gecko-dev/dom/xhr/XMLHttpRequestString.h

/* -*- 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"

namespace mozilla {
namespace dom {

class DOMString;
class XMLHttpRequestStringBuffer;
class XMLHttpRequestStringSnapshot;
class XMLHttpRequestStringWriterHelper;
class XMLHttpRequestStringSnapshotReaderHelper;

// 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.
  MOZ_MUST_USE 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);

  /**
   * The existing length of the string. Do not call during BulkWrite().
   */
  uint32_t
  Length() const;

  mozilla::BulkWriteHandle<char16_t>
  BulkWrite(uint32_t aCapacity, nsresult& aRv);

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;
  friend class XMLHttpRequestStringSnapshotReaderHelper;

public:
  XMLHttpRequestStringSnapshot();
  ~XMLHttpRequestStringSnapshot();

  XMLHttpRequestStringSnapshot& operator=(const XMLHttpRequestStringSnapshot&);

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

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

  bool IsVoid() const
  {
    return mVoid;
  }

  bool IsEmpty() const
  {
    return !mLength;
  }

  MOZ_MUST_USE bool GetAsString(DOMString& aString) 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;
};

// This class locks the buffer and allows the callee to read data from it.
class MOZ_STACK_CLASS XMLHttpRequestStringSnapshotReaderHelper final
{
public:
  explicit XMLHttpRequestStringSnapshotReaderHelper(XMLHttpRequestStringSnapshot& aSnapshot);

  const char16_t*
  Buffer() const;

  uint32_t
  Length() const;

private:
  XMLHttpRequestStringSnapshotReaderHelper(const XMLHttpRequestStringSnapshotReaderHelper&) = delete;
  XMLHttpRequestStringSnapshotReaderHelper& operator=(const XMLHttpRequestStringSnapshotReaderHelper&) = delete;
  XMLHttpRequestStringSnapshotReaderHelper& operator=(const XMLHttpRequestStringSnapshotReaderHelper&&) = delete;

  RefPtr<XMLHttpRequestStringBuffer> mBuffer;
  MutexAutoLock mLock;
};

} // dom namespace
} // mozilla namespace

#endif // mozilla_dom_XMLHttpRequestString_h