diff --git a/examples/src/main/java/org/capnproto/examples/AddressbookMain.java b/examples/src/main/java/org/capnproto/examples/AddressbookMain.java
index 024c4d6..d0570e6 100644
--- a/examples/src/main/java/org/capnproto/examples/AddressbookMain.java
+++ b/examples/src/main/java/org/capnproto/examples/AddressbookMain.java
@@ -1,11 +1,12 @@
 package org.capnproto.examples;
 
 import java.io.FileOutputStream;
+import java.io.FileInputStream;
 import java.io.FileDescriptor;
 
 import org.capnproto.MessageBuilder;
 import org.capnproto.MessageReader;
-import org.capnproto.InputStreamMessageReader;
+import org.capnproto.ByteChannelMessageReader;
 import org.capnproto.Serialize;
 import org.capnproto.StructList;
 import org.capnproto.Text;
@@ -47,7 +48,8 @@ public class AddressbookMain {
     }
 
     public static void printAddressBook() throws java.io.IOException {
-        MessageReader message = InputStreamMessageReader.create(System.in);
+        MessageReader message = ByteChannelMessageReader.create(
+            (new FileInputStream(FileDescriptor.in)).getChannel());
         AddressBook.Reader addressbook = message.getRoot(AddressBook.factory);
         for(Person.Reader person : addressbook.getPeople()) {
             System.out.println(person.getName() + ": " + person.getEmail());
diff --git a/runtime/src/main/java/org/capnproto/InputStreamMessageReader.java b/runtime/src/main/java/org/capnproto/ByteChannelMessageReader.java
similarity index 53%
rename from runtime/src/main/java/org/capnproto/InputStreamMessageReader.java
rename to runtime/src/main/java/org/capnproto/ByteChannelMessageReader.java
index 5435d0b..0ca0fa3 100644
--- a/runtime/src/main/java/org/capnproto/InputStreamMessageReader.java
+++ b/runtime/src/main/java/org/capnproto/ByteChannelMessageReader.java
@@ -1,37 +1,33 @@
 package org.capnproto;
 
 import java.io.IOException;
-import java.io.InputStream;
 import java.nio.ByteBuffer;
 import java.nio.ByteOrder;
+import java.nio.channels.ReadableByteChannel;
 import java.util.ArrayList;
 
-public final class InputStreamMessageReader {
+public final class ByteChannelMessageReader {
 
-    static byte[] readExact(InputStream is, int length) throws IOException {
-        byte[] bytes = new byte[length];
-
-        int bytesRead = 0;
-        while (bytesRead < length) {
-            int r = is.read(bytes, bytesRead, length - bytesRead);
-            if (r < 0) {
-                throw new IOException("premature EOF");
-            }
-            bytesRead += r;
-        }
-
-        return bytes;
-    }
-
-    static ByteBuffer makeByteBuffer(byte[] bytes) {
-        ByteBuffer result = ByteBuffer.wrap(bytes);
+    static ByteBuffer makeByteBuffer(int bytes) {
+        ByteBuffer result = ByteBuffer.allocate(bytes);
         result.order(ByteOrder.LITTLE_ENDIAN);
         result.mark();
         return result;
     }
 
-    public static MessageReader create(InputStream is) throws IOException {
-        ByteBuffer firstWord = makeByteBuffer(readExact(is, 8));
+    static void fillBuffer(ByteBuffer buffer, ReadableByteChannel bc) throws IOException {
+        while(buffer.hasRemaining()) {
+            int r = bc.read(buffer);
+            if (r < 0) {
+                throw new IOException("premature EOF");
+            }
+            // TODO check for r == 0 ?.
+        }
+    }
+
+    public static MessageReader create(ReadableByteChannel bc) throws IOException {
+        ByteBuffer firstWord = makeByteBuffer(Constants.BYTES_PER_WORD);
+        fillBuffer(firstWord, bc);
 
         int segmentCount = 1 + firstWord.getInt(0);
 
@@ -50,7 +46,8 @@ public final class InputStreamMessageReader {
         ArrayList<Integer> moreSizes = new ArrayList<Integer>();
 
         if (segmentCount > 1) {
-            ByteBuffer moreSizesRaw = makeByteBuffer(readExact(is, 4 * (segmentCount & ~1)));
+            ByteBuffer moreSizesRaw = makeByteBuffer(4 * (segmentCount & ~1));
+            fillBuffer(moreSizesRaw, bc);
             for (int ii = 0; ii < segmentCount - 1; ++ii) {
                 int size = moreSizesRaw.getInt(ii * 4);
                 moreSizes.add(size);
@@ -60,18 +57,23 @@ public final class InputStreamMessageReader {
 
         // TODO check that totalWords is reasonable
 
-        byte[] allSegments = readExact(is, totalWords * 8);
+        ByteBuffer allSegments = makeByteBuffer(totalWords * Constants.BYTES_PER_WORD);
+        fillBuffer(allSegments, bc);
 
         ByteBuffer[] segmentSlices = new ByteBuffer[segmentCount];
 
-        segmentSlices[0] = ByteBuffer.wrap(allSegments, 0, segment0Size * 8);
+        segmentSlices[0] = ByteBuffer.wrap(allSegments.array(),
+                                           0,
+                                           segment0Size * Constants.BYTES_PER_WORD);
         segmentSlices[0].order(ByteOrder.LITTLE_ENDIAN);
         segmentSlices[0].mark();
 
         int offset = segment0Size;
 
         for (int ii = 1; ii < segmentCount; ++ii) {
-            segmentSlices[ii] = ByteBuffer.wrap(allSegments, offset * 8, moreSizes.get(ii - 1) * 8);
+            segmentSlices[ii] = ByteBuffer.wrap(allSegments.array(),
+                                                offset * Constants.BYTES_PER_WORD,
+                                                moreSizes.get(ii - 1) * Constants.BYTES_PER_WORD);
             segmentSlices[ii].order(ByteOrder.LITTLE_ENDIAN);
             segmentSlices[ii].mark();
             offset += moreSizes.get(ii - 1);