1 files changed, 139 insertions, 0 deletions
diff --git a/parser/html/nsHtml5String.h b/parser/html/nsHtml5String.h
new file mode 100644
index 0000000000..f725630f9e
--- /dev/null
+++ b/parser/html/nsHtml5String.h
@@ -0,0 +1,139 @@
+/* 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 nsHtml5String_h
+#define nsHtml5String_h
+
+#include "nsAtom.h"
+#include "nsString.h"
+#include "nsStringBuffer.h"
+
+class nsHtml5TreeBuilder;
+
+/**
+ * A pass-by-value type that can represent
+ *  * nullptr
+ *  * empty string
+ *  * Non-empty string as exactly-sized (capacity is length) `nsStringBuffer*`
+ *  * Non-empty string as an nsAtom*
+ *
+ * Holding or passing this type is as unsafe as holding or passing
+ * `nsStringBuffer*`/`nsAtom*`.
+ */
+class nsHtml5String final {
+ private:
+  static const uintptr_t kKindMask = uintptr_t(3);
+
+  static const uintptr_t kPtrMask = ~kKindMask;
+
+  enum Kind : uintptr_t {
+    eNull = 0,
+    eEmpty = 1,
+    eStringBuffer = 2,
+    eAtom = 3,
+  };
+
+  inline Kind GetKind() const { return (Kind)(mBits & kKindMask); }
+
+  inline nsStringBuffer* AsStringBuffer() const {
+    MOZ_ASSERT(GetKind() == eStringBuffer);
+    return reinterpret_cast<nsStringBuffer*>(mBits & kPtrMask);
+  }
+
+  inline nsAtom* AsAtom() const {
+    MOZ_ASSERT(GetKind() == eAtom);
+    return reinterpret_cast<nsAtom*>(mBits & kPtrMask);
+  }
+
+  inline const char16_t* AsPtr() const {
+    switch (GetKind()) {
+      case eStringBuffer:
+        return reinterpret_cast<char16_t*>(AsStringBuffer()->Data());
+      case eAtom:
+        return AsAtom()->GetUTF16String();
+      default:
+        return nsCharTraits<char16_t>::sEmptyBuffer;
+    }
+  }
+
+ public:
+  /**
+   * Default constructor.
+   */
+  inline nsHtml5String() : nsHtml5String(nullptr) {}
+
+  /**
+   * Constructor from nullptr.
+   */
+  inline MOZ_IMPLICIT nsHtml5String(decltype(nullptr)) : mBits(eNull) {}
+
+  inline uint32_t Length() const {
+    switch (GetKind()) {
+      case eStringBuffer:
+        return (AsStringBuffer()->StorageSize() / sizeof(char16_t) - 1);
+      case eAtom:
+        return AsAtom()->GetLength();
+      default:
+        return 0;
+    }
+  }
+
+  /**
+   * False iff the string is logically null
+   */
+  inline MOZ_IMPLICIT operator bool() const { return mBits; }
+
+  /**
+   * Get the underlying nsAtom* or nullptr if this nsHtml5String
+   * does not hold an atom.
+   */
+  inline nsAtom* MaybeAsAtom() {
+    if (GetKind() == eAtom) {
+      return AsAtom();
+    }
+    return nullptr;
+  }
+
+  void ToString(nsAString& aString);
+
+  void CopyToBuffer(char16_t* aBuffer) const;
+
+  bool LowerCaseEqualsASCII(const char* aLowerCaseLiteral) const;
+
+  bool EqualsASCII(const char* aLiteral) const;
+
+  bool LowerCaseStartsWithASCII(const char* aLowerCaseLiteral) const;
+
+  bool Equals(nsHtml5String aOther) const;
+
+  nsHtml5String Clone();
+
+  void Release();
+
+  static nsHtml5String FromBuffer(char16_t* aBuffer, int32_t aLength,
+                                  nsHtml5TreeBuilder* aTreeBuilder);
+
+  static nsHtml5String FromLiteral(const char* aLiteral);
+
+  static nsHtml5String FromString(const nsAString& aString);
+
+  static nsHtml5String FromAtom(already_AddRefed<nsAtom> aAtom);
+
+  static nsHtml5String EmptyString();
+
+ private:
+  /**
+   * Constructor from raw bits.
+   */
+  explicit nsHtml5String(uintptr_t aBits) : mBits(aBits){};
+
+  /**
+   * Zero if null, one if empty, otherwise tagged pointer
+   * to either nsAtom or nsStringBuffer. The two least-significant
+   * bits are tag bits.
+   */
+  uintptr_t mBits;
+};
+
+#endif  // nsHtml5String_h