[NaCl SDK] Expose Google Drive to nacl_io.

native_client_sdk/src/libraries/nacl_io/googledrivefs/googledrivefs.cc

+// Copyright 2016 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 "nacl_io/googledrivefs/googledrivefs.h"
+
+#include <fcntl.h>
+
+#include <map>
+#include <algorithm>
+#include <cstdio>
+
+#include "ppapi/cpp/url_request_info.h"
+#include "ppapi/cpp/url_response_info.h"
+#include "ppapi/cpp/url_loader.h"
+#include "ppapi/cpp/file_ref.h"
+#include "ppapi/cpp/file_io.h"
+
+#include "nacl_io/error.h"
+#include "nacl_io/pepper_interface.h"
+#include "ppapi/c/pp_completion_callback.h"
+
+#include "json/reader.h"

[binji, 2016/07/18 23:24:02]

nacl_io currently does not depend on json; We're not going to want to add it as
a new dependency.

[chanpatorikku, 2016/08/07 02:41:02]

Done.

Thanks.
Not going to add it as a new dependency.

+#include "json/writer.h"
+
+#include "nacl_io/filesystem.h"
+#include "nacl_io/kernel_handle.h"
+#include "nacl_io/getdents_helper.h"
+
+#ifdef WIN32
+#include <windows.h>

[binji, 2016/07/18 23:24:02]

what is this needed for?

[chanpatorikku, 2016/08/07 02:41:02]

This used to be needed for Sleep() from windows.h.
Originally the implementation used usleep().
I saw that in Windows, Sleep(), but not usleep(), is used, and Sleep() is
included from windows.h.
The current submission removes windows.h and does not use Sleep() & usleep().
 

+#else
+#include <unistd.h>
+#endif
+
+namespace nacl_io {
+
+namespace {
+
+std::string MapToHeaders(
+    const std::map<std::string, std::string>& header_field_map) {
+  std::string request_headers = "";
+
+  for (std::map<std::string, std::string>::const_iterator it =
+           header_field_map.begin();
+       it != header_field_map.end(); ++it) {
+    request_headers += it->first;
+    request_headers += ": ";
+    request_headers += it->second;
+    request_headers += "\n";
+  }
+  return request_headers;
+}
+
+// Continuing DJB2a hash
+ino_t HashPathSegment(ino_t hash, const char* str, size_t len) {
+  // First add the path seperator
+  hash = (hash * static_cast<ino_t>(33)) ^ '/';
+  while (len--) {
+    hash = (hash * static_cast<ino_t>(33)) ^ *str++;
+  }
+  return hash;
+}
+
+ino_t HashPath(const Path& path) {

[binji, 2016/07/18 23:24:02]

better to share the code with Html5Fs rather than duplicating it here.

[chanpatorikku, 2016/08/07 02:41:02]

Done.

Thanks.
Shared the code with Html5Fs.
 

+  // Prime the DJB2a hash
+  ino_t hash = 5381;
+
+  // Apply a running DJB2a to each part of the path
+  for (size_t segment = 0; segment < path.Size(); segment++) {
+    const std::string& part = path.Part(segment);
+    hash = HashPathSegment(hash, part.c_str(), part.length());
+  }
+  return hash;
+}
+
+// A Google Drive item is a file or a directory.
+// RequestDirId requests to see if a directory with dir_name
+// and a parent with ID parent_dir_id is there.
+// If it is, dir_id is set.
+// RequestDirId returns ENOENT when a file with dir_name is there
+// but a directory with dir_name is not.
+Error RequestDirId(const std::string& parent_dir_id,
+                   const std::string& dir_name,
+                   Filesystem* filesystem,
+                   std::string& dir_id) {
+  dir_id = "";
+
+  std::string url = "https://www.googleapis.com/drive/v3/files";

[binji, 2016/07/18 23:24:02]

It's better to have these strings be constants (as much as possible) rather than
build them up inside the function.

[chanpatorikku, 2016/08/07 02:41:02]

Each URL may be different.
I don't know if the current submission, which imitates how the Drive example
implements the URL strings, 
is practical.
Please review the codes that imitates the Drive example on implementing the URL
strings.
The lines of codes are commented for review.

+  url += "?";
+  url += "q=";
+  url += "%27";
+  url += parent_dir_id;
+  url += "%27+in+parents";
+  url += "+and+";
+  url += "mimeType+=+";
+  url += "%27application/vnd.google-apps.folder%27";
+  url += "+and+";
+  url += "name+=+%27" + dir_name + "%27";
+
+  GoogleDriveFs* googledrivefs = dynamic_cast<GoogleDriveFs*>(filesystem);

[binji, 2016/07/18 23:24:02]

don't use dynamic_cast, it relies on RTTI. static_cast is sufficient, as these
functions should never be called when the filesystem is not a GoogleDriveFs.

[chanpatorikku, 2016/08/07 02:41:02]

Done.

Thanks.
static_cast is called in the current submission.

+  if (googledrivefs == NULL) {
+    return EINVAL;
+  }
+
+  pp::URLLoader loader(pp::InstanceHandle(googledrivefs->instance()));

[binji, 2016/07/18 23:24:02]

nacl_io uses the Pepper C interface, not the C++ interface.

[chanpatorikku, 2016/08/07 02:41:02]

Done.

Thanks.
Pepper C interface is used in the current submission.

+  pp::URLRequestInfo request(pp::InstanceHandle(googledrivefs->instance()));
+
+  bool set_url_ok = request.SetURL(url);

[binji, 2016/07/18 23:24:02]

it's better to just inline this than to create a new variable that's only used
once

[chanpatorikku, 2016/08/07 02:41:02]

I don't know exactly about inlining.
Please review the codes that attempts inlining.
The lines of codes are commented for review.

+  if (!set_url_ok) {
+    return EPERM;
+  }
+
+  bool set_method_ok = request.SetMethod("GET");
+  if (!set_method_ok) {
+    return EPERM;
+  }
+
+  std::map<std::string, std::string> headers_map;

[binji, 2016/07/18 23:24:02]

This seems to be duplicated a number of times in the file, it should probably be
a function.

You might try factoring it in a similar way as done in the Drive example.

[chanpatorikku, 2016/08/07 02:41:02]

Done.

Thanks.
Tried factoring it in a similar way as done in the Drive example.

+  headers_map["Content-type"] = "application/json";
+  std::string authorization_value = "Bearer ";
+  authorization_value += googledrivefs->token();
+  headers_map["Authorization"] = authorization_value;
+
+  std::string headers = MapToHeaders(headers_map);
+
+  bool set_headers_ok = request.SetHeaders(headers);
+  if (!set_headers_ok) {
+    return EPERM;
+  }
+
+  bool set_allow_cross_origin_requests_ok =
+      request.SetAllowCrossOriginRequests(true);
+  if (!set_allow_cross_origin_requests_ok) {
+    return EPERM;
+  }
+
+  bool set_stream_to_file_ok = request.SetStreamToFile(true);
+  if (!set_stream_to_file_ok) {
+    return EPERM;
+  }
+
+  int32_t err = loader.Open(request, pp::BlockUntilComplete());
+  if (err < 0) {
+    return PPERROR_TO_ERRNO(err);
+  }
+
+  pp::URLResponseInfo response = loader.GetResponseInfo();
+  if (response.GetStatusCode() != 200) {
+    return EPERM;
+  }
+
+  pp::FileRef file_ref = response.GetBodyAsFileRef();
+  pp::FileIO file_io(pp::InstanceHandle(googledrivefs->instance()));
+
+  int32_t open_result =
+      file_io.Open(file_ref, PP_FILEOPENFLAG_READ, pp::BlockUntilComplete());
+  if (open_result < 0) {
+    return PPERROR_TO_ERRNO(open_result);
+  }
+
+  int BUFFER_SIZE = 1024;
+  char buffer[BUFFER_SIZE];

[binji, 2016/07/18 23:24:02]

What if the result is greater than 1024 bytes?

[chanpatorikku, 2016/08/07 02:41:02]

Done.

Thanks.
Code is rewritten for the result greater than 1024 bytes in the current
submission.

+
+  int32_t byte_read =
+      file_io.Read(0, buffer, BUFFER_SIZE, pp::BlockUntilComplete());
+  while (byte_read == 0) {

[binji, 2016/07/18 23:24:02]

This loop is strange, what problem are you trying to fix? Ultimately, the
responsibility of retrying a failed read is up to the caller.

[chanpatorikku, 2016/08/07 02:41:02]

Done.

The problem I was trying to fix was that FileIoInterface Read() returned 0 bytes
for multiple calls
before returning >0 bytes.  The original work around was to have a while loop
with usleep() so the 
bytes could be read until >0 bytes were read from FileIoInterface Read().

The problem has been fixed by using URLLoaderInterface FinishStreamingToFile().
Calling URLLoaderInterface FinishStreamingToFile before FileIoInterface Read()
reads >0 bytes
in the first call of FileIoInterface Read().

+#ifdef WIN32
+    Sleep(1000);
+#else
+    usleep(1000000);

[binji, 2016/07/18 23:24:02]

We never want to call sleep in nacl_io, it's usually a sign that there is a
timing bug.

[chanpatorikku, 2016/08/07 02:41:02]

Done.

Sleep is not called in nacl_io in the current submission.

+#endif
+
+    byte_read = file_io.Read(0, buffer, BUFFER_SIZE, pp::BlockUntilComplete());
+  }
+
+  if (byte_read < 0) {
+    return PPERROR_TO_ERRNO(byte_read);
+  }
+
+  std::string output(buffer);
+
+  Json::Value root;
+
+  Json::Reader reader(Json::Features::strictMode());
+  if (!reader.parse(output, root, false)) {
+    return EPERM;
+  }
+
+  if (!root.isMember("files")) {
+    return EPERM;
+  }
+
+  Json::Value files_array = root["files"];
+  if (!files_array.isArray()) {
+    return EPERM;
+  }
+  if (files_array.size() == 0) {
+    return ENOENT;
+  }
+
+  dir_id = files_array[0]["id"].asString();
+
+  return 0;
+}
+
+// A Google Drive item is a file or a directory.
+// RequestItemId requests to see if either a file with item_name
+// or a directory with item_name is there.
+// If it is, item_id is set.
+Error RequestItemId(const std::string& parent_dir_id,
+                    const std::string& item_name,
+                    Filesystem* filesystem,
+                    std::string& item_id) {
+  item_id = "";
+
+  std::string url = "https://www.googleapis.com/drive/v3/files";
+  url += "?";
+  url += "q=";
+  url += "%27";
+  url += parent_dir_id;
+  url += "%27+in+parents";
+  url += "+and+";
+  url += "name+=+%27" + item_name + "%27";
+
+  GoogleDriveFs* googledrivefs = dynamic_cast<GoogleDriveFs*>(filesystem);
+  if (googledrivefs == NULL) {
+    return EINVAL;
+  }
+
+  pp::URLLoader loader(pp::InstanceHandle(googledrivefs->instance()));
+  pp::URLRequestInfo request(pp::InstanceHandle(googledrivefs->instance()));
+
+  bool set_url_ok = request.SetURL(url);
+  if (!set_url_ok) {
+    return EPERM;
+  }
+
+  bool set_method_ok = request.SetMethod("GET");
+  if (!set_method_ok) {
+    return EPERM;
+  }
+
+  std::map<std::string, std::string> headers_map;
+  headers_map["Content-type"] = "application/json";
+  std::string authorization_value = "Bearer ";
+  authorization_value += googledrivefs->token();
+  headers_map["Authorization"] = authorization_value;
+
+  std::string headers = MapToHeaders(headers_map);
+
+  bool set_headers_ok = request.SetHeaders(headers);
+  if (!set_headers_ok) {
+    return EPERM;
+  }
+
+  bool set_allow_cross_origin_requests_ok =
+      request.SetAllowCrossOriginRequests(true);
+  if (!set_allow_cross_origin_requests_ok) {
+    return EPERM;
+  }
+
+  bool set_stream_to_file_ok = request.SetStreamToFile(true);
+  if (!set_stream_to_file_ok) {
+    return EPERM;
+  }
+
+  int32_t err = loader.Open(request, pp::BlockUntilComplete());
+  if (err < 0) {
+    return PPERROR_TO_ERRNO(err);
+  }
+
+  pp::URLResponseInfo response = loader.GetResponseInfo();
+  if (response.GetStatusCode() != 200) {
+    return EPERM;
+  }
+
+  pp::FileRef file_ref = response.GetBodyAsFileRef();
+  pp::FileIO file_io(pp::InstanceHandle(googledrivefs->instance()));
+
+  int32_t open_result =
+      file_io.Open(file_ref, PP_FILEOPENFLAG_READ, pp::BlockUntilComplete());
+  if (open_result < 0) {
+    return PPERROR_TO_ERRNO(open_result);
+  }
+
+  int BUFFER_SIZE = 1024;
+  char buffer[BUFFER_SIZE];
+
+  int32_t byte_read =
+      file_io.Read(0, buffer, BUFFER_SIZE, pp::BlockUntilComplete());
+  while (byte_read == 0) {
+#ifdef WIN32
+    Sleep(1000);
+#else
+    usleep(1000000);
+#endif
+
+    byte_read = file_io.Read(0, buffer, BUFFER_SIZE, pp::BlockUntilComplete());
+  }
+
+  if (byte_read < 0) {
+    return PPERROR_TO_ERRNO(byte_read);
+  }
+
+  std::string output(buffer);
+
+  Json::Value root;
+
+  Json::Reader reader(Json::Features::strictMode());
+  if (!reader.parse(output, root, false)) {
+    return EPERM;
+  }
+
+  if (!root.isMember("files")) {
+    return EPERM;
+  }
+
+  Json::Value files_array = root["files"];
+
+  if (!files_array.isArray()) {
+    return EPERM;
+  }
+  if (files_array.size() == 0) {
+    return ENOENT;
+  }
+
+  item_id = files_array[0]["id"].asString();
+
+  return 0;
+}
+
+Error RequestParentDirId(const Path& path,
+                         Filesystem* filesystem,
+                         std::string& parent_dir_id) {

[binji, 2016/07/18 23:24:02]

Out parameters should be pointers, not references, according to the style guide.

[chanpatorikku, 2016/08/07 02:41:02]

Done.

Thanks.
Out parameters are pointers and are placed at last parameters in a function from
what the style guide writes.

+  parent_dir_id = "";
+
+  if (path.Size() < 2) {
+    return EINVAL;
+  }
+
+  std::string helper_parent_dir_id = "root";
+
+  for (unsigned int i = 1; i < path.Size() - 1; ++i) {
+    std::string dir_name = path.Range(i, i + 1);
+
+    std::string dir_id = "";
+    Error error =
+        RequestDirId(helper_parent_dir_id, dir_name, filesystem, dir_id);
+    if (error) {
+      return error;
+    }
+
+    helper_parent_dir_id = dir_id;
+  }
+  parent_dir_id = helper_parent_dir_id;
+
+  return 0;
+}
+}
+
+class GoogleDriveFsNode : public Node {

[binji, 2016/07/18 23:24:02]

It's generally nicer when the nodes are defined in a separate file.

[chanpatorikku, 2016/08/07 02:41:02]

Done.

Thanks.
Nodes are defined in a separate file in the current submission.

+ public:
+  GoogleDriveFsNode(Filesystem* filesystem, Path path)
+      : Node(filesystem), path_(path) {}
+
+  Error GetDents(size_t offs,
+                 struct dirent* pdir,
+                 size_t size,
+                 int* out_bytes) {
+    if (!IsaDir()) {
+      return ENOTDIR;
+    }
+
+    const ino_t kCurDirIno = -1;
+    const ino_t kParentDirIno = -2;
+    GetDentsHelper helper(kCurDirIno, kParentDirIno);
+
+    std::vector<std::string> dirent_names;
+    Error error = RequestDirent(dirent_names);
+    if (error) {
+      return error;
+    }
+
+    for (unsigned int i = 0; i < dirent_names.size(); ++i) {
+      Path child_path(path_);
+      child_path = child_path.Append("/" + dirent_names[i]);
+      ino_t child_ino = HashPath(child_path);
+
+      helper.AddDirent(child_ino, dirent_names[i].c_str(),
+                       dirent_names[i].size());
+    }
+
+    return helper.GetDents(offs, pdir, size, out_bytes);
+  }
+
+  Error GetStat(struct stat* pstat) {
+    Error error = GetSize(&pstat->st_size);
+    if (error) {
+      return error;
+    }
+    return 0;
+  }
+
+  Error Write(const HandleAttr& attr,
+              const void* buf,
+              size_t count,
+              int* out_bytes) {
+    *out_bytes = 0;
+
+    if (IsaDir()) {
+      return EISDIR;
+    }
+
+    off_t file_size = 0;
+    Error error = GetSize(&file_size);
+    if (error) {
+      return error;
+    }
+
+    off_t file_buf_size = std::max((unsigned long long int)file_size,
+                                   (unsigned long long int)attr.offs + count);
+    char file_buf[file_buf_size];

[binji, 2016/07/18 23:24:02]

This will allocate space for the file on the stack. Typical stack sizes are
measured in megabytes, so this won't allow for files larger than that.

[chanpatorikku, 2016/08/07 02:41:02]

Done.

Thanks.
Heap memory, as automatically allocated in string class and vector class, is
used in the current submission.

+
+    if (file_size > 0) {
+      int read_helper_out_bytes = 0;
+
+      error = ReadHelper(0, file_size - 1, file_buf, file_size,
+                         &read_helper_out_bytes);
+
+      if (error) {
+        return error;
+      }
+
+      if (read_helper_out_bytes != file_size) {
+        return EPERM;
+      }
+    }
+
+    char* pChar = (char*)buf;
+    for (unsigned int i = 0; i < count; ++i) {
+      file_buf[attr.offs + i] = pChar[i];
+    }
+
+    error = WriteHelper(file_buf, file_buf_size);
+    if (error) {
+      return error;
+    }
+
+    *out_bytes = count;
+
+    return 0;
+  }
+
+  Error FTruncate(off_t length) {
+    if (IsaDir()) {
+      return EISDIR;
+    }
+
+    off_t file_size = 0;
+    Error error = GetSize(&file_size);
+    if (error) {
+      return error;
+    }
+
+    char file_buf[length];
+
+    if (file_size > 0) {
+      int read_helper_out_bytes = 0;
+
+      error = ReadHelper(0, file_size - 1, file_buf, file_size,
+                         &read_helper_out_bytes);
+      if (error) {
+        return error;
+      }
+
+      if (read_helper_out_bytes != file_size) {
+        return EPERM;
+      }
+    }
+
+    for (int i = file_size; i < length; ++i) {
+      file_buf[i] = '\0';
+    }
+
+    error = WriteHelper(file_buf, length);
+    if (error) {
+      return error;
+    }
+
+    return 0;
+  }
+
+  Error Read(const HandleAttr& attr, void* buf, size_t count, int* out_bytes) {
+    *out_bytes = 0;
+
+    if (IsaDir()) {
+      return EISDIR;
+    }
+
+    Error error =
+        ReadHelper(attr.offs, attr.offs + count - 1, buf, count, out_bytes);
+    if (error) {
+      return error;
+    }
+
+    return 0;
+  }
+
+  int GetType() { return IsaDir() ? S_IFDIR : S_IFREG; }
+
+  Error GetSize(off_t* out_size) {
+    *out_size = 0;
+
+    if (IsaDir()) {
+      return 0;
+    }
+
+    GoogleDriveFs* googledrivefs = dynamic_cast<GoogleDriveFs*>(filesystem_);
+    if (googledrivefs == NULL) {
+      return EINVAL;
+    }
+
+    pp::URLLoader loader(pp::InstanceHandle(googledrivefs->instance()));
+    pp::URLRequestInfo request(pp::InstanceHandle(googledrivefs->instance()));
+
+    std::string url = "https://www.googleapis.com/drive/v3/files/";
+    url += item_id_;
+    url += "?";
+    url += "fields=size";
+
+    bool set_url_ok = request.SetURL(url);
+    if (!set_url_ok) {
+      return EPERM;
+    }
+
+    bool set_method_ok = request.SetMethod("GET");
+    if (!set_method_ok) {
+      return EPERM;
+    }
+
+    std::map<std::string, std::string> headers_map;
+    headers_map["Content-type"] = "application/json";
+    std::string authorization_value = "Bearer ";
+    authorization_value += googledrivefs->token();
+    headers_map["Authorization"] = authorization_value;
+
+    std::string headers = MapToHeaders(headers_map);
+
+    bool set_headers_ok = request.SetHeaders(headers);
+    if (!set_headers_ok) {
+      return EPERM;
+    }
+
+    bool set_allow_cross_origin_requests_ok =
+        request.SetAllowCrossOriginRequests(true);
+    if (!set_allow_cross_origin_requests_ok) {
+      return EPERM;
+    }
+
+    bool set_stream_to_file_ok = request.SetStreamToFile(true);
+    if (!set_stream_to_file_ok) {
+      return EPERM;
+    }
+
+    int32_t err = loader.Open(request, pp::BlockUntilComplete());
+    if (err < 0) {
+      return PPERROR_TO_ERRNO(err);
+    }
+
+    pp::URLResponseInfo response = loader.GetResponseInfo();
+    if (response.GetStatusCode() != 200) {
+      return EPERM;
+    }
+
+    pp::FileRef file_ref = response.GetBodyAsFileRef();
+    pp::FileIO file_io(pp::InstanceHandle(googledrivefs->instance()));
+    int32_t open_result =
+        file_io.Open(file_ref, PP_FILEOPENFLAG_READ, pp::BlockUntilComplete());
+
+    if (open_result < 0) {
+      return PPERROR_TO_ERRNO(open_result);
+    }
+
+    int BUFFER_SIZE = 1024;
+    char buffer[BUFFER_SIZE];
+
+    int32_t byte_read =
+        file_io.Read(0, buffer, BUFFER_SIZE, pp::BlockUntilComplete());
+    while (byte_read == 0) {
+#ifdef WIN32
+      Sleep(1000);
+#else
+      usleep(1000000);
+#endif
+
+      byte_read =
+          file_io.Read(0, buffer, BUFFER_SIZE, pp::BlockUntilComplete());
+    }
+    if (byte_read < 0) {
+      return PPERROR_TO_ERRNO(byte_read);
+    }
+
+    std::string output(buffer);
+    Json::Value root;
+
+    Json::Reader reader(Json::Features::strictMode());
+    if (!reader.parse(output, root, false)) {
+      return EPERM;
+    }
+
+    if (!root.isMember("size")) {
+      return EPERM;
+    }
+
+    Json::Value size_value = root["size"];
+
+    *out_size = (off_t)atoi(size_value.asCString());
+
+    return 0;
+  }
+
+  Error Init(int open_flags) {
+    Error error = Node::Init(open_flags);
+
+    if (error) {
+      return error;
+    }
+
+    if (path_.Size() == 1) {
+      parent_dir_id_ = "";
+      item_id_ = "root";
+      is_dir_item_ = true;
+      return 0;
+    }
+
+    error = RequestParentDirId(path_, filesystem_, parent_dir_id_);
+    if (error) {
+      return error;
+    }
+
+    // Request the ID of an item, which is a file or a directory
+    error =
+        RequestItemId(parent_dir_id_, path_.Basename(), filesystem_, item_id_);
+
+    if (error == ENOENT) {
+      // Only files are open as mode O_CREAT
+      if ((open_flags & O_CREAT) != 0) {
+        error = CreateEmptyFile();
+        if (error) {
+          return error;
+        }
+        error = RequestItemId(parent_dir_id_, path_.Basename(), filesystem_,
+                              item_id_);
+        if (error) {
+          return error;
+        }
+        is_dir_item_ = false;
+      } else {
+        return ENOENT;
+      }
+    } else if (error) {
+      return error;
+    } else {
+      std::string dir_id = "";
+      error =
+          RequestDirId(parent_dir_id_, path_.Basename(), filesystem_, dir_id);
+      if (error == ENOENT) {
+        is_dir_item_ = false;
+      } else if (error) {
+        return error;
+      } else {
+        is_dir_item_ = true;
+      }
+
+      if (open_flags == 0) {
+        // open_flags == 0 for file opened on fopen with mode r and directory
+        // opened on opendir
+        return 0;
+      } else if (is_dir_item_ && open_flags != 0) {
+        return EPERM;
+      } else if ((open_flags & O_TRUNC) != 0) {
+        error = WriteHelper(NULL, 0);
+        if (error) {
+          return error;
+        }
+      }
+    }
+
+    return 0;
+  }
+
+  void Destroy() { Node::Destroy(); }
+
+  bool IsaDir() { return is_dir_item_; }
+
+ private:
+  Error ReadHelper(off_t start,
+                   off_t end,
+                   void* buf,
+                   size_t count,
+                   int* out_bytes) {
+    *out_bytes = 0;
+
+    GoogleDriveFs* googledrivefs = dynamic_cast<GoogleDriveFs*>(filesystem_);
+    if (googledrivefs == NULL) {
+      return EINVAL;
+    }
+
+    pp::URLLoader loader(pp::InstanceHandle(googledrivefs->instance()));
+    pp::URLRequestInfo request(pp::InstanceHandle(googledrivefs->instance()));
+
+    std::string url = "https://www.googleapis.com/download/drive/v3/files/";
+    url += item_id_;
+    url += "?";
+    url += "alt=media";
+
+    bool set_url_ok = request.SetURL(url);
+    if (!set_url_ok) {
+      return EPERM;
+    }
+
+    bool set_method_ok = request.SetMethod("GET");
+    if (!set_method_ok) {
+      return EPERM;
+    }
+
+    std::map<std::string, std::string> headers_map;
+    headers_map["Content-type"] = "application/json";
+    std::string authorization_value = "Bearer ";
+    authorization_value += googledrivefs->token();
+    headers_map["Authorization"] = authorization_value;
+    char range_value_buffer[1024];
+    int char_written = sprintf(range_value_buffer, "bytes=%lli-%lli",
+                               (long long int)start, (long long int)end);
+    if (char_written < 0) {
+      return EPERM;
+    }
+    std::string range_value(range_value_buffer);
+    headers_map["Range"] = range_value;
+
+    std::string headers = MapToHeaders(headers_map);
+
+    bool set_headers_ok = request.SetHeaders(headers);
+    if (!set_headers_ok) {
+      return EPERM;
+    }
+
+    bool set_allow_cross_origin_requests_ok =
+        request.SetAllowCrossOriginRequests(true);
+    if (!set_allow_cross_origin_requests_ok) {
+      return EPERM;
+    }
+
+    bool set_stream_to_file_ok = request.SetStreamToFile(true);
+    if (!set_stream_to_file_ok) {
+      return EPERM;
+    }
+
+    int32_t err = loader.Open(request, pp::BlockUntilComplete());
+    if (err < 0) {
+      return PPERROR_TO_ERRNO(err);
+    }
+
+    pp::URLResponseInfo response = loader.GetResponseInfo();
+
+    if (response.GetStatusCode() == 200 || response.GetStatusCode() == 206) {

[binji, 2016/07/18 23:24:02]

use consts for the status codes instead (see http_fs_node.cc)

[chanpatorikku, 2016/08/07 02:41:02]

Done.

Thanks.
Used consts for the status codes, and shared the status codes with
http_fs_node.cc.

+      pp::FileRef file_ref = response.GetBodyAsFileRef();
+      pp::FileIO file_io(pp::InstanceHandle(googledrivefs->instance()));
+
+      int32_t open_result = file_io.Open(file_ref, PP_FILEOPENFLAG_READ,
+                                         pp::BlockUntilComplete());
+      if (open_result < 0) {
+        return PPERROR_TO_ERRNO(open_result);
+      }
+
+      int32_t byte_read =
+          file_io.Read(0, (char*)buf, count, pp::BlockUntilComplete());
+      while (byte_read == 0) {
+#ifdef WIN32
+        Sleep(1000);
+#else
+        usleep(1000000);
+#endif
+
+        byte_read =
+            file_io.Read(0, (char*)buf, count, pp::BlockUntilComplete());
+      }
+
+      if (byte_read < 0) {
+        return PPERROR_TO_ERRNO(byte_read);
+      }
+
+      *out_bytes = byte_read;
+
+      return 0;
+
+    } else if (response.GetStatusCode() == 416) {
+      *out_bytes = 0;
+
+      char* pChar = (char*)buf;
+      pChar[0] = '\0';
+
+      return 0;
+    }
+
+    return EPERM;
+  }
+
+  Error WriteHelper(const void* request_body_data, uint32_t request_body_size) {
+    GoogleDriveFs* googledrivefs = dynamic_cast<GoogleDriveFs*>(filesystem_);
+    if (googledrivefs == NULL) {
+      return EINVAL;
+    }
+
+    pp::URLLoader loader(pp::InstanceHandle(googledrivefs->instance()));
+    pp::URLRequestInfo request(pp::InstanceHandle(googledrivefs->instance()));
+
+    std::string url = "https://www.googleapis.com/upload/drive/v3/files/";
+    url += item_id_;
+    url += "?";
+    url += "uploadType=media";
+
+    bool set_url_ok = request.SetURL(url);
+    if (!set_url_ok) {
+      return EPERM;
+    }
+    bool set_method_ok = request.SetMethod("PATCH");
+    if (!set_method_ok) {
+      return EPERM;
+    }
+
+    std::map<std::string, std::string> headers_map;
+    headers_map["Content-type"] = "application/json";
+    std::string authorization_value = "Bearer ";
+    authorization_value += googledrivefs->token();
+    headers_map["Authorization"] = authorization_value;
+
+    std::string headers = MapToHeaders(headers_map);
+
+    bool set_headers_ok = request.SetHeaders(headers);
+    if (!set_headers_ok) {
+      return EPERM;
+    }
+
+    bool set_allow_cross_origin_requests_ok =
+        request.SetAllowCrossOriginRequests(true);
+    if (!set_allow_cross_origin_requests_ok) {
+      return EPERM;
+    }
+
+    bool set_stream_to_file_ok = request.SetStreamToFile(true);
+    if (!set_stream_to_file_ok) {
+      return EPERM;
+    }
+
+    bool append_data_to_body_ok =
+        request.AppendDataToBody(request_body_data, request_body_size);
+    if (!append_data_to_body_ok) {
+      return EPERM;
+    }
+
+    int32_t err = loader.Open(request, pp::BlockUntilComplete());
+    if (err < 0) {
+      return PPERROR_TO_ERRNO(err);
+    }
+
+    pp::URLResponseInfo response = loader.GetResponseInfo();
+    if (response.GetStatusCode() != 200) {
+      return EPERM;
+    }
+
+    return 0;
+  }
+
+  Error CreateEmptyFile() {
+    std::string url =
+        "https://www.googleapis.com/upload/drive/v3/files?uploadType=multipart";
+
+    GoogleDriveFs* googledrivefs = dynamic_cast<GoogleDriveFs*>(filesystem_);
+    if (googledrivefs == NULL) {
+      return EINVAL;
+    }
+
+    pp::URLLoader loader(pp::InstanceHandle(googledrivefs->instance()));
+    pp::URLRequestInfo request(pp::InstanceHandle(googledrivefs->instance()));
+
+    bool set_url_ok = request.SetURL(url);
+    if (!set_url_ok) {
+      return EPERM;
+    }
+
+    bool set_method_ok = request.SetMethod("POST");
+    if (!set_method_ok) {
+      return EPERM;
+    }
+
+    std::string BOUNDARY_VALUE = "foo_bar_baz";
+
+    std::map<std::string, std::string> headers_map;
+    headers_map["Content-type"] =
+        "multipart/related; boundary=" + BOUNDARY_VALUE;
+    std::string authorization_value = "Bearer ";
+    authorization_value += googledrivefs->token();
+    headers_map["Authorization"] = authorization_value;
+
+    std::string headers = MapToHeaders(headers_map);
+
+    bool set_headers_ok = request.SetHeaders(headers);
+    if (!set_headers_ok) {
+      return EPERM;
+    }
+
+    bool set_allow_cross_origin_requests_ok =
+        request.SetAllowCrossOriginRequests(true);
+    if (!set_allow_cross_origin_requests_ok) {
+      return EPERM;
+    }
+
+    bool set_stream_to_file_ok = request.SetStreamToFile(true);
+    if (!set_stream_to_file_ok) {
+      return EPERM;
+    }
+
+    std::string request_body = "--";
+    request_body += BOUNDARY_VALUE;
+    request_body += "\n";
+
+    request_body += "Content-Type: application/json; charset=UTF-8";
+    request_body += "\n";
+
+    request_body += "\n";
+
+    request_body += "{";
+    request_body += "\n";
+
+    request_body += "  \"name\": ";
+    request_body += "\"";
+    request_body += path_.Basename();
+    request_body += "\"";
+    request_body += ",";
+    request_body += "\n";
+
+    request_body += "  \"parents\": ";
+    request_body += "[";
+    request_body += "\n";
+
+    request_body += "    \"";
+    request_body += parent_dir_id_;
+    request_body += "\"";
+    request_body += "\n";
+
+    request_body += "  ]";
+    request_body += "\n";
+
+    request_body += "}";
+    request_body += "\n";
+
+    request_body += "\n";
+
+    request_body += "--";
+    request_body += BOUNDARY_VALUE;
+    request_body += "\n";
+
+    request_body += "Content-Type: text/plain";
+    request_body += "\n";
+
+    request_body += "\n";
+
+    request_body += "\n";
+
+    request_body += "--";
+    request_body += BOUNDARY_VALUE;
+    request_body += "--";
+
+    bool append_data_to_body_ok =
+        request.AppendDataToBody(request_body.data(), request_body.size());
+    if (!append_data_to_body_ok) {
+      return EPERM;
+    }
+
+    int32_t err = loader.Open(request, pp::BlockUntilComplete());
+    if (err < 0) {
+      return PPERROR_TO_ERRNO(err);
+    }
+
+    pp::URLResponseInfo response = loader.GetResponseInfo();
+    if (response.GetStatusCode() != 200) {
+      return EPERM;
+    }
+
+    return 0;
+  }
+
+  Error RequestDirent(std::vector<std::string>& dirent_names) {
+    std::string url = "https://www.googleapis.com/drive/v3/files";
+    url += "?";
+    url += "q=";
+    url += "%27";
+    url += item_id_;
+    url += "%27+in+parents";
+
+    GoogleDriveFs* googledrivefs = dynamic_cast<GoogleDriveFs*>(filesystem_);
+    if (googledrivefs == NULL) {
+      return EINVAL;
+    }
+
+    pp::URLLoader loader(pp::InstanceHandle(googledrivefs->instance()));
+    pp::URLRequestInfo request(pp::InstanceHandle(googledrivefs->instance()));
+
+    bool set_url_ok = request.SetURL(url);
+    if (!set_url_ok) {
+      return EPERM;
+    }
+
+    bool set_method_ok = request.SetMethod("GET");
+    if (!set_method_ok) {
+      return EPERM;
+    }
+
+    std::map<std::string, std::string> headers_map;
+    headers_map["Content-type"] = "application/json";
+    std::string authorization_value = "Bearer ";
+    authorization_value += googledrivefs->token();
+    headers_map["Authorization"] = authorization_value;
+
+    std::string headers = MapToHeaders(headers_map);
+
+    bool set_headers_ok = request.SetHeaders(headers);
+    if (!set_headers_ok) {
+      return EPERM;
+    }
+
+    bool set_allow_cross_origin_requests_ok =
+        request.SetAllowCrossOriginRequests(true);
+    if (!set_allow_cross_origin_requests_ok) {
+      return EPERM;
+    }
+
+    bool set_stream_to_file_ok = request.SetStreamToFile(true);
+    if (!set_stream_to_file_ok) {
+      return EPERM;
+    }
+
+    int32_t err = loader.Open(request, pp::BlockUntilComplete());
+    if (err < 0) {
+      return PPERROR_TO_ERRNO(err);
+    }
+
+    pp::URLResponseInfo response = loader.GetResponseInfo();
+    if (response.GetStatusCode() != 200) {
+      return EPERM;
+    }
+
+    pp::FileRef file_ref = response.GetBodyAsFileRef();
+    pp::FileIO file_io(pp::InstanceHandle(googledrivefs->instance()));
+
+    int32_t open_result =
+        file_io.Open(file_ref, PP_FILEOPENFLAG_READ, pp::BlockUntilComplete());
+    if (open_result < 0) {
+      return PPERROR_TO_ERRNO(open_result);
+    }
+
+    std::string output = "";
+    int BUFFER_SIZE = 1024;
+    char buffer[BUFFER_SIZE];
+    int byte_read =
+        file_io.Read(0, buffer, BUFFER_SIZE, pp::BlockUntilComplete());
+
+    while (byte_read == 0) {
+#ifdef WIN32
+      Sleep(1000);
+#else
+      usleep(1000000);
+#endif
+
+      byte_read =
+          file_io.Read(0, buffer, BUFFER_SIZE, pp::BlockUntilComplete());
+    }
+
+    while (byte_read > 0) {
+      output += buffer;
+
+      byte_read = file_io.Read(byte_read, buffer, BUFFER_SIZE,
+                               pp::BlockUntilComplete());
+    }
+
+    if (byte_read < 0) {
+      return PPERROR_TO_ERRNO(byte_read);
+    }
+
+    Json::Value root;
+
+    Json::Reader reader(Json::Features::strictMode());
+    if (!reader.parse(output, root, false)) {
+      return EPERM;
+    }
+
+    if (!root.isMember("files")) {
+      return EPERM;
+    }
+
+    Json::Value files_array = root["files"];
+
+    if (!files_array.isArray()) {
+      return EPERM;
+    }
+
+    for (unsigned int i = 0; i < files_array.size(); ++i) {
+      dirent_names.push_back(files_array[i]["name"].asString());
+    }
+
+    // TODO: Too many entries result in nextPageToken in API response and
+    // out-of-memory in output variable.
+
+    return 0;
+  }
+
+  std::string parent_dir_id_;
+  std::string item_id_;
+  bool is_dir_item_;
+  Path path_;
+
+  friend class GoogleDriveFs;
+};
+
+GoogleDriveFs::GoogleDriveFs() {}
+
+GoogleDriveFs::~GoogleDriveFs() {}
+
+Error GoogleDriveFs::Init(const FsInitArgs& args) {
+  Error error = Filesystem::Init(args);
+  if (error) {
+    return error;
+  }
+
+  std::map<std::string, std::string>::const_iterator instance_it =
+      args.string_map.find("instance");
+
+  if (instance_it == args.string_map.end()) {
+    return EINVAL;
+  }
+
+  instance_ = atoi(instance_it->second.c_str());
+
+  std::map<std::string, std::string>::const_iterator token_it =
+      args.string_map.find("token");
+
+  if (token_it == args.string_map.end()) {
+    return EINVAL;
+  }
+
+  token_ = token_it->second;
+
+  return 0;
+}
+
+void GoogleDriveFs::Destroy() {}
+
+Error GoogleDriveFs::OpenWithMode(const Path& path,
+                                  int open_flags,
+                                  mode_t mode,
+                                  ScopedNode* out_node) {
+  ScopedNode node(new GoogleDriveFsNode(this, path));
+
+  Error error = node->Init(open_flags);
+  if (error) {
+    return error;
+  }
+
+  *out_node = node;
+
+  return 0;
+}
+
+Error GoogleDriveFs::Rename(const Path& path, const Path& newPath) {
+  LOG_ERROR("rename not supported.");
+  return EPERM;
+}
+
+Error GoogleDriveFs::Unlink(const Path& path) {
+  LOG_ERROR("unlink not supported.");
+  return EPERM;
+}
+
+Error GoogleDriveFs::Mkdir(const Path& path, int permissions) {
+  std::string parent_dir_id = "";
+  Error error = RequestParentDirId(path, this, parent_dir_id);
+  if (error) {
+    return error;
+  }
+
+  std::string item_id = "";
+  error = RequestItemId(parent_dir_id, path.Basename(), this, item_id);
+
+  // mkdir does not create a directory when a file with path.Basename()
+  // already exists
+  if (error == ENOENT) {
+    std::string url = "https://www.googleapis.com/drive/v3/files";
+
+    pp::URLLoader loader(pp::InstanceHandle(this->instance()));
+    pp::URLRequestInfo request(pp::InstanceHandle(this->instance()));
+
+    bool set_url_ok = request.SetURL(url);
+    if (!set_url_ok) {
+      return EPERM;
+    }
+
+    bool set_method_ok = request.SetMethod("POST");
+    if (!set_method_ok) {
+      return EPERM;
+    }
+
+    std::map<std::string, std::string> headers_map;
+    headers_map["Content-type"] = "application/json";
+    std::string authorization_value = "Bearer ";
+    authorization_value += token_;
+    headers_map["Authorization"] = authorization_value;
+
+    std::string headers = MapToHeaders(headers_map);
+
+    bool set_headers_ok = request.SetHeaders(headers);
+    if (!set_headers_ok) {
+      return EPERM;
+    }
+
+    Json::Value json_value;
+    json_value["name"] = path.Basename();
+    json_value["mimeType"] = "application/vnd.google-apps.folder";
+    Json::FastWriter fast_writer;
+    std::string request_body = fast_writer.write(json_value);
+
+    bool append_data_to_body_ok =
+        request.AppendDataToBody(request_body.data(), request_body.size());
+    if (!append_data_to_body_ok) {
+      return EPERM;
+    }
+
+    bool set_allow_cross_origin_requests_ok =
+        request.SetAllowCrossOriginRequests(true);
+    if (!set_allow_cross_origin_requests_ok) {
+      return EPERM;
+    }
+
+    bool set_stream_to_file_ok = request.SetStreamToFile(true);
+    if (!set_stream_to_file_ok) {
+      return EPERM;
+    }
+
+    int32_t err = loader.Open(request, pp::BlockUntilComplete());
+    if (err < 0) {
+      return PPERROR_TO_ERRNO(err);
+    }
+
+    pp::URLResponseInfo response = loader.GetResponseInfo();
+    if (response.GetStatusCode() != 200) {
+      return EPERM;
+    }
+
+    return 0;
+  }
+
+  return EEXIST;
+}
+
+Error GoogleDriveFs::Rmdir(const Path& path) {
+  std::string parent_dir_id = "";
+  Error error = RequestParentDirId(path, this, parent_dir_id);
+  if (error) {
+    return error;
+  }
+
+  std::string dir_id = "";
+  error = RequestDirId(parent_dir_id, path.Basename(), this, dir_id);
+  if (error) {
+    return error;
+  }
+
+  std::string url = "https://www.googleapis.com/drive/v3/files";
+
+  url += "/";
+  url += dir_id;
+
+  pp::URLLoader loader(pp::InstanceHandle(this->instance()));
+  pp::URLRequestInfo request(pp::InstanceHandle(this->instance()));
+
+  bool set_url_ok = request.SetURL(url);
+  if (!set_url_ok) {
+    return EPERM;
+  }
+  bool set_method_ok = request.SetMethod("DELETE");
+  if (!set_method_ok) {
+    return EPERM;
+  }
+
+  std::map<std::string, std::string> headers_map;
+  headers_map["Content-type"] = "application/json";
+  std::string authorization_value = "Bearer ";
+  authorization_value += token_;
+  headers_map["Authorization"] = authorization_value;
+
+  std::string headers = MapToHeaders(headers_map);
+
+  bool set_headers_ok = request.SetHeaders(headers);
+  if (!set_headers_ok) {
+    return EPERM;
+  }
+
+  bool set_allow_cross_origin_requests_ok =
+      request.SetAllowCrossOriginRequests(true);
+  if (!set_allow_cross_origin_requests_ok) {
+    return EPERM;
+  }
+
+  bool set_stream_to_file_ok = request.SetStreamToFile(true);
+  if (!set_stream_to_file_ok) {
+    return EPERM;
+  }
+
+  int32_t err = loader.Open(request, pp::BlockUntilComplete());
+  if (err < 0) {
+    return PPERROR_TO_ERRNO(err);
+  }
+
+  pp::URLResponseInfo response = loader.GetResponseInfo();
+  if (response.GetStatusCode() != 204) {
+    return EPERM;
+  }
+
+  return 0;
+}
+
+Error GoogleDriveFs::Remove(const Path& path) {
+  LOG_ERROR("remove not supported.");
+  return EPERM;
+}
+
+std::string GoogleDriveFs::token() {
+  return token_;
+}
+
+PP_Instance GoogleDriveFs::instance() {
+  return instance_;
+}
+
+}  // namespace nacl_io