Channels <chan.h>

The functions described here allow programs to access the basic communication facility of the Diamond model, which is to transfer a message across a channel.

The header chan.h defines the following:

The chan.h functions must always include in their parameter list the address of a channel. This could be the address of a user-declared variable of type CHAN.

For example:

CHAN mychan;

int value;

chan_init(&mychan);

...

chan_out_word(value, &mychan);

Alternatively, it could be a port:

int main(int argc, char *argv[], char *envp[],

         CHAN * in_ports[], int ins,

         CHAN *out_ports[], int outs) {

   int value;

   ...

   chan_out_word(value, out_ports[0]);

   ...

}

Note that the channels passed in through the port vector arguments of main must not be initialized; all others, such as mychan above, must be initialized by calls to chan_init.

The functions provided in chan.h are listed below. Messages of any type and size can be transmitted by the two general-purpose functions chan_in_message and chan_out_message. The word functions are simply convenient shorthands for four-octet messages.

Note that most inter-processor links support only transfers that are multiples of 4 octets.