(foreign-declare "
#include <errno.h>
#include<sys/socket.h>
#include<sys/types.h>
#include <sys/uio.h>")

;; (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 tmpoffset = (off_t)offset;"
;;        "if((posix_fadvise(src,0,0,POSIX_FADV_SEQUENTIAL) < 0) && errno != ENOSYS){"
;;        "  C_return(-1);"
;;        "}"
;;        "if(sendfile(src,dst,tmpoffset,to_send,NULL,&res,0) < 0){"
;;        "  if(errno == EAGAIN){"
;;        "    C_return(res == 0 ? -2 : (double)(tmpoffset + res));"
;;        "  }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)(tmpoffset + res));")))
;;   (else
;;    (define %sendfile-implementation
;;      (foreign-lambda*  double ((integer src) (integer dst) (double offset) (unsigned-integer to_send))
;;        "size_t res = 0;"
;;        "off_t tmpoffset = (off_t)offset;"
;;        "if(sendfile(src,dst,tmpoffset,to_send,NULL,&res,0) < 0){"
;;        "  if(errno == EAGAIN){"
;;        "    C_return(res == 0 ? -2 : (double)(tmpoffset + res));"
;;        "  }else{"
;;        "    C_return(-1);"
;;        "  }"
;;        "}"
;;        "C_return((double)(tmpoffset + res));"))))

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