vlShmQueue.h

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/*********************************************************************
** Copyright (c) 1992-2025 MAK Technologies, Inc
** All rights reserved.
*********************************************************************/
#pragma once

#include "vlMachineTypes.h" 

#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/sem.h>

#define DT_QCONTROL_VALID      0
#define DT_QCONTROL_DEAD_SPACE 1
#define DT_QCONTROL_END        2

#define DtSMQFrontLockSem   0
#define DtSMQPacketCountSem 1

#define DtSMQByteCountSem   0

#define DtCsSemaphoresUsed  2

#define DtSMQDontGoYet      0
#define DtSMQIAmGoingAway   1
#define DtSMQYouMustGoAway  2

#define DtSMQExternal       0
#define DtSMQInternal       1

#ifdef DtUSE_UTILITIES_NAMESPACE
namespace DtUSE_UTILITIES_NAMESPACE
{
#endif

typedef struct Dt_Q_Elmt_Hdr
{
    short read;
    short control;
    int size;
} DtQueueElementHdr;

typedef struct Dt_Msg_Queue_Element
{
    DtQueueElementHdr hdr;
    char data[8];
} DtMsgQueueElement;


typedef struct Dt_Q_Hdr
{
    DtInt32 front;
    DtU32   notifyReader; 

    unsigned char goAway;
    unsigned char internal;
    DtU16         padding1;

    unsigned char blockingRead;
    unsigned char blockingWrite;
    unsigned char dropOldest;
    unsigned char padding2;

} DtShmQueueHdr;

typedef struct Dt_Shm_Msg_Queue
{
    DtShmQueueHdr hdr;
    char data[8];
} DtShmMsgQueue;



class DT_DLL_VLUTIL DtShmMsgQueueManager
{
  friend class DtShmMsgQueueReader;
  friend class DtShmMsgQueueWriter;

  public:

    DtShmMsgQueueManager(DtShmMsgQueue *q, int size, int sem, int firstSem,
   bool pleaseInit, bool dropOldest);

    virtual ~DtShmMsgQueueManager(void);

    void setBlockingRead(bool mode) 
   { queue->hdr.blockingRead = mode ? 1 : 0; }

    void setBlockingWrite(bool mode) 
   { queue->hdr.blockingWrite = mode ? 1 : 0; }

    bool isBlockingRead() 
   { return queue->hdr.blockingRead ? true : false; }

    bool isBlockingWrite() 
   { return queue->hdr.blockingWrite ? true : false; }

    bool isDropOldest() 
   { return queue->hdr.dropOldest ? true : false; }

    int getGoAway() { return queue->hdr.goAway; }

    DtU32 notifyReader();

    void setNotifyReader(DtU32 count) { queue->hdr.notifyReader = count; } 

  private:

    int lockFront(int wait);
    void unlockFront(void);

    void incrPacketCount(int amount);
    void incrByteCount(int amount);
    void decrByteCount(int amount);
    void decrPacketCount(int amount);

    int getPhysEnd() { return physEnd; }

    void setFront(int newFront) { queue->hdr.front = newFront; }
    int getFront() { return queue->hdr.front; }

    void setGoAway(int reason) { queue->hdr.goAway = reason; }

    void setDropOldest(bool mode) 
   { queue->hdr.dropOldest = mode ? 1 : 0; }

    void setInternal(int mode) { queue->hdr.internal = mode; }
    bool isInternal() { return queue->hdr.internal ? true : false; }

    DtMsgQueueElement *getQueueElement(int i) 
   { return (DtMsgQueueElement *) & queue->data[i]; }


  protected:

    DtShmMsgQueue *queue;
    int physEnd;
    int semid;

    struct sembuf testAndSetLock;
    struct sembuf clearLock;
    struct sembuf addBytes;
    struct sembuf subBytes;
    struct sembuf addPackets;
    struct sembuf subPackets;

      
};

#ifdef DtUSE_UTILITIES_NAMESPACE
} 
#endif