/*
*********************************************************************************************************
*                                                uC/OS-II
*                                          The Real-Time Kernel
*                                       MESSAGE MAILBOX MANAGEMENT
*
*                          (c) Copyright 1992-2002, Jean J. Labrosse, Weston, FL
*                                           All Rights Reserved
*
* File : OS_MBOX.C
* By   : Jean J. Labrosse
* 翻譯： likee
*********************************************************************************************************
*/

#ifndef  OS_MASTER_FILE
#include "includes.h"
#endif

#if OS_MBOX_EN > 0
/*
*********************************************************************************************************
*                                     ACCEPT MESSAGE FROM MAILBOX
*
* Description: This function checks the mailbox to see if a message is available.  Unlike OSMboxPend(),
*              OSMboxAccept() does not suspend the calling task if a message is not available.
*
* Arguments  : pevent        is a pointer to the event control block
*
* Returns    : != (void *)0  is the message in the mailbox if one is available.  The mailbox is cleared
*                            so the next time OSMboxAccept() is called, the mailbox will be empty.
*              == (void *)0  if the mailbox is empty or,
*                            if 'pevent' is a NULL pointer or,
*                            if you didn't pass the proper event pointer.
*********************************************************************************************************
*/
/*
*********************************************************************************************************
                                                    無(wú)等待地從郵箱中得到一則消息
描述：此函數(shù)檢查郵箱中是否有消息，不同于OSMboxPend()，如果沒(méi)有可行消息，
                OSMboxAccept() 不會(huì)掛起調(diào)用此函數(shù)的任務(wù)
參數(shù)；：pevent：是指向事件控制塊的指針
返回：!= (void *)0 如果郵箱有消息，它指向郵箱中的一則消息，郵箱被清空，
                     如果下一次調(diào)用，它將是空的。
                 == (void *)0 如果郵箱為空，或者pevent指向空指針，或者沒(méi)有傳遞一個(gè)合理事件
                                指針
*********************************************************************************************************
*/


#if OS_MBOX_ACCEPT_EN > 0
void  *OSMboxAccept (OS_EVENT *pevent)
{
#if OS_CRITICAL_METHOD == 3                      /* Allocate storage for CPU status register           */
    OS_CPU_SR  cpu_sr;
#endif    
    void      *msg;


#if OS_ARG_CHK_EN > 0//允許參數(shù)檢驗(yàn)
    if (pevent == (OS_EVENT *)0) {                        /* Validate 'pevent'                         */
        return ((void *)0);//如果事件無(wú)效，返回零
    }
    if (pevent->OSEventType != OS_EVENT_TYPE_MBOX) {      /* Validate event block type                 */
		//檢查pevent所指向的事件控制塊是不是由OS_EVENT_TYPE_MBOX建立
        return ((void *)0);
    }
#endif
    OS_ENTER_CRITICAL();
    msg                = pevent->OSEventPtr;//函數(shù)得到郵箱的當(dāng)前內(nèi)容
    pevent->OSEventPtr = (void *)0;                       /* Clear the mailbox     *///清空郵箱
    OS_EXIT_CRITICAL();
    return (msg);   /* Return the message received (or NULL)     *///將郵箱中的內(nèi)容返回，以供調(diào)用
}
#endif
/*$PAGE*/
/*
*********************************************************************************************************
*                                        CREATE A MESSAGE MAILBOX
*
* Description: This function creates a message mailbox if free event control blocks are available.
*
* Arguments  : msg           is a pointer to a message that you wish to deposit in the mailbox.  If
*                            you set this value to the NULL pointer (i.e. (void *)0) then the mailbox
*                            will be considered empty.
*
* Returns    : != (OS_EVENT *)0  is a pointer to the event control clock (OS_EVENT) associated with the
*                                created mailbox
*              == (OS_EVENT *)0  if no event control blocks were available
*********************************************************************************************************
*/
/*
*********************************************************************************************************
                                            建立一個(gè)郵箱
描述：如果空余事件控制塊允許，就建立一個(gè)消息郵箱
參數(shù)：msg:指向你想存入郵箱的消息指針，如果存入零，我們認(rèn)為它為空
返回：!= (OS_EVENT *)0：指向所建立郵箱的事件控制塊指針
                 == (OS_EVENT *)0：如果沒(méi)有可行事件控制塊
*********************************************************************************************************
*/



OS_EVENT  *OSMboxCreate (void *msg)
{
#if OS_CRITICAL_METHOD == 3                      /* Allocate storage for CPU status register           */
    OS_CPU_SR  cpu_sr;
#endif    
    OS_EVENT  *pevent;


    if (OSIntNesting > 0) {                      /* See if called from ISR ...                         */
        return ((OS_EVENT *)0);                  /* ... can't CREATE from an ISR                       */
    }//此函數(shù)不能由中斷服務(wù)程序調(diào)用
    OS_ENTER_CRITICAL();
    pevent = OSEventFreeList;                    /* Get next free event control block                  */
	//得到一塊新的事件控制塊
    if (OSEventFreeList != (OS_EVENT *)0) {      /* See if pool of free ECB pool was empty             */
        OSEventFreeList = (OS_EVENT *)OSEventFreeList->OSEventPtr;
    }//如果空余事件控制鏈表不為空，則進(jìn)行適當(dāng)調(diào)整，指向下一塊空余事件控制塊
    OS_EXIT_CRITICAL();
    if (pevent != (OS_EVENT *)0) {
        pevent->OSEventType = OS_EVENT_TYPE_MBOX;//如果ECB可用，則將其設(shè)置為郵箱型
        pevent->OSEventCnt  = 0;//信號(hào)量，郵箱中不使用它
        pevent->OSEventPtr  = msg;               /* Deposit message in event control block             */
		//保存消息在ECB中
        OS_EventWaitListInit(pevent);//對(duì)事件控制塊的等待任務(wù)列表進(jìn)行初始化
    }
    return (pevent);                             /* Return pointer to event control block              */
	//返回事件控制塊的指針，對(duì)郵箱的操作都通過(guò)此指針完成。
}
/*$PAGE*/
/*
*********************************************************************************************************
*                                         DELETE A MAIBOX
*
* Description: This function deletes a mailbox and readies all tasks pending on the mailbox.
*
* Arguments  : pevent        is a pointer to the event control block associated with the desired
*                            mailbox.
*
*              opt           determines delete options as follows:
*                            opt == OS_DEL_NO_PEND   Delete the mailbox ONLY if no task pending
*                            opt == OS_DEL_ALWAYS    Deletes the mailbox even if tasks are waiting.
*                                                    In this case, all the tasks pending will be readied.
*
*              err           is a pointer to an error code that can contain one of the following values:
*                            OS_NO_ERR               The call was successful and the mailbox was deleted
*                            OS_ERR_DEL_ISR          If you attempted to delete the mailbox from an ISR
*                            OS_ERR_INVALID_OPT      An invalid option was specified
*                            OS_ERR_TASK_WAITING     One or more tasks were waiting on the mailbox
*                            OS_ERR_EVENT_TYPE       If you didn't pass a pointer to a mailbox
*                            OS_ERR_PEVENT_NULL      If 'pevent' is a NULL pointer.
*
* Returns    : pevent        upon error
*              (OS_EVENT *)0 if the mailbox was successfully deleted.
*
* Note(s)    : 1) This function must be used with care.  Tasks that would normally expect the presence of
*                 the mailbox MUST check the return code of OSMboxPend().
*              2) OSMboxAccept() callers will not know that the intended mailbox has been deleted!
*              3) This call can potentially disable interrupts for a long time.  The interrupt disable
*                 time is directly proportional to the number of tasks waiting on the mailbox.
*              4) Because ALL tasks pending on the mailbox will be readied, you MUST be careful in
*                 applications where the mailbox is used for mutual exclusion because the resource(s)
*                 will no longer be guarded by the mailbox.
                                             刪除一個(gè)郵箱
描述：此任務(wù)刪除一個(gè)郵箱，準(zhǔn)備好郵箱中掛起的所有任務(wù)
參數(shù)：pevent：指向想要郵箱的ECB的指針
                 opt：確定刪除選項(xiàng)如下：
                 opt == OS_DEL_NO_PEND：如果沒(méi)有任務(wù)掛起就刪除郵箱
                 opt == OS_DEL_ALWAYS：即使任務(wù)等待也刪除郵箱，這種情況下，所有掛起的任務(wù)將就緒
                 err：包含以下值的錯(cuò)誤代碼指針：
                 OS_NO_ERR：調(diào)用成功，刪除郵箱
                 OS_ERR_DEL_ISR   ：如果從ISR中刪除郵箱
*               OS_ERR_INVALID_OPT ：指定了不合理選項(xiàng)
*               OS_ERR_TASK_WAITING ：一個(gè)或者幾個(gè)任務(wù)在郵箱中等待
*               OS_ERR_EVENT_TYPE ：沒(méi)有傳遞指針給郵箱
*               OS_ERR_PEVENT_NULL :pevent是空指針，即郵箱的ECB為空。
返回：pevent：操作錯(cuò)誤
                 (OS_EVENT *)0：郵箱成功刪除
備注：1、此函數(shù)必須小心使用，任務(wù)希望在場(chǎng)的郵箱檢查OSMboxPend()的返回代碼
                2、OSMboxAccept()調(diào)用將不知道想要的郵箱已經(jīng)被刪除
                3、這個(gè)函數(shù)將潛在地關(guān)中斷一長(zhǎng)段時(shí)間，關(guān)中斷時(shí)間與在郵箱中等待的任務(wù)
                       數(shù)成正比
                4、因?yàn)樗性卩]箱中掛起的任務(wù)將就緒，你必須在郵箱相互排斥情況下小心使用
                       因?yàn)橘Y源不再被郵箱保護(hù)
*********************************************************************************************************
*/


#if OS_MBOX_DEL_EN > 0
OS_EVENT  *OSMboxDel (OS_EVENT *pevent, INT8U opt, INT8U *err)
{
#if OS_CRITICAL_METHOD == 3                                /* Allocate storage for CPU status register */
    OS_CPU_SR  cpu_sr;
#endif    
    BOOLEAN    tasks_waiting;//typedef unsigned char BOOLEAN


    if (OSIntNesting > 0) {                                /* See if called from ISR ...               */
        *err = OS_ERR_DEL_ISR;                             /* ... can't DELETE from an ISR             */
        return (pevent);//如果在中斷中調(diào)用，不能刪除
    }
#if OS_ARG_CHK_EN > 0
    if (pevent == (OS_EVENT *)0) {                         /* Validate 'pevent'                        */
        *err = OS_ERR_PEVENT_NULL;
        return (pevent);//如果pevent不合理
    }