[thirdparty/squid.git] / src / ipc / QuestionerId.h

/*
 * Copyright (C) 1996-2021 The Squid Software Foundation and contributors
 *
 * Squid software is distributed under GPLv2+ license and includes
 * contributions from numerous individuals and organizations.
 * Please see the COPYING and CONTRIBUTORS files for details.
 */

#ifndef SQUID_SRC_IPC_QUESTIONERID_H
#define SQUID_SRC_IPC_QUESTIONERID_H

#include "ipc/forward.h"

#include <iosfwd>

namespace Ipc
{

/// Identifies a kid process sending IPC messages that require an answer.
/// Must be unique across all kids with pending questions.
class QuestionerId
{
public:
    /// to-be-determined ID
    QuestionerId() = default;

    /// for sending the ID of the asking process
    void pack(TypedMsgHdr &) const;

    /// for receiving the ID of the asking process
    void unpack(const TypedMsgHdr &);

    /// does nothing but throws if the questioner was not the current process
    void rejectAnswerIfStale() const;

    /// reports the stored opaque ID value (for debugging)
    void print(std::ostream &) const;

private:
    /// for MyQuestionerId() convenience
    explicit QuestionerId(const pid_t aPid): pid(aPid) {}
    friend QuestionerId MyQuestionerId();

    /// OS process ID of the asking kid. If the kid restarts, it is assumed
    /// not to wrap back to the old value until the answer is received.
    pid_t pid = -1;
};

/// the questioner ID of the current/calling process
QuestionerId MyQuestionerId();

/// Convenience wrapper for rejecting (freshly parsed) stale answers.
/// All answers are assumed to have a "QuestionerId intendedRecepient()" member.
template <class Answer>
const Answer &
Mine(const Answer &answer)
{
    answer.intendedRecepient().rejectAnswerIfStale();
    return answer;
}

inline std::ostream &
operator <<(std::ostream &os, const QuestionerId &qid)
{
    qid.print(os);
    return os;
}

} // namespace Ipc;

#endif /* SQUID_SRC_IPC_QUESTIONERID_H */
Commit	Line	Data
4c218615	1	/*
f70aedc4	2	* Copyright (C) 1996-2021 The Squid Software Foundation and contributors
4c218615 EB	3	*
	4	* Squid software is distributed under GPLv2+ license and includes
	5	* contributions from numerous individuals and organizations.
	6	* Please see the COPYING and CONTRIBUTORS files for details.
	7	*/
	8
	9	#ifndef SQUID_SRC_IPC_QUESTIONERID_H
	10	#define SQUID_SRC_IPC_QUESTIONERID_H
	11
	12	#include "ipc/forward.h"
	13
	14	#include <iosfwd>
	15
	16	namespace Ipc
	17	{
	18
	19	/// Identifies a kid process sending IPC messages that require an answer.
	20	/// Must be unique across all kids with pending questions.
	21	class QuestionerId
	22	{
	23	public:
	24	/// to-be-determined ID
	25	QuestionerId() = default;
	26
	27	/// for sending the ID of the asking process
	28	void pack(TypedMsgHdr &) const;
	29
	30	/// for receiving the ID of the asking process
	31	void unpack(const TypedMsgHdr &);
	32
	33	/// does nothing but throws if the questioner was not the current process
	34	void rejectAnswerIfStale() const;
	35
	36	/// reports the stored opaque ID value (for debugging)
	37	void print(std::ostream &) const;
	38
	39	private:
	40	/// for MyQuestionerId() convenience
	41	explicit QuestionerId(const pid_t aPid): pid(aPid) {}
	42	friend QuestionerId MyQuestionerId();
	43
	44	/// OS process ID of the asking kid. If the kid restarts, it is assumed
	45	/// not to wrap back to the old value until the answer is received.
	46	pid_t pid = -1;
	47	};
	48
	49	/// the questioner ID of the current/calling process
	50	QuestionerId MyQuestionerId();
	51
	52	/// Convenience wrapper for rejecting (freshly parsed) stale answers.
	53	/// All answers are assumed to have a "QuestionerId intendedRecepient()" member.
	54	template <class Answer>
	55	const Answer &
	56	Mine(const Answer &answer)
	57	{
	58	answer.intendedRecepient().rejectAnswerIfStale();
	59	return answer;
	60	}
	61
	62	inline std::ostream &
	63	operator <<(std::ostream &os, const QuestionerId &qid)
	64	{
	65	qid.print(os);
	66	return os;
67	}
68
69	} // namespace Ipc;
70
71	#endif /* SQUID_SRC_IPC_QUESTIONERID_H */
72