variable is assigned a unique id of this type. Negative ids are reserved for
// system variables and non-negative ids are allocated for user variables.
using Id = int64_t;
/**
* Generates Variables::Id and keeps track of the number of Ids handed out.
*/
class IdGenerator {
public:
IdGenerator() : _nextId(0) {}
Variables::Id generateId() {
return _nextId++;
}
private:
Variables::Id _nextId;
};
Variables() = default;
static void uassertValidNameForUserWrite(StringData varName);
static void uassertValidNameForUserRead(StringData varName);
// Ids for builtin variables.
static constexpr Variables::Id kRootId = Id(-1);
static constexpr Variables::Id kRemoveId = Id(-2);
// Map from builtin var name to reserved id number.
static const StringMap<Id> kBuiltinVarNameToId;
/**
* Sets the value of a user-defined variable. Illegal to use with the reserved builtin variables
* defined above.
*/
void setValue(Variables::Id id, const Value& value);
/**
* Gets the value of a user-defined or system variable. If the 'id' provided represents the
* special ROOT variable, then we return 'root' in Value form.
*/
Value getValue(Variables::Id id, const Document& root) const;
/**
* Returns Document() for non-document values, but otherwise identical to getValue(). If the
* 'id' provided represents the special ROOT variable, then we return 'root'.
*/
Document getDocument(Variables::Id id, const Document& root) const;
IdGenerator* useIdGenerator() {
return &_idGenerator;
}
private:
IdGenerator _idGenerator;
std::vector<Value> _valueList;
};
/**
* This class represents the Variables that are defined in an Expression tree.
*
* All copies from a given instance share enough information to ensure unique Ids are assigned
* and to propagate back to the original instance enough information to correctly construct a
* Variables instance.
*/
class VariablesParseState {
public:
explicit VariablesParseState(Variables::IdGenerator* variableIdGenerator)
: _idGenerator(variableIdGenerator) {}
/**
* Assigns a named variable a unique Id. This differs from all other variables, even
* others with the same name.
*
* The special variables ROOT and CURRENT are always implicitly defined with CURRENT
* equivalent to ROOT. If CURRENT is explicitly defined by a call to this function, it
* breaks that equivalence.
*
* NOTE: Name validation is responsibility of caller.
*/
Variables::Id defineVariable(StringData name);
/**
* Returns the current Id for a variable. uasserts if the variable isn't defined.
*/
Variables::Id getVariable(StringData name) const;
private:
// Not owned here.
Variables::IdGenerator* _idGenerator;
StringMap<Variables::Id> _variables;
};
} // namespace mongo
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