[Chromoting] GetHostAttributes with tests

remoting/host/host_attributes.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 "remoting/host/host_attributes.h"
+
+#include <type_traits>
+
+#include "base/atomicops.h"
+#include "base/logging.h"
+#include "build/build_config.h"
+#if defined(OS_WIN)
+#include "remoting/host/host_attributes_win.h"
+#else
+#include "remoting/host/host_attributes_empty.h"
+#endif
+
+namespace remoting {
+
+namespace {
+static constexpr char kSeparator[] = ",";
+}  // namespace
+
+static_assert(std::is_pod<DynamicAttribute>::value,
+              "DynamicAttribute should be POD.");
+static_assert(std::is_pod<StaticAttribute>::value,
+              "StaticAttribute should be POD.");
+
+const char* StaticAttribute::name() const {
+  return attribute.name;
+}
+
+bool StaticAttribute::EvaluatedValue() {
+  if (evaluated) {
+    return value;
+  } else {
+    value = attribute.value();
+    base::subtle::MemoryBarrier();
+    evaluated = true;
+    return value;
+  }
+}
+
+std::string GetHostAttributes() {
+  std::string result;
+  // By using ranged for-loop, MSVC throws error C3316:
+  // 'const remoting::StaticAttribute [0]':
+  // an array of unknown size cannot be used in a range-based for statement.
+  //
+  // By using arraysize() macro in base/macros.h, it's illegal,
+  // error: no matching function for call to 'ArraySizeHelper'
+  // note: candidate template ignored: substitution failure
+  // [with T = const remoting::StaticAttribute, N = 0]:
+  // zero-length arrays are not permitted in C++.
+  //
+  // So a traditional sizeof is used here.
+#define SIZE_OF_ARRAY(x, y) static_cast<int>(sizeof(x) / sizeof(y))

[Sergey Ulanov, 2016/11/07 20:11:33]

Add something in kDynamicAttributes and use arraysize() from base/macros.h

[Hzj_jie, 2016/11/08 01:29:53]

Done.

+  for (int i = 0;
+       i < SIZE_OF_ARRAY(kStaticAttributes, StaticAttribute);
+       i++) {
+    auto& static_attribute = kStaticAttributes[i];
+    DCHECK(std::string(static_attribute.name()).find(kSeparator) ==
+           std::string::npos);
+    if (static_attribute.EvaluatedValue()) {
+      if (!result.empty()) {
+        result.append(kSeparator);
+      }
+      result.append(static_attribute.name());
+    }
+  }
+
+  for (int i = 0;
+       i < SIZE_OF_ARRAY(kDynamicAttributes, StaticAttribute);

[Sergey Ulanov, 2016/11/07 20:11:33]

type is wrong here. This macro could be implemented as (sizeof(x) /
sizeof(x[0])), i.e. you don't really need the second argument, but it's better
to use arraysize().

[Hzj_jie, 2016/11/08 01:29:54]

Done.

+       i++) {
+    const auto& dynamic_attribute = kDynamicAttributes[i];
+    DCHECK(std::string(dynamic_attribute.name).find(kSeparator) ==
+           std::string::npos);
+    if (dynamic_attribute.value()) {
+      if (!result.empty()) {
+        result.append(kSeparator);
+      }
+      result.append(dynamic_attribute.name);
+    }
+  }
+#undef SIZE_OF_ARRAY
+
+  return result;
+}
+
+}  // namespace remoting