c_from_ruby.c

#include <stdlib.h>
#include <stdio.h>
#include <mruby.h>
#include <mruby/compile.h>





/******************************************************************************
 * 1. CONSTANTS :
 ******************************************************************************/
#define RUBY_CODE "c_from_ruby.rb"





/******************************************************************************
 * 2. FUNCTION PROTOTYPES :
 ******************************************************************************/
mrb_value add_c(mrb_state *mrb,mrb_value self);





/******************************************************************************
 * 3. MAIN :
 ******************************************************************************/
int main(void) {

    // 3.1 Initializing mRuby :
    mrb_state *mrb = mrb_open();
    if (mrb == NULL) {
      printf("Can't initilizing mRuby. Aborting.");
      exit(1);
    }

    struct RClass *a_module = mrb_define_module(mrb, "AModule");
    mrb_define_module_function(mrb, a_module, "add", add_c, MRB_ARGS_REQ(2));
  
  
    // 3.2 Loading the Ruby source code :
    FILE *ruby_code   = fopen(RUBY_CODE, "r");
    char *ruby_string = NULL;

    if(ruby_code == NULL) {
      printf("Can't open file %s. Aborting.", RUBY_CODE);
      exit(1);
    }

    if (fseek(ruby_code, 0L, SEEK_END) == 0) {
      long file_size  = ftell(ruby_code);
      ruby_string     = malloc(sizeof(char) * (file_size + 1));

      fseek(ruby_code, 0L, SEEK_SET);

      size_t length = fread(ruby_string, sizeof(char), file_size, ruby_code);
      ruby_string[length] = '\0';
    }


    // 3.3 Execute Ruby source code :
    mrb_load_string(mrb, ruby_string);
    mrb_close(mrb);


    // 3.4 Cleanup :
    free(ruby_string);
    fclose(ruby_code);

    return 0;
}





/******************************************************************************
 * 4. FUNCTION DEFINITIONS :
 ******************************************************************************/
mrb_value add_c(mrb_state *mrb,mrb_value self) {
  mrb_int a, b;

  mrb_get_args(mrb, "ii", &a, &b);  // getting the arguments according to :
                                    // https://github.com/mruby/mruby/blob/master/include/mruby.h
                                    // line 915

  printf("From the C side, add_c arguments are: %lld, %lld\n", a, b);

  return mrb_fixnum_value((mrb_int)(a + b));
}

c_from_ruby.rb

puts "From the mRuby side, does AModule respond to :add ? -> #{AModule.respond_to?(:add) ? 'yes' : 'no'}"
puts "From the mRuby side, :add call result: #{AModule::add(1, 2)}"

Makefile

CC=gcc
CFLAGS=-std=c99 -lm
MRUBY_INCLUDE=../../mruby-3.1.0/include
MRUBY_LIB=../../mruby-3.1.0/build/host/lib/libmruby.a
SOURCE=c_from_ruby

all:
  $(CC) $(CFLAGS) -I$(MRUBY_INCLUDE) $(SOURCE).c -o $(SOURCE) $(MRUBY_LIB)

clean:
  rm -f $(SOURCE)