io.ports: calling '0 read' now returns an empty sequence without blocking (reported by Brennan Cheung)

basis/io/pipes/pipes-tests.factor

@@ -1,7 +1,7 @@
 USING: io io.pipes io.streams.string io.encodings.utf8
-io.streams.duplex io.encodings io.timeouts namespaces
-continuations tools.test kernel calendar destructors
-accessors debugger math ;
+io.encodings.binary io.streams.duplex io.encodings io.timeouts
+namespaces continuations tools.test kernel calendar destructors
+accessors debugger math sequences ;
 IN: io.pipes.tests
 
 [ "Hello" ] [
@@ -28,7 +28,7 @@ IN: io.pipes.tests
 
 [
     utf8 <pipe> [
-        5 seconds over set-timeout
+        1 seconds over set-timeout
         stream-readln
     ] with-disposal
 ] must-fail
@@ -42,3 +42,12 @@ IN: io.pipes.tests
         ] curry ignore-errors
     ] times
 ] unit-test
+
+! 0 read should not block
+[ f ] [
+    [
+        binary <pipe> &dispose
+        in>>
+        [ 0 read ] with-input-stream
+    ] with-destructors
+] unit-test

basis/io/ports/ports.factor

@@ -46,11 +46,17 @@ M: input-port stream-read1
     dup wait-to-read [ drop f ] [ buffer>> buffer-pop ] if ; inline
 
 : read-step ( count port -- byte-array/f )
-    dup wait-to-read [ 2drop f ] [ buffer>> buffer-read ] if ;
+    {
+        { [ over 0 = ] [ 2drop f ] }
+        { [ dup wait-to-read ] [ 2drop f ] }
+        [ buffer>> buffer-read ]
+    } cond ;
+
+: prepare-read ( count stream -- count stream )
+    dup check-disposed [ 0 max >fixnum ] dip ; inline
 
 M: input-port stream-read-partial ( max stream -- byte-array/f )
-    dup check-disposed
-    [ 0 max >integer ] dip read-step ;
+    prepare-read read-step ;
 
 : read-loop ( count port accum -- )
     pick over length - dup 0 > [
@@ -64,8 +70,7 @@ M: input-port stream-read-partial ( max stream -- byte-array/f )
     ] if ;
 
 M: input-port stream-read
-    dup check-disposed
-    [ 0 max >fixnum ] dip
+    prepare-read
     2dup read-step dup [
         pick over length > [
             pick <byte-vector>