lock_request_list.h

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#pragma once

#include "mongo/db/concurrency/lock_manager_defs.h"
#include "mongo/util/assert_util.h"

namespace mongo {

class LockRequestList {
public:
    void push_front(LockRequest* request) {
        // Sanity check that we do not reuse entries without cleaning them up
        invariant(request->next == NULL);
        invariant(request->prev == NULL);

        if (_front == NULL) {
            _front = _back = request;
        } else {
            request->next = _front;

            _front->prev = request;
            _front = request;
        }
    }

    void push_back(LockRequest* request) {
        // Sanity check that we do not reuse entries without cleaning them up
        invariant(request->next == NULL);
        invariant(request->prev == NULL);

        if (_front == NULL) {
            _front = _back = request;
        } else {
            request->prev = _back;

            _back->next = request;
            _back = request;
        }
    }

    void remove(LockRequest* request) {
        if (request->prev != NULL) {
            request->prev->next = request->next;
        } else {
            _front = request->next;
        }

        if (request->next != NULL) {
            request->next->prev = request->prev;
        } else {
            _back = request->prev;
        }

        request->prev = NULL;
        request->next = NULL;
    }

    void reset() {
        _front = _back = NULL;
    }

    bool empty() const {
        return _front == NULL;
    }

    // Pointers to the beginning and the end of the list
    LockRequest* _front;
    LockRequest* _back;
};

}  // namespace mongo