intarray internals

Hi,

I'm reading through the source code of intarray contrib module. Despite
being at the beginning, I've some questions to ask. I'd be so
appreciated if anybody can help.

[1]
What's the function of execute() in _int_bool.c? As far as I can
understand, some other functions (eg. execconsistent()) calling
execute() with specific check methods (like checkcondition_bit()) but
I still couldn't figure out which functionality execute() stands for.

[2]
In g_int_decompress(), shouldn't

if (ARRISVOID(in))
PG_RETURN_POINTER(entry);

part be replaced with

if (ARRISVOID(in))
{
if (in != (ArrayType *) DatumGetPointer(entry->key))
pfree(in);
PG_RETURN_POINTER(entry)
}

[3]
Again, in g_int_decompress(), I couldn't figure out the functionality of
below lines:

din = ARRPTR(in);
lenr = internal_size(din, lenin);

for (i = 0; i < lenin; i += 2)
for (j = din[i]; j <= din[i + 1]; j++)
if ((!i) || *(dr - 1) != j)
*dr++ = j;

If I understand right, above loop, tries to reconstruct array with more
smaller intervals - to be able to make more accurate predicates while
digging into nodes. If so, AFAICS, g_int_compress() and
g_int_decompress() methods can be (quite?) improved.

Furthermore, I've tested above functions with some random input and
couldn't create any cases hold for a[i] == a[i - 1] (which is used
in internal_size() method's loop.) Did I miss something obvious?

Regards.

P.S. Instead of an explanation to questions, pointings to right files to
read (at least for the beginning) would be appreciated too.