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 /* 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;

 class nsCString;

 // 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 MOZ_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_t())) {

       NS_ABORT_OOM(GetLength());

     }

   }

   /**

    * Append the contents of this string fragment to aString

    * @return false if an out of memory condition is detected, true otherwise

    */

   bool AppendTo(nsAString& aString,

                 const mozilla::fallible_t&) const NS_WARN_UNUSED_RESULT {

     if (mState.mIs2b) {

       bool ok = aString.Append(m2b, mState.mLength, mozilla::fallible_t());

       if (!ok) {

         return false;

       }

       return true;

     } else {

       return AppendASCIItoUTF16(Substring(m1b, mState.mLength), aString,

                                 mozilla::fallible_t());

     }

   }

   /**

    * 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_t())) {

       NS_ABORT_OOM(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

    */

   bool AppendTo(nsAString& aString, int32_t aOffset, int32_t aLength,

                 const mozilla::fallible_t&) const NS_WARN_UNUSED_RESULT

   {

     if (mState.mIs2b) {

       bool ok = aString.Append(m2b + aOffset, aLength, mozilla::fallible_t());

       if (!ok) {

         return false;

       }

       return true;

     } else {

       return AppendASCIItoUTF16(Substring(m1b + aOffset, aLength), aString,

                                 mozilla::fallible_t());

     }

   }

   /**

    * 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___ */