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/**
* Copyright (C) 2012 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/>.
*
* 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 <boost/optional.hpp>
#include <iosfwd>
#include <string>
#include <vector>
#include "mongo/base/disallow_copying.h"
#include "mongo/base/string_data.h"
namespace mongo {
/**
* A FieldPath represents a path in a document, starting from the root. The path
* is made of "field parts" separated by dots. The class provides an efficient means to
* "split" the dotted fields in its parts, but no validation is done.
*
* Any field part may be replaced, after the "original" field reference was parsed. Any
* part can be accessed through a StringData object.
*
* The class is not thread safe.
*/
class FieldRef {
MONGO_DISALLOW_COPYING(FieldRef);
public:
FieldRef();
explicit FieldRef(StringData path);
/**
* Field parts accessed through getPart() calls no longer would be valid, after the
* destructor ran.
*/
~FieldRef() {}
/**
* Builds a field path out of each field part in 'dottedField'.
*/
void parse(StringData dottedField);
/**
* Sets the 'i-th' field part to point to 'part'. Assumes i < size(). Behavior is
* undefined otherwise.
*/
void setPart(size_t i, StringData part);
/**
* Adds a new field to the end of the path, increasing its size by 1.
*/
void appendPart(StringData part);
/**
* Removes the last part from the path, decreasing its size by 1. Has no effect on a
* FieldRef with size 0.
*/
void removeLastPart();
/**
* Returns the 'i-th' field part. Assumes i < size(). Behavior is undefined otherwise.
*/
StringData getPart(size_t i) const;
/**
* Returns true when 'this' FieldRef is a prefix of 'other'. Equality is not considered
* a prefix.
*/
bool isPrefixOf(const FieldRef& other) const;
/**
* Returns the number of field parts in the prefix that 'this' and 'other' share.
*/
size_t commonPrefixSize(const FieldRef& other) const;
/**
* Returns a StringData of the full dotted field in its current state (i.e., some parts may
* have been replaced since the parse() call).
*/
StringData dottedField(size_t offsetFromStart = 0) const;
/**
* Returns a StringData of parts of the dotted field from startPart to endPart in its
* current state (i.e., some parts may have been replaced since the parse() call).
*/
StringData dottedSubstring(size_t startPart, size_t endPart) const;
/**
* Compares the full dotted path represented by this FieldRef to other
*/
bool equalsDottedField(StringData other) const;
/**
* Return 0 if 'this' is equal to 'other' lexicographically, -1 if is it less than or
* +1 if it is greater than.
*/
int compare(const FieldRef& other) const;
/**
* Resets the internal state. See note in parse() call.
*/
void clear();
//
// accessors
//
/**
* Returns the number of parts in this FieldRef.
*/
size_t numParts() const {
return _size;
}
bool empty() const {
return numParts() == 0;
}
private:
// Dotted fields are most often not longer than four parts. We use a mixed structure
// here that will not require any extra memory allocation when that is the case. And
// handle larger dotted fields if it is. The idea is not to penalize the common case
// with allocations.
static const size_t kReserveAhead = 4;
/** Converts the field part index to the variable part equivalent */
size_t getIndex(size_t i) const {
return i - kReserveAhead;
}
/**
* Returns the new number of parts after appending 'part' to this field path. This is
* private, because it is only intended for use by the parse function.
*/
size_t appendParsedPart(StringData part);
/**
* Re-assemble _dotted from components, including any replacements in _replacements,
* and update the StringData components in _fixed and _variable to refer to the parts
* of the new _dotted. This is used to make the storage for the current value of this
* FieldRef contiguous so it can be returned as a StringData from the dottedField
* method above.
*/
void reserialize() const;
// number of field parts stored
size_t _size;
// Number of field parts in the cached dotted name (_dotted).
mutable size_t _cachedSize;
/**
* First kResevedAhead field components.
*
* Each component is either a StringData backed by the _dotted string or boost::none
* to indicate that getPart() should read the string from the _replacements list.
*/
mutable boost::optional<StringData> _fixed[kReserveAhead];
// Remaining field components. (See comment above _fixed.)
mutable std::vector<boost::optional<StringData>> _variable;
/**
* Cached copy of the complete dotted name string. The StringData objects in "_fixed"
* and "_variable" reference this string.
*/
mutable std::string _dotted;
/**
* String storage for path parts that have been replaced with setPart() or added with
* appendPart() since the lasted time "_dotted" was materialized.
*/
mutable std::vector<std::string> _replacements;
};
inline bool operator==(const FieldRef& lhs, const FieldRef& rhs) {
return lhs.compare(rhs) == 0;
}
inline bool operator!=(const FieldRef& lhs, const FieldRef& rhs) {
return lhs.compare(rhs) != 0;
}
inline bool operator<(const FieldRef& lhs, const FieldRef& rhs) {
return lhs.compare(rhs) < 0;
}
inline bool operator<=(const FieldRef& lhs, const FieldRef& rhs) {
return lhs.compare(rhs) <= 0;
}
inline bool operator>(const FieldRef& lhs, const FieldRef& rhs) {
return lhs.compare(rhs) > 0;
}
inline bool operator>=(const FieldRef& lhs, const FieldRef& rhs) {
return lhs.compare(rhs) >= 0;
}
std::ostream& operator<<(std::ostream& stream, const FieldRef& value);
} // namespace mongo
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