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On 2011/2/1 12:08 PM, Aaron Albertson wrote:
... here's something similar you can
do in RPG (formatting is off, but you get the idea):
D container_t ds qualified template
D i 10i 0
D j 10i 0
D container ds likeds(container_t)
D offsets ds likeds(container_t)
D pNode s *
D pContainer s *
/free
pNode = %addr(container.j);
pContainer = pNode - (%addr(offsets.j) - %addr(offsets));
Earlier today, I hadn't looked carefully enough for the README that
Mihael pointed to. I was puzzled over how such a macro would be used,
since the names of the structure and the structure member would have to
be known at compile time.
Here's the sample function from the README:
int my_cmp(const struct avltree_node *a,
const struct avltree_node *b)
{
struct my_struct *p = avltree_container_of(a, my_struct, node);
struct my_struct *q = avltree_container_of(b, my_struct, node);
return p->key - q->key;
}
Here's an equivalent function in RPG (unformatted and untested). I
marked the extra code needed to handle the C macro with ***, and the
code that replaces the macro with "mac".
P my_cmp b
D my_cmp pi
D a * value
D b * value
D p ds likeds(my_struct_t)
D based(p_ptr)
D q ds likeds(my_struct_t)
D based(q_ptr)
*** D offsets ds likeds(my_struct_t)
*** D nodeOffset s 10i 0
/free
*** nodeOffset = %addr(offsets.node) - %addr(offsets);
mac p_ptr = a - nodeOffset;
mac q_ptr = b - nodeOffset;
return p.key - q.key;
/end-free
P e
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