add io_canread and io_canwrite

io/io_canread.c

@@ -0,0 +1,17 @@
+#include <unistd.h>
+#include <sys/time.h>
+#include <poll.h>
+#include <errno.h>
+#include "io_internal.h"
+
+int64 io_canread() {
+  io_entry* e;
+  if (first_readable==-1) return -1;
+  e=array_get(&io_fds,sizeof(io_entry),first_readable);
+  if (e && e->canread) {
+    int64 r=first_readable;
+    first_readable=e->next_read;
+    return r;
+  }
+  return -1;
+}

io/io_canwrite.c

@@ -0,0 +1,17 @@
+#include <unistd.h>
+#include <sys/time.h>
+#include <poll.h>
+#include <errno.h>
+#include "io_internal.h"
+
+int64 io_canwrite() {
+  io_entry* e;
+  if (first_writeable==-1) return -1;
+  e=array_get(&io_fds,sizeof(io_entry),first_writeable);
+  if (e && e->canwrite) {
+    int64 r=first_writeable;
+    first_writeable=e->next_write;
+    return r;
+  }
+  return -1;
+}