Tidy up internal logic and return value of IOOperations.poll.

Author: aardvark179

lib/truffle/io/wait.rb

@@ -14,18 +14,18 @@ def nread
 
   def ready?
     ensure_open_and_readable
-    Truffle::IOOperations.poll(self, Truffle::IOOperations::POLLIN, 0) > 0
+    Truffle::IOOperations.poll(self, Truffle::IOOperations::POLLIN, 0)
   end
 
   def wait(timeout = nil)
     ensure_open_and_readable
-    Truffle::IOOperations.poll(self, Truffle::IOOperations::POLLIN, timeout) > 0 ? self : nil
+    Truffle::IOOperations.poll(self, Truffle::IOOperations::POLLIN, timeout) ? self : nil
   end
 
   alias_method :wait_readable, :wait
 
   def wait_writable(timeout = nil)
     ensure_open_and_writable
-    Truffle::IOOperations.poll(self, Truffle::IOOperations::POLLOUT, timeout) > 0 ? self : nil
+    Truffle::IOOperations.poll(self, Truffle::IOOperations::POLLOUT, timeout) ? self : nil
   end
 end

src/main/ruby/truffleruby/core/truffle/io_operations.rb

@@ -199,6 +199,9 @@ def self.select(readables, readable_ios, writables, writable_ios, errorables, er
 
     end
 
+    # This method will return a true if poll returned without error
+    # with an event within the timeout, false if the timeout expired,
+    # or raises an exception for an errno.
     def self.poll(io, events, timeout)
       if (events & POLLIN) != 0
         return 1 unless io.__send__(:buffer_empty?)
@@ -212,8 +215,9 @@ def self.poll(io, events, timeout)
         raise ArgumentError, 'timeout must be positive' if timeout < 0
 
         # Microseconds, rounded down
-        timeout = remaining_timeout = Integer(timeout * 1_000)
+        timeout = remaining_timeout = (timeout * 1_000).to_i
         start = Process.clock_gettime(Process::CLOCK_MONOTONIC, :millisecond)
+        deadline = start + timeout
       else
         remaining_timeout = -1
       end
@@ -231,11 +235,10 @@ def self.poll(io, events, timeout)
                 if timeout
                   # Update timeout
                   now = Process.clock_gettime(Process::CLOCK_MONOTONIC, :millisecond)
-                  waited = now - start
-                  if waited >= timeout
-                    nil # timeout
+                  if now >= deadline
+                    false # timeout
                   else
-                    remaining_timeout = timeout - waited
+                    remaining_timeout = deadline - now
                     :retry
                   end
                 else
@@ -245,7 +248,7 @@ def self.poll(io, events, timeout)
                 Errno.handle_errno(errno)
               end
             else
-              primitive_result
+              primitive_result > 0
             end
         end while result == :retry
       ensure