From a2fabf160552344bf75c4c3b46da866c53891088 Mon Sep 17 00:00:00 2001
From: Tony Garnock-Jones <tonygarnockjones@gmail.com>
Date: Fri, 31 Dec 2010 17:26:39 -0500
Subject: [PATCH] Make IOHandles shareable

---
 harness.c | 55 +++++++++++++++++++++++++++++++------------------------
 harness.h |  2 +-
 2 files changed, 32 insertions(+), 25 deletions(-)

diff --git a/harness.c b/harness.c
index 3339c18..861e756 100644
--- a/harness.c
+++ b/harness.c
@@ -115,39 +115,44 @@ void nap(long millis) {
   schedule();
 }
 
+static void awaken_waiters(IOHandle *h, short mask) {
+  Process *prev = NULL;
+  Process *p;
+  Process *next;
+  for (p = h->waiters; p != NULL; p = next) {
+    next = p->link;
+    assert(p->state == PROCESS_WAITING);
+    if ((p->wait_flags & mask) != 0) {
+      if (prev == NULL) {
+	h->waiters = next;
+      } else {
+	prev->link = next;
+      }
+      enqueue_runlist(p);
+    } else {
+      prev = p;
+    }
+  }
+}
+
 static void input_isr(struct bufferevent *bufev, IOHandle *h) {
-  //info("input_isr %p r %d w %d\n", h->p, EVBUFFER_LENGTH(bufev->input), EVBUFFER_LENGTH(bufev->output));
-  assert((h->p->state == PROCESS_WAITING) && (h->p->wait_flags & EV_READ));
-  enqueue_runlist(h->p);
+  awaken_waiters(h, EV_READ);
 }
 
 static void output_isr(struct bufferevent *bufev, IOHandle *h) {
-  //info("output_isr %p r %d w %d\n", h->p, EVBUFFER_LENGTH(bufev->input), EVBUFFER_LENGTH(bufev->output));
-  if ((h->p->state == PROCESS_WAITING) && (h->p->wait_flags & EV_WRITE)) {
-    enqueue_runlist(h->p);
-  }
+  awaken_waiters(h, EV_WRITE);
 }
 
 static void error_isr(struct bufferevent *bufev, short what, IOHandle *h) {
-  info("error_isr 0x%04X %p\n", what, h->p);
+  info("error_isr 0x%04X\n", what);
   h->error_direction = what & (EVBUFFER_READ | EVBUFFER_WRITE);
   h->error_kind = what & ~(EVBUFFER_READ | EVBUFFER_WRITE);
-  if ((h->p->state == PROCESS_WAITING)
-      && (h->p->wait_flags & (EV_READ | EV_WRITE))) {
-    enqueue_runlist(h->p);
-  } else {
-    warn("Um, not sure what to do here. Error what %d, fd %d, ioh %p process %p\n",
-	 what,
-	 bufev->ev_read.ev_fd,
-	 h,
-	 h->p);
-  }
+  awaken_waiters(h, EV_READ | EV_WRITE);
 }
 
 IOHandle *new_iohandle(int fd) {
   IOHandle *h = malloc(sizeof(*h));
-  assert(current_process != NULL);
-  h->p = current_process;
+  h->waiters = NULL;
   h->fd = fd;
   h->io = bufferevent_new(fd,
 			  (evbuffercb) input_isr,
@@ -171,11 +176,13 @@ void iohandle_clear_error(IOHandle *h) {
 }
 
 static void block_on_io(IOHandle *h, short event) {
-  assert(current_process == h->p);
-  h->p->state = PROCESS_WAITING;
-  h->p->wait_flags |= event;
+  assert(current_process->link == NULL);
+  current_process->link = h->waiters;
+  h->waiters = current_process;
+  current_process->state = PROCESS_WAITING;
+  current_process->wait_flags |= event;
   schedule();
-  h->p->wait_flags &= ~event;
+  current_process->wait_flags &= ~event;
 }
 
 cmsg_bytes_t iohandle_readwait(IOHandle *h, size_t at_least) {
diff --git a/harness.h b/harness.h
index 7926e0b..f171f52 100644
--- a/harness.h
+++ b/harness.h
@@ -18,7 +18,7 @@ typedef struct Process {
 } Process;
 
 typedef struct IOHandle {
-  Process *p;
+  Process *waiters;
   int fd;
   struct bufferevent *io;
   unsigned short error_direction;