cnet's Application Programming Interface

NAME

CNET_read_physical - read a data frame from the Physical Layer

SYNOPSIS

#include <cnet.h> int CNET_read_physical(int *link, void *frame, size_t *length);

DESCRIPTION

CNET_read_physical requests that a data frame be read from the Physical Layer. The specified maximum number of bytes from the Physical Layer are copied to the address pointed to by frame. On invocation, length must point to an integer indicating the maximum number of bytes that may be copied into frame.

Each node has a fixed number of links, the first available physical link is number 1, the second is number 2, and so on. As a special case, a node may reliably transmit a frame to itself by requesting the LOOPBACK(=0) link.

On return, the integer pointed to by length will contain the number of bytes read from the Physical Layer. If link is not NULL, then the integer pointed to by link will contain the link number on which the frame arrived.

RETURN VALUE

The value 0 is returned on success. On failure, the value -1 is returned, and the global variable cnet_errno is set to one of the following values to describe the error:

ER_BADARG

Either frame or length is a NULL pointer.

ER_BADSIZE

The value of length is shorter than next available data frame.

ER_CORRUPTFRAME

The recently arrived data frame was corrupted in the Physical Layer and the -e command-line option was given.

ER_NOTREADY

The current node has not yet finished rebooting.

SEE ALSO

CNET_write_physical, CNET_write_physical_reliable, and CNET_write_direct