2.10.3 A Sample Interface

The HELLO method used in the previos subsection could be implemented as follows:

/* world_code.c */
#include <txx.h>
#include <string.h>

int world_hello S2(char *s, XCELL n) {
        while (n--)
                write(1, s, strlen(s));
        return 0;
}

The name of the procedure implementing the interface procedure is a combination of the name of the file containing the procedure (without any suffixes), an underscore, and the name of the interface procedure:

fileName_interfaceName

The proper arguments to compile this code to an extension object depends on the host environment. However, the following requirements must be met:

• the code must be compiled to a relocatible object file
• the include path of the txx.h file must be specified
• the LIBRARY macro must be defined, if compiling to an extension object
• the LIBRARY macro must be undefined, if the interface procedures in the module will be linked against the Virtual Tcode Machine

To compile the above interface code to an extension object on a generic Unix system, a command like this may be used:

cc -o world_code.o -I /usr/local/include -DLIBRARY -c world_code.c

When compiling an object to be linked against TXX, -DLIBRARY should be omitted.