1 files changed, 135 insertions, 0 deletions
diff --git a/dom/localstorage/LSValue.h b/dom/localstorage/LSValue.h
new file mode 100644
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+++ b/dom/localstorage/LSValue.h
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+/* -*- 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_localstorage_LSValue_h
+#define mozilla_dom_localstorage_LSValue_h
+
+#include <cstdint>
+#include "ErrorList.h"
+#include "SnappyUtils.h"
+#include "mozilla/Assertions.h"
+#include "mozilla/Span.h"
+#include "nsString.h"
+#include "nsStringFwd.h"
+#include "nsTStringRepr.h"
+
+class mozIStorageStatement;
+
+namespace IPC {
+template <typename>
+struct ParamTraits;
+}
+
+namespace mozilla::dom {
+
+/**
+ * Represents a LocalStorage value. From content's perspective, values (if
+ * present) are always DOMStrings. This is also true from a quota-tracking
+ * perspective. However, for memory and disk efficiency it's preferable to store
+ * the value in alternate compressed or utf-8 encoding representations. The
+ * LSValue type exists to support these alternate representations, dynamically
+ * decompressing/re-encoding to utf-16 while still tracking value size on a
+ * utf-16 basis for quota purposes.
+ */
+class LSValue final {
+  friend struct IPC::ParamTraits<LSValue>;
+
+ public:
+  enum class ConversionType : uint8_t {
+    NONE = 0u,
+    UTF16_UTF8 = 1u,
+    NUM_TYPES = 2u
+  };
+
+  enum class CompressionType : uint8_t {
+    UNCOMPRESSED = 0u,
+    SNAPPY = 1u,
+    NUM_TYPES = 2u
+  };
+
+  nsCString mBuffer;
+  uint32_t mUTF16Length;
+  ConversionType mConversionType;
+  CompressionType mCompressionType;
+
+  explicit LSValue()
+      : mUTF16Length(0u),
+        mConversionType(ConversionType::NONE),
+        mCompressionType(CompressionType::UNCOMPRESSED) {
+    SetIsVoid(true);
+  }
+
+  bool InitFromString(const nsAString& aBuffer);
+
+  nsresult InitFromStatement(mozIStorageStatement* aStatement, uint32_t aIndex);
+
+  bool IsVoid() const { return mBuffer.IsVoid(); }
+
+  void SetIsVoid(bool aVal) { mBuffer.SetIsVoid(aVal); }
+
+  /**
+   * This represents the "physical" length that the parent process uses for
+   * the size of value/item computation. This can also be used to see how much
+   * memory the value is using at rest or what the cost is for sending the value
+   * over IPC.
+   */
+  uint32_t Length() const { return mBuffer.Length(); }
+
+  /*
+   * This represents the "logical" length that content sees and that is also
+   * used for quota management purposes.
+   */
+  uint32_t UTF16Length() const { return mUTF16Length; }
+
+  ConversionType GetConversionType() const { return mConversionType; }
+
+  CompressionType GetCompressionType() const { return mCompressionType; }
+
+  bool Equals(const LSValue& aOther) const {
+    return mBuffer == aOther.mBuffer &&
+           mBuffer.IsVoid() == aOther.mBuffer.IsVoid() &&
+           mUTF16Length == aOther.mUTF16Length &&
+           mConversionType == aOther.mConversionType &&
+           mCompressionType == aOther.mCompressionType;
+  }
+
+  bool operator==(const LSValue& aOther) const { return Equals(aOther); }
+
+  bool operator!=(const LSValue& aOther) const { return !Equals(aOther); }
+
+  constexpr const nsCString& AsCString() const { return mBuffer; }
+
+  class Converter {
+    nsString mBuffer;
+
+   public:
+    explicit Converter(const LSValue& aValue);
+    Converter(Converter&& aOther) = default;
+    ~Converter() = default;
+
+    operator const nsString&() const { return mBuffer; }
+
+   private:
+    Converter() = delete;
+    Converter(const Converter&) = delete;
+    Converter& operator=(const Converter&) = delete;
+    Converter& operator=(const Converter&&) = delete;
+  };
+
+  Converter AsString() const { return Converter{*this}; }
+};
+
+const LSValue& VoidLSValue();
+
+/**
+ * XXX: This function doesn't have to be public
+ * once the support for shadow writes is removed.
+ */
+bool PutCStringBytesToString(const nsACString& aSrc, nsString& aDest);
+
+}  // namespace mozilla::dom
+
+#endif  // mozilla_dom_localstorage_LSValue_h