X-Git-Url: http://www.chiark.greenend.org.uk/ucgi/~mdw/git/disorder/blobdiff_plain/7958ad2fb52937f935ca99ede9755b5a61be32bb..0e843521df080e255a855565e210b7e0caa64511:/lib/event.c

diff --git a/lib/event.c b/lib/event.c
index bb9d4ea..56278f6 100644
--- a/lib/event.c
+++ b/lib/event.c
@@ -388,6 +388,7 @@ int ev_fd_cancel(ev_source *ev, ev_fdmode mode, int fd) {
  * cancelled.
  */
 int ev_fd_enable(ev_source *ev, ev_fdmode mode, int fd) {
+  assert(fd >= 0);
   D(("enabling mode %s fd %d", modenames[mode], fd));
   FD_SET(fd, &ev->mode[mode].enabled);
   return 0;
@@ -406,6 +407,8 @@ int ev_fd_disable(ev_source *ev, ev_fdmode mode, int fd) {
   D(("disabling mode %s fd %d", modenames[mode], fd));
   FD_CLR(fd, &ev->mode[mode].enabled);
   FD_CLR(fd, &ev->mode[mode].tripped);
+  /* Suppress any pending callbacks */
+  ev->escape = 1;
   return 0;
 }
 
@@ -416,15 +419,17 @@ void ev_report(ev_source *ev) {
   struct dynstr d[1];
   char b[4096];
 
+  if(!debugging)
+    return;
   dynstr_init(d);
   for(mode = 0; mode < ev_nmodes; ++mode) {
-    info("mode %s maxfd %d", modenames[mode], ev->mode[mode].maxfd);
+    D(("mode %s maxfd %d", modenames[mode], ev->mode[mode].maxfd));
     for(n = 0; n < ev->mode[mode].nfds; ++n) {
       fd = ev->mode[mode].fds[n].fd;
-      info("fd %s %d%s%s (%s)", modenames[mode], fd,
-	   FD_ISSET(fd, &ev->mode[mode].enabled) ? " enabled" : "",
-	   FD_ISSET(fd, &ev->mode[mode].tripped) ? " tripped" : "",
-	   ev->mode[mode].fds[n].what);
+      D(("fd %s %d%s%s (%s)", modenames[mode], fd,
+	 FD_ISSET(fd, &ev->mode[mode].enabled) ? " enabled" : "",
+	 FD_ISSET(fd, &ev->mode[mode].tripped) ? " tripped" : "",
+	 ev->mode[mode].fds[n].what));
     }
     d->nvec = 0;
     for(fd = 0; fd <= ev->mode[mode].maxfd; ++fd) {
@@ -442,7 +447,7 @@ void ev_report(ev_source *ev) {
       dynstr_append_string(d, b);
     }
     dynstr_terminate(d);
-    info("%s enabled:%s", modenames[mode], d->vec);
+    D(("%s enabled:%s", modenames[mode], d->vec));
   }
 }
 
@@ -490,13 +495,17 @@ int ev_timeout(ev_source *ev,
 
 /** @brief Cancel a timeout
  * @param ev Event loop
- * @param handle Handle returned from ev_timeout()
+ * @param handle Handle returned from ev_timeout(), or 0
  * @return 0 on success, non-0 on error
+ *
+ * If @p handle is 0 then this is a no-op.
  */
 int ev_timeout_cancel(ev_source *ev,
 		      ev_timeout_handle handle) {
   struct timeout *t = handle, *p, **pp;
 
+  if(!t)
+    return 0;
   for(pp = &ev->timeouts; (p = *pp) && p != t; pp = &p->next)
     ;
   if(p) {
@@ -882,44 +891,167 @@ static void buffer_space(struct buffer *b, size_t bytes) {
      (void *)b->base, (void *)b->start, (void *)b->end, (void *)b->top));
 }
 
-/* buffered writer ************************************************************/
+/* readers and writers *******************************************************/
 
 /** @brief State structure for a buffered writer */
 struct ev_writer {
+  /** @brief Sink used for writing to the buffer */
   struct sink s;
+
+  /** @brief Output buffer */
   struct buffer b;
+
+  /** @brief File descriptor to write to */
   int fd;
+
+  /** @brief Set if there'll be no more output */
   int eof;
+
+  /** @brief Error/termination callback */
   ev_error_callback *callback;
+
+  /** @brief Passed to @p callback */
   void *u;
+
+  /** @brief Parent event source */
   ev_source *ev;
+
+  /** @brief Maximum amount of time between succesful writes, 0 = don't care */
+  int timebound;
+  /** @brief Maximum amount of data to buffer, 0 = don't care */
+  int spacebound;
+  /** @brief Error code to pass to @p callback (see writer_shutdown()) */
+  int error;
+  /** @brief Timeout handle for @p timebound (or 0) */
+  ev_timeout_handle timeout;
+
+  /** @brief Description of this writer */
+  const char *what;
+
+  /** @brief Tied reader or 0 */
+  ev_reader *reader;
 };
 
+/** @brief State structure for a buffered reader */
+struct ev_reader {
+  /** @brief Input buffer */
+  struct buffer b;
+  /** @brief File descriptor read from */
+  int fd;
+  /** @brief Called when new data is available */
+  ev_reader_callback *callback;
+  /** @brief Called on error and shutdown */
+  ev_error_callback *error_callback;
+  /** @brief Passed to @p callback and @p error_callback */
+  void *u;
+  /** @brief Parent event loop */
+  ev_source *ev;
+  /** @brief Set when EOF is detected */
+  int eof;
+  /** @brief Error code to pass to error callback */
+  int error;
+  /** @brief Tied writer or NULL */
+  ev_writer *writer;
+};
+
+/* buffered writer ************************************************************/
+
+/** @brief Shut down the writer
+ *
+ * This is called to shut down a writer.  The error callback is not called
+ * through any other path.  Also we do not cancel @p fd from anywhere else,
+ * though we might disable it.
+ *
+ * It has the signature of a timeout callback so that it can be called from a
+ * time=0 timeout.
+ *
+ * Calls @p callback with @p w->syntherr as the error code (which might be 0).
+ */
+static int writer_shutdown(ev_source *ev,
+			   const attribute((unused)) struct timeval *now,
+			   void *u) {
+  ev_writer *w = u;
+
+  if(w->fd == -1)
+    return 0;				/* already shut down */
+  D(("writer_shutdown fd=%d error=%d", w->fd, w->error));
+  ev_timeout_cancel(ev, w->timeout);
+  ev_fd_cancel(ev, ev_write, w->fd);
+  w->timeout = 0;
+  if(w->reader) {
+    D(("found a tied reader"));
+    /* If there is a reader still around we just untie it */
+    w->reader->writer = 0;
+    shutdown(w->fd, SHUT_WR);		/* there'll be no more writes */
+  } else {
+    D(("no tied reader"));
+    /* There's no reader so we are free to close the FD */
+    xclose(w->fd);
+  }
+  w->fd = -1;
+  return w->callback(ev, w->error, w->u);
+}
+
+/** @brief Called when a writer's @p timebound expires */
+static int writer_timebound_exceeded(ev_source *ev,
+				     const struct timeval *now,
+				     void *u) {
+  ev_writer *const w = u;
+
+  error(0, "abandoning writer %s because no writes within %ds",
+	w->what, w->timebound);
+  w->error = ETIMEDOUT;
+  return writer_shutdown(ev, now, u);
+}
+
+/** @brief Set the time bound callback (if not set already) */
+static void writer_set_timebound(ev_writer *w) {
+  if(w->timebound && !w->timeout) {
+    struct timeval when;
+    ev_source *const ev = w->ev;
+    
+    xgettimeofday(&when, 0);
+    when.tv_sec += w->timebound;
+    ev_timeout(ev, &w->timeout, &when, writer_timebound_exceeded, w);
+  }
+}
+
 /** @brief Called when a writer's file descriptor is writable */
 static int writer_callback(ev_source *ev, int fd, void *u) {
-  ev_writer *w = u;
+  ev_writer *const w = u;
   int n;
 
   n = write(fd, w->b.start, w->b.end - w->b.start);
   D(("callback for writer fd %d, %ld bytes, n=%d, errno=%d",
      fd, (long)(w->b.end - w->b.start), n, errno));
   if(n >= 0) {
+    /* Consume bytes from the buffer */
     w->b.start += n;
+    /* Suppress any outstanding timeout */
+    ev_timeout_cancel(ev, w->timeout);
+    w->timeout = 0;
     if(w->b.start == w->b.end) {
+      /* The buffer is empty */
       if(w->eof) {
-	ev_fd_cancel(ev, ev_write, fd);
-	return w->callback(ev, fd, 0, w->u);
+	/* We're done, we can shut down this writer */
+	w->error = 0;
+	return writer_shutdown(ev, 0, w);
       } else
+	/* There might be more to come but we don't need writer_callback() to
+	 * be called for the time being */
 	ev_fd_disable(ev, ev_write, fd);
-    }
+    } else
+      /* The buffer isn't empty, set a timeout so we give up if we don't manage
+       * to write some more within a reasonable time */
+      writer_set_timebound(w);
   } else {
     switch(errno) {
     case EINTR:
     case EAGAIN:
       break;
     default:
-      ev_fd_cancel(ev, ev_write, fd);
-      return w->callback(ev, fd, errno, w->u);
+      w->error = errno;
+      return writer_shutdown(ev, 0, w);
     }
   }
   return 0;
@@ -934,12 +1066,30 @@ static int writer_callback(ev_source *ev, int fd, void *u) {
  */
 static int ev_writer_write(struct sink *sk, const void *s, int n) {
   ev_writer *w = (ev_writer *)sk;
-  
+
+  if(!n)
+    return 0;				/* avoid silliness */
+  if(w->fd == -1)
+    error(0, "ev_writer_write on %s after shutdown", w->what);
+  if(w->spacebound && w->b.end - w->b.start + n > w->spacebound) {
+    /* The new buffer contents will exceed the space bound.  We assume that the
+     * remote client has gone away and TCP hasn't noticed yet, or that it's got
+     * hopelessly stuck. */
+    error(0, "abandoning writer %s because buffer has reached %td bytes",
+	  w->what, w->b.end - w->b.start);
+    ev_fd_disable(w->ev, ev_write, w->fd);
+    w->error = EPIPE;
+    return ev_timeout(w->ev, 0, 0, writer_shutdown, w);
+  }
+  /* Make sure there is space */
   buffer_space(&w->b, n);
+  /* If the buffer was formerly empty then we'll need to re-enable the FD */
   if(w->b.start == w->b.end)
     ev_fd_enable(w->ev, ev_write, w->fd);
   memcpy(w->b.end, s, n);
   w->b.end += n;
+  /* Arrange a timeout if there wasn't one set already */
+  writer_set_timebound(w);
   return 0;
 }
 
@@ -950,6 +1100,12 @@ static int ev_writer_write(struct sink *sk, const void *s, int n) {
  * @param u Passed to @p callback
  * @param what Text description
  * @return New writer or @c NULL
+ *
+ * Writers own their file descriptor and close it when they have finished with
+ * it.
+ *
+ * If you pass the same fd to a reader and writer, you must tie them together
+ * with ev_tie().
  */ 
 ev_writer *ev_writer_new(ev_source *ev,
 			 int fd,
@@ -964,12 +1120,60 @@ ev_writer *ev_writer_new(ev_source *ev,
   w->callback = callback;
   w->u = u;
   w->ev = ev;
+  w->timebound = 10 * 60;
+  w->spacebound = 512 * 1024;
+  w->what = what;
   if(ev_fd(ev, ev_write, fd, writer_callback, w, what))
     return 0;
+  /* Buffer is initially empty so we don't want a callback */
   ev_fd_disable(ev, ev_write, fd);
   return w;
 }
 
+/** @brief Get/set the time bound
+ * @param w Writer
+ * @param new_time_bound New bound or -1 for no change
+ * @return Latest time bound
+ *
+ * If @p new_time_bound is negative then the current time bound is returned.
+ * Otherwise it is set and the new value returned.
+ *
+ * The time bound is the number of seconds allowed between writes.  If it takes
+ * longer than this to flush a buffer then the peer will be assumed to be dead
+ * and an error will be synthesized.  0 means "don't care".  The default time
+ * bound is 10 minutes.
+ *
+ * Note that this value does not take into account kernel buffering and
+ * timeouts.
+ */
+int ev_writer_time_bound(ev_writer *w,
+			 int new_time_bound) {
+  if(new_time_bound >= 0)
+    w->timebound = new_time_bound;
+  return w->timebound;
+}
+
+/** @brief Get/set the space bound
+ * @param w Writer
+ * @param new_space_bound New bound or -1 for no change
+ * @return Latest space bound
+ *
+ * If @p new_space_bound is negative then the current space bound is returned.
+ * Otherwise it is set and the new value returned.
+ *
+ * The space bound is the number of bytes allowed between in the buffer.  If
+ * the buffer exceeds this size an error will be synthesized.  0 means "don't
+ * care".  The default space bound is 512Kbyte.
+ *
+ * Note that this value does not take into account kernel buffering.
+ */
+int ev_writer_space_bound(ev_writer *w,
+			  int new_space_bound) {
+  if(new_space_bound >= 0)
+    w->spacebound = new_space_bound;
+  return w->spacebound;
+}
+
 /** @brief Return the sink associated with a writer
  * @param w Writer
  * @return Pointer to sink
@@ -978,21 +1182,11 @@ ev_writer *ev_writer_new(ev_source *ev,
  * descriptor as and when it is writable.
  */
 struct sink *ev_writer_sink(ev_writer *w) {
+  if(!w)
+    fatal(0, "ev_write_sink called with null writer");
   return &w->s;
 }
 
-/** @brief Shutdown callback
- *
- * See ev_writer_close().
- */
-static int writer_shutdown(ev_source *ev,
-			   const attribute((unused)) struct timeval *now,
-			   void *u) {
-  ev_writer *w = u;
-
-  return w->callback(ev, w->fd, 0, w->u);
-}
-
 /** @brief Close a writer
  * @param w Writer to close
  * @return 0 on success, non-0 on error
@@ -1006,29 +1200,17 @@ static int writer_shutdown(ev_source *ev,
  */
 int ev_writer_close(ev_writer *w) {
   D(("close writer fd %d", w->fd));
+  if(w->eof)
+    return 0;				/* already closed */
   w->eof = 1;
   if(w->b.start == w->b.end) {
-    /* we're already finished */
-    ev_fd_cancel(w->ev, ev_write, w->fd);
+    /* We're already finished */
+    w->error = 0;			/* no error */
     return ev_timeout(w->ev, 0, 0, writer_shutdown, w);
   }
   return 0;
 }
 
-/** @brief Cancel a writer discarding any buffered data
- * @param w Writer to close
- * @return 0 on success, non-0 on error
- *
- * This cancels a writer immediately.  Any unwritten buffered data is discarded
- * and the error callback is never called.  This is appropriate to call if (for
- * instance) the read half of a TCP connection is known to have failed and the
- * writer is therefore obsolete.
- */
-int ev_writer_cancel(ev_writer *w) {
-  D(("cancel writer fd %d", w->fd));
-  return ev_fd_cancel(w->ev, ev_write, w->fd);
-}
-
 /** @brief Attempt to flush a writer
  * @param w Writer to flush
  * @return 0 on success, non-0 on error
@@ -1042,16 +1224,41 @@ int ev_writer_flush(ev_writer *w) {
 
 /* buffered reader ************************************************************/
 
-/** @brief State structure for a buffered reader */
-struct ev_reader {
-  struct buffer b;
-  int fd;
-  ev_reader_callback *callback;
-  ev_error_callback *error_callback;
-  void *u;
-  ev_source *ev;
-  int eof;
-};
+/** @brief Shut down a reader*
+ *
+ * This is the only path through which we cancel and close the file descriptor.
+ * As with the writer case it is given timeout signature to allow it be
+ * deferred to the next iteration of the event loop.
+ *
+ * We only call @p error_callback if @p error is nonzero (unlike the writer
+ * case).
+ */
+static int reader_shutdown(ev_source *ev,
+			   const attribute((unused)) struct timeval *now,
+			   void *u) {
+  ev_reader *const r = u;
+
+  if(r->fd == -1)
+    return 0;				/* already shut down */
+  D(("reader_shutdown fd=%d", r->fd));
+  ev_fd_cancel(ev, ev_read, r->fd);
+  r->eof = 1;
+  if(r->writer) {
+    D(("found a tied writer"));
+    /* If there is a writer still around we just untie it */
+    r->writer->reader = 0;
+    shutdown(r->fd, SHUT_RD);		/* there'll be no more reads */
+  } else {
+    D(("no tied writer found"));
+    /* There's no writer so we are free to close the FD */
+    xclose(r->fd);
+  }
+  r->fd = -1;
+  if(r->error)
+    return r->error_callback(ev, r->error, r->u);
+  else
+    return 0;
+}
 
 /** @brief Called when a reader's @p fd is readable */
 static int reader_callback(ev_source *ev, int fd, void *u) {
@@ -1064,19 +1271,22 @@ static int reader_callback(ev_source *ev, int fd, void *u) {
      fd, (int)(r->b.top - r->b.end), n, errno));
   if(n > 0) {
     r->b.end += n;
-    return r->callback(ev, r, fd, r->b.start, r->b.end - r->b.start, 0, r->u);
+    return r->callback(ev, r, r->b.start, r->b.end - r->b.start, 0, r->u);
   } else if(n == 0) {
-    r->eof = 1;
-    ev_fd_cancel(ev, ev_read, fd);
-    return r->callback(ev, r, fd, r->b.start, r->b.end - r->b.start, 1, r->u);
+    /* No more read callbacks needed */
+    ev_fd_disable(r->ev, ev_read, r->fd);
+    ev_timeout(r->ev, 0, 0, reader_shutdown, r);
+    /* Pass the remaining data and an eof indicator to the user */
+    return r->callback(ev, r, r->b.start, r->b.end - r->b.start, 1, r->u);
   } else {
     switch(errno) {
     case EINTR:
     case EAGAIN:
       break;
     default:
-      ev_fd_cancel(ev, ev_read, fd);
-      return r->error_callback(ev, fd, errno, r->u);
+      /* Fatal error, kill the reader now */
+      r->error = errno;
+      return reader_shutdown(ev, 0, r);
     }
   }
   return 0;
@@ -1090,6 +1300,11 @@ static int reader_callback(ev_source *ev, int fd, void *u) {
  * @param u Passed to callbacks
  * @param what Text description
  * @return New reader or @c NULL
+ *
+ * Readers own their fd and close it when they are finished with it.
+ *
+ * If you pass the same fd to a reader and writer, you must tie them together
+ * with ev_tie().
  */
 ev_reader *ev_reader_new(ev_source *ev,
 			 int fd,
@@ -1129,10 +1344,16 @@ void ev_reader_consume(ev_reader *r, size_t n) {
 /** @brief Cancel a reader
  * @param r Reader
  * @return 0 on success, non-0 on error
+ *
+ * No further callbacks will be made, and the FD will be closed (in a later
+ * iteration of the event loop).
  */
 int ev_reader_cancel(ev_reader *r) {
   D(("cancel reader fd %d", r->fd));
-  return ev_fd_cancel(r->ev, ev_read, r->fd);
+  if(r->fd == -1)
+    return 0;				/* already thoroughly cancelled */
+  ev_fd_disable(r->ev, ev_read, r->fd);
+  return ev_timeout(r->ev, 0, 0, reader_shutdown, r);
 }
 
 /** @brief Temporarily disable a reader
@@ -1144,7 +1365,7 @@ int ev_reader_cancel(ev_reader *r) {
  */
 int ev_reader_disable(ev_reader *r) {
   D(("disable reader fd %d", r->fd));
-  return r->eof ? 0 : ev_fd_disable(r->ev, ev_read, r->fd);
+  return ev_fd_disable(r->ev, ev_read, r->fd);
 }
 
 /** @brief Called from ev_run() for ev_reader_incomplete() */
@@ -1154,8 +1375,13 @@ static int reader_continuation(ev_source attribute((unused)) *ev,
   ev_reader *r = u;
 
   D(("reader continuation callback fd %d", r->fd));
-  if(ev_fd_enable(r->ev, ev_read, r->fd)) return -1;
-  return r->callback(ev, r, r->fd, r->b.start, r->b.end - r->b.start, r->eof, r->u);
+  /* If not at EOF turn the FD back on */
+  if(!r->eof)
+    if(ev_fd_enable(r->ev, ev_read, r->fd))
+      return -1;
+  /* We're already in a timeout callback so there's no reason we can't call the
+   * user callback directly (compare ev_reader_enable()). */
+  return r->callback(ev, r, r->b.start, r->b.end - r->b.start, r->eof, r->u);
 }
 
 /** @brief Arrange another callback
@@ -1178,7 +1404,7 @@ static int reader_enabled(ev_source *ev,
   ev_reader *r = u;
 
   D(("reader enabled callback fd %d", r->fd));
-  return r->callback(ev, r, r->fd, r->b.start, r->b.end - r->b.start, r->eof, r->u);
+  return r->callback(ev, r, r->b.start, r->b.end - r->b.start, r->eof, r->u);
 }
 
 /** @brief Re-enable reading
@@ -1194,11 +1420,38 @@ static int reader_enabled(ev_source *ev,
  * re-enable.  You'll automatically get another callback directly from the
  * event loop (i.e. not from inside ev_reader_enable()) so you can handle the
  * next line (or whatever) if the whole thing has in fact already arrived.
+ *
+ * The difference between this process and calling ev_reader_incomplete() is
+ * ev_reader_incomplete() deals with the case where you can process now but
+ * would rather yield to other clients of the event loop, while using
+ * ev_reader_disable() and ev_reader_enable() deals with the case where you
+ * cannot process input yet because some other process is actually not
+ * complete.
  */
 int ev_reader_enable(ev_reader *r) {
   D(("enable reader fd %d", r->fd));
-  return ((r->eof ? 0 : ev_fd_enable(r->ev, ev_read, r->fd))
-	  || ev_timeout(r->ev, 0, 0, reader_enabled, r)) ? -1 : 0;
+
+  /* First if we're not at EOF then we re-enable reading */
+  if(!r->eof)
+    if(ev_fd_enable(r->ev, ev_read, r->fd))
+      return -1;
+  /* Arrange another callback next time round the event loop */
+  return ev_timeout(r->ev, 0, 0, reader_enabled, r);
+}
+
+/** @brief Tie a reader and a writer together
+ * @param r Reader
+ * @param w Writer
+ * @return 0 on success, non-0 on error
+ *
+ * This function must be called if @p r and @p w share a file descritptor.
+ */
+int ev_tie(ev_reader *r, ev_writer *w) {
+  assert(r->writer == 0);
+  assert(w->reader == 0);
+  r->writer = w;
+  w->reader = r;
+  return 0;
 }
 
 /*