F77_ZMQ

A Fortran 77 binding library for ZeroMQ

This binding works with ZeroMQ 4.3.1.

Usage

Copy the f77_zmq.h or f77_zmq_free.h and libf77zmq.so or libf77zmq.a files into your project. The f77_zmq.h is for fixed format and f77_zmq_free.h is for free format.

In your Fortran source files, include the f77_zmq.h or f77_zmq_free.h file. This will define all the ZMQ_* constants. All the pointers (to sockets, messages, polling items, etc) are defined as integer(ZMQ_PTR) in order to handle 32-bit or 64-bit pointers.

In your Makefile, compile as follows:

$(FC) -o $(TARGET) $(OBJ) -lzmq -lf77zmq 

or

$(FC) -o $(TARGET) $(OBJ) -lzmq libf77zmq.a

Be sure that libzmq.so.5 is present in your LD_LIBRARY_PATH before executing the program.

Installation instructions

Python3 is required to create the f77_zmq.h and f77_zmq_free.h files.

If zmq.h is not in yout CPATH, set the ZMQ_H environment variable to the absolute path of zmq.h, and run make. The default compiler is gcc.

For example:

$ export ZMQ_H=/usr/include/zmq.h
$ make

Differences with the C API

In Fortran77 structs don't exist: they have been introduced with Fortran90. To maintain F77 compatibility, the structs are created using C functions and their pointers are passed to the Fortran. This implies the addition of a few functions.

Additional Message-related functions

• integer(ZMQ_PTR) f77_zmq_msg_new() : Allocates a zmq_msg_t and returns the pointer

• integer f77_zmq_msg_destroy(msg) : Deallocates the zmq_msg_t. Return value is 0.

  • integer(ZMQ_PTR) msg : message

• integer(ZMQ_PTR) f77_zmq_msg_data_new(size, buffer, size_buffer) : Allocates a data buffer for messages, and copies the buffer into the data segment. If size_buffer is 0, the data segement is uninitialized. The return value is a pointer to the data segment.

  • integer size : Size of the data segment to allocate
  • buffer : Buffer to copy. Fortran array or string.
  • integer size_buffer : Number of bytes to copy from the buffer

• integer f77_zmq_msg_destroy_data(data) : Deallocates a data segment. Return value is 0.

  • integer(ZMQ_PTR) data : pointer to the data segment to deallocate.

• integer f77_zmq_msg_copy_from_data(msg, buffer) : Copies the data segment of a message into a buffer.

  • integer(ZMQ_PTR) msg : message
  • buffer : fortran array of string

• integer f77_zmq_msg_copy_to_data(msg, buffer, size) : Copies the data segment of a message into a buffer.

  • integer(ZMQ_PTR) msg : message
  • buffer : fortran array of string
  • integer size : Number of bytes to copy

Additional Polling-related functions

• integer(ZMQ_PTR) f77_zmq_pollitem_new() : Allocates a zmq_pollitem_t and returns the pointer

• integer f77_zmq_pollitem_destroy(item) : Deallocates the zmq_pollitem_t. Return value is 0.

  • integer(ZMQ_PTR) item : poll item struct

Improvements

This interface is quite old. Now, Fortran has introduced the iso_c_bindings module which allows to call C functions in a standard and portable way. This interface should be rewritten using iso_c_bindings to be more portable. I don't have time to do it myself, but if somebody wants to start this project I will be happy to help.