[Media Router] Parse device description xml in utility process

chrome/utility/media_router/dial_device_description_parser_impl.cc

+// Copyright 2017 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/utility/media_router/dial_device_description_parser_impl.h"
+
+#include <libxml/parser.h>
+#include <libxml/tree.h>
+#include <libxml/xpath.h>
+#include <utility>
+
+#include "base/memory/ptr_util.h"
+#include "base/strings/stringprintf.h"
+#include "mojo/public/cpp/bindings/strong_binding.h"
+#include "third_party/libxml/chromium/libxml_utils.h"
+
+namespace {
+
+enum ErrorType {
+  NONE,
+  MISSING_UNIQUE_ID,
+  MISSING_FRIENDLY_NAME,
+};
+
+ErrorType Validate(const chrome::mojom::DialDeviceDescription& description) {
+  if (description.unique_id.empty()) {
+    return ErrorType::MISSING_UNIQUE_ID;
+  }
+  if (description.friendly_name.empty()) {
+    return ErrorType::MISSING_FRIENDLY_NAME;
+  }
+  return ErrorType::NONE;
+}
+
+// If friendly name does not exist, fall back to use model name + last 4
+// digits of UUID as friendly name.
+void ComputeFriendlyName(const chrome::mojom::DialDeviceDescriptionPtr& out) {
+  auto& model_name = out->model_name;
+  auto& unique_id = out->unique_id;
+
+  if (model_name.empty() || unique_id.length() < 4)
+    return;
+
+  std::string trimmed_unique_id = unique_id.substr(unique_id.length() - 4);
+  out->friendly_name = base::StringPrintf("%s [%s]", model_name.c_str(),
+                                          trimmed_unique_id.c_str());
+}
+
+}  // namespace
+
+namespace media_router {
+
+DialDeviceDescriptionParserImpl::DialDeviceDescriptionParserImpl() = default;
+DialDeviceDescriptionParserImpl::~DialDeviceDescriptionParserImpl() {
+  DCHECK(thread_checker_.CalledOnValidThread());
+}
+
+// static
+void DialDeviceDescriptionParserImpl::Create(
+    chrome::mojom::DialDeviceDescriptionParserRequest request) {
+  mojo::MakeStrongBinding(base::MakeUnique<DialDeviceDescriptionParserImpl>(),
+                          std::move(request));
+}
+
+void DialDeviceDescriptionParserImpl::ParseDialDeviceDescription(
+    const std::string& device_description_xml_data,
+    const ParseDialDeviceDescriptionCallback& callback) {
+  DCHECK(thread_checker_.CalledOnValidThread());
+  DCHECK(!callback.is_null());
+
+  chrome::mojom::DialDeviceDescriptionPtr device_description =
+      chrome::mojom::DialDeviceDescription::New();
+  bool result = Parse(device_description_xml_data, device_description);
+
+  if (result) {
+    callback.Run(result, std::move(device_description));
+  } else {
+    callback.Run(result, chrome::mojom::DialDeviceDescriptionPtr());
+  }
+}
+
+bool DialDeviceDescriptionParserImpl::Parse(
+    const std::string& xml,
+    chrome::mojom::DialDeviceDescriptionPtr& out) {

[dcheng, 2017/03/25 00:59:38]

Nit: mutable ref arguments aren't permitted in Chrome.

One option is to just have this function return the struct directly (which
should obviate the need to have a result parameter in the mojom at all: we can
just check that we have a result)

[zhaobin, 2017/03/27 19:16:55]

Done.

+  DCHECK(out);
+
+  XmlReader xml_reader;
+  if (!xml_reader.Load(xml))
+    return false;
+
+  while (xml_reader.Read()) {
+    xml_reader.SkipToElement();
+    std::string node_name(xml_reader.NodeName());
+
+    if (node_name == "UDN") {
+      if (!xml_reader.ReadElementContent(&out->unique_id))
+        return false;
+    } else if (node_name == "friendlyName") {
+      if (!xml_reader.ReadElementContent(&out->friendly_name))
+        return false;
+    } else if (node_name == "modelName") {
+      if (!xml_reader.ReadElementContent(&out->model_name))
+        return false;
+    } else if (node_name == "deviceType") {
+      if (!xml_reader.ReadElementContent(&out->device_type))
+        return false;
+    }
+  }
+
+  if (out->friendly_name.empty())
+    ComputeFriendlyName(out);
+
+  ErrorType error = Validate(*out);
+  if (error != ErrorType::NONE) {
+    DLOG(WARNING) << "Device description failed to validate: " << error;
+    return false;
+  }
+
+  return true;
+}
+
+}  // namespace media_router