Simple ruby-ffi Demo by yang
Tue, Dec 8, 2015Simple ruby-ffi Demo
It is a demo use ruby-ffi to call c code. Only tested it on ubuntu(15.04). The libcal just calculate the sum of two integer number. You can see all of the code here.
Steps
- write the
callib code - generate .so shared lib
- write test for this .so shared lib
- write ruby file with ruby-ffi
Generate .so shared lib
// cal.h
int sum(int a, int b);
// cal.c
#include "cal.h"
int sum(int a, int b) {
return a + b;
}
gcc -fPIC -shared -o libcal.so cal.c
sudo mv cal.h /usr/local/include
sudo mv libcal.so /usr/local/lib
sudo chmod 0755 /usr/local/lib/libcal.so
sudo ldconfig
ldconfig -p | grep cal
Test it in main function
// main.c
#include <stdio.h>
#include "cal.h"
int main(int argc, char const *argv[]) {
int total;
total = sum(1, 4);
printf("sum is %d\n", total);
return 0;
}
gcc -Wall -o main main.c -I/usr/local/include -L/usr/local/lib -lcal
ldd main
./main
Ruby ffi
gem install ffi
require 'ffi'
module MyCal
extend FFI::Library
ffi_lib 'c' # use libc
attach_function :puts, [:string], :int # puts function is from libc
ffi_lib 'cal' # use libcal write by myself
attach_function :sum, [:int, :int], :int # sum function is from libcal
end
MyCal.puts 'I am using libcal write by myself.'
total = MyCal.sum(1, 3)
p "sum 1 and 3 is #{total}"
ruby cal.rb # => "sum 1 and 3 is 4"