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 struct JSContext;
  14 class JSString;
  15
  16 namespace mozilla::dom {
  17
  18 class ArrayBufferBuilder;
  19 class BlobImpl;
  20 class DOMString;
  21 class XMLHttpRequestStringBuffer;
  22 class XMLHttpRequestStringSnapshot;
  23 class XMLHttpRequestStringWriterHelper;
  24
  25 // We want to avoid the dup of strings when XHR in workers has access to
  26 // responseText for events dispatched during the loading state. For this reason
  27 // we use this class, able to create snapshots of the current size of itself
  28 // without making extra copies.
  29 class XMLHttpRequestString final {
  30   friend class XMLHttpRequestStringWriterHelper;
  31
  32  public:
  33   XMLHttpRequestString();
  34   ~XMLHttpRequestString();
  35
  36   void Truncate();
  37
  38   uint32_t Length() const;
  39
  40   void Append(const nsAString& aString);
  41
  42   // This method should be called only when the string is really needed because
  43   // it can cause the duplication of the strings in case the loading of the XHR
  44   // is not completed yet.
  45   [[nodiscard]] bool GetAsString(nsAString& aString) const;
  46
  47   size_t SizeOfThis(MallocSizeOf aMallocSizeOf) const;
  48
  49   const char16_t* Data() const;
  50
  51   bool IsEmpty() const;
  52
  53   void CreateSnapshot(XMLHttpRequestStringSnapshot& aSnapshot);
  54
  55  private:
  56   XMLHttpRequestString(const XMLHttpRequestString&) = delete;
  57   XMLHttpRequestString& operator=(const XMLHttpRequestString&) = delete;
  58   XMLHttpRequestString& operator=(const XMLHttpRequestString&&) = delete;
  59
  60   RefPtr<XMLHttpRequestStringBuffer> mBuffer;
  61 };
  62
  63 // This class locks the buffer and allows the callee to write data into it.
  64 class MOZ_STACK_CLASS XMLHttpRequestStringWriterHelper final {
  65  public:
  66   explicit XMLHttpRequestStringWriterHelper(XMLHttpRequestString& aString);
  67   ~XMLHttpRequestStringWriterHelper();
  68
  69   /**
  70    * The existing length of the string. Do not call during BulkWrite().
  71    */
  72   uint32_t Length() const;
  73
  74   mozilla::Result<mozilla::BulkWriteHandle<char16_t>, nsresult> BulkWrite(
  75       uint32_t aCapacity);
  76
  77  private:
  78   XMLHttpRequestStringWriterHelper(const XMLHttpRequestStringWriterHelper&) =
  79       delete;
  80   XMLHttpRequestStringWriterHelper& operator=(
  81       const XMLHttpRequestStringWriterHelper&) = delete;
  82   XMLHttpRequestStringWriterHelper& operator=(
  83       const XMLHttpRequestStringWriterHelper&&) = delete;
  84
  85   RefPtr<XMLHttpRequestStringBuffer> mBuffer;
  86   MutexAutoLock mLock;
  87 };
  88
  89 // This class is the internal XMLHttpRequestStringBuffer of the
  90 // XMLHttpRequestString plus the current length. GetAsString will return the
  91 // string with that particular length also if the XMLHttpRequestStringBuffer is
  92 // grown in the meantime.
  93 class XMLHttpRequestStringSnapshot final {
  94   friend class XMLHttpRequestStringBuffer;
  95
  96  public:
  97   XMLHttpRequestStringSnapshot();
  98   ~XMLHttpRequestStringSnapshot();
  99
 100   XMLHttpRequestStringSnapshot& operator=(const XMLHttpRequestStringSnapshot&) =
 101       delete;
 102
 103   void Reset() { ResetInternal(false /* isVoid */); }
 104
 105   void SetVoid() { ResetInternal(true /* isVoid */); }
 106
 107   bool IsVoid() const { return mVoid; }
 108
 109   bool IsEmpty() const { return !mLength; }
 110
 111   [[nodiscard]] bool GetAsString(DOMString& aString) const;
 112
 113   JSString* GetAsJSStringCopy(JSContext* aCx) const;
 114
 115  private:
 116   XMLHttpRequestStringSnapshot(const XMLHttpRequestStringSnapshot&) = delete;
 117   XMLHttpRequestStringSnapshot& operator=(
 118       const XMLHttpRequestStringSnapshot&&) = delete;
 119
 120   void Set(XMLHttpRequestStringBuffer* aBuffer, uint32_t aLength);
 121
 122   void ResetInternal(bool aIsVoid);
 123
 124   RefPtr<XMLHttpRequestStringBuffer> mBuffer;
 125   uint32_t mLength;
 126   bool mVoid;
 127 };
 128
 129 }  // namespace mozilla::dom
 130
 131 #endif  // mozilla_dom_XMLHttpRequestString_h