CRX FileSystem Pepper private API

ppapi/examples/crxfs/crxfs.cc

+// Copyright (c) 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 <stdio.h>
+#include "ppapi/c/ppb_file_io.h"
+#include "ppapi/cpp/file_io.h"
+#include "ppapi/cpp/instance.h"
+#include "ppapi/cpp/module.h"
+#include "ppapi/cpp/private/ext_crx_file_system_private.h"
+#include "ppapi/utility/completion_callback_factory.h"
+
+// When compiling natively on Windows, PostMessage can be #define-d to
+// something else.
+#ifdef PostMessage
+#undef PostMessage
+#endif
+
+// Buffer size for reading network data.
+const int kBufSize = 1024;

[palmer, 2013/05/02 21:30:09]

size_t

[victorhsieh, 2013/05/03 17:26:58]

Done.

+
+class MyInstance : public pp::Instance {
+ public:
+  explicit MyInstance(PP_Instance instance)
+      : pp::Instance(instance),
+        handle_(instance) {
+    factory_.Initialize(this);
+  }
+  virtual ~MyInstance() {
+  }
+
+  // Handler for the page sending us messages.
+  virtual void HandleMessage(const pp::Var& message_data);
+
+ private:
+  void OpenCrxFsAndReadFile(const std::string& filename);
+
+  void CrxFileSystemCallback(int32_t pp_error, pp::FileSystem file_system);
+  void FileIOOpenCallback(int32_t pp_error);
+  void FileIOReadCallback(int32_t pp_error);
+
+  // Forwards the given string to the page.
+  void ReportResponse(const char* name, int32_t pp_error);
+
+  // Generates completion callbacks scoped to this class.
+  pp::CompletionCallbackFactory<MyInstance> factory_;
+
+  pp::InstanceHandle handle_;
+  pp::ExtCrxFileSystemPrivate crxfs_;
+  pp::FileSystem fs_;
+  pp::FileRef file_ref_;
+  pp::FileIO file_io_;
+  std::string filename_;
+  char read_buf_[8192];

[palmer, 2013/05/02 21:30:09]

Not kBufSize?

[victorhsieh, 2013/05/03 17:26:58]

Done.

+};
+
+void MyInstance::HandleMessage(const pp::Var& message_data) {
+  if (!message_data.is_string()) {
+    ReportResponse("HandleMessage: not a string", 0);
+    return;
+  }
+  std::string filename = message_data.AsString();
+  OpenCrxFsAndReadFile(filename);
+}
+
+void MyInstance::OpenCrxFsAndReadFile(const std::string& filename) {
+  filename_ = filename;
+
+  pp::CompletionCallbackWithOutput<pp::FileSystem>

[palmer, 2013/05/02 21:30:09]

Nit:

  pp::CompletionCallbackWithOutput<pp::FileSystem> callback = 
      factory_.NewCallbackWithOutput(&MyInstance::CrxFileSystemCallback);

[victorhsieh, 2013/05/03 17:26:58]

Done.

+      callback = factory_.NewCallbackWithOutput(
+          &MyInstance::CrxFileSystemCallback);
+
+  crxfs_ = pp::ExtCrxFileSystemPrivate(this);
+  int32_t rv = crxfs_.Open(callback);
+  if (rv != PP_OK_COMPLETIONPENDING)
+    ReportResponse("ExtCrxFileSystemPrivate::Open", rv);
+}
+
+void MyInstance::CrxFileSystemCallback(int32_t pp_error,
+                                       pp::FileSystem file_system) {
+  if (pp_error != PP_OK) {
+    ReportResponse("CrxFileSystemCallback", pp_error);
+    return;
+  }
+
+  file_io_ = pp::FileIO(handle_);
+  file_ref_ = pp::FileRef(file_system, filename_.c_str());
+  int32_t rv = file_io_.Open(
+      file_ref_, PP_FILEOPENFLAG_READ,
+      factory_.NewCallback(&MyInstance::FileIOOpenCallback));
+  if (rv != PP_OK_COMPLETIONPENDING)
+    ReportResponse("FileIO::Open", rv);
+}
+
+void MyInstance::FileIOOpenCallback(int32_t pp_error) {
+  if (pp_error != PP_OK) {
+    ReportResponse("FileIOOpenCallback", pp_error);
+    return;
+  }
+
+  int32_t rv = file_io_.Read(0, read_buf_, sizeof(read_buf_),
+      factory_.NewCallback(&MyInstance::FileIOReadCallback));
+  if (rv != PP_OK_COMPLETIONPENDING) {
+    ReportResponse("FileIO::Read", rv);
+    return;
+  }
+}
+
+void MyInstance::FileIOReadCallback(int32_t pp_error) {
+  if (pp_error < 0) {
+    ReportResponse("FileIOReadCallback", pp_error);
+    return;
+  }
+
+  std::string content;
+  content.append(read_buf_, pp_error);

[palmer, 2013/05/02 21:30:09]

Check that pp_error is not > sizeof(read_buf_), and then also
static_cast<size_t>.

[victorhsieh, 2013/05/03 17:26:58]

I think this is a serious API bug if it's true.  FileIO::Read guarantee to read
at most sizeof(read_buf_) bytes.  And I'd keep this simple to understand as this
is an example.

+  PostMessage(pp::Var(content));
+}
+
+void MyInstance::ReportResponse(const char* name, int32_t rv) {
+  char buf[1024];
+  snprintf(buf, sizeof(buf), "%s failed, pp_error: %d", name, rv);

[palmer, 2013/05/02 21:30:09]

Why not StringPrintf?

Alternately, check the return value of snprintf to verify that the output string
did not have to be truncated to fit in sizeof(buf) chars.

[victorhsieh, 2013/05/03 17:26:58]

I think most developer don't have StringPrintf, so we better not use it in this
example.

+  PostMessage(pp::Var(buf));
+}
+
+// This object is the global object representing this plugin library as long
+// as it is loaded.
+class MyModule : public pp::Module {
+ public:
+  MyModule() : pp::Module() {}
+  virtual ~MyModule() {}
+
+  // Override CreateInstance to create your customized Instance object.
+  virtual pp::Instance* CreateInstance(PP_Instance instance) {
+    return new MyInstance(instance);
+  }
+};
+
+namespace pp {
+
+// Factory function for your specialization of the Module object.
+Module* CreateModule() {
+  return new MyModule();
+}
+
+}  // namespace pp
+