Add an utility interface ReaderProxy and its implementation for local file.

chrome/browser/chromeos/drive/drive_file_stream_reader_unittest.cc

+// Copyright 2013 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "chrome/browser/chromeos/drive/drive_file_stream_reader.h"
+
+#include <string>
+
+#include "base/file_util.h"
+#include "base/files/file_path.h"
+#include "base/message_loop.h"
+#include "chrome/browser/google_apis/test_util.h"
+#include "content/public/test/test_browser_thread.h"
+#include "net/base/file_stream.h"
+#include "net/base/io_buffer.h"
+#include "net/base/net_errors.h"
+#include "net/base/test_completion_callback.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+using content::BrowserThread;
+
+namespace drive {
+namespace internal {
+
+TEST(LocalReaderProxyTest, Read) {
+  // Prepare the test content.
+  const base::FilePath kTestFile(
+      google_apis::test_util::GetTestFilePath("chromeos/drive/applist.json"));
+  std::string expected_content;
+  ASSERT_TRUE(file_util::ReadFileToString(kTestFile, &expected_content));
+
+  // The LocaReaderProxy should live on IO thread.
+  MessageLoopForIO io_loop;
+  content::TestBrowserThread io_thread(BrowserThread::IO, &io_loop);
+
+  // Open the file first.
+  scoped_ptr<net::FileStream> file_stream(new net::FileStream(NULL));
+  net::TestCompletionCallback callback;
+  int result = file_stream->Open(
+      google_apis::test_util::GetTestFilePath("chromeos/drive/applist.json"),
+      base::PLATFORM_FILE_OPEN | base::PLATFORM_FILE_READ |
+      base::PLATFORM_FILE_ASYNC,
+      callback.callback());
+  ASSERT_EQ(net::OK, callback.GetResult(result));
+
+  // Test instance.
+  LocalReaderProxy proxy(file_stream.Pass());
+
+  // Prepare the buffer, whose size is smaller than the whole data size.
+  const int kBufferSize = 10;
+  ASSERT_LE(static_cast<size_t>(kBufferSize), expected_content.size());
+  scoped_refptr<net::IOBuffer> buffer(new net::IOBuffer(kBufferSize));
+
+  // Read repeatedly, until it is finished.
+  std::string concatenated_content;
+  while (concatenated_content.size() < expected_content.size()) {
+    result = proxy.Read(buffer.get(), kBufferSize, callback.callback());
+    result = callback.GetResult(result);
+
+    // The read content size should be smaller than the buffer size.
+    ASSERT_GT(result, 0);
+    ASSERT_LE(result, kBufferSize);
+    concatenated_content.append(buffer->data(), result);
+  }
+
+  // Make sure the read contant is as same as the file.
+  EXPECT_EQ(expected_content, concatenated_content);
+}
+
+}  // namespace internal
+}  // namespace drive