Amiga Tools 4/Amiga Tools 4.iso/tools/dfue/term 4.6(?)/extras/source/term-source.lha/MsgQueue.c

C/C++ Source or Header | 1996-03-18 | 7KB | 400 lines

/*
**    MsgQueue.c
**
**    Special MsgPort like queue management
**
**    Copyright © 1990-1996 by Olaf `Olsen' Barthel
**        All Rights Reserved
*/

#ifndef _GLOBAL_H
#include "Global.h"
#endif

    /* DestroyPooled(struct MsgItem *Item):
     *
     *    Default destructor for CreateMsgItem().
     */

STATIC VOID __stdargs
DestroyPooled(struct MsgItem *Item)
{
    FreeVecPooled(Item);
}

    /* GetMsgItem(struct MsgQueue *Queue):
     *
     *    Get the next message from the queue handle,
     *    similar to GetMsg().
     */

APTR
GetMsgItem(struct MsgQueue *Queue)
{
        // Valid handle?

    if(Queue)
    {
        APTR Item;

            // Gain access

        ObtainSemaphore(&Queue -> Access);

            // Any item available?

        if(Queue -> MsgList . mlh_Head -> mln_Succ)
        {
                // Remove the first item

            Remove((struct Node *)(Item = Queue -> MsgList . mlh_Head));

                // Are there any tasks waiting for the queue to become smaller?

            if(Queue -> WaitList . mlh_Head -> mln_Succ)
            {
                struct SemaphoreRequest *WaitRequest = (struct SemaphoreRequest *)Queue -> WaitList . mlh_Head;

                    // Remove one waiting task from the list

                Remove((struct Node *)WaitRequest);

                    // Wake the task up

                Signal(WaitRequest -> sr_Waiter,SIGF_SINGLE);
            }

                // One message taken

            if(Queue -> QueueSize)
                Queue -> QueueSize--;
        }
        else
            Item = NULL;

            // Drop the semaphore

        ReleaseSemaphore(&Queue -> Access);

            // Return the item read

        return(Item);
    }
    else
        return(NULL);
}

    /* PutMsgItem(struct MsgQueue *Queue,struct MsgItem *Item):
     *
     *    Add a message item to a queue handle, similar to
     *    PutMsg().
     */

VOID
PutMsgItem(struct MsgQueue *Queue,struct MsgItem *Item)
{
        // Valid data?

    if(Queue && Item)
    {
            // Gain access to the handle

        ObtainSemaphore(&Queue -> Access);

            // Are we to discard this message?

        if(Queue -> Discard)
        {
            ReleaseSemaphore(&Queue -> Access);

            DeleteMsgItem(Item);
        }
        else
        {
                // Are we to watch for a maximum queue size?

            if(Queue -> MaxSize)
            {
                    // Maximum queue size already reached?

                if(Queue -> MaxSize == Queue -> QueueSize)
                {
                    struct SemaphoreRequest WaitRequest;

                        // That's me

                    WaitRequest . sr_Waiter = FindTask(NULL);

                        // Add this task to the waiting list

                    AddTail((struct List *)&Queue -> WaitList,(struct Node *)&WaitRequest);

                        // Careful, please

                    Forbid();

                        // Drop the semaphore

                    ReleaseSemaphore(&Queue -> Access);

                        // Clear the one-shot flag

                    ClrSignal(SIGF_SINGLE);

                        // Wait for the queue to become smaller

                    Wait(SIGF_SINGLE);

                        // Gain access to the handle

                    ObtainSemaphore(&Queue -> Access);

                        // Reenable multitasking

                    Permit();
                }

                    // We are going to make the queue longer

                Queue -> QueueSize++;
            }

                // Add the item to the list

            AddTail((struct List *)&Queue -> MsgList,(struct Node *)Item);

                // Wake up the owner

            Signal(Queue -> SigTask,Queue -> SigMask);

                // Drop the semaphore

            ReleaseSemaphore(&Queue -> Access);
        }
    }
}

    /* DeleteMsgItem(struct MsgItem *Item):
     *
     *    Clean up after a message item.
     */

VOID
DeleteMsgItem(struct MsgItem *Item)
{
        // Valid data?

    if(Item)
    {
            // Do we have a destructor for this item?

        if(Item -> Destructor)
            (*Item -> Destructor)(Item);
    }
}

    /* CreateMsgItem(LONG Size):
     *
     *    Allocate a new message item.
     */

struct MsgItem *
CreateMsgItem(LONG Size)
{
    struct MsgItem    *Item;

        // Allocate space for the item and add the default destructor

    if(Item = (struct MsgItem *)AllocVecPooled(Size,MEMF_ANY))
        Item -> Destructor = DestroyPooled;

    return(Item);
}

    /* CreateMinMsgItem(LONG Size):
     *
     *    Allocate a new message item, make sure that the header
     *    is present.
     */

struct MsgItem *
CreateMinMsgItem(LONG Size)
{
    struct MsgItem    *Item;

        // Allocate space for the item and add the default destructor

    if(Item = (struct MsgItem *)AllocVecPooled(sizeof(struct MsgItem) + Size,MEMF_ANY))
        Item -> Destructor = DestroyPooled;

    return(Item);
}

    /* UnlockMsgQueue(struct MsgQueue *Queue):
     *
     *    Wake up all tasks waiting for the queue to become
     *    smaller. Note: this will change the maximum queue
     *    size.
     */

VOID
UnlockMsgQueue(struct MsgQueue *Queue)
{
        // Valid data?

    if(Queue)
    {
        struct SemaphoreRequest *WaitRequest;

            // Gain access to the handle

        ObtainSemaphore(&Queue -> Access);

            // Notify all waiting tasks

        for(WaitRequest = (struct SemaphoreRequest *)Queue -> WaitList . mlh_Head ; WaitRequest -> sr_Link . mln_Succ ; WaitRequest = (struct SemaphoreRequest *)WaitRequest -> sr_Link . mln_Succ)
            Signal(WaitRequest -> sr_Waiter,SIGF_SINGLE);

            // Reset the maximum queue size

        Queue -> MaxSize = 0;

            // Drop the semaphore

        ReleaseSemaphore(&Queue -> Access);
    }
}

    /* DeleteMsgQueue(struct MsgQueue *Queue):
     *
     *    Free a queue handle.
     */

VOID
DeleteMsgQueue(struct MsgQueue *Queue)
{
        // Valid data?

    if(Queue)
    {
        struct MsgItem *Item,*Next;

            // Make sure no tasks is waiting in the list

        UnlockMsgQueue(Queue);

            // Disable multitasking

        Forbid();

            // Clear the queue signal

        ClrSignal(Queue -> SigMask);

            // Wait until all tasks are finished

        while(Queue -> QueueSize)
            Wait(Queue -> SigMask);

            // Reenable multitasking

        Permit();

            // Remove each item from the list

        for(Item = (struct MsgItem *)Queue -> MsgList . mlh_Head ; Next = (struct MsgItem *)Item -> Link . mln_Succ ; Item = Next)
            DeleteMsgItem(Item);

            // Free the signal bit if necessary

        if(Queue -> SigBit != -1)
            FreeSignal(Queue -> SigBit);

            // Free the handle

        FreeVecPooled(Queue);
    }
}

    /* CreateMsgQueue(ULONG SigMask,LONG MaxSize):
     *
     *    Allocate a queue handle.
     */

struct MsgQueue *
CreateMsgQueue(ULONG SigMask,LONG MaxSize)
{
    struct MsgQueue    *Queue;

        // Allocate the queue handle

    if(Queue = (struct MsgQueue *)AllocVecPooled(sizeof(struct MsgQueue),MEMF_ANY | MEMF_PUBLIC | MEMF_CLEAR))
    {
            // Initialize the access semaphore

        InitSemaphore(&Queue -> Access);

            // Initialize the message item list

        NewList((struct List *)&Queue -> MsgList);

            // Reset the size data

        Queue -> QueueSize    = 0;
        Queue -> MaxSize    = MaxSize;

            // Initialize the queue wait list

        NewList((struct List *)&Queue -> WaitList);

            // Store the owner address

        Queue -> SigTask = FindTask(NULL);

            // Do we have a signal mask ready?

        if(SigMask)
        {
                // Use it

            Queue -> SigMask    = SigMask;
            Queue -> SigBit        = -1;
        }
        else
        {
                // Allocate a new signal

            if((Queue -> SigBit = AllocSignal(-1)) == -1)
            {
                FreeVecPooled(Queue);

                return(NULL);
            }
            else
                Queue -> SigMask = (1L << Queue -> SigBit);
        }
    }

    return(Queue);
}

    /* SetQueueDiscard(struct MsgQueue *Queue,BOOLEAN Mode):
     *
     *    Set whether new items should be added to the
     *    queue or whether they should rather get
     *    discarded instead.
     */

VOID
SetQueueDiscard(struct MsgQueue *Queue,BOOL Mode)
{
    if(Queue)
    {
        ObtainSemaphore(&Queue -> Access);

        Queue -> Discard = Mode;

        ReleaseSemaphore(&Queue -> Access);
    }
}