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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 {
namespace 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>;
nsCString mBuffer;
uint32_t mUTF16Length;
bool mCompressed;
public:
LSValue() : mUTF16Length(0), mCompressed(false) { 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; }
bool IsCompressed() const { return mCompressed; }
bool Equals(const LSValue& aOther) const {
return mBuffer == aOther.mBuffer &&
mBuffer.IsVoid() == aOther.mBuffer.IsVoid() &&
mUTF16Length == aOther.mUTF16Length &&
mCompressed == aOther.mCompressed;
}
bool operator==(const LSValue& aOther) const { return Equals(aOther); }
bool operator!=(const LSValue& aOther) const { return !Equals(aOther); }
operator const nsCString&() const { return mBuffer; }
operator Span<const char>() const { return mBuffer; }
class Converter {
nsString mBuffer;
public:
explicit Converter(const LSValue& aValue) {
if (aValue.mBuffer.IsVoid()) {
mBuffer.SetIsVoid(true);
} else if (aValue.mCompressed) {
nsCString buffer;
MOZ_ALWAYS_TRUE(SnappyUncompress(aValue.mBuffer, buffer));
CopyUTF8toUTF16(buffer, mBuffer);
} else {
CopyUTF8toUTF16(aValue.mBuffer, mBuffer);
}
}
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();
} // namespace dom
} // namespace mozilla
#endif // mozilla_dom_localstorage_LSValue_h
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