Detect file system errors during downloads.

net/base/mock_file_stream.h

+// Copyright (c) 2011 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.
+
+// This file defines MockFileStream, a test class for FileStream.
+
+#ifndef NET_BASE_MOCK_FILE_STREAM_H_
+#define NET_BASE_MOCK_FILE_STREAM_H_
+#pragma once
+
+#include "base/basictypes.h"
+#include "base/compiler_specific.h"
+#include "base/file_path.h"
+#include "net/base/file_stream.h"
+#include "net/base/net_errors.h"
+
+namespace testing {

[wtc, 2011/08/29 18:17:05]

IMPORTANT: I believe the top-level namespace "testing" is
used by gtest.  So we should either just use our namespace
"net", or make this nested inside our namespace "net".

[ahendrickson, 2011/08/29 19:42:38]

Now using the net::testing namespace.

+
+class MockFileStream : public net::FileStream {
+ public:
+  MockFileStream() : forced_error_(net::OK) {}
+
+  MockFileStream(base::PlatformFile file, int flags)
+      : net::FileStream(file, flags), forced_error_(net::OK) {}
+
+  // FileStream methods.
+  virtual int Open(const FilePath& path, int open_flags) OVERRIDE;
+  virtual int64 Seek(net::Whence whence, int64 offset) OVERRIDE;
+  virtual int64 Available() OVERRIDE;
+  virtual int Read(char* buf,
+                   int buf_len,
+                   net::CompletionCallback* callback) OVERRIDE;
+  virtual int ReadUntilComplete(char *buf, int buf_len) OVERRIDE;
+  virtual int Write(const char* buf,
+                    int buf_len,
+                    net::CompletionCallback* callback) OVERRIDE;
+  virtual int64 Truncate(int64 bytes) OVERRIDE;
+  virtual int Flush() OVERRIDE;

[wtc, 2011/08/29 18:17:05]

IMPORTANT: You didn't override the following methods:
  virtual void Close();
  virtual bool IsOpen() const;

Is that intentional?

[ahendrickson, 2011/08/29 19:42:38]

Yes.  Close() does not return an error code, so it doesn't need an override.

IsOpen() only reports the current state of the file handle, so it doesn't
either.

[wtc, 2011/08/29 20:03:59]

It seems that if MockFileStream::Open() fails, then
MockFileStream::IsOpen() should return false to be
consistent.  Is this guaranteed?  Anyway, this is just
a nit.  I just wanted to ask you to consider this.

+
+  void set_forced_error(int error) { forced_error_ = error; }
+  void clear_forced_error() { forced_error_ = net::OK; }
+  const FilePath& get_path() const { return path_; }
+
+ private:
+  int ReturnError(int function_error) {
+    if (forced_error_ != net::OK) {
+      int ret = forced_error_;
+      clear_forced_error();
+      return ret;
+    }
+
+    return function_error;
+  }
+
+  int64 ReturnError64(int64 function_error) {
+    if (forced_error_ != net::OK) {
+      int64 ret = forced_error_;
+      clear_forced_error();
+      return ret;
+    }
+
+    return function_error;
+  }
+
+  int forced_error_;
+  FilePath path_;
+};
+
+}  // namespace testing
+
+#endif  // NET_BASE_MOCK_FILE_STREAM_H_