Writing Ruby Extensions in go

build.sh

go build -buildmode=c-shared -o hello.so hello.go

# if no error is returned you can check that the shared library is exporting
# the right symbols by executing
# $ nm -gU ./hello.so | grep hello
# 0000000000002050 T __cgoexp_d4a435ec6890_hello_world
# 0000000000001ae0 T _hello_world <--- ALL SYSTEMS ARE GO
                   

go_fast_blank.go

package main

/*
#include "ruby.h"

extern inline VALUE go_fast_blank(VALUE);
*/
import "C"
import (
	"fmt"
	"strings"
	"unicode"
	"unsafe"
)

//export go_fast_blank
func go_fast_blank(s C.VALUE) C.VALUE {
	gs := C.GoString(C.rb_string_value_cstr(&s))

	if gs == "" || strings.TrimLeftFunc(gs, unicode.IsSpace) == "" {
		return C.Qtrue
	}

	return C.Qfalse
}

//export Init_go_fast_blank
func Init_go_fast_blank() {
	fmt.Println("go_fast_blank init")
	cs := C.CString("blank?")
	defer C.free(unsafe.Pointer(cs))

	C.rb_define_method(C.rb_cString, cs, (*[0]byte)(C.go_fast_blank), 0)
}

func main() {} // Required but ignored

hello_world.go

package main

import "C"
import "fmt"

//export hello_world
func hello_world() {
    fmt.Println("hello world")
}

func main() {} // Required but ignored

hello_world.rb

# copy and paste inside irb or other ruby repl
require 'ffi'

module Say
  extend FFI::Library
  ffi_lib './hello.so'
  attach_function :hello_world, [], :void
end

Say.hello_world
# hello world
#  => nil 

preamble.c

/* Created by "go tool cgo" - DO NOT EDIT. */

/* package command-line-arguments */

/* Start of preamble from import "C" comments.  */


#line 3 "/Users/name/path/ext/go_fast_blank/go_fast_blank.go"

#include "ruby.h"

extern inline VALUE go_fast_blank(VALUE);



/* End of preamble from import "C" comments.  */