Add buffering to _FileInputStream implementation.

tests/standalone/io/file_input_stream_test.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 // Testing file input stream, VM-only, standalone test.
 
 #import("dart:io");
 #import("dart:isolate");
 
 // Helper method to be able to run the test from the runtime
 // directory, or the top directory.
 String getFilename(String path) =>
     new File(path).existsSync() ? path : '../$path';
 
 void testStringInputStreamSync() {
   String fileName = getFilename("tests/standalone/io/readuntil_test.dat");
   // File contains "Hello Dart\nwassup!\n"
   File file = new File(fileName);
+  int linesRead = 0;
   StringInputStream x = new StringInputStream(file.openInputStream());
   x.onLine = () {
-    // The file input stream is known (for now) to have read the whole
-    // file when the data handler is called.
     String line = x.readLine();
-    Expect.equals("Hello Dart", line);
-    line = x.readLine();
-    Expect.equals("wassup!", line);
+    linesRead++;
+    if (linesRead == 1) {
+      Expect.equals("Hello Dart", line);
+    } else if (linesRead == 2) {
+      Expect.equals("wassup!", line);
+    } else {
+      Expect.fail("More or less than 2 lines read ($linesRead lines read).");
+    }
   };
 }
 
 void testInputStreamAsync() {
   String fileName = getFilename("tests/standalone/io/readuntil_test.dat");
   // File contains "Hello Dart\nwassup!\n"
   var expected = "Hello Dart\nwassup!\n".charCodes();
   InputStream x = (new File(fileName)).openInputStream();
   var byteCount = 0;
   x.onData = () {
     Expect.equals(expected[byteCount], x.read(1)[0]);
     byteCount++;
   };
   x.onClosed = () {
     Expect.equals(expected.length, byteCount);
   };
 }
 
-
 void testStringInputStreamAsync(String name, int length) {
   String fileName = getFilename("tests/standalone/io/$name");
   // File contains 10 lines.
   File file = new File(fileName);
   Expect.equals(length, file.openSync().lengthSync());
   StringInputStream x = new StringInputStream(file.openInputStream());
   int lineCount = 0;
   x.onLine = () {
     var line = x.readLine();
     lineCount++;
     Expect.isTrue(lineCount <= 10);
     if (line[0] != "#") {
       Expect.equals("Line $lineCount", line);
     }
   };
   x.onClosed = () {
     Expect.equals(10, lineCount);
   };
 }
 
-
 void testChunkedInputStream() {
   // Force the test to timeout if it does not finish.
   ReceivePort done = new ReceivePort();
   done.receive((message, replyTo) { done.close(); });
 
   String fileName = getFilename("tests/standalone/io/readuntil_test.dat");
   // File contains 19 bytes ("Hello Dart\nwassup!")
   File file = new File(fileName);
   ChunkedInputStream x = new ChunkedInputStream(file.openInputStream());
   x.chunkSize = 9;
   x.onData = () {
     List<int> chunk = x.read();
     Expect.equals(9, chunk.length);
     x.chunkSize = 5;
     x.onData = () {
       chunk = x.read();
       Expect.equals(5, chunk.length);
       x.onData = () {
         chunk = x.read();
         Expect.equals(5, chunk.length);
         chunk = x.read();
         Expect.equals(null, chunk);
         done.toSendPort().send(null);
       };
     };
   };
 }
 
+void testUnreadyInputStream() {
+  String fileName = getFilename("tests/standalone/io/readuntil_test.dat");
+  var expected = "Hello Dart\nwassup!\n".charCodes();
+  InputStream x = (new File(fileName)).openInputStream();
+  List<int> buffer = new List<int>(100);
+
+  x.onData = () {
+    Expect.fail("Input stream closed before opening called onData handler.");
+  };
+
+  x.onClosed = () { };
+
+  // Called before stream is ready.
+  int read = x.readInto(buffer);
+  Expect.equals(0, read);
+
+  // Called before stream is ready.
+  x.close();
+}
+
 
 main() {
   testStringInputStreamSync();
   testInputStreamAsync();
   // Check the length of these files as both are text files where one
   // is without a terminating line separator which can easily be added
   // back if accidentally opened in a text editor.
   testStringInputStreamAsync("readline_test1.dat", 111);
   testStringInputStreamAsync("readline_test2.dat", 114);
   testChunkedInputStream();
+  testUnreadyInputStream();
 }