From: Ross Bamford <rosco@...>
Date: 2007-01-03T18:35:07+09:00
Subject: Re: How to do Hash#each_pair from C extension?

On Wed, 03 Jan 2007 05:05:21 -0000, Bill Kelly <billk@cts.com> wrote:

> From: "Ross Bamford" <rosco@roscopeco.remove.co.uk>
>> On Fri, 29 Dec 2006 08:22:34 -0000, Bill Kelly <billk@cts.com> wrote:
>>  > I'm trying to copy all the key/value pairs from a Ruby
>> > hash into an STL hash.  (BTW, I'm using Ruby 1.8.4 and
>> > cannot change the ruby version easily.)
>>
>> Maybe try something like:
>>  static VALUE hsh_iterfunc(VALUE data_ary, VALUE hsh) {
>>    VALUE key = rb_ary_entry(data_ary, 0);
>>    VALUE value = rb_ary_entry(data_ary, 1);
>>     // do whatever, e.g.
>>    rb_funcall(rb_mKernel, rb_intern("puts"), 2, key, value);
>>     return data_ary;
>> }
>>   VALUE ruby_iterhsh(VALUE self, VALUE hsh) {
>>    return rb_iterate(rb_each, hsh, hsh_iterfunc, hsh);
>> }
>
> Thanks!  Works great.
>

No problem :)

> What I'm passing in as the second parameter isn't really a VALUE,
> it's a pointer to the STL hash.  As far as I could tell from grepping
> the ruby sources, that *seems* to be legal (some ruby code passes
> a NODE* for the second parameter, masquerading as a VALUE.)
>
> (Unless a NODE* really is a VALUE, in which case my passing in
> a fake VALUE maybe isn't so good after all.  I'm a little uncomfortable
> not knowing for sure...)
>

No, that should be fine - ruby guarantees that VALUE casts to void*, and  
the second argument is purely for your use.

Cheers,
-- 
Ross Bamford - rosco@roscopeco.remove.co.uk