XMLHttpRequestString.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_XMLHttpRequestString_h

#define mozilla_dom_XMLHttpRequestString_h

#include "mozilla/Mutex.h"

#include "nsString.h"

struct JSContext;

class JSString;

namespace mozilla::dom {

class ArrayBufferBuilder;

class BlobImpl;

class DOMString;

class XMLHttpRequestStringBuffer;

class XMLHttpRequestStringSnapshot;

class XMLHttpRequestStringWriterHelper;

// We want to avoid the dup of strings when XHR in workers has access to

// responseText for events dispatched during the loading state. For this reason

// we use this class, able to create snapshots of the current size of itself

// without making extra copies.

class XMLHttpRequestString final {

  friend class XMLHttpRequestStringWriterHelper;

 public:

  XMLHttpRequestString();

  ~XMLHttpRequestString();

  void Truncate();

  uint32_t Length() const;

  void Append(const nsAString& aString);

  // This method should be called only when the string is really needed because

  // it can cause the duplication of the strings in case the loading of the XHR

  // is not completed yet.

  [[nodiscard]] bool GetAsString(nsAString& aString) const;

  size_t SizeOfThis(MallocSizeOf aMallocSizeOf) const;

  const char16_t* Data() const;

  bool IsEmpty() const;

  void CreateSnapshot(XMLHttpRequestStringSnapshot& aSnapshot);

 private:

  XMLHttpRequestString(const XMLHttpRequestString&) = delete;

  XMLHttpRequestString& operator=(const XMLHttpRequestString&) = delete;

  XMLHttpRequestString& operator=(const XMLHttpRequestString&&) = delete;

  RefPtr<XMLHttpRequestStringBuffer> mBuffer;

};

// This class locks the buffer and allows the callee to write data into it.

class MOZ_STACK_CLASS XMLHttpRequestStringWriterHelper final {

 public:

  explicit XMLHttpRequestStringWriterHelper(XMLHttpRequestString& aString);

  ~XMLHttpRequestStringWriterHelper();

/**

   * The existing length of the string. Do not call during BulkWrite().

*/

  uint32_t Length() const;

  mozilla::Result<mozilla::BulkWriteHandle<char16_t>, nsresult> BulkWrite(

      uint32_t aCapacity);

 private:

  XMLHttpRequestStringWriterHelper(const XMLHttpRequestStringWriterHelper&) =

      delete;

  XMLHttpRequestStringWriterHelper& operator=(

      const XMLHttpRequestStringWriterHelper&) = delete;

  XMLHttpRequestStringWriterHelper& operator=(

      const XMLHttpRequestStringWriterHelper&&) = delete;

  RefPtr<XMLHttpRequestStringBuffer> mBuffer;

  MutexAutoLock mLock;

};

// This class is the internal XMLHttpRequestStringBuffer of the

// XMLHttpRequestString plus the current length. GetAsString will return the

// string with that particular length also if the XMLHttpRequestStringBuffer is

// grown in the meantime.

class XMLHttpRequestStringSnapshot final {

  friend class XMLHttpRequestStringBuffer;

 public:

  XMLHttpRequestStringSnapshot();

  ~XMLHttpRequestStringSnapshot();

  XMLHttpRequestStringSnapshot& operator=(const XMLHttpRequestStringSnapshot&) =

      delete;

  void Reset() { ResetInternal(false /* isVoid */); }

  void SetVoid() { ResetInternal(true /* isVoid */); }

  bool IsVoid() const { return mVoid; }

  bool IsEmpty() const { return !mLength; }

  [[nodiscard]] bool GetAsString(DOMString& aString) const;

  JSString* GetAsJSStringCopy(JSContext* aCx) const;

 private:

  XMLHttpRequestStringSnapshot(const XMLHttpRequestStringSnapshot&) = delete;

  XMLHttpRequestStringSnapshot& operator=(

      const XMLHttpRequestStringSnapshot&&) = delete;

  void Set(XMLHttpRequestStringBuffer* aBuffer, uint32_t aLength);

  void ResetInternal(bool aIsVoid);

  RefPtr<XMLHttpRequestStringBuffer> mBuffer;

  uint32_t mLength;

  bool mVoid;

};

}  // namespace mozilla::dom

#endif  // mozilla_dom_XMLHttpRequestString_h