dom/xhr/XMLHttpRequestString.h

   1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
   3 /* This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this
   5  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 #ifndef mozilla_dom_XMLHttpRequestString_h
   8 #define mozilla_dom_XMLHttpRequestString_h
   9
  10 #include "mozilla/Mutex.h"
  11 #include "nsString.h"
  12
  13 namespace mozilla::dom {
  14
  15 class ArrayBufferBuilder;
  16 class BlobImpl;
  17 class DOMString;
  18 class XMLHttpRequestStringBuffer;
  19 class XMLHttpRequestStringSnapshot;
  20 class XMLHttpRequestStringWriterHelper;
  21 class XMLHttpRequestStringSnapshotReaderHelper;
  22
  23 // We want to avoid the dup of strings when XHR in workers has access to
  24 // responseText for events dispatched during the loading state. For this reason
  25 // we use this class, able to create snapshots of the current size of itself
  26 // without making extra copies.
  27 class XMLHttpRequestString final {
  28   friend class XMLHttpRequestStringWriterHelper;
  29
  30  public:
  31   XMLHttpRequestString();
  32   ~XMLHttpRequestString();
  33
  34   void Truncate();
  35
  36   uint32_t Length() const;
  37
  38   void Append(const nsAString& aString);
  39
  40   // This method should be called only when the string is really needed because
  41   // it can cause the duplication of the strings in case the loading of the XHR
  42   // is not completed yet.
  43   [[nodiscard]] bool GetAsString(nsAString& aString) const;
  44
  45   size_t SizeOfThis(MallocSizeOf aMallocSizeOf) const;
  46
  47   const char16_t* Data() const;
  48
  49   bool IsEmpty() const;
  50
  51   void CreateSnapshot(XMLHttpRequestStringSnapshot& aSnapshot);
  52
  53  private:
  54   XMLHttpRequestString(const XMLHttpRequestString&) = delete;
  55   XMLHttpRequestString& operator=(const XMLHttpRequestString&) = delete;
  56   XMLHttpRequestString& operator=(const XMLHttpRequestString&&) = delete;
  57
  58   RefPtr<XMLHttpRequestStringBuffer> mBuffer;
  59 };
  60
  61 // This class locks the buffer and allows the callee to write data into it.
  62 class MOZ_STACK_CLASS XMLHttpRequestStringWriterHelper final {
  63  public:
  64   explicit XMLHttpRequestStringWriterHelper(XMLHttpRequestString& aString);
  65   ~XMLHttpRequestStringWriterHelper();
  66
  67   /**
  68    * The existing length of the string. Do not call during BulkWrite().
  69    */
  70   uint32_t Length() const;
  71
  72   mozilla::Result<mozilla::BulkWriteHandle<char16_t>, nsresult> BulkWrite(
  73       uint32_t aCapacity);
  74
  75  private:
  76   XMLHttpRequestStringWriterHelper(const XMLHttpRequestStringWriterHelper&) =
  77       delete;
  78   XMLHttpRequestStringWriterHelper& operator=(
  79       const XMLHttpRequestStringWriterHelper&) = delete;
  80   XMLHttpRequestStringWriterHelper& operator=(
  81       const XMLHttpRequestStringWriterHelper&&) = delete;
  82
  83   RefPtr<XMLHttpRequestStringBuffer> mBuffer;
  84   MutexAutoLock mLock;
  85 };
  86
  87 // This class is the internal XMLHttpRequestStringBuffer of the
  88 // XMLHttpRequestString plus the current length. GetAsString will return the
  89 // string with that particular length also if the XMLHttpRequestStringBuffer is
  90 // grown in the meantime.
  91 class XMLHttpRequestStringSnapshot final {
  92   friend class XMLHttpRequestStringBuffer;
  93   friend class XMLHttpRequestStringSnapshotReaderHelper;
  94
  95  public:
  96   XMLHttpRequestStringSnapshot();
  97   ~XMLHttpRequestStringSnapshot();
  98
  99   XMLHttpRequestStringSnapshot& operator=(const XMLHttpRequestStringSnapshot&) =
 100       delete;
 101
 102   void Reset() { ResetInternal(false /* isVoid */); }
 103
 104   void SetVoid() { ResetInternal(true /* isVoid */); }
 105
 106   bool IsVoid() const { return mVoid; }
 107
 108   bool IsEmpty() const { return !mLength; }
 109
 110   [[nodiscard]] bool GetAsString(DOMString& aString) const;
 111
 112  private:
 113   XMLHttpRequestStringSnapshot(const XMLHttpRequestStringSnapshot&) = delete;
 114   XMLHttpRequestStringSnapshot& operator=(
 115       const XMLHttpRequestStringSnapshot&&) = delete;
 116
 117   void Set(XMLHttpRequestStringBuffer* aBuffer, uint32_t aLength);
 118
 119   void ResetInternal(bool aIsVoid);
 120
 121   RefPtr<XMLHttpRequestStringBuffer> mBuffer;
 122   uint32_t mLength;
 123   bool mVoid;
 124 };
 125
 126 // This class locks the buffer and allows the callee to read data from it.
 127 class MOZ_STACK_CLASS XMLHttpRequestStringSnapshotReaderHelper final {
 128  public:
 129   explicit XMLHttpRequestStringSnapshotReaderHelper(
 130       XMLHttpRequestStringSnapshot& aSnapshot);
 131   ~XMLHttpRequestStringSnapshotReaderHelper();
 132
 133   const char16_t* Buffer() const;
 134
 135   uint32_t Length() const;
 136
 137  private:
 138   XMLHttpRequestStringSnapshotReaderHelper(
 139       const XMLHttpRequestStringSnapshotReaderHelper&) = delete;
 140   XMLHttpRequestStringSnapshotReaderHelper& operator=(
 141       const XMLHttpRequestStringSnapshotReaderHelper&) = delete;
 142   XMLHttpRequestStringSnapshotReaderHelper& operator=(
 143       const XMLHttpRequestStringSnapshotReaderHelper&&) = delete;
 144
 145   RefPtr<XMLHttpRequestStringBuffer> mBuffer;
 146   MutexAutoLock mLock;
 147 };
 148
 149 }  // namespace mozilla::dom
 150
 151 #endif  // mozilla_dom_XMLHttpRequestString_h