examples/PIPS/opencmessagequeuelibraryex/engine/src/msgqinternals.c

#include <stdlib.h>
#include "MsgQInternal.h"


/* Declaration and definition of Internal Functions and data structures */
MSGQ_INFO_PTR        MsgQInfo[MSGQ_TBL_SZ];
MSGQ_INFO_LIST_PTR   MsgQListHead = NULL;

inline unsigned int HashIndex(ULONG qName);

/*************** INTERNAL FUNCTIONS ******************************/

/***************************************************************************
*  InstallMsqQTable (qName, qid, semId, sendState, numMsgs, err)
*  Function: This function installs a queue into the hash table
****************************************************************************/

int InstallMsqQTable(ULONG qName, int qId, int semId, int* err) {

        MSGQ_INFO_PTR pMsgQInfo = NULL;
        unsigned int  index;

        if ((pMsgQInfo = MsgQTableLookup(qName)) == NULL) {
                pMsgQInfo = (MSGQ_INFO_PTR)malloc(sizeof(*pMsgQInfo));

                if(pMsgQInfo != NULL) {
                        index = HashIndex(qName);

                        pMsgQInfo->next  = MsgQInfo[index];
                        MsgQInfo[index]   = pMsgQInfo;
                        pMsgQInfo->qName = qName;
                        pMsgQInfo->qId   = qId;
                        pMsgQInfo->semId = semId;
                        pMsgQInfo->sendState = MSG_Q_READY;
                        pMsgQInfo->numMsgs   = 0;

                        *err = OK;
                        return (OK);
                }
                else
                        *err = KMsgQLibNoMemoryErr;
        }
        else
                *err = KMsgQLibQIdErr;

        return(ERROR);

}


/******************************************************************************
*  HashIndex
*  Function: This function returns the hash index
*******************************************************************************/

inline unsigned int HashIndex(ULONG qName) {
        return(qName % MSGQ_TBL_SZ);
}


/************************************************************************
*  MsgQTableLookup (qName)
*  Function: This function finds the block pointer for each queue
*************************************************************************/

MSGQ_INFO* MsgQTableLookup(ULONG qName) {
        MSGQ_INFO_PTR pMsgQInfo = NULL;

        for (pMsgQInfo = MsgQInfo[HashIndex(qName)]; pMsgQInfo != NULL; pMsgQInfo = pMsgQInfo->next) {
                if (qName == pMsgQInfo->qName)
                        return(pMsgQInfo);
        }

        return(NULL);
}


/*************************************************************************
*  RemoveFromMsqQTable (qName, err)
*  Function: This function removes a queue from the hash table
**************************************************************************/


int RemoveFromMsqQTable(ULONG qName, int* err) {
        unsigned int  index = 0;
        MSGQ_INFO_PTR prev = NULL;
        MSGQ_INFO_PTR pMsgQInfo = NULL;

        index = HashIndex(qName);
        for (pMsgQInfo = MsgQInfo[index]; pMsgQInfo != NULL; pMsgQInfo = pMsgQInfo->next) {
                if (qName == pMsgQInfo->qName)
                        break;
                prev = pMsgQInfo;
        }

        if (pMsgQInfo != NULL) {
                if (prev == NULL)
                        MsgQInfo[index] = pMsgQInfo->next;
                else
                        prev->next = pMsgQInfo->next;

                free((void*)pMsgQInfo);
                *err = OK;
                return (OK);
        }
        else
                *err = KMsgQLibQIdErr;

        return(ERROR);
}


/************************************************************************
*  AddToMsgQTable (qName)
*  Function: Adding a queue to list
*************************************************************************/

void AddToMsgQTable(ULONG qName) {
        MSGQ_INFO_LIST_PTR tempNext;

        if (MsgQListHead != NULL) {
                /* subsequent entries */
                tempNext = MsgQListHead->next;

                if ((MsgQListHead->next = (MSGQ_INFO_LIST*)malloc(sizeof(MSGQ_INFO_LIST))) != NULL)             {
                        MsgQListHead->next->next = tempNext;
                        MsgQListHead->next->qName = qName;
                }
                else 
                        MsgQListHead->next = tempNext;
        }
        else {
                if ((MsgQListHead = (MSGQ_INFO_LIST*)malloc(sizeof(MSGQ_INFO_LIST))) != NULL) {
                        MsgQListHead->next = NULL;
                        MsgQListHead->qName = qName;
                }
        }
}

/************************************************************************
*  DeleteFromMsgQTable (qName)
*  Function:  removing a queu entry from  list
*************************************************************************/

void DeleteFromMsgQTable(ULONG qName) {
        MSGQ_INFO_LIST_PTR prev = NULL;
        MSGQ_INFO_LIST_PTR pMsgQInfo = NULL;

        for (pMsgQInfo = MsgQListHead; pMsgQInfo != NULL; pMsgQInfo = pMsgQInfo->next) {
                if (qName == pMsgQInfo->qName)
                        break;
                prev = pMsgQInfo;
        }

        if (pMsgQInfo != NULL) {
                /* Check whether prev pointer is null or not. If it is Null, update Head pointer */
                if( prev == NULL )
                        MsgQListHead = MsgQListHead->next ;

                /* Else update the linked list by removing present node and updating prev next pointer */
                else
                        prev->next = pMsgQInfo->next;

                /* Now free up the memory used by the present node */
                free((void*) pMsgQInfo);
        }
}

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