请问：IFIFO读取数据失败

#define STR_TEST_FIFO_W        "fifo:/~/foobar?mode=w"boolean BrewFifoWrite_InitAppData(BrewFifoWrite* pMe){    int nRet = 0;    pMe->DeviceInfo.wStructSize = sizeof(pMe->DeviceInfo);    ISHELL_GetDeviceInfo(pMe->a.m_pIShell,&pMe->DeviceInfo);    nRet = ISHELL_CreateInstance(pMe->a.m_pIShell, AEECLSID_FIFO, &pMe->m_pIFIFO);    nRet = IFIFO_Open(pMe->m_pIFIFO, STR_TEST_FIFO_W);    return TRUE;}void BrewFifoWrite_FreeAppData(BrewFifoWrite* pMe){    IFIFO_Close(pMe->m_pIFIFO);}// 在按1的时候，对IFIFO写数据：case EVT_KEY:    switch (wParam)    {    case AVK_1:    {            PrintInfo(pMe->a.m_pIDisplay, szPost);            Mms_StartPostMessage(pMe);    }// 写数据的实现：void Mms_StartPostMessage(BrewFifoWrite* pMe){    uint8                    DataBuffer[MAX_BUFFER_SIZE] = {'t', 'e', 's', 't', ' ', 'f', 'i', 'f', 'o', 0};    int                        nRet;    int                        nFileSize;    // 向IFIFO中写数据    nRet = IFIFO_Write(pMe->m_pIFIFO, DataBuffer, STRLEN(DataBuffer) * sizeof(uint8));    // 启动读程序    nRet = ISHELL_StartApplet(pMe->a.m_pIShell, AEECLSID_BREWFIFOREAD);    // 发信号告诉读程序，可以读取消息了    nRet = ISHELL_PostEvent(pMe->a.m_pIShell, AEECLSID_BREWFIFOREAD, UEVT_READ_FIFO, 0, 0);}

// 在收到消息UEVT_READ_FIFOcase UEVT_READ_FIFO:    Mms_StartGetMessage(pMe);    return TRUE;// 读IFIFO的实现#define STR_TEST_FIFO_R        "fifo:/~/foobar?mode=r"void Mms_StartGetMessage(BrewFifoRead* pMe){    IFIFO*            pIFIFO;    int                nRet;    uint8*            pucDataBuffer;    pucDataBuffer = (uint8*)MALLOC(sizeof(uint8) * MAX_BUFFER_SIZE);    nRet = ISHELL_CreateInstance(pMe->a.m_pIShell, AEECLSID_FIFO, &pIFIFO);    nRet = IFIFO_Open(pIFIFO, STR_TEST_FIFO_R);    nRet = IFIFO_Read(pIFIFO, pucDataBuffer, MAX_BUFFER_SIZE);    IFIFO_Close(pIFIFO);    return;}