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 {
+
+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) {}
+
+  void set_forced_error(int error) { forced_error_ = error; }
+  void clear_forced_error() { forced_error_ = net::OK; }
+
+  virtual int Open(const FilePath& path, int open_flags) OVERRIDE {
+    path_ = path;
+    return ReturnError(net::FileStream::Open(path, open_flags));
+  }
+
+  virtual int64 Seek(net::Whence whence, int64 offset) OVERRIDE {
+    return ReturnError64(net::FileStream::Seek(whence, offset));
+  }
+
+  virtual int64 Available() OVERRIDE {
+    return ReturnError64(net::FileStream::Available());
+  }
+
+  virtual int Read(char* buf, int buf_len, net::CompletionCallback* callback)
+      OVERRIDE {

[wtc, 2011/08/26 20:51:50]

Nit: it may be better to list net::CompletionCallback* callback)
on a separate line:
  virtual int Read(char* buf,
                   int buf_len,
                   net::CompletionCallback* callback) OVERRIDE {

This is how you formatted the Write() method.

[ahendrickson, 2011/08/26 21:06:54]

Done.

+    return ReturnError(net::FileStream::Read(buf, buf_len, callback));
+  }
+
+  virtual int ReadUntilComplete(char *buf, int buf_len) OVERRIDE {
+    return ReturnError(net::FileStream::ReadUntilComplete(buf, buf_len));
+  }
+
+  virtual int Write(const char* buf,
+                    int buf_len,
+                    net::CompletionCallback* callback) OVERRIDE {
+    return ReturnError(net::FileStream::Write(buf, buf_len, callback));
+  }
+
+  virtual int64 Truncate(int64 bytes) OVERRIDE {
+    return ReturnError64(net::FileStream::Truncate(bytes));
+  }
+
+  virtual int Flush() OVERRIDE {
+    return ReturnError(net::FileStream::Flush());
+  }
+
+  const FilePath& get_path() const { return path_; }

[wtc, 2011/08/26 20:51:50]

Nit: list get_path() along with the set_forced_error()
and clear_forced_error() methods above, because they're all
simple getters/setters.

[ahendrickson, 2011/08/26 21:06:54]

Done.

+
+ 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_