/* on linux 2.4.x you get either sendfile or LFS */
#if defined HAVE_SYS_SENDFILE_H && defined HAVE_SENDFILE && (!defined _LARGEFILE_SOURCE || defined HAVE_SENDFILE64) && defined HAVE_WRITEV && defined(__linux__) && !defined HAVE_SENDFILE_BROKEN
# define USE_LINUX_SENDFILE
# include <sys/sendfile.h>
# include <sys/uio.h>
#endif
/* all the Async IO backends need GTHREAD support */
#if defined(USE_GTHREAD)
# if defined(USE_LINUX_SENDFILE)
# if 0 && defined(HAVE_LIBAIO_H)
/** disabled for now as not all FSs are async-io capable */
# define USE_LINUX_AIO_SENDFILE
# endif
# define USE_GTHREAD_SENDFILE
# endif
# if defined(HAVE_AIO_H) && (!defined(__FreeBSD__))
/* FreeBSD has no SIGEV_THREAD for us */
# define USE_POSIX_AIO
# include <sys/types.h> /* macosx wants it */
# include <aio.h>
# endif
# ifdef HAVE_MMAP
# define USE_GTHREAD_AIO
# endif
#endif
#if defined HAVE_SYS_UIO_H && defined HAVE_SENDFILE && defined HAVE_WRITEV && (defined(__FreeBSD__) || defined(__DragonFly__))
# define USE_FREEBSD_SENDFILE
# include <sys/uio.h>
#endif
#if defined HAVE_SYS_SENDFILE_H && defined HAVE_SENDFILEV && defined HAVE_WRITEV && defined(__sun)
# define USE_SOLARIS_SENDFILEV
# include <sys/sendfile.h>
# include <sys/uio.h>
#endif
#if defined HAVE_SYS_UIO_H && defined HAVE_WRITEV
# define USE_WRITEV
# include <sys/uio.h>
#endif
#if defined HAVE_SYS_MMAN_H && defined HAVE_MMAP
# define USE_MMAP
# include <sys/mman.h>
/* NetBSD 1.3.x needs it */
# ifndef MAP_FAILED
# define MAP_FAILED -1
# endif
#if defined(MAP_ANON)
#define HAVE_MEM_MMAP_ANON
#else
/* let's try /dev/zero */
#define HAVE_MEM_MMAP_ZERO
#endif
#endif
#if defined HAVE_SYS_UIO_H && defined HAVE_WRITEV && defined HAVE_SEND_FILE && defined(__aix)