1 files changed, 103 insertions, 0 deletions
diff --git a/dom/quota/UsageInfo.h b/dom/quota/UsageInfo.h
new file mode 100644
index 0000000000..7f7bf5f85a
--- /dev/null
+++ b/dom/quota/UsageInfo.h
@@ -0,0 +1,103 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_dom_quota_usageinfo_h__
+#define mozilla_dom_quota_usageinfo_h__
+
+#include <cstdint>
+#include <utility>
+#include "mozilla/CheckedInt.h"
+#include "mozilla/Maybe.h"
+
+namespace mozilla::dom::quota {
+
+enum struct UsageKind { Database, File };
+
+namespace detail {
+inline void AddCapped(Maybe<uint64_t>& aValue, const Maybe<uint64_t> aDelta) {
+  if (aDelta.isSome()) {
+    CheckedUint64 value = aValue.valueOr(0);
+
+    value += aDelta.value();
+
+    aValue = Some(value.isValid() ? value.value() : UINT64_MAX);
+  }
+}
+
+template <UsageKind Kind>
+struct Usage {
+  explicit Usage(Maybe<uint64_t> aValue = Nothing{}) : mValue(aValue) {}
+
+  Maybe<uint64_t> GetValue() const { return mValue; }
+
+  Usage& operator+=(const Usage aDelta) {
+    AddCapped(mValue, aDelta.mValue);
+
+    return *this;
+  }
+
+  Usage operator+(const Usage aDelta) const {
+    Usage res = *this;
+    res += aDelta;
+    return res;
+  }
+
+ private:
+  Maybe<uint64_t> mValue;
+};
+}  // namespace detail
+
+using DatabaseUsageType = detail::Usage<UsageKind::Database>;
+using FileUsageType = detail::Usage<UsageKind::File>;
+
+class UsageInfo final {
+ public:
+  UsageInfo() = default;
+
+  explicit UsageInfo(const DatabaseUsageType aUsage) : mDatabaseUsage(aUsage) {}
+
+  explicit UsageInfo(const FileUsageType aUsage) : mFileUsage(aUsage) {}
+
+  UsageInfo operator+(const UsageInfo& aUsageInfo) {
+    UsageInfo res = *this;
+    res += aUsageInfo;
+    return res;
+  }
+
+  UsageInfo& operator+=(const UsageInfo& aUsageInfo) {
+    mDatabaseUsage += aUsageInfo.mDatabaseUsage;
+    mFileUsage += aUsageInfo.mFileUsage;
+    return *this;
+  }
+
+  UsageInfo& operator+=(const DatabaseUsageType aUsage) {
+    mDatabaseUsage += aUsage;
+    return *this;
+  }
+
+  UsageInfo& operator+=(const FileUsageType aUsage) {
+    mFileUsage += aUsage;
+    return *this;
+  }
+
+  Maybe<uint64_t> DatabaseUsage() const { return mDatabaseUsage.GetValue(); }
+
+  Maybe<uint64_t> FileUsage() const { return mFileUsage.GetValue(); }
+
+  Maybe<uint64_t> TotalUsage() const {
+    Maybe<uint64_t> res = mDatabaseUsage.GetValue();
+    detail::AddCapped(res, FileUsage());
+    return res;
+  }
+
+ private:
+  DatabaseUsageType mDatabaseUsage;
+  FileUsageType mFileUsage;
+};
+
+}  // namespace mozilla::dom::quota
+
+#endif  // mozilla_dom_quota_usageinfo_h__