📄 pic.c
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/* 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 return status. */
status = suspend_ptr -> pi_return_status;
}
else
{
/* Return a status of NU_PIPE_FULL because there is no
room in the pipe for the message. */
status = NU_PIPE_FULL;
#ifdef NU_PROFILE_PLUS
PRF_PLUS_PIC_SEND_TO_PIPE_1
#endif /* NU_PROFILE_PLUS */
}
}
else
{
/* Determine if a task is waiting on an empty pipe. */
if ((pipe -> pi_suspension_list) && (pipe -> pi_messages == 0))
{
/* Task is waiting on pipe for a message. */
/* Decrement the number of tasks waiting on pipe. */
pipe -> pi_tasks_waiting--;
#ifdef NU_PROFILE_PLUS
PRF_PLUS_PIC_SEND_TO_PIPE_2
#endif /* NU_PROFILE_PLUS */
/* Remove the first suspended block from the list. */
suspend_ptr = pipe -> pi_suspension_list;
CSC_Remove_From_List((CS_NODE **) &(pipe -> pi_suspension_list),
&(suspend_ptr -> pi_suspend_link));
/* Setup the source and destination pointers. */
source = (BYTE_PTR) message;
destination = suspend_ptr -> pi_message_area;
/* Initialize the return status. */
suspend_ptr -> pi_return_status = NU_SUCCESS;
/* Loop to actually copy the message. */
i = (INT) size;
do
{
*(destination++) = *(source);
if ((--i) == 0)
break;
source++;
} while(1);
/* Return the size of the message copied. */
suspend_ptr -> pi_actual_size = size;
/* Wakeup the waiting task and check for preemption. */
preempt =
TCC_Resume_Task((NU_TASK *) suspend_ptr -> pi_suspended_task,
NU_PIPE_SUSPEND);
/* Determine if preemption needs to take place. */
if (preempt)
/* Transfer control to the system if the resumed task function
detects a preemption condition. */
TCT_Control_To_System();
}
else
{
/* There is enough room in the pipe and no task is waiting. */
/* Setup the source pointer. */
source = (BYTE_PTR) message;
destination = pipe -> pi_write;
/* Process according to the type of message supported. */
if (pipe -> pi_fixed_size)
{
/* Fixed-size messages are supported by this pipe. */
/* Loop to copy the message into the pipe area. */
i = (INT) size;
do
{
*(destination++) = *(source);
if ((--i) == 0)
break;
source++;
} while (1);
}
else
{
/* 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
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++;
#ifdef NU_PROFILE_PLUS
PRF_PLUS_PIC_SEND_TO_PIPE_3
#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_Receive_From_Pipe */
/* */
/* DESCRIPTION */
/* */
/* This function receives a message from the specified pipe. The */
/* size of the message is specified by the caller. If there is a */
/* message currently in the pipe, the message is removed from the */
/* pipe and placed in the caller's area. Suspension is possible */
/* if the request cannot be satisfied. */
/* */
/* CALLED BY */
/* */
/* Application */
/* PICE_Receive_From_Pipe Error checking shell */
/* */
/* CALLS */
/* */
/* CSC_Place_On_List Place on suspend list */
/* CSC_Remove_From_List Remove from suspend list */
/* [HIC_Make_History_Entry] Make entry in history log */
/* TCC_Resume_Task Resume a suspended task */
/* TCC_Suspend_Task Suspend calling task */
/* TCC_Task_Priority Pickup task's priority */
/* [TCT_Check_Stack] Stack checking function */
/* TCT_Control_To_System Transfer control to system */
/* TCT_Current_Thread Pickup current thread pointer*/
/* TCT_System_Protect Protect pipe */
/* TCT_Unprotect Release protection */
/* */
/* INPUTS */
/* */
/* pipe_ptr Pipe control block pointer */
/* message Pointer to message to send */
/* size Size of the message */
/* actual_size Size of message received */
/* suspend Suspension option if empty */
/* */
/* OUTPUTS */
/* */
/* NU_SUCCESS If service is successful */
/* NU_PIPE_EMPTY If pipe is currently empty */
/* NU_TIMEOUT If timeout on service expires*/
/* NU_PIPE_DELETED If pipe was deleted during */
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