📄 pic.c
字号:
/* Variable-size messages are supported. Processing must
check for pipe wrap-around conditions. */
/* Place message size in first location. */
*((UNSIGNED *) destination) = size;
destination = destination + sizeof(UNSIGNED);
/* Check for a wrap-around condition on the pipe. */
if (destination >= pipe -> pi_end)
/* Wrap the write pointer back to the top of the pipe
area. */
destination = pipe -> pi_start;
/* Decrement the number of bytes remaining for this
extra word of overhead. */
pipe -> pi_available = pipe -> pi_available -
sizeof(UNSIGNED);
/* Calculate the number of bytes remaining from the write
pointer to the bottom of the pipe. */
copy_size = pipe -> pi_end - destination;
/* Determine if the message needs to be wrapped around the
edge of the pipe area. */
if (copy_size >= size)
{
/* Copy the whole message at once. */
i = (INT) size;
do
{
*(destination++) = *(source);
if ((--i) == 0)
break;
source++;
} while (1);
}
else
{
/* Copy the first half of the message. */
i = (INT) copy_size;
do
{
*(destination) = *(source++);
if ((--i) == 0)
break;
destination++;
} while (1);
/* Copy the second half of the message. */
destination = pipe -> pi_start;
i = (INT) (size - copy_size);
do
{
*(destination++) = *(source);
if ((--i) == 0)
break;
source++;
} while (1);
}
}
/* Check again for wrap-around condition on the write
pointer. */
if (destination >= pipe -> pi_end)
/* Move the write pointer to the top of the pipe area. */
destination = pipe -> pi_start;
/* Determine if the pipe supports variable-length messages. If
so, pad bytes are needed to keep UNSIGNED alignment. */
if (pad)
{
/* Variable-size message. Add pad bytes to the write
pointer. */
/* Calculate the number of bytes remaining from the write
pointer to the bottom of the pipe. */
copy_size = pipe -> pi_end - destination;
/* If there is not enough room at the bottom of the pipe,
the pad bytes must be wrapped around to the top. */
if (copy_size <= pad)
/* Move write pointer to the top of the pipe and make
the necessary adjustment. */
destination = pipe -> pi_start + (pad - copy_size);
else
/* There is enough room in the pipe to simply add
the pad bytes to the write pointer. */
destination = destination + pad;
/* Decrement the number of available bytes. */
pipe -> pi_available = pipe -> pi_available - pad;
}
/* Update the actual write pointer. */
pipe -> pi_write = destination;
/* Decrement the number of available bytes. */
pipe -> pi_available = pipe -> pi_available - size;
/* Increment the number of messages in the pipe. */
pipe -> pi_messages++;
/* Decrement the number of tasks waiting counter. */
pipe -> pi_tasks_waiting--;
/* Remove the first suspended block from the list. */
CSC_Remove_From_List((CS_NODE **)
&(pipe -> pi_suspension_list),
&(suspend_ptr -> pi_suspend_link));
/* Return a successful status. */
suspend_ptr -> pi_return_status = NU_SUCCESS;
/* Resume the suspended task. */
preempt = preempt |
TCC_Resume_Task((NU_TASK *) suspend_ptr -> pi_suspended_task,
NU_PIPE_SUSPEND);
/* Setup suspend pointer to the head of the list. */
suspend_ptr = pipe -> pi_suspension_list;
/* Determine if there really is another suspended block. If
there is and the pipe supports variable length messages,
calculate new size and padding parameters. */
if ((suspend_ptr) && (!pipe -> pi_fixed_size))
{
/* Get the next message size. */
size = suspend_ptr -> pi_message_size;
/* Variable messages have one additional word of
overhead. */
i = sizeof(UNSIGNED);
/* Calculate the number of pad bytes necessary to
keep the pipe write pointer on an UNSIGNED data element
alignment. */
pad = (((size + sizeof(UNSIGNED) - 1)/sizeof(UNSIGNED)) *
sizeof(UNSIGNED)) - size;
/* Insure that padding is included in the overhead. */
i = i + ((INT) pad);
}
}
/* Determine if a preempt condition is present. */
if (preempt)
/* Transfer control to the system if the resumed task function
detects a preemption condition. */
TCT_Control_To_System();
}
}
else
{
/* pipe is empty. Determine if the task wants to suspend. */
if (suspend)
{
/* Increment the number of tasks waiting on the pipe counter. */
pipe -> pi_tasks_waiting++;
#ifdef NU_PROFILE_PLUS
PRF_PLUS_PIC_RECEIVE_FROM_PIPE_1
#endif /* NU_PROFILE_PLUS */
/* Setup the suspend block and suspend the calling task. */
suspend_ptr = &suspend_block;
suspend_ptr -> pi_pipe = pipe;
suspend_ptr -> pi_suspend_link.cs_next = NU_NULL;
suspend_ptr -> pi_suspend_link.cs_previous = NU_NULL;
suspend_ptr -> pi_message_area = (BYTE_PTR) message;
suspend_ptr -> pi_message_size = size;
task = (TC_TCB *) TCT_Current_Thread();
suspend_ptr -> pi_suspended_task = task;
/* Determine if priority or FIFO suspension is associated with the
pipe. */
if (pipe -> pi_fifo_suspend)
{
/* FIFO suspension is required. Link the suspend block into
the list of suspended tasks on this pipe. */
CSC_Place_On_List((CS_NODE **) &(pipe -> pi_suspension_list),
&(suspend_ptr -> pi_suspend_link));
}
else
{
/* Get the priority of the current thread so the suspend block
can be placed in the appropriate place. */
suspend_ptr -> pi_suspend_link.cs_priority =
TCC_Task_Priority(task);
CSC_Priority_Place_On_List((CS_NODE **)
&(pipe -> pi_suspension_list),
&(suspend_ptr -> pi_suspend_link));
}
/* Finally, suspend the calling task. Note that the suspension call
automatically clears the protection on the pipe. */
TCC_Suspend_Task((NU_TASK *) task, NU_PIPE_SUSPEND,
PIC_Cleanup, suspend_ptr, suspend);
/* Pickup the status of the request. */
status = suspend_ptr -> pi_return_status;
*actual_size = suspend_ptr -> pi_actual_size;
}
else
{
/* Return a status of NU_PIPE_EMPTY because there are no
messages in the pipe. */
status = NU_PIPE_EMPTY;
#ifdef NU_PROFILE_PLUS
PRF_PLUS_PIC_RECEIVE_FROM_PIPE_2
#endif /* NU_PROFILE_PLUS */
}
}
/* Release protection against access to the pipe. */
TCT_Unprotect();
/* Return to user mode */
NU_USER_MODE();
/* Return the completion status. */
return(status);
}
/*************************************************************************/
/* */
/* FUNCTION */
/* */
/* PIC_Cleanup */
/* */
/* DESCRIPTION */
/* */
/* This function is responsible for removing a suspension block */
/* from a pipe. It is not called unless a timeout or a task */
/* terminate is in progress. Note that protection is already in */
/* effect - the same protection at suspension time. This routine */
/* must be called from Supervisor mode in Supervisor/User mode */
/* switching kernels. */
/* */
/* CALLED BY */
/* */
/* TCC_Timeout Task timeout */
/* TCC_Terminate Task terminate */
/* */
/* CALLS */
/* */
/* CSC_Remove_From_List Remove suspend block from */
/* the suspension list */
/* */
/* INPUTS */
/* */
/* information Pointer to suspend block */
/* */
/* OUTPUTS */
/* */
/* None */
/* */
/*************************************************************************/
VOID PIC_Cleanup(VOID *information)
{
PI_SUSPEND *suspend_ptr; /* Suspension block pointer */
NU_SUPERV_USER_VARIABLES
/* Switch to supervisor mode */
NU_SUPERVISOR_MODE();
/* Use the information pointer as a suspend pointer. */
suspend_ptr = (PI_SUSPEND *) information;
/* By default, indicate that the service timed-out. It really does not
matter if this function is called from a terminate request since
the task does not resume. */
suspend_ptr -> pi_return_status = NU_TIMEOUT;
/* Decrement the number of tasks waiting counter. */
(suspend_ptr -> pi_pipe) -> pi_tasks_waiting--;
/* Determine if the suspend block is one the urgent list. */
if ((suspend_ptr -> pi_pipe) -> pi_urgent_list)
{
/* Unlink the suspend block from the urgent list. */
⌨️ 快捷键说明
复制代码
Ctrl + C
搜索代码
Ctrl + F
全屏模式
F11
切换主题
Ctrl + Shift + D
显示快捷键
?
增大字号
Ctrl + =
减小字号
Ctrl + -