1 files changed, 242 insertions, 0 deletions
diff --git a/dom/base/nsTextFragment.h b/dom/base/nsTextFragment.h
new file mode 100644
index 0000000000..47624d7211
--- /dev/null
+++ b/dom/base/nsTextFragment.h
@@ -0,0 +1,242 @@
+/* -*- 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/. */
+
+/*
+ * A class which represents a fragment of text (eg inside a text
+ * node); if only codepoints below 256 are used, the text is stored as
+ * a char*; otherwise the text is stored as a char16_t*
+ */
+
+#ifndef nsTextFragment_h___
+#define nsTextFragment_h___
+
+#include "mozilla/Attributes.h"
+#include "mozilla/MemoryReporting.h"
+
+#include "nsString.h"
+#include "nsReadableUtils.h"
+#include "nsISupportsImpl.h"
+
+class nsString;
+
+// XXX should this normalize the code to keep a \u0000 at the end?
+
+// XXX nsTextFragmentPool?
+
+/**
+ * A fragment of text. If mIs2b is 1 then the m2b pointer is valid
+ * otherwise the m1b pointer is valid. If m1b is used then each byte
+ * of data represents a single ucs2 character with the high byte being
+ * zero.
+ *
+ * This class does not have a virtual destructor therefore it is not
+ * meant to be subclassed.
+ */
+class nsTextFragment final {
+public:
+  static nsresult Init();
+  static void Shutdown();
+
+  /**
+   * Default constructor. Initialize the fragment to be empty.
+   */
+  nsTextFragment()
+    : m1b(nullptr), mAllBits(0)
+  {
+    MOZ_COUNT_CTOR(nsTextFragment);
+    NS_ASSERTION(sizeof(FragmentBits) == 4, "Bad field packing!");
+  }
+
+  ~nsTextFragment();
+
+  /**
+   * Change the contents of this fragment to be a copy of the
+   * the argument fragment, or to "" if unable to allocate enough memory.
+   */
+  nsTextFragment& operator=(const nsTextFragment& aOther);
+
+  /**
+   * Return true if this fragment is represented by char16_t data
+   */
+  bool Is2b() const
+  {
+    return mState.mIs2b;
+  }
+
+  /**
+   * Return true if this fragment contains Bidi text
+   * For performance reasons this flag is only set if explicitely requested (by
+   * setting the aUpdateBidi argument on SetTo or Append to true).
+   */
+  bool IsBidi() const
+  {
+    return mState.mIsBidi;
+  }
+
+  /**
+   * Get a pointer to constant char16_t data.
+   */
+  const char16_t *Get2b() const
+  {
+    NS_ASSERTION(Is2b(), "not 2b text"); 
+    return m2b;
+  }
+
+  /**
+   * Get a pointer to constant char data.
+   */
+  const char *Get1b() const
+  {
+    NS_ASSERTION(!Is2b(), "not 1b text"); 
+    return (const char *)m1b;
+  }
+
+  /**
+   * Get the length of the fragment. The length is the number of logical
+   * characters, not the number of bytes to store the characters.
+   */
+  uint32_t GetLength() const
+  {
+    return mState.mLength;
+  }
+
+  bool CanGrowBy(size_t n) const
+  {
+    return n < (1 << 29) && mState.mLength + n < (1 << 29);
+  }
+
+  /**
+   * Change the contents of this fragment to be a copy of the given
+   * buffer. If aUpdateBidi is true, contents of the fragment will be scanned,
+   * and mState.mIsBidi will be turned on if it includes any Bidi characters.
+   */
+  bool SetTo(const char16_t* aBuffer, int32_t aLength, bool aUpdateBidi);
+
+  /**
+   * Append aData to the end of this fragment. If aUpdateBidi is true, contents
+   * of the fragment will be scanned, and mState.mIsBidi will be turned on if
+   * it includes any Bidi characters.
+   */
+  bool Append(const char16_t* aBuffer, uint32_t aLength, bool aUpdateBidi);
+
+  /**
+   * Append the contents of this string fragment to aString
+   */
+  void AppendTo(nsAString& aString) const {
+    if (!AppendTo(aString, mozilla::fallible)) {
+      aString.AllocFailed(aString.Length() + GetLength());
+    }
+  }
+
+  /**
+   * Append the contents of this string fragment to aString
+   * @return false if an out of memory condition is detected, true otherwise
+   */
+  MOZ_MUST_USE
+  bool AppendTo(nsAString& aString,
+                const mozilla::fallible_t& aFallible) const {
+    if (mState.mIs2b) {
+      bool ok = aString.Append(m2b, mState.mLength, aFallible);
+      if (!ok) {
+        return false;
+      }
+
+      return true;
+    } else {
+      return AppendASCIItoUTF16(Substring(m1b, mState.mLength), aString,
+                                aFallible);
+    }
+  }
+
+  /**
+   * Append a substring of the contents of this string fragment to aString.
+   * @param aOffset where to start the substring in this text fragment
+   * @param aLength the length of the substring
+   */
+  void AppendTo(nsAString& aString, int32_t aOffset, int32_t aLength) const {
+    if (!AppendTo(aString, aOffset, aLength, mozilla::fallible)) {
+      aString.AllocFailed(aString.Length() + aLength);
+    }
+  }
+
+  /**
+   * Append a substring of the contents of this string fragment to aString.
+   * @param aString the string in which to append
+   * @param aOffset where to start the substring in this text fragment
+   * @param aLength the length of the substring
+   * @return false if an out of memory condition is detected, true otherwise
+   */
+  MOZ_MUST_USE
+  bool AppendTo(nsAString& aString, int32_t aOffset, int32_t aLength,
+                const mozilla::fallible_t& aFallible) const
+  {
+    if (mState.mIs2b) {
+      bool ok = aString.Append(m2b + aOffset, aLength, aFallible);
+      if (!ok) {
+        return false;
+      }
+
+      return true;
+    } else {
+      return AppendASCIItoUTF16(Substring(m1b + aOffset, aLength), aString,
+                                aFallible);
+    }
+  }
+
+  /**
+   * Make a copy of the fragments contents starting at offset for
+   * count characters. The offset and count will be adjusted to
+   * lie within the fragments data. The fragments data is converted if
+   * necessary.
+   */
+  void CopyTo(char16_t *aDest, int32_t aOffset, int32_t aCount);
+
+  /**
+   * Return the character in the text-fragment at the given
+   * index. This always returns a char16_t.
+   */
+  char16_t CharAt(int32_t aIndex) const
+  {
+    NS_ASSERTION(uint32_t(aIndex) < mState.mLength, "bad index");
+    return mState.mIs2b ? m2b[aIndex] : static_cast<unsigned char>(m1b[aIndex]);
+  }
+
+  struct FragmentBits {
+    // uint32_t to ensure that the values are unsigned, because we
+    // want 0/1, not 0/-1!
+    // Making these bool causes Windows to not actually pack them,
+    // which causes crashes because we assume this structure is no more than
+    // 32 bits!
+    uint32_t mInHeap : 1;
+    uint32_t mIs2b : 1;
+    uint32_t mIsBidi : 1;
+    uint32_t mLength : 29;
+  };
+
+  size_t SizeOfExcludingThis(mozilla::MallocSizeOf aMallocSizeOf) const;
+
+private:
+  void ReleaseText();
+
+  /**
+   * Scan the contents of the fragment and turn on mState.mIsBidi if it
+   * includes any Bidi characters.
+   */
+  void UpdateBidiFlag(const char16_t* aBuffer, uint32_t aLength);
+ 
+  union {
+    char16_t *m2b;
+    const char *m1b; // This is const since it can point to shared data
+  };
+
+  union {
+    uint32_t mAllBits;
+    FragmentBits mState;
+  };
+};
+
+#endif /* nsTextFragment_h___ */
+