管道：實用程式服務和資料結構

Pipes: utility services and data structures

管道公用設施

Nucleus RTOS有四個API呼叫，它們提供與管道相關的實用程式函式：重置管道、返回有關管道的資訊、返回應用程式中管道的數量以及返回指向應用程式中所有管道的指標。前三個在Nucleus SE中實現。

重置管道

此API呼叫將管道恢復到其未使用的初始狀態。管道中儲存的所有訊息都將丟失。在管道上暫停的任何任務都將恢復，並收到NUSE_pipe_WAS_RESET的返回程式碼。

Nucleus RTOS API Call for Resetting a Pipe

Service call prototype:

STATUS NU_Reset_Pipe(NU_PIPE *pipe;

Parameters:

pipe– pointer to user-defined pipe control block

Returns:

NU_SUCCESS– the call was completed successfully
NU_INVALID_PIPE– the pipe pointer is not valid

Nucleus SE API Call for Resetting a Pipe

This API call supports the key functionality of the Nucleus RTOS API.

Service call prototype:

STATUS NUSE_Pipe_Reset(NUSE_PIPE pipe);

Parameters:

pipe– the index (ID) of the pipe to be reset

Returns:

NUSE_SUCCESS– the call was completed successfully
NUSE_INVALID_PIPE– the pipe index is not valid

管道復位的Nucleus-SE實現

NUSE_Pipe_Reset（）API函式的初始部分（在引數檢查之後）非常簡單。頭和尾索引以及管道的訊息計數都設定為零。

啟用阻塞時，其他程式碼負責喚醒任何掛起的任務，因此：

while(NUSE_Pipe_Blocking_Count[pipe]!=0){U8index;/*checkwhetheranytasksareblocked*//*onthispipe*/for(index=0;index<NUSE_TASK_NUMBER;index++){if((LONIB(NUSE_Task_Status[index])==NUSE_PIPE_SUSPEND)&&(HINIB(NUSE_Task_Status[index])==pipe)){NUSE_Task_Blocking_Return[index]=NUSE_PIPE_RESET;NUSE_Task_Status[index]=NUSE_READY;break;}}NUSE_Pipe_Blocking_Count[pipe]--;}#ifNUSE_SCHEDULER_TYPE==NUSE_PRIORITY_SCHEDULERNUSE_Reschedule(NUSE_NO_TASK);#endif

管道上掛起的每個任務都標記為“就緒”，掛起返回程式碼NUSE_pipe_WAS_RESET。此過程完成後，如果正在使用優先順序排程程式，則會呼叫NUSE_Reschedule（），因為一個或多個優先順序較高的任務可能已準備就緒，需要允許其執行。

管道資訊

此服務呼叫獲取有關管道的資訊選擇。Nucleus SE實現與Nucleus RTOS的不同之處在於，它返回的資訊較少，因為不支援物件命名、可變訊息大小和掛起順序，並且可能無法啟用任務掛起。

Nucleus RTOS API呼叫管道資訊

Service call prototype:

STATUS NU_Pipe_Information(NU_PIPE *pipe, CHAR *name,
VOID **start_address,UNSIGNED *pipe_size, UNSIGNED *available,
UNSIGNED *messages, OPTION *message_type, UNSIGNED *message_size,
OPTION *suspend_type, UNSIGNED *tasks_waiting,
NU_TASK **first_task);

Parameters:

pipe– pointer to the user-supplied pipe control block
name– pointer to an 8-character destination area for the message-pipe’s name
start_address– a pointer to a pointer, which will receive the address of the start of the pipe’s data area
pipe_size– a pointer to a variable for holding the total number of bytes in the pipe
available– a pointer to a variable for holding the number of available bytes in the pipe
messages– a pointer to a variable for holding the number of messages currently in the pipe
message_type– pointer to a variable for holding the type of messages supported by the pipe; valid message types areNU_FIXED_SIZEandNU_ VARIABLE_SIZE
message_size– pointer to a variable for holding the number of bytes in each pipe message; if the pipe supports variable-length messages, this number is the maximum message size
suspend_type– pointer to a variable for holding the task suspend type. Valid task suspend types areNU_FIFOandNU_PRIORITY
tasks_waiting– a pointer to a variable which will receive the number of tasks suspended on this pipe
first_task– a pointer to a task pointer; the pointer of the first suspended task is placed in this task pointer

Returns:

NU_SUCCESS– the call was completed successfully
NU_INVALID_PIPE– the pipe pointer is not valid

Nucleus SE API Call for Pipe Information

This API call supports the key functionality of the Nucleus RTOS API.

Service call prototype:

STATUS NUSE_Pipe_Information(NUSE_PIPE pipe,
ADDR *start_address, U8 *pipe_size, U8 *available, U8 *messages,
U8 *message_size, U8 *tasks_waiting, NUSE_TASK *first_task);

Parameters:

pipe– the index of the pipe about which information is being requested
start_address– a pointer to a variable of typeADDR, which will receive the address of the start of the pipe’s data area
pipe_size– a pointer to a variable of typeU8, which will receive the total number of messages for which the pipe has capacity
available– a pointer to a variable of typeU8, which will receive the number of messages for which the pipe has currently remaining capacity
messages– a pointer to a variable of typeU8, which will receive the number of messages currently in the pipe
message size– a pointer to a variable of typeU8, which will receive the size of messages handled by this pipe
tasks_waiting– a pointer to a variable which will receive the number of tasks suspended on this pipe (nothing returned if task suspend is disabled)
first_task– a pointer to a variable of typeNUSE_TASKwhich will receive the index of the first suspended task (nothing returned if task suspend is disabled)

Returns:

NUSE_SUCCESS– the call was completed successfully
NUSE_INVALID_PIPE– the pipe index is not valid
NUSE_INVALID_POINTER– one or more of the pointer parameters is invalid

Nucleus SE Implementation of Pipe Information

The implementation of this API call is quite straightforward:

*start_address=NUSE_Pipe_Data[pipe];*pipe_size=NUSE_Pipe_Size[pipe];*available=NUSE_Pipe_Size[pipe]-NUSE_Pipe_Items[pipe];*messages=NUSE_Pipe_Items[pipe];*message_size=NUSE_Pipe_Message_Size[pipe];#ifNUSE_BLOCKING_ENABLE*tasks_waiting=NUSE_Pipe_Blocking_Count[pipe];if(NUSE_Pipe_Blocking_Count[pipe]!=0){U8index;for(index=0;index<NUSE_TASK_NUMBER;index++){if((LONIB(NUSE_Task_Status[index])==NUSE_PIPE_SUSPEND)&&(HINIB(NUSE_Task_Status[index])==pipe)){*first_task=index;break;}}}else{*first_task=0;}#else*tasks_waiting=0;*first_task=0;#endif

函式返回管道狀態。然後，如果啟用了阻塞API呼叫，則返回等待的任務數和第一個任務的索引（否則這兩個引數設定為0）。

獲取管道數量

此服務呼叫返回應用程式中配置的管道數。而在Nucleus RTOS中，這將隨時間而變化，返回的值將表示當前的管道數，而在Nucleus SE中，返回的值是在構建時設定的，不能更改。

Nucleus RTOS API Call for Pipe Count

Service call prototype:

UNSIGNED NU_Established_Pipes(VOID);

Parameters:

None

Returns:

The number of created pipes in the system.

Nucleus SE API Call for Pipe Count

This API call supports the key functionality of the Nucleus RTOS API.

Service call prototype:

U8 NUSE_Pipe_Count(void);

Parameters:

None

Returns:

The number of configured pipes in the application

Nucleus SE Implementation of Pipe Count

管道計數的Nucleus SE實現

這個API呼叫的實現非常簡單：返回#define符號NUSE_PIPE_編號的值。

資料結構

管道使用六個或七個資料結構—全部在RAM和ROM中—與其他Nucleus SE物件一樣，這些資料結構是一系列表，根據配置的管道數量和選擇的選項進行包含和標註。

我強烈建議應用程式程式碼不要直接訪問這些資料結構，而是使用提供的API函式。這避免了與Nucleus SE未來版本的不相容和不必要的副作用，並簡化了將應用程式移植到Nucleus RTOS的過程。這裡包含資料結構的詳細資訊，以便更容易地理解服務呼叫程式碼的工作方式和除錯。

Kernel RAM Data

These data structures are:

NUSE_Pipe_Head[]– This is an array of typeU8, with one entry for each configured pipe, which represents a pointer to the front of the pipe of messages. It is used as an index off of the addresses inNUSE_Pipe_Data[](see below).
NUSE_Pipe_Tail[]– This is an array of typeU8, with one entry for each configured pipe, which represents a pointer to the end of the pipe of messages. It is used as an index off of the addresses inNUSE_Pipe_Data[](see below).
NUSE_Pipe_Items[]– This is an array of typeU8, with one entry for each configured pipe, which represents a count of the current number of messages in the pipe. This data is arguably redundant, as its value can be derived from the head and tail indexes, but storing the count simplifies the code.
NUSE_Pipe_Blocking_Count[]– This typeU8array contains the counts of how many tasks are blocked on each pipe. This array only exists if blocking API call support is enabled.

當Nucleus SE啟動時，這些資料結構都由NUSE_Init_Pipe（）初始化為零。這是合乎邏輯的，因為它將每個管道渲染為空（未使用）。未來的文章將全面描述Nucleus SE的啟動過程。 以下是nuse_init.c檔案中這些資料結構的定義：

RAMU8NUSE_Pipe_Head[NUSE_PIPE_NUMBER];RAMU8NUSE_Pipe_Tail[NUSE_PIPE_NUMBER];RAMU8NUSE_Pipe_Items[NUSE_PIPE_NUMBER];#ifNUSE_BLOCKING_ENABLERAMU8NUSE_Pipe_Blocking_Count[NUSE_PIPE_NUMBER];#endif

使用者RAM

使用者應負責為每個配置的管道提供一個RAM區域用於資料儲存。這個RAM區域的大小必須容納一個U8型別的陣列，該陣列的大小足以容納管道中的所有訊息。

ROM Data

These data structures are:

NUSE_Pipe_Data[]– This is an array of typeADDR, with one entry for each configured pipe, which represents a pointer to the data area (discussed inUser RAMabove) for each pipe.
NUSE_Pipe_Size[]– This is an array of typeU8, with one entry for each configured pipe, which represents the number of messages that may be accommodated by each pipe.
NUSE_Pipe_Message_Size[] – This is an array of typeU8, with one entry for each configured pipe, which represents the size of messages (in bytes) that may be accommodated by each pipe.

These data structures are all declared and initialized (statically, of course) innuse_config.c, thus:

ROMADDR*NUSE_Pipe_Data[NUSE_PIPE_NUMBER]={/*addressesofpipedataareas------*/};ROMU8NUSE_Pipe_Size[NUSE_PIPE_NUMBER]={/*pipesizes------*/};ROMU8NUSE_Pipe_Message_Size[NUSE_PIPE_NUMBER]={/*pipemessagesizes------*/};

管道資料示意圖

與Nucleus SE中的所有核心物件一樣，管道所需的資料記憶體量也很容易預測。

應用程式中所有管道的ROM資料佔用（位元組）可以這樣計算：

NUSE_PIPE_NUMBER * (sizeof(ADDR) + 2)

啟用阻塞API呼叫時，應用程式中所有管道的核心RAM資料佔用（位元組）可以這樣計算：

NUSE_PIPE_NUMBER * 4

Otherwise it is:

NUSE_PIPE_NUMBER * 3

The amount of user RAM (in bytes) required for the pipe with indexpipeis:

NUSE_Pipe_Size[pipe] * NUSE_Pipe_Message_Size[pipe]

Unimplemented API Calls

Four pipe API calls found in Nucleus RTOS are not implemented in Nucleus SE:

Create Pipe

This API call creates a pipe. It is not needed with Nucleus SE, as pipes are created statically.

Service call prototype:

STATUS NU_Create_Pipe(NU_PIPE *pipe, char *name,
VOID *start_address, UNSIGNED pipe_size, OPTION message_type,
UNSIGNED message_size, OPTION suspend_type);

Parameters:

pipe– pointer to a user-supplied pipe control block; this will be used as a “handle” for the pipe in other API calls
name– pointers to a 7-character, null-terminated name for the pipe
start_address– starting address for the pipe
pipe_size– the total number of bytes in the pipe
message_type– type of message supported by the pipe; may beNU_FIXED_SIZEorNU_VARIABLE_SIZE
message_size –if the pipe supports fixed size messages, this parameter specifies the exact size of each message; otherwise, if the pipe supports variable sized messages, this is the maximum message size
suspend_type– specifies how tasks suspend on the pipe. Valid options for this parameter areNU_FIFOandNU_PRIORITY, which represent First-In-First-Out (FIFO) and priority-order task suspension, respectively

Returns:

NU_SUCCESS– indicates successful completion of the service
NU_INVALID_PIPE– indicates the pipe control block pointer isNULLor already in use
NU_INVALID_MEMORY– indicates the memory area specified by thestart_addressis invalid
NU_INVALID_MESSAGE– indicates that themessage_typeparameter is invalid
NU_INVALID_SIZE– indicates that either the message size is greater than the pipe size, or that the pipe size or message size is zero
NU_INVALID_SUSPEND– indicates that thesuspend_typeparameter is invalid

Delete Pipe

This API call deletes a previously created pipe. It is not needed with Nucleus SE, as pipes are created statically and cannot be deleted.

Service call prototype:

STATUS NU_Delete_Pipe(NU_PIPE *pipe);

Parameters:

pipe– pointer to pipe control block

Returns:

NU_SUCCESS– indicates successful completion of the service
NU_INVALID_PIPE– indicates the pipe pointer is invalid

Pipe Pointers

This API call builds a sequential list of pointers to all pipes in the system. It is not needed with Nucleus SE, as pipes are identified by a simple index, not a pointer, and it would be redundant.

Service call prototype:

UNSIGNED NU_Pipe_Pointers(NU_PIPE **pointer_list,
UNSIGNED maximum_pointers);

Parameters:

pointer_list– pointer to an array ofNU_PIPEpointers; this array will be filled with pointers to established pipes in the system
maximum_pointers– the maximum number of pointers to place in the array

Returns:

The number ofNU_PIPEpointers placed into the array

Broadcast to Pipe

This API call broadcasts a message to all tasks waiting for a message from the specified pipe. It is not implemented with Nucleus SE, as it would have added excessive complexity.

Service call prototype:

STATUS NU_Broadcast_To_Pipe(NU_PIPE *pipe, VOID *message,
UNSIGNED size, UNSIGNED suspend);

Parameters:

pipe– pointer to pipe control block
message– pointer to the broadcast message
size– the number ofUNSIGNEDdata elements in the message. If the pipe supports variable-length messages, this parameter must be equal to or less than the message size supported by the pipe. If the pipe supports fixed-size messages, this parameter must be exactly the same as the message size supported by the pipe
suspend– specifies whether or not to suspend the calling task if the pipe is already full; valid options for this parameter areNU_NO_SUSPEND,NU_SUSPENDor a timeout value.

Returns:

NU_SUCCESS– indicates successful completion of the service
NU_INVALID_PIPE– indicates the pipe pointer is invalid
NU_INVALID_POINTER– indicates that the message pointer isNULL
NU_INVALID_SIZE– Indicates that the message size specified is not compatible with the size specified when the pipe was created
NU_INVALID_SUSPEND– indicates that suspend attempted from a non-task thread
NU_PIPE_FULL– indicates that there is insufficient space in the pipe for the message
NU_TIMEOUT– indicates the pipe is still full after the timeout has expired
NU_PIPE_DELETED– pipe was deleted while task was suspended
NU_PIPE_RESET– pipe was reset while the task was suspended

Compatibility with Nucleus RTOS

With all aspects of Nucleus SE, it was my goal to maintain as high a level of applications code compatibility with Nucleus RTOS as possible. Pipes are no exception, and, from a user’s perspective, they are implemented in much the same way as in Nucleus RTOS. There are areas of incompatibility, which have come about where I determined that such an incompatibility would be acceptable, given that the resulting code is easier to understand, or, more likely, could be made more memory efficient. Otherwise, Nucleus RTOS API calls may be almost directly mapped onto Nucleus SE calls. A future article will include further information on using Nucleus SE for users of Nucleus RTOS.

Object Identifiers

In Nucleus RTOS, all objects are described by a data structure – a control block – which has a specific data type. A pointer to this control block serves as an identifier for the pipe. In Nucleus SE, I decided that a different approach was needed for memory efficiency, and all kernel objects are described by a number of tables in RAM and/or ROM. The size of these tables is determined by the number of each object type that is configured. The identifier for a specific object is simply an index into those tables. So, I have definedNUSE_PIPEas being equivalent toU8; a variable – not a pointer – of this type then serves as the pipe identifier. This is a small incompatibility, which is easily handled if code is ported to or from Nucleus RTOS. Object identifiers are normally just stored and passed around and not operated upon in any way.

Nucleus RTOS also supports naming of pipes. These names are only used for target-based debug facilities. I omitted them from Nucleus SE to save memory.

Message Size and Variability

In Nucleus RTOS, a pipe may be configured to handle messages which are comprised of an arbitrary number of bytes of data. Likewise, in Nucleus SE. Nucleus RTOS also supports pipes with variable size messages, where only the maximum size is specified at creation time. Variable size messages are not supported by Nucleus SE.

Pipe Size

The number of messages in a pipe in Nucleus SE is limited to 256, as all the index variables and constants are typeU8. Nucleus RTOS is not limited in this way.

Unimplemented API Calls

Nucleus RTOS supports ten service calls to work with pipes. Of these, four are not implemented in Nucleus SE. Details of these and of the decision to omit them may be found inUnimplemented API Callsearlier in this article.

The nextRTOS Revealedarticle will look at system time.