📄 pic.c
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/* suspension */
/* NU_PIPE_RESET If pipe was reset during */
/* suspension */
/* */
/*************************************************************************/
STATUS PIC_Receive_From_Pipe(NU_PIPE *pipe_ptr, VOID *message,
UNSIGNED size, UNSIGNED *actual_size, UNSIGNED suspend)
{
R1 PI_PCB *pipe; /* Pipe control block ptr */
PI_SUSPEND suspend_block; /* Allocate suspension block */
PI_SUSPEND *suspend_ptr; /* Pointer to suspend block */
R2 BYTE_PTR source; /* Pointer to source */
R3 BYTE_PTR destination; /* Pointer to destination */
TC_TCB *task; /* Task pointer */
UNSIGNED copy_size; /* Number of bytes to copy */
UNSIGNED pad = 0; /* Number of pad bytes */
R4 INT i; /* Working counter */
STATUS preempt; /* Preemption flag */
STATUS status; /* Completion status */
NU_SUPERV_USER_VARIABLES
/* Switch to supervisor mode */
NU_SUPERVISOR_MODE();
/* Move input pipe pointer into internal pointer. */
pipe = (PI_PCB *) pipe_ptr;
#ifdef NU_ENABLE_STACK_CHECK
/* Call stack checking function to check for an overflow condition. */
TCT_Check_Stack();
#endif
#ifdef NU_ENABLE_HISTORY
/* Make an entry that corresponds to this function in the system history
log. */
HIC_Make_History_Entry(NU_RECEIVE_FROM_PIPE_ID, (UNSIGNED) pipe,
(UNSIGNED) message, (UNSIGNED) size);
#endif
/* Initialize the status as successful. */
status = NU_SUCCESS;
/* Protect against simultaneous access to the pipe. */
TCT_System_Protect();
/* Determine if an urgent message request is currently suspended. */
if (pipe -> pi_urgent_list)
{
/* If so, copy the message from the suspended request block and
resume the associated task. */
/* Decrement the number of tasks waiting on pipe. */
pipe -> pi_tasks_waiting--;
/* Remove the first suspended block from the list. */
suspend_ptr = pipe -> pi_urgent_list;
CSC_Remove_From_List((CS_NODE **) &(pipe -> pi_urgent_list),
&(suspend_ptr -> pi_suspend_link));
/* Setup the source and destination pointers. */
destination = (BYTE_PTR) message;
source = 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. */
*actual_size = suspend_ptr -> pi_message_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();
}
/* Determine if there are messages in the pipe. */
else if (pipe -> pi_messages)
{
/* Copy message from pipe into the caller's area. */
/* Setup the source and destination pointers. */
destination = (BYTE_PTR) message;
source = pipe -> pi_read;
/* Process according to the type of message supported by the pipe. */
if (pipe -> pi_fixed_size)
{
/* Pipe supports fixed-size messages. */
/* Copy the message from the pipe area into the destination. */
i = (INT) size;
do
{
*(destination) = *(source++);
if ((--i) == 0)
break;
destination++;
} while (1);
}
else
{
/* Pipe supports variable-size messages. */
/* Variable length message size is actually in the pipe area. */
size = *((UNSIGNED *) source);
source = source + sizeof(UNSIGNED);
/* Check for a wrap-around condition on the pipe. */
if (source >= pipe -> pi_end)
/* Wrap the read pointer back to the top of the pipe
area. */
source = pipe -> pi_start;
/* Increment the number of available bytes in the pipe. */
pipe -> pi_available = pipe -> pi_available + sizeof(UNSIGNED);
/* Calculate the number of pad bytes necessary to keep
the pipe read pointer on an UNSIGNED data element alignment.*/
pad = (((size + sizeof(UNSIGNED) - 1)/sizeof(UNSIGNED)) *
sizeof(UNSIGNED)) - size;
/* Calculate the number of bytes remaining from the read pointer
to the bottom of the pipe. */
copy_size = pipe -> pi_end - source;
/* 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;
destination++;
} while (1);
}
else
{
/* Copy the first half of the message. */
i = (INT) copy_size;
do
{
*(destination++) = *(source);
if ((--i) == 0)
break;
source++;
} while (1);
/* Copy the second half of the message. */
source = pipe -> pi_start;
i = (INT) (size - copy_size);
do
{
*(destination) = *(source++);
if ((--i) == 0)
break;
destination++;
} while (1);
}
}
/* Check again for wrap-around condition on the read pointer. */
if (source >= pipe -> pi_end)
/* Move the read pointer to the top of the pipe area. */
source = 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 read
pointer. */
/* Calculate the number of bytes remaining from the read
pointer to the bottom of the pipe. */
copy_size = pipe -> pi_end - source;
/* 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 read pointer to the top of the pipe and make the
necessary adjustment. */
source = pipe -> pi_start + (pad - copy_size);
else
/* There is enough room in the pipe to simply add the
the pad bytes to the read pointer. */
source = source + pad;
/* Add pad bytes to the available bytes count. */
pipe -> pi_available = pipe -> pi_available + pad;
}
/* Adjust the actual read pointer. */
pipe -> pi_read = source;
/* Increment the number of available bytes. */
pipe -> pi_available = pipe -> pi_available + size;
/* Decrement the number of messages in the pipe. */
pipe -> pi_messages--;
/* Return the number of bytes received. */
*actual_size = size;
#ifdef NU_PROFILE_PLUS
PRF_PLUS_PIC_RECEIVE_FROM_PIPE_0
#endif /* NU_PROFILE_PLUS */
/* Determine if any tasks suspended on a full pipe can be woken
up. */
if (pipe -> pi_suspension_list)
{
/* Pickup the suspension list and examine suspension blocks
to see if the message could now fit in the pipe. */
suspend_ptr = pipe -> pi_suspension_list;
preempt = NU_FALSE;
size = suspend_ptr -> pi_message_size;
i = 0;
pad = 0;
/* Overhead of each pipe message. */
if (!pipe -> pi_fixed_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);
}
while ((suspend_ptr) && ((size + i) <= pipe -> pi_available))
{
/* Place the suspended task's message into the pipe. */
/* Setup the source and destination pointers. */
source = suspend_ptr -> pi_message_area;
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
{
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