X-Git-Url: http://www.chiark.greenend.org.uk/ucgi/~mdw/git/disorder/blobdiff_plain/cb9a695c5b6058d2c319789ca154f555d6c0815c..16fb2830d52c1420afdee555a566d72a065d9616:/lib/event.c

diff --git a/lib/event.c b/lib/event.c
index 3d6d1f6..ee25024 100644
--- a/lib/event.c
+++ b/lib/event.c
@@ -1,27 +1,25 @@
 /*
  * This file is part of DisOrder.
- * Copyright (C) 2004, 2005, 2007 Richard Kettlewell
+ * Copyright (C) 2004, 2005, 2007, 2008 Richard Kettlewell
  *
- * This program is free software; you can redistribute it and/or modify
+ * This program is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
- * the Free Software Foundation; either version 2 of the License, or
+ * the Free Software Foundation, either version 3 of the License, or
  * (at your option) any later version.
- *
- * This program is distributed in the hope that it will be useful, but
- * WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
- * General Public License for more details.
- *
+ * 
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ * 
  * You should have received a copy of the GNU General Public License
- * along with this program; if not, write to the Free Software
- * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
- * USA
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
 /** @file lib/event.c
  * @brief DisOrder event loop
  */
 
-#include <config.h>
+#include "common.h"
 
 #include <unistd.h>
 #include <fcntl.h>
@@ -31,15 +29,11 @@
 #include <sys/wait.h>
 #include <sys/stat.h>
 #include <unistd.h>
-#include <assert.h>
 #include <signal.h>
 #include <errno.h>
-#include <string.h>
-#include <limits.h>
 #include <sys/socket.h>
 #include <netinet/in.h>
 #include <sys/un.h>
-#include <stdio.h>
 #include "event.h"
 #include "mem.h"
 #include "log.h"
@@ -47,6 +41,8 @@
 #include "printf.h"
 #include "sink.h"
 #include "vector.h"
+#include "timeval.h"
+#include "heap.h"
 
 /** @brief A timeout */
 struct timeout {
@@ -54,9 +50,18 @@ struct timeout {
   struct timeval when;
   ev_timeout_callback *callback;
   void *u;
-  int resolve;
+  int active;
 };
 
+/** @brief Comparison function for timeouts */
+static int timeout_lt(const struct timeout *a,
+		      const struct timeout *b) {
+  return tvlt(&a->when, &b->when);
+}
+
+HEAP_TYPE(timeout_heap, struct timeout *, timeout_lt);
+HEAP_DEFINE(timeout_heap, struct timeout *, timeout_lt);
+
 /** @brief A file descriptor in one mode */
 struct fd {
   int fd;
@@ -106,11 +111,8 @@ struct ev_source {
   /** @brief File descriptors, per mode */
   struct fdmode mode[ev_nmodes];
 
-  /** @brief Sorted linked list of timeouts
-   *
-   * We could use @ref HEAP_TYPE now, but there aren't many timeouts.
-   */
-  struct timeout *timeouts;
+  /** @brief Heap of timeouts */
+  struct timeout_heap timeouts[1];
 
   /** @brief Array of handled signals */
   struct signal signals[NSIG];
@@ -146,27 +148,6 @@ static const char *modenames[] = { "read", "write", "except" };
 
 /* utilities ******************************************************************/
 
-/** @brief Great-than comparison for timevals
- *
- * Ought to be in @file lib/timeval.h
- */
-static inline int gt(const struct timeval *a, const struct timeval *b) {
-  if(a->tv_sec > b->tv_sec)
-    return 1;
-  if(a->tv_sec == b->tv_sec
-     && a->tv_usec > b->tv_usec)
-    return 1;
-  return 0;
-}
-
-/** @brief Greater-than-or-equal comparison for timevals
- *
- * Ought to be in @file lib/timeval.h
- */
-static inline int ge(const struct timeval *a, const struct timeval *b) {
-  return !gt(b, a);
-}
-
 /* creation *******************************************************************/
 
 /** @brief Create a new event loop */
@@ -179,6 +160,7 @@ ev_source *ev_new(void) {
     FD_ZERO(&ev->mode[n].enabled);
   ev->sigpipe[0] = ev->sigpipe[1] = -1;
   sigemptyset(&ev->sigmask);
+  timeout_heap_init(ev->timeouts);
   return ev;
 }
 
@@ -194,7 +176,7 @@ int ev_run(ev_source *ev) {
     int n, mode;
     int ret;
     int maxfd;
-    struct timeout *t, **tt;
+    struct timeout *timeouts, *t, **tt;
     struct stat sb;
 
     xgettimeofday(&now, 0);
@@ -202,10 +184,24 @@ int ev_run(ev_source *ev) {
      * while we're handling them (otherwise we'd have to break out of infinite
      * loops, preferrably without starving better-behaved subsystems).  Hence
      * the slightly complicated two-phase approach here. */
-    for(t = ev->timeouts;
-	t && ge(&now, &t->when);
-	t = t->next) {
-      t->resolve = 1;
+    /* First we read those timeouts that have triggered out of the heap.  We
+     * keep them in the same order they came out of the heap in. */
+    tt = &timeouts;
+    while(timeout_heap_count(ev->timeouts)
+	  && tvle(&timeout_heap_first(ev->timeouts)->when, &now)) {
+      /* This timeout has reached its trigger time; provided it has not been
+       * cancelled we add it to the timeouts list. */
+      t = timeout_heap_remove(ev->timeouts);
+      if(t->active) {
+	*tt = t;
+	tt = &t->next;
+      }
+    }
+    *tt = 0;
+    /* Now we can run the callbacks for those timeouts.  They might add further
+     * timeouts that are already in the past but they won't trigger until the
+     * next time round the event loop. */
+    for(t = timeouts; t; t = t->next) {
       D(("calling timeout for %ld.%ld callback %p %p",
 	 (long)t->when.tv_sec, (long)t->when.tv_usec,
 	 (void *)t->callback, t->u));
@@ -213,13 +209,6 @@ int ev_run(ev_source *ev) {
       if(ret)
 	return ret;
     }
-    tt = &ev->timeouts;
-    while((t = *tt)) {
-      if(t->resolve)
-	*tt = t->next;
-      else
-	tt = &t->next;
-    }
     maxfd = 0;
     for(mode = 0; mode < ev_nmodes; ++mode) {
       ev->mode[mode].tripped = ev->mode[mode].enabled;
@@ -228,10 +217,11 @@ int ev_run(ev_source *ev) {
     }
     xsigprocmask(SIG_UNBLOCK, &ev->sigmask, 0);
     do {
-      if(ev->timeouts) {
+      if(timeout_heap_count(ev->timeouts)) {
+	t = timeout_heap_first(ev->timeouts);
 	xgettimeofday(&now, 0);
-	delta.tv_sec = ev->timeouts->when.tv_sec - now.tv_sec;
-	delta.tv_usec = ev->timeouts->when.tv_usec - now.tv_usec;
+	delta.tv_sec = t->when.tv_sec - now.tv_sec;
+	delta.tv_usec = t->when.tv_usec - now.tv_usec;
 	if(delta.tv_usec < 0) {
 	  delta.tv_usec += 1000000;
 	  --delta.tv_sec;
@@ -321,6 +311,8 @@ int ev_fd(ev_source *ev,
 
   D(("registering %s fd %d callback %p %p", modenames[mode], fd,
      (void *)callback, u));
+  if(fd >= FD_SETSIZE)
+    return -1;
   assert(mode < ev_nmodes);
   if(ev->mode[mode].nfds >= ev->mode[mode].fdslots) {
     ev->mode[mode].fdslots = (ev->mode[mode].fdslots
@@ -388,6 +380,7 @@ 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 +399,8 @@ 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 +411,17 @@ 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 +439,7 @@ 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));
   }
 }
 
@@ -450,7 +447,7 @@ void ev_report(ev_source *ev) {
 
 /** @brief Register a timeout
  * @param ev Event source
- * @param handle Where to store timeout handle, or @c NULL
+ * @param handlep Where to store timeout handle, or @c NULL
  * @param when Earliest time to call @p callback, or @c NULL
  * @param callback Function to call at or after @p when
  * @param u Passed to @p callback
@@ -468,7 +465,7 @@ int ev_timeout(ev_source *ev,
 	       const struct timeval *when,
 	       ev_timeout_callback *callback,
 	       void *u) {
-  struct timeout *t, *p, **pp;
+  struct timeout *t;
 
   D(("registering timeout at %ld.%ld callback %p %p",
      when ? (long)when->tv_sec : 0, when ? (long)when->tv_usec : 0,
@@ -478,11 +475,8 @@ int ev_timeout(ev_source *ev,
     t->when = *when;
   t->callback = callback;
   t->u = u;
-  pp = &ev->timeouts;
-  while((p = *pp) && gt(&t->when, &p->when))
-    pp = &p->next;
-  t->next = p;
-  *pp = t;
+  t->active = 1;
+  timeout_heap_insert(ev->timeouts, t);
   if(handlep)
     *handlep = t;
   return 0;
@@ -495,19 +489,13 @@ int ev_timeout(ev_source *ev,
  *
  * If @p handle is 0 then this is a no-op.
  */
-int ev_timeout_cancel(ev_source *ev,
+int ev_timeout_cancel(ev_source attribute((unused)) *ev,
 		      ev_timeout_handle handle) {
-  struct timeout *t = handle, *p, **pp;
+  struct timeout *t = handle;
 
-  if(!t)
-    return 0;
-  for(pp = &ev->timeouts; (p = *pp) && p != t; pp = &p->next)
-    ;
-  if(p) {
-    *pp = p->next;
-    return 0;
-  } else
-    return -1;
+  if(t)
+    t->active = 0;
+  return 0;
 }
 
 /* signals ********************************************************************/
@@ -531,7 +519,9 @@ static void sighandler(int s) {
 
   /* probably the reader has stopped listening for some reason */
   if(write(sigfd[s], &sc, 1) < 0) {
-    write(2, errmsg, sizeof errmsg - 1);
+	/* do the best we can as we're about to abort; shut _up_, gcc */
+	int _ignore = write(2, errmsg, sizeof errmsg - 1);
+	(void)_ignore;
     abort();
   }
 }
@@ -886,31 +876,82 @@ 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 Synthesized error code */
-  int syntherror;
+  /** @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 Set when abandoned */
+  int abandoned;
 };
 
-/** @brief Synthesized error callback
+/** @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).
  */
@@ -919,20 +960,39 @@ static int writer_shutdown(ev_source *ev,
 			   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;
-  return w->callback(ev, w->fd, w->syntherror, w->u);
+  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 attribute((unused)) *now,
+				     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);
-  return w->callback(ev, w->fd, ETIMEDOUT, w->u);
+  if(!w->abandoned) {
+    w->abandoned = 1;
+    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) */
@@ -956,16 +1016,24 @@ static int writer_callback(ev_source *ev, int fd, void *u) {
   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) {
@@ -973,8 +1041,8 @@ static int writer_callback(ev_source *ev, int fd, void *u) {
     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;
@@ -992,21 +1060,30 @@ static int ev_writer_write(struct sink *sk, const void *s, int n) {
 
   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. */
+    if(!w->abandoned) {
+      w->abandoned = 1;
+      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);
+    } else
+      return 0;
+  }
+  /* 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;
-  if(w->spacebound && w->b.end - w->b.start > w->spacebound) {
-    /* Buffer contents have exceeded 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);
-    w->syntherror = EPIPE;
-    ev_fd_cancel(w->ev, ev_write, w->fd);
-    return ev_timeout(w->ev, 0, 0, writer_shutdown, w);
-  }
+  /* Arrange a timeout if there wasn't one set already */
   writer_set_timebound(w);
   return 0;
 }
@@ -1018,6 +1095,12 @@ 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,
@@ -1037,6 +1120,7 @@ ev_writer *ev_writer_new(ev_source *ev,
   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;
 }
@@ -1111,33 +1195,17 @@ struct sink *ev_writer_sink(ev_writer *w) {
  */
 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 */
-    w->syntherror = 0;			/* no error */
-    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) {
-  ev_source *const ev = w->ev;
-  D(("cancel writer fd %d", w->fd));
-  ev_timeout_cancel(ev, w->timeout);
-  w->timeout = 0;
-  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
@@ -1151,16 +1219,41 @@ 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) {
@@ -1173,19 +1266,22 @@ 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;
@@ -1199,6 +1295,11 @@ 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,
@@ -1238,10 +1339,16 @@ 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
@@ -1253,7 +1360,7 @@ 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() */
@@ -1263,8 +1370,13 @@ 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
@@ -1287,7 +1399,7 @@ 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
@@ -1303,11 +1415,38 @@ 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;
 }
 
 /*