Memory mapping in Objective-C

gistfile1.txt

const char* cstr = [string UTF8String];

void* anon = mmap(0, sizeof(char) * (string.length + 1), PROT_WRITE|PROT_READ, MAP_ANON|MAP_PRIVATE, 0, 0);
if (anon == MAP_FAILED) {
  NSLog(@"Failed to map memory.");
  return;
}
strcpy(anon, cstr);

// How do I get a file descriptor for use here?
markdownin = fdopen(fd, "r");

http://jverkoey.github.com/fmemopen/

Thanks gang!