Here's my early draft of C rewrite/port

[alexisnaveros]

Hey people, here's an early version of my C rewrite/port of Clipper2. The API looks like this:
http://www.rayforce.net/clipper2c/clipper2c.h

And the rest of the code can be found here:
http://www.rayforce.net/clipper2c/

Results are identical to Clipper2's on July 9th... (okay, it seems some bugs have been fixed since that date, I need to check them out).

Based on one random test, this preliminary C version appears to be 6% faster than the C++ version?... I have reversed a couple experimental optimizations to maintain the code's structure closer to Clipper2, for now. I'll wait a bit for bug fixes and/or the outcome of scalability experiments (it's going to be messy if the code is completely transformed).

(ideally compile with -O3 -flto -march=native -mtune=native, or at least -msse4.1 -msse4.2, some optimizations are based on SSE 4.1/4.2 intrinsics)

[gtoal]

Alexis, the clipper2c.h file is missing from your site (and isn't in the Wayback machine). Also could you give an example of using your port from C please? I'm having a hard time mapping the calls to the calls described in the Clipper2 documentation.

By the way, in cchybridsort.h

size_t ccHybridSortLog2( size_t v )
{
  size_t r = 0;
  if (sizeof(size_t) > 4)
  {
    if( (long long int)v & 0xFFFFFFFF00000000LL )
    {
      v = (long long int)v >> 32LL;
...

on hardware that supports 64 bit ints but uses 32 bit pointers and 32 bit size_t, the original 'v >>= 32' caused a compiler warning (even though the code will never be executed) - which using the cast above avoids. Other than that it was a remarkably clean compilation. I threw together a fairly basic Makefile:

CFLAGS=-O3 -flto -march=native -mtune=native

all: mmheap.o mmslab.o polyarea.o polyclip.o polyoffset.o polywithin.o
        echo All up to date.

clean:
        rm -f mmheap.o  mmslab.o  polyarea.o  polyclip.o  polyoffset.o  polywithin.o

mmheap.o: mmheap.c mmheap.h

mmslab.o: mmslab.c mmslab.h

polyarea.o: polyarea.c mathshewchuk.h polyarea.h mmslab.h mmheap.h mathlineline.h mathshewchuk.h polyclip.h polywithin.h mmvector.h ccradixsort.h cchybridsort.h ccmergesort.h

polyoffset.o: polyoffset.c polyclip.h polyarea.h mmvector.h

polywithin.o: polywithin.c polywithin.h