diff --git a/basis/alien/data/data.factor b/basis/alien/data/data.factor
index 7bde58c7e9..ac7478d24a 100644
--- a/basis/alien/data/data.factor
+++ b/basis/alien/data/data.factor
@@ -2,7 +2,7 @@
 USING: accessors alien alien.arrays alien.c-types alien.strings
 arrays byte-arrays combinators combinators.short-circuit
 cpu.architecture fry generalizations io io.streams.memory kernel
-libc macros math math.functions parser sequences
+libc locals macros math math.functions parser sequences
 stack-checker.dependencies summary words ;
 QUALIFIED: math
 IN: alien.data
@@ -93,11 +93,13 @@ M: bad-byte-array-length summary
 : malloc-string ( string encoding -- alien )
     string>alien malloc-byte-array ;
 
-M: memory-stream stream-read
-    [
-        [ index>> ] [ alien>> ] bi <displaced-alien>
-        swap memory>byte-array
-    ] [ [ + ] change-index drop ] 2bi ;
+INSTANCE: memory-stream noncopying-reader
+M:: memory-stream stream-read-unsafe ( n buf stream -- count )
+    stream alien>> :> src
+    buf src n memcpy
+    n src <displaced-alien> stream alien<<
+    n ; inline
+M: memory-stream stream-read-partial-unsafe stream-read-unsafe ; inline
 
 M: value-type c-type-rep drop int-rep ;
 
diff --git a/core/io/streams/memory/memory-tests.factor b/core/io/streams/memory/memory-tests.factor
new file mode 100644
index 0000000000..d6810084e3
--- /dev/null
+++ b/core/io/streams/memory/memory-tests.factor
@@ -0,0 +1,28 @@
+! (c)2011 Joe Groff bsd license
+USING: alien.data destructors io io.streams.memory kernel libc
+tools.test ;
+IN: io.streams.memory.tests
+
+{ 1 2 3 } [
+    B{ 1 2 3 } <memory-stream>
+    [ stream-read1 ] [ stream-read1 ] [ stream-read1 ] tri
+] unit-test
+
+{ 1 2 3 } [
+    [
+        B{ 1 2 3 } malloc-byte-array &free <memory-stream>
+        [ stream-read1 ] [ stream-read1 ] [ stream-read1 ] tri
+    ] with-destructors
+] unit-test
+
+{ B{ 1 2 3 } B{ 4 5 6 7 8 } } [
+    B{ 1 2 3 4 5 6 7 8 } <memory-stream>
+    [ 3 swap stream-read ] [ 5 swap stream-read ] bi
+] unit-test
+
+{ B{ 1 2 3 } B{ 4 5 6 7 8 } } [
+    [
+        B{ 1 2 3 4 5 6 7 8 } malloc-byte-array &free <memory-stream>
+        [ 3 swap stream-read ] [ 5 swap stream-read ] bi
+    ] with-destructors
+] unit-test
diff --git a/core/io/streams/memory/memory.factor b/core/io/streams/memory/memory.factor
index e7b4338388..67dc53844e 100644
--- a/core/io/streams/memory/memory.factor
+++ b/core/io/streams/memory/memory.factor
@@ -3,13 +3,13 @@
 USING: kernel accessors alien alien.accessors math io ;
 IN: io.streams.memory
 
-TUPLE: memory-stream alien index ;
+TUPLE: memory-stream alien ;
 
 : <memory-stream> ( alien -- stream )
-    0 memory-stream boa ;
+    memory-stream boa ;
 
 M: memory-stream stream-element-type drop +byte+ ;
 
 M: memory-stream stream-read1
-    [ [ alien>> ] [ index>> ] bi alien-unsigned-1 ]
-    [ [ 1 + ] change-index drop ] bi ;
+    [ 1 over <displaced-alien> ] change-alien drop
+    0 alien-unsigned-1 ; inline