kv_prefix.h

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#pragma once

#include "mongo/bson/bsonelement.h"
#include "mongo/bson/util/builder.h"
#include "mongo/db/namespace_string.h"
#include "mongo/db/storage/storage_options.h"
#include "mongo/stdx/mutex.h"

namespace mongo {

class KVPrefix {
public:
    // Represents a table that is not grouped and should not have its keys prefixed.
    static const KVPrefix kNotPrefixed;

    bool isPrefixed() const {
        return _value >= 0;
    }

    int64_t toBSONValue() const {
        return _value;
    }

    int64_t repr() const {
        return _value;
    }

    std::string toString() const;

    inline bool operator<(const KVPrefix& rhs) const {
        return _value < rhs._value;
    }

    inline bool operator==(const KVPrefix& rhs) const {
        return _value == rhs._value;
    }

    inline bool operator!=(const KVPrefix& rhs) const {
        return _value != rhs._value;
    }

    static KVPrefix fromBSONElement(const BSONElement value);

    static void setLargestPrefix(KVPrefix largestPrefix);

    static KVPrefix getNextPrefix(const NamespaceString& ns);

    static KVPrefix generateNextPrefix();

private:
    explicit KVPrefix(int64_t value) : _value(value) {}
    int64_t _value;

    static stdx::mutex _nextValueMutex;
    static int64_t _nextValue;
};

inline std::ostream& operator<<(std::ostream& s, const KVPrefix& prefix) {
    return (s << prefix.toString());
}
}