1 files changed, 151 insertions, 0 deletions
diff --git a/dom/xhr/XMLHttpRequestString.h b/dom/xhr/XMLHttpRequestString.h
new file mode 100644
index 0000000000..76e072d78b
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+++ b/dom/xhr/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"
+
+namespace mozilla::dom {
+
+class ArrayBufferBuilder;
+class BlobImpl;
+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.
+  [[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;
+  friend class XMLHttpRequestStringSnapshotReaderHelper;
+
+ 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;
+
+ 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);
+  ~XMLHttpRequestStringSnapshotReaderHelper();
+
+  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;
+};
+
+}  // namespace mozilla::dom
+
+#endif  // mozilla_dom_XMLHttpRequestString_h