+ /** \brief encodes the changes in the Cache as a EDSP solution
+ *
+ * The markers in the Cache are observed and send to given
+ * file. The solution isn't checked for consistency or alike,
+ * so even broken solutions can be written successfully,
+ * but the front-end revicing it will properly fail then.
+ *
+ * \param Cache which represents the solution
+ * \param output to write the stanzas forming the solution to
+ *
+ * \return true if solution could be written, otherwise false
+ */
+ bool WriteSolution(pkgDepCache &Cache, FILE* output);
+
+ /** \brief sends a progress report
+ *
+ * \param percent of the solving completed
+ * \param message the solver wants the user to see
+ * \param output the front-end listens for progress report
+ */
+ bool WriteProgress(unsigned short const percent, const char* const message, FILE* output);
+
+ /** \brief sends an error report
+ *
+ * Solvers are expected to execute successfully even if
+ * they were unable to calculate a solution for a given task.
+ * Obviously they can't send a solution through, so this
+ * methods deals with formatting an error message correctly
+ * so that the front-ends can receive and display it.
+ *
+ * The first line of the message should be a short description
+ * of the error so it can be used for dialog titles or alike
+ *
+ * \param uuid of this error message
+ * \param message is free form text to describe the error
+ * \param output the front-end listens for error messages
+ */
+ bool WriteError(char const * const uuid, std::string const &message, FILE* output);
+
+
+ /** \brief executes the given solver and returns the pipe ends
+ *
+ * The given solver is executed if it can be found in one of the
+ * configured directories and setup for it is performed.
+ *
+ * \param solver to execute
+ * \param[out] solver_in will be the stdin of the solver
+ * \param[out] solver_out will be the stdout of the solver
+ *
+ * \return PID of the started solver or 0 if failure occurred
+ */
+ pid_t ExecuteSolver(const char* const solver, int * const solver_in, int * const solver_out, bool /*overload*/);
+ APT_DEPRECATED bool ExecuteSolver(const char* const solver, int *solver_in, int *solver_out);
+
+ /** \brief call an external resolver to handle the request
+ *
+ * This method wraps all the methods above to call an external solver
+ *
+ * \param solver to execute
+ * \param Cache with the problem and as universe to work in
+ * \param upgrade is true if it is a request like apt-get upgrade
+ * \param distUpgrade is true if it is a request like apt-get dist-upgrade
+ * \param autoRemove is true if unneeded packages should be removed
+ * \param Progress is an instance to report progress to
+ *
+ * \return true if the solver has successfully solved the problem,
+ * otherwise false
+ */
+ bool ResolveExternal(const char* const solver, pkgDepCache &Cache,
+ bool const upgrade, bool const distUpgrade,
+ bool const autoRemove, OpProgress *Progress = NULL);
+}