Support Windows registry access

ci/licenses_golden/licenses_flutter

@@ -1580,6 +1580,9 @@ FILE: ../../../flutter/shell/platform/windows/platform_handler_win32.h
 FILE: ../../../flutter/shell/platform/windows/platform_handler_winuwp.cc
 FILE: ../../../flutter/shell/platform/windows/platform_handler_winuwp.h
 FILE: ../../../flutter/shell/platform/windows/public/flutter_windows.h
+FILE: ../../../flutter/shell/platform/windows/registry.cc
+FILE: ../../../flutter/shell/platform/windows/registry.h
+FILE: ../../../flutter/shell/platform/windows/registry_unittests.cc
 FILE: ../../../flutter/shell/platform/windows/string_conversion.cc
 FILE: ../../../flutter/shell/platform/windows/string_conversion.h
 FILE: ../../../flutter/shell/platform/windows/string_conversion_unittests.cc

shell/platform/windows/BUILD.gn

@@ -171,6 +171,18 @@ source_set("flutter_windows_source") {
   ]
 }
 
+# Windows registry utilities.
+source_set("registry") {
+  sources = [
+    "registry.cc",
+    "registry.h",
+  ]
+
+  if (target_os == "winuwp") {
+    cflags = [ "/EHsc" ]
+  }
+}
+
 # String encoding conversion utilities.
 source_set("string_conversion") {
   sources = [
@@ -179,7 +191,6 @@ source_set("string_conversion") {
   ]
 
   if (target_os == "winuwp") {
-    configs += [ ":cppwinrt_defs" ]
     cflags = [ "/EHsc" ]
   }
 }
@@ -222,6 +233,7 @@ executable("flutter_windows_unittests") {
   sources = [
     # "flutter_project_bundle_unittests.cc", //TODO failing due to switches test failing.  Blocked on https://github.com/flutter/flutter/issues/74153
     # "flutter_windows_engine_unittests.cc", //TODO failing to send / receive platform message get plugins working first.  Blocked on https://github.com/flutter/flutter/issues/74155
+    "registry_unittests.cc",
     "string_conversion_unittests.cc",
     "system_utils_unittests.cc",
     "testing/engine_modifier.h",
@@ -260,6 +272,7 @@ executable("flutter_windows_unittests") {
     ":flutter_windows_fixtures",
     ":flutter_windows_headers",
     ":flutter_windows_source",
+    ":registry",
     "//flutter/shell/platform/common:common_cpp",
     "//flutter/shell/platform/embedder:embedder_as_internal_library",
     "//flutter/shell/platform/embedder:embedder_test_utils",

shell/platform/windows/registry.cc

@@ -0,0 +1,87 @@
+// Copyright 2013 The Flutter 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 "flutter/shell/platform/windows/registry.h"
+
+#include <cassert>
+#include <memory>
+
+namespace flutter {
+
+RegistryKey::RegistryKey(HKEY key, REGSAM access)
+    : RegistryKey(key, L"", access) {}
+
+RegistryKey::RegistryKey(HKEY parent_key,
+                         const std::wstring_view subkey,
+                         REGSAM access) {
+  LSTATUS result = ::RegOpenKeyEx(parent_key, subkey.data(), 0, access, &key_);
+  if (result != ERROR_SUCCESS) {
+    key_ = nullptr;
+  }
+}
+
+RegistryKey::RegistryKey(const RegistryKey& parent_key,
+                         const std::wstring_view subkey,
+                         REGSAM access)
+    : RegistryKey(parent_key.key_, subkey, access) {}
+
+RegistryKey::~RegistryKey() {
+  Close();
+}
+
+void RegistryKey::Close() {
+  if (IsValid()) {
+    ::RegCloseKey(key_);
+    key_ = nullptr;
+  }
+}
+
+std::vector<std::wstring> RegistryKey::GetSubKeyNames() const {
+  if (!IsValid()) {
+    return {};
+  }
+
+  // Get the count of subkeys, and maximum key size in wchar_t.
+  DWORD max_key_buf_size;
+  DWORD subkey_count;
+  LSTATUS result = ::RegQueryInfoKey(
+      key_, nullptr, nullptr, nullptr, &subkey_count, &max_key_buf_size,
+      nullptr, nullptr, nullptr, nullptr, nullptr, nullptr);
+
+  // Collect all subkey names.
+  std::vector<std::wstring> subkey_names;
+  for (int i = 0; i < subkey_count; ++i) {
+    DWORD key_buf_size = max_key_buf_size;
+    auto key_buf = std::make_unique<wchar_t[]>(max_key_buf_size);
+    result = ::RegEnumKeyEx(key_, i, key_buf.get(), &key_buf_size, nullptr,
+                            nullptr, nullptr, nullptr);
+    if (result == ERROR_SUCCESS) {
+      subkey_names.emplace_back(key_buf.get());
+    }
+  }
+  return subkey_names;
+}
+
+LONG RegistryKey::ReadValue(const std::wstring_view name,
+                            std::wstring* out_value) const {
+  assert(out_value != nullptr);
+
+  // Get the value size, in bytes.
+  DWORD value_size;
+  LSTATUS result = ::RegGetValueW(key_, L"", name.data(), RRF_RT_REG_SZ,
+                                  nullptr, nullptr, &value_size);
+  if (result != ERROR_SUCCESS) {
+    return result;
+  }
+
+  auto value_buf = std::make_unique<wchar_t[]>(value_size / sizeof(wchar_t));
+  result = ::RegGetValueW(key_, L"", name.data(), RRF_RT_REG_SZ, nullptr,
+                          value_buf.get(), &value_size);
+  if (result == ERROR_SUCCESS) {
+    *out_value = value_buf.get();
+  }
+  return result;
+}
+
+}  // namespace flutter

shell/platform/windows/registry.h

@@ -0,0 +1,61 @@
+// Copyright 2013 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef FLUTTER_SHELL_PLATFORM_WINDOWS_REGISTRY_H_
+#define FLUTTER_SHELL_PLATFORM_WINDOWS_REGISTRY_H_
+
+#include <Windows.h>
+#include <Winreg.h>
+
+#include <string>
+#include <vector>
+
+namespace flutter {
+
+// A Windows Registry key.
+//
+// The Windows registry is structured as a hierarchy of named keys, each of
+// which may contain a set of named values of various datatypes. RegistryKey
+// objects own the underlying HKEY handle and ensure cleanup at or prior to
+// destruction.
+class RegistryKey {
+ public:
+  // Opens the specified key.
+  RegistryKey(HKEY key, REGSAM access);
+
+  // Opens a key relative to the specified parent key.
+  RegistryKey(HKEY parent_key, const std::wstring_view subkey, REGSAM access);
+
+  // Opens a key relative to the specified parent key.
+  RegistryKey(const RegistryKey& parent_key,
+              const std::wstring_view subkey,
+              REGSAM access);
+
+  ~RegistryKey();
+
+  // Prevent copying.
+  RegistryKey(const RegistryKey& other) = delete;
+  RegistryKey& operator=(const RegistryKey& other) = delete;
+
+  // Closes the registry key and releases resources.
+  void Close();
+
+  // Returns true if the key is valid.
+  bool IsValid() const { return key_ != nullptr; }
+
+  // Returns a list of all direct subkey names for this key.
+  std::vector<std::wstring> GetSubKeyNames() const;
+
+  // Reads a string value from the key.
+  //
+  // Returns ERROR_SUCCESS on success.
+  LONG ReadValue(const std::wstring_view name, std::wstring* out_value) const;
+
+ private:
+  HKEY key_ = nullptr;
+};
+
+}  // namespace flutter
+
+#endif  // FLUTTER_SHELL_PLATFORM_WINDOWS_REGISTRY_H_

shell/platform/windows/registry_unittests.cc

@@ -0,0 +1,50 @@
+// Copyright 2013 The Flutter 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 "flutter/shell/platform/windows/registry.h"
+
+#include <Windows.h>
+#include <Winreg.h>
+
+#include <vector>
+
+#include "gtest/gtest.h"
+
+namespace flutter {
+namespace testing {
+
+// TODO(cbracken): write registry values to be tested, then cleanup.
+// https://github.com/flutter/flutter/issues/82095
+
+// Verify that a registry key is marked invalid after close.
+TEST(RegistryKey, CloseInvalidates) {
+  RegistryKey key(HKEY_USERS, L".DEFAULT\\Environment", KEY_READ);
+  ASSERT_TRUE(key.IsValid());
+  key.Close();
+  ASSERT_FALSE(key.IsValid());
+}
+
+// Verify that subkeys can be read.
+TEST(RegistryKey, GetSubKeyNames) {
+  RegistryKey key(HKEY_USERS, L".DEFAULT", KEY_READ);
+  ASSERT_TRUE(key.IsValid());
+
+  std::vector<std::wstring> subkey_names = key.GetSubKeyNames();
+  EXPECT_GE(subkey_names.size(), 1);
+  EXPECT_TRUE(std::find(subkey_names.begin(), subkey_names.end(),
+                        L"Environment") != subkey_names.end());
+}
+
+// Verify that values can be read.
+TEST(RegistryKey, GetValue) {
+  RegistryKey key(HKEY_USERS, L".DEFAULT\\Environment", KEY_READ);
+  ASSERT_TRUE(key.IsValid());
+
+  std::wstring path;
+  ASSERT_EQ(key.ReadValue(L"Path", &path), ERROR_SUCCESS);
+  EXPECT_FALSE(path.empty());
+}
+
+}  // namespace testing
+}  // namespace flutter