(foreign-declare "
#include <sys/sendfile.h>
#include <fcntl.h>
#include<errno.h>")

;; This is temporarily disable until we find a way to reliably
;; detect if this is supported

;; (cond-expand
;;   (posix-fadvise
;;    (foreign-declare "#define READ_AHEAD (4 * 1024 * 1024)")
;;    (define %sendfile-implementation
;;      (foreign-lambda* double ((integer src) (integer dst) (double offset) (unsigned-integer to_send))
;;        "size_t res = 0;"
;;        "off_t curoffset = (off_t)offset;"
;;        "if((posix_fadvise(src,0,0,POSIX_FADV_SEQUENTIAL) < 0) && errno != ENOSYS){ C_return(-1); }"
;;        "if(sendfile(dst,src,&curoffset,to_send) < 0){"
;;        "   if(errno == EAGAIN || errno == EINTR){ "
;;        "     C_return(curoffset == 0 ? -2 : (double)(curoffset)); "
;;        "   }else{"
;;        "     C_return(-1);"
;;        "   }"
;;        "}"
;;        " if(((off_t)offset & ~(READ_AHEAD - 1)) != (((off_t)offset + res) & ~(READ_AHEAD - 1))){"
;;        "  if(posix_fadvise(src,((off_t)offset + res) & ~(READ_AHEAD - 1),READ_AHEAD,POSIX_FADV_NOREUSE) < 0){"
;;        "    C_return(-1);"
;;        "  }"
;;        "}"
;;        "C_return((double)curoffset);")))
;;   (else
;;    (define %sendfile-implementation
;;      (foreign-lambda*  double ((integer src) (integer dst) (double offset) (unsigned-integer to_send))
;;        "off_t curoffset = (off_t)offset;"
;;        "if(sendfile(dst,src,&curoffset,to_send) < 0){"
;;        "   if(errno == EAGAIN || errno == EINTR){    "
;;        "     C_return(curoffset == 0 ? -2 : (double)(curoffset)); "
;;        "   }else{ "
;;        "     C_return(-1);"
;;        "   }"
;;        "}"
;;        "C_return((double)curoffset);"))))

(define %sendfile-implementation
  (foreign-lambda*  double ((integer src) (integer dst) (double offset) (unsigned-integer to_send))
    "off_t curoffset = (off_t)offset;"
    "if(sendfile(dst,src,&curoffset,to_send) < 0){"
    "   if(errno == EAGAIN || errno == EINTR){    "
    "     C_return(curoffset == 0 ? -2 : (double)(curoffset)); "
    "   }else{ "
    "     C_return(-1);"
    "   }"
    "}"
    "C_return((double)curoffset);"))