From: "Mauricio Fernández" <batsman.geo@...>
Date: 2003-11-22T23:55:13+09:00
Subject: Re: Invoking method with a block in C extension

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On Sat, Nov 22, 2003 at 10:34:27PM +0900, Dmitry V. Sabanin wrote:
> Hi.
> I'm converting some of my ruby code to C extension for better perfomance. 
> I ran into problems with executing methods that take blocks.
> I.e. in ruby i have 
> 	string.gsub!(/regexp/) { |subst| ... }
> and i can't find the way to translate it to C. I tried to search through 
> ruby-talk archives, but I couldn't find anything usefull.
> As far as I was looking at problem, I found rb_iterate, rb_yield, but I 
> couldn't clearly understand what's their purpose, and how to get them all 
> together to achieve what I want.
> Could somebody please explain me how can I implement this ruby code in C?
> I'd really appreciate any help. Thanks in advance!

I was surprised to see that rb_funcall propagates the block passed with
rb_iterate, so there's 2 solutions (attached).

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require "mkmf"

create_makefile("gsub_example")


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#include <ruby.h>
#include <stdio.h>

VALUE mCTest;

static
VALUE
block(VALUE args)
{
  VALUE str = rb_ary_entry(args, 0);
  Check_Type(str, T_STRING);
  printf("Inside block, with string: %s.\n", RSTRING(str)->ptr);
  return rb_funcall(str, rb_intern("upcase"), 0);
}

static
VALUE
block2(VALUE str)
{
  Check_Type(str, T_STRING);
  printf("Inside block, with string: %s.\n", RSTRING(str)->ptr);
  return rb_funcall(str, rb_intern("upcase"), 0);
}

static
VALUE
foo(VALUE self, VALUE str, VALUE re)
{
  VALUE proc;

  proc = rb_proc_new(block, Qnil);
  return rb_funcall(str, rb_intern("_gsub!"), 2, re, proc);
}

static
VALUE
call_gsub(VALUE args)
{
 VALUE str, re;
 str = rb_ary_entry(args, 0);
 re = rb_ary_entry(args, 1);

 return rb_funcall(str, rb_intern("gsub!"), 1, re);
}

static
VALUE
foo2(VALUE self, VALUE str, VALUE re)
{
  VALUE args;
  args = rb_ary_new();
  rb_ary_push(args, str);
  rb_ary_push(args, re);

  return rb_iterate(call_gsub, args, block2, str);
}

void
Init_gsub_example()
{
 mCTest = rb_define_module("CTest");
 rb_define_singleton_method(mCTest, "foo", foo, 2);
 rb_define_singleton_method(mCTest, "foo2", foo2, 2);
 
 rb_eval_string("class String; def _gsub!(re,block); gsub!(re,&block) end end");
}


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require "gsub_example"

a = "hello, world!"
CTest.foo(a, /[ehl]/)
p a

b = "hello, world!"
CTest.foo2(b, /[ehl]/)
p b

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