[KinoSearch] C method-invocation API improvement

[Marvin Humphrey]

Greets,

Today, I believe I solved a problem with the C-space OO implementation  
in KS.  Method calls have been implemented as "unsafe macros", so  
called because they evaluate an argument twice.  Here's an example  
from the current dev release, 0.20_051:

     #define Kino_SegPList_Next(self) \
         (self)->_->next((kino_PostingList*)self)

The problem with such macros is that they can cause problems if the  
multi-evaluated argument has side effects.  For example, invoking this  
method once causes i to be incremented twice...

     SegPList_Next(seg_posting_lists[i++]);

... as the macro expands out to this:

     (seg_posting_lists[i++])->_- 
 >next((kino_PostingList*)seg_posting_lists[i++]);

The solution is to use static inline functions instead of macros:

     extern size_t Kino_SegPList_Next_OFFSET;
     static CHY_INLINE chy_u32_t
     Kino_SegPList_Next(const void *vself)
     {
         kino_PostingList *const self = (kino_PostingList *)vself;
         char *const method_address = (char*)self->_ +  
Kino_SegPList_Next_OFFSET;
         const kino_PList_next_t method =  
*((kino_PList_next_t*)method_address);
         return method(self);
     }

Any optimizing compiler ought to have no trouble reducing that to  
extremely efficient machine code.  I did a little experiment today and  
GCC gave me *exactly* the assembler I wanted.  Furthermore, the  
compiled size of the shared library was the same before and after the  
change.

Now, when we publish a C API for KinoSearch, there should be no need  
for caveats or caution regarding method invocation syntax.

Marvin Humphrey
Rectangular Research
http://www.rectangular.com/


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