How to do Hash#each_pair from C extension?

Ruby
1

Hi,

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.)

It looks like rb_hash_foreach() in hash.c does exactly
what I want–allows me to pass in a function pointer,
which it will invoke yielding each key/value pair–but
it’s declared static in hash.c.

I looked at duplicating that functionality in my own
C code, but it requires “st.h” as well as constants
such as HASH_DELETED which are defined privately in
hash.c.

Is there a different way I should be going about this?

Thanks for any help,

Bill

2

On Fri, 29 Dec 2006 08:22:34 -0000, Bill K. [email protected] wrote:

I looked at duplicating that functionality in my own
C code, but it requires “st.h” as well as constants
such as HASH_DELETED which are defined privately in
hash.c.

Is there a different way I should be going about this?

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);
}

// … later,

rb_define_method(cSomeClass, “iterhsh”, ruby_iterhsh, 1);

Hope that helps,
Ross

3

From: “Ross B.” [email protected]

VALUE value = rb_ary_entry(data_ary, 1);
}
Thanks! Works great.

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…)

Regards,

Bill

4

On Wed, 03 Jan 2007 05:05:21 -0000, Bill K. [email protected] wrote:

// 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 :slight_smile:

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,