- (or (not (eql (fd-stream-ibuf-head fd-stream)
- (fd-stream-ibuf-tail fd-stream)))
- (fd-stream-listen fd-stream)
- (setf (fd-stream-listen fd-stream)
- (eql (sb!unix:with-restarted-syscall ()
- (sb!alien:with-alien ((read-fds (sb!alien:struct
- sb!unix:fd-set)))
- (sb!unix:fd-zero read-fds)
- (sb!unix:fd-set (fd-stream-fd fd-stream) read-fds)
- (sb!unix:unix-fast-select (1+ (fd-stream-fd fd-stream))
- (sb!alien:addr read-fds)
- nil nil 0 0)))
- 1))))
+ (labels ((do-listen ()
+ (or (not (eql (fd-stream-ibuf-head fd-stream)
+ (fd-stream-ibuf-tail fd-stream)))
+ (fd-stream-listen fd-stream)
+ #!+win32
+ (sb!win32:fd-listen (fd-stream-fd fd-stream))
+ #!-win32
+ ;; If the read can block, LISTEN will certainly return NIL.
+ (if (sysread-may-block-p fd-stream)
+ nil
+ ;; Otherwise select(2) and CL:LISTEN have slightly
+ ;; different semantics. The former returns that an FD
+ ;; is readable when a read operation wouldn't block.
+ ;; That includes EOF. However, LISTEN must return NIL
+ ;; at EOF.
+ (progn (catch 'eof-input-catcher
+ ;; r-b/f too calls select, but it shouldn't
+ ;; block as long as read can return once w/o
+ ;; blocking
+ (refill-buffer/fd fd-stream))
+ ;; At this point either IBUF-HEAD != IBUF-TAIL
+ ;; and FD-STREAM-LISTEN is NIL, in which case
+ ;; we should return T, or IBUF-HEAD ==
+ ;; IBUF-TAIL and FD-STREAM-LISTEN is :EOF, in
+ ;; which case we should return :EOF for this
+ ;; call and all future LISTEN call on this stream.
+ ;; Call ourselves again to determine which case
+ ;; applies.
+ (do-listen))))))
+ (do-listen)))