xpcom/string/nsTString.h
author Kartikaya Gupta <kgupta@mozilla.com>
Tue, 23 May 2017 10:50:42 -0400
changeset 408330 fa1a20ec07bfb15ddb9101853ad0cedde28ad7a7
parent 397485 533f7d421ef64569130ddbaf69425b702a837d69
child 414464 2915d4b7849612e583048650beabe33bad2cfeca
permissions -rw-r--r--
Bug 1364525 - Update APIs to allow APZ to produce scrollbar transforms. r=pchang,botond This allows the APZCTreeManager::PushStateToWR function to also produce a set of transforms to be applied to scrollbar thumbs. The PushStateToWR function will be updated in the next patch to actually produce the transforms. This patch also rearranges code in WebRenderBridgeParent::CompositeToTarget so that either OMTA or APZ can produce animation updates. MozReview-Commit-ID: 1ghvVG32TC5

/* -*- 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/. */
// IWYU pragma: private, include "nsString.h"

/**
 * This is the canonical null-terminated string class.  All subclasses
 * promise null-terminated storage.  Instances of this class allocate
 * strings on the heap.
 *
 * NAMES:
 *   nsString for wide characters
 *   nsCString for narrow characters
 *
 * This class is also known as nsAFlat[C]String, where "flat" is used
 * to denote a null-terminated string.
 */
class nsTString_CharT : public nsTSubstring_CharT
{
public:

  typedef nsTString_CharT self_type;

public:

  /**
   * constructors
   */

  nsTString_CharT()
    : substring_type()
  {
  }

  explicit
  nsTString_CharT(const char_type* aData, size_type aLength = size_type(-1))
    : substring_type()
  {
    Assign(aData, aLength);
  }

#if defined(CharT_is_PRUnichar) && defined(MOZ_USE_CHAR16_WRAPPER)
  explicit
  nsTString_CharT(char16ptr_t aStr, size_type aLength = size_type(-1))
    : substring_type()
  {
    Assign(static_cast<const char16_t*>(aStr), aLength);
  }
#endif

  nsTString_CharT(const self_type& aStr)
    : substring_type()
  {
    Assign(aStr);
  }

  MOZ_IMPLICIT nsTString_CharT(const substring_tuple_type& aTuple)
    : substring_type()
  {
    Assign(aTuple);
  }

  explicit
  nsTString_CharT(const substring_type& aReadable)
    : substring_type()
  {
    Assign(aReadable);
  }


  // |operator=| does not inherit, so we must define our own
  self_type& operator=(char_type aChar)
  {
    Assign(aChar);
    return *this;
  }
  self_type& operator=(const char_type* aData)
  {
    Assign(aData);
    return *this;
  }
  self_type& operator=(const self_type& aStr)
  {
    Assign(aStr);
    return *this;
  }
#if defined(CharT_is_PRUnichar) && defined(MOZ_USE_CHAR16_WRAPPER)
  self_type& operator=(const char16ptr_t aStr)
  {
    Assign(static_cast<const char16_t*>(aStr));
    return *this;
  }
#endif
  self_type& operator=(const substring_type& aStr)
  {
    Assign(aStr);
    return *this;
  }
  self_type& operator=(const substring_tuple_type& aTuple)
  {
    Assign(aTuple);
    return *this;
  }

  /**
   * returns the null-terminated string
   */

#if defined(CharT_is_PRUnichar) && defined(MOZ_USE_CHAR16_WRAPPER)
  char16ptr_t get() const
#else
  const char_type* get() const
#endif
  {
    return mData;
  }


  /**
   * returns character at specified index.
   *
   * NOTE: unlike nsTSubstring::CharAt, this function allows you to index
   *       the null terminator character.
   */

  char_type CharAt(index_type aIndex) const
  {
    NS_ASSERTION(aIndex <= mLength, "index exceeds allowable range");
    return mData[aIndex];
  }

  char_type operator[](index_type aIndex) const
  {
    return CharAt(aIndex);
  }


#if MOZ_STRING_WITH_OBSOLETE_API


  /**
   *  Search for the given substring within this string.
   *
   *  @param   aString is substring to be sought in this
   *  @param   aIgnoreCase selects case sensitivity
   *  @param   aOffset tells us where in this string to start searching
   *  @param   aCount tells us how far from the offset we are to search. Use
   *           -1 to search the whole string.
   *  @return  offset in string, or kNotFound
   */

  int32_t Find(const nsCString& aString, bool aIgnoreCase = false,
               int32_t aOffset = 0, int32_t aCount = -1) const;
  int32_t Find(const char* aString, bool aIgnoreCase = false,
               int32_t aOffset = 0, int32_t aCount = -1) const;

#ifdef CharT_is_PRUnichar
  int32_t Find(const nsAFlatString& aString, int32_t aOffset = 0,
               int32_t aCount = -1) const;
  int32_t Find(const char16_t* aString, int32_t aOffset = 0,
               int32_t aCount = -1) const;
#ifdef MOZ_USE_CHAR16_WRAPPER
  int32_t Find(char16ptr_t aString, int32_t aOffset = 0,
               int32_t aCount = -1) const
  {
    return Find(static_cast<const char16_t*>(aString), aOffset, aCount);
  }
#endif
#endif


  /**
   * This methods scans the string backwards, looking for the given string
   *
   * @param   aString is substring to be sought in this
   * @param   aIgnoreCase tells us whether or not to do caseless compare
   * @param   aOffset tells us where in this string to start searching.
   *          Use -1 to search from the end of the string.
   * @param   aCount tells us how many iterations to make starting at the
   *          given offset.
   * @return  offset in string, or kNotFound
   */

  int32_t RFind(const nsCString& aString, bool aIgnoreCase = false,
                int32_t aOffset = -1, int32_t aCount = -1) const;
  int32_t RFind(const char* aCString, bool aIgnoreCase = false,
                int32_t aOffset = -1, int32_t aCount = -1) const;

#ifdef CharT_is_PRUnichar
  int32_t RFind(const nsAFlatString& aString, int32_t aOffset = -1,
                int32_t aCount = -1) const;
  int32_t RFind(const char16_t* aString, int32_t aOffset = -1,
                int32_t aCount = -1) const;
#endif


  /**
   *  Search for given char within this string
   *
   *  @param   aChar is the character to search for
   *  @param   aOffset tells us where in this string to start searching
   *  @param   aCount tells us how far from the offset we are to search.
   *           Use -1 to search the whole string.
   *  @return  offset in string, or kNotFound
   */

  // int32_t FindChar( char16_t aChar, int32_t aOffset=0, int32_t aCount=-1 ) const;
  int32_t RFindChar(char16_t aChar, int32_t aOffset = -1,
                    int32_t aCount = -1) const;


  /**
   * This method searches this string for the first character found in
   * the given string.
   *
   * @param aString contains set of chars to be found
   * @param aOffset tells us where in this string to start searching
   *        (counting from left)
   * @return offset in string, or kNotFound
   */

  int32_t FindCharInSet(const char* aString, int32_t aOffset = 0) const;
  int32_t FindCharInSet(const self_type& aString, int32_t aOffset = 0) const
  {
    return FindCharInSet(aString.get(), aOffset);
  }

#ifdef CharT_is_PRUnichar
  int32_t FindCharInSet(const char16_t* aString, int32_t aOffset = 0) const;
#endif


  /**
   * This method searches this string for the last character found in
   * the given string.
   *
   * @param aString contains set of chars to be found
   * @param aOffset tells us where in this string to start searching
   *        (counting from left)
   * @return offset in string, or kNotFound
   */

  int32_t RFindCharInSet(const char_type* aString, int32_t aOffset = -1) const;
  int32_t RFindCharInSet(const self_type& aString, int32_t aOffset = -1) const
  {
    return RFindCharInSet(aString.get(), aOffset);
  }


  /**
   * Compares a given string to this string.
   *
   * @param   aString is the string to be compared
   * @param   aIgnoreCase tells us how to treat case
   * @param   aCount tells us how many chars to compare
   * @return  -1,0,1
   */

#ifdef CharT_is_char
  int32_t Compare(const char* aString, bool aIgnoreCase = false,
                  int32_t aCount = -1) const;
#endif


  /**
   * Equality check between given string and this string.
   *
   * @param   aString is the string to check
   * @param   aIgnoreCase tells us how to treat case
   * @param   aCount tells us how many chars to compare
   * @return  boolean
   */
#ifdef CharT_is_char
  bool EqualsIgnoreCase(const char* aString, int32_t aCount = -1) const
  {
    return Compare(aString, true, aCount) == 0;
  }
#else
  bool EqualsIgnoreCase(const char* aString, int32_t aCount = -1) const;


#endif // !CharT_is_PRUnichar

  /**
   * Perform string to double-precision float conversion.
   *
   * @param   aErrorCode will contain error if one occurs
   * @return  double-precision float rep of string value
   */
  double ToDouble(nsresult* aErrorCode) const;

  /**
   * Perform string to single-precision float conversion.
   *
   * @param   aErrorCode will contain error if one occurs
   * @return  single-precision float rep of string value
   */
  float ToFloat(nsresult* aErrorCode) const
  {
    return (float)ToDouble(aErrorCode);
  }


  /**
   * Perform string to int conversion.
   * @param   aErrorCode will contain error if one occurs
   * @param   aRadix tells us which radix to assume; kAutoDetect tells us to determine the radix for you.
   * @return  int rep of string value, and possible (out) error code
   */
  int32_t ToInteger(nsresult* aErrorCode, uint32_t aRadix = kRadix10) const;

  /**
   * Perform string to 64-bit int conversion.
   * @param   aErrorCode will contain error if one occurs
   * @param   aRadix tells us which radix to assume; kAutoDetect tells us to determine the radix for you.
   * @return  64-bit int rep of string value, and possible (out) error code
   */
  int64_t ToInteger64(nsresult* aErrorCode, uint32_t aRadix = kRadix10) const;


  /**
   * |Left|, |Mid|, and |Right| are annoying signatures that seem better almost
   * any _other_ way than they are now.  Consider these alternatives
   *
   * aWritable = aReadable.Left(17);   // ...a member function that returns a |Substring|
   * aWritable = Left(aReadable, 17);  // ...a global function that returns a |Substring|
   * Left(aReadable, 17, aWritable);   // ...a global function that does the assignment
   *
   * as opposed to the current signature
   *
   * aReadable.Left(aWritable, 17);    // ...a member function that does the assignment
   *
   * or maybe just stamping them out in favor of |Substring|, they are just duplicate functionality
   *
   * aWritable = Substring(aReadable, 0, 17);
   */

  size_type Mid(self_type& aResult, uint32_t aStartPos, uint32_t aCount) const;

  size_type Left(self_type& aResult, size_type aCount) const
  {
    return Mid(aResult, 0, aCount);
  }

  size_type Right(self_type& aResult, size_type aCount) const
  {
    aCount = XPCOM_MIN(mLength, aCount);
    return Mid(aResult, mLength - aCount, aCount);
  }


  /**
   * Set a char inside this string at given index
   *
   * @param aChar is the char you want to write into this string
   * @param anIndex is the ofs where you want to write the given char
   * @return TRUE if successful
   */

  bool SetCharAt(char16_t aChar, uint32_t aIndex);


  /**
   *  These methods are used to remove all occurrences of the
   *  characters found in aSet from this string.
   *
   *  @param  aSet -- characters to be cut from this
   */
#ifdef CharT_is_PRUnichar
  using nsTSubstring_CharT::StripChars;
#endif
  void StripChars(const char* aSet);
  bool StripChars(const char* aSet, const fallible_t&);


  /**
   *  This method strips whitespace throughout the string.
   */
  void StripWhitespace();
  bool StripWhitespace(const fallible_t&);


  /**
   *  swaps occurence of 1 string for another
   */

  void ReplaceChar(char_type aOldChar, char_type aNewChar);
  void ReplaceChar(const char* aSet, char_type aNewChar);
#ifdef CharT_is_PRUnichar
  void ReplaceChar(const char16_t* aSet, char16_t aNewChar);
#endif
  /**
   * Replace all occurrences of aTarget with aNewValue.
   * The complexity of this function is O(n+m), n being the length of the string
   * and m being the length of aNewValue.
   */
  void ReplaceSubstring(const self_type& aTarget, const self_type& aNewValue);
  void ReplaceSubstring(const char_type* aTarget, const char_type* aNewValue);
  MOZ_MUST_USE bool ReplaceSubstring(const self_type& aTarget,
                                     const self_type& aNewValue,
                                     const fallible_t&);
  MOZ_MUST_USE bool ReplaceSubstring(const char_type* aTarget,
                                     const char_type* aNewValue,
                                     const fallible_t&);


  /**
   *  This method trims characters found in aTrimSet from
   *  either end of the underlying string.
   *
   *  @param   aSet -- contains chars to be trimmed from both ends
   *  @param   aEliminateLeading
   *  @param   aEliminateTrailing
   *  @param   aIgnoreQuotes -- if true, causes surrounding quotes to be ignored
   *  @return  this
   */
  void Trim(const char* aSet, bool aEliminateLeading = true,
            bool aEliminateTrailing = true, bool aIgnoreQuotes = false);

  /**
   *  This method strips whitespace from string.
   *  You can control whether whitespace is yanked from start and end of
   *  string as well.
   *
   *  @param   aEliminateLeading controls stripping of leading ws
   *  @param   aEliminateTrailing controls stripping of trailing ws
   */
  void CompressWhitespace(bool aEliminateLeading = true,
                          bool aEliminateTrailing = true);


  /**
   * assign/append/insert with _LOSSY_ conversion
   */

  void AssignWithConversion(const nsTAString_IncompatibleCharT& aString);
  void AssignWithConversion(const incompatible_char_type* aData,
                            int32_t aLength = -1);

#endif // !MOZ_STRING_WITH_OBSOLETE_API

  /**
   * Allow this string to be bound to a character buffer
   * until the string is rebound or mutated; the caller
   * must ensure that the buffer outlives the string.
   */
  void Rebind(const char_type* aData, size_type aLength);

  /**
   * verify restrictions for dependent strings
   */
  void AssertValidDependentString()
  {
    NS_ASSERTION(mData, "nsTDependentString must wrap a non-NULL buffer");
    NS_ASSERTION(mLength != size_type(-1), "nsTDependentString has bogus length");
    NS_ASSERTION(mData[mLength] == 0,
                 "nsTDependentString must wrap only null-terminated strings. "
                 "You are probably looking for nsTDependentSubstring.");
  }


protected:

  // allow subclasses to initialize fields directly
  nsTString_CharT(char_type* aData, size_type aLength, uint32_t aFlags)
    : substring_type(aData, aLength, aFlags)
  {
  }

  struct Segment {
    uint32_t mBegin, mLength;
    Segment(uint32_t aBegin, uint32_t aLength)
      : mBegin(aBegin)
      , mLength(aLength)
    {}
  };
};


class nsTFixedString_CharT : public nsTString_CharT
{
public:

  typedef nsTFixedString_CharT self_type;
  typedef nsTFixedString_CharT fixed_string_type;

public:

  /**
   * @param aData
   *        fixed-size buffer to be used by the string (the contents of
   *        this buffer may be modified by the string)
   * @param aStorageSize
   *        the size of the fixed buffer
   * @param aLength (optional)
   *        the length of the string already contained in the buffer
   */

  nsTFixedString_CharT(char_type* aData, size_type aStorageSize)
    : string_type(aData, uint32_t(char_traits::length(aData)),
                  F_TERMINATED | F_FIXED | F_CLASS_FIXED)
    , mFixedCapacity(aStorageSize - 1)
    , mFixedBuf(aData)
  {
  }

  nsTFixedString_CharT(char_type* aData, size_type aStorageSize,
                       size_type aLength)
    : string_type(aData, aLength, F_TERMINATED | F_FIXED | F_CLASS_FIXED)
    , mFixedCapacity(aStorageSize - 1)
    , mFixedBuf(aData)
  {
    // null-terminate
    mFixedBuf[aLength] = char_type(0);
  }

  // |operator=| does not inherit, so we must define our own
  self_type& operator=(char_type aChar)
  {
    Assign(aChar);
    return *this;
  }
  self_type& operator=(const char_type* aData)
  {
    Assign(aData);
    return *this;
  }
  self_type& operator=(const substring_type& aStr)
  {
    Assign(aStr);
    return *this;
  }
  self_type& operator=(const substring_tuple_type& aTuple)
  {
    Assign(aTuple);
    return *this;
  }

protected:

  friend class nsTSubstring_CharT;

  size_type  mFixedCapacity;
  char_type* mFixedBuf;
};


/**
 * nsTAutoString_CharT
 *
 * Subclass of nsTString_CharT that adds support for stack-based string
 * allocation.  It is normally not a good idea to use this class on the
 * heap, because it will allocate space which may be wasted if the string
 * it contains is significantly smaller or any larger than 64 characters.
 *
 * NAMES:
 *   nsAutoString for wide characters
 *   nsAutoCString for narrow characters
 */
class MOZ_NON_MEMMOVABLE nsTAutoString_CharT : public nsTFixedString_CharT
{
public:

  typedef nsTAutoString_CharT self_type;

public:

  /**
   * constructors
   */

  nsTAutoString_CharT()
    : fixed_string_type(mStorage, kDefaultStorageSize, 0)
  {
  }

  explicit
  nsTAutoString_CharT(char_type aChar)
    : fixed_string_type(mStorage, kDefaultStorageSize, 0)
  {
    Assign(aChar);
  }

  explicit
  nsTAutoString_CharT(const char_type* aData, size_type aLength = size_type(-1))
    : fixed_string_type(mStorage, kDefaultStorageSize, 0)
  {
    Assign(aData, aLength);
  }

#if defined(CharT_is_PRUnichar) && defined(MOZ_USE_CHAR16_WRAPPER)
  explicit
  nsTAutoString_CharT(char16ptr_t aData, size_type aLength = size_type(-1))
    : nsTAutoString_CharT(static_cast<const char16_t*>(aData), aLength)
  {
  }
#endif

  nsTAutoString_CharT(const self_type& aStr)
    : fixed_string_type(mStorage, kDefaultStorageSize, 0)
  {
    Assign(aStr);
  }

  explicit
  nsTAutoString_CharT(const substring_type& aStr)
    : fixed_string_type(mStorage, kDefaultStorageSize, 0)
  {
    Assign(aStr);
  }

  MOZ_IMPLICIT nsTAutoString_CharT(const substring_tuple_type& aTuple)
    : fixed_string_type(mStorage, kDefaultStorageSize, 0)
  {
    Assign(aTuple);
  }

  // |operator=| does not inherit, so we must define our own
  self_type& operator=(char_type aChar)
  {
    Assign(aChar);
    return *this;
  }
  self_type& operator=(const char_type* aData)
  {
    Assign(aData);
    return *this;
  }
#if defined(CharT_is_PRUnichar) && defined(MOZ_USE_CHAR16_WRAPPER)
  self_type& operator=(char16ptr_t aStr)
  {
    Assign(aStr);
    return *this;
  }
#endif
  self_type& operator=(const self_type& aStr)
  {
    Assign(aStr);
    return *this;
  }
  self_type& operator=(const substring_type& aStr)
  {
    Assign(aStr);
    return *this;
  }
  self_type& operator=(const substring_tuple_type& aTuple)
  {
    Assign(aTuple);
    return *this;
  }

  enum
  {
    kDefaultStorageSize = 64
  };

private:

  char_type mStorage[kDefaultStorageSize];
};


//
// nsAutoString stores pointers into itself which are invalidated when an
// nsTArray is resized, so nsTArray must not be instantiated with nsAutoString
// elements!
//
template<class E> class nsTArrayElementTraits;
template<>
class nsTArrayElementTraits<nsTAutoString_CharT>
{
public:
  template<class A> struct Dont_Instantiate_nsTArray_of;
  template<class A> struct Instead_Use_nsTArray_of;

  static Dont_Instantiate_nsTArray_of<nsTAutoString_CharT>*
  Construct(Instead_Use_nsTArray_of<nsTString_CharT>* aE)
  {
    return 0;
  }
  template<class A>
  static Dont_Instantiate_nsTArray_of<nsTAutoString_CharT>*
  Construct(Instead_Use_nsTArray_of<nsTString_CharT>* aE, const A& aArg)
  {
    return 0;
  }
  static Dont_Instantiate_nsTArray_of<nsTAutoString_CharT>*
  Destruct(Instead_Use_nsTArray_of<nsTString_CharT>* aE)
  {
    return 0;
  }
};

/**
 * nsTXPIDLString extends nsTString such that:
 *
 *   (1) mData can be null
 *   (2) objects of this type can be automatically cast to |const CharT*|
 *   (3) getter_Copies method is supported to adopt data allocated with
 *       moz_xmalloc, such as "out string" parameters in XPIDL.
 *
 * NAMES:
 *   nsXPIDLString for wide characters
 *   nsXPIDLCString for narrow characters
 */
class nsTXPIDLString_CharT : public nsTString_CharT
{
public:

  typedef nsTXPIDLString_CharT self_type;

public:

  nsTXPIDLString_CharT()
    : string_type(char_traits::sEmptyBuffer, 0, F_TERMINATED | F_VOIDED)
  {
  }

  // copy-constructor required to avoid default
  nsTXPIDLString_CharT(const self_type& aStr)
    : string_type(char_traits::sEmptyBuffer, 0, F_TERMINATED | F_VOIDED)
  {
    Assign(aStr);
  }

  // return nullptr if we are voided
#if defined(CharT_is_PRUnichar) && defined(MOZ_USE_CHAR16_WRAPPER)
  char16ptr_t get() const
#else
  const char_type* get() const
#endif
  {
    return (mFlags & F_VOIDED) ? nullptr : mData;
  }

  // this case operator is the reason why this class cannot just be a
  // typedef for nsTString
  operator const char_type*() const
  {
    return get();
  }

  // need this to diambiguous operator[int]
  char_type operator[](int32_t aIndex) const
  {
    return CharAt(index_type(aIndex));
  }

  // |operator=| does not inherit, so we must define our own
  self_type& operator=(char_type aChar)
  {
    Assign(aChar);
    return *this;
  }
  self_type& operator=(const char_type* aStr)
  {
    Assign(aStr);
    return *this;
  }
  self_type& operator=(const self_type& aStr)
  {
    Assign(aStr);
    return *this;
  }
  self_type& operator=(const substring_type& aStr)
  {
    Assign(aStr);
    return *this;
  }
  self_type& operator=(const substring_tuple_type& aTuple)
  {
    Assign(aTuple);
    return *this;
  }
};


/**
 * getter_Copies support for use with raw string out params:
 *
 *    NS_IMETHOD GetBlah(char**);
 *
 *    void some_function()
 *    {
 *      nsXPIDLCString blah;
 *      GetBlah(getter_Copies(blah));
 *      // ...
 *    }
 */
class MOZ_STACK_CLASS nsTGetterCopies_CharT
{
public:
  typedef CharT char_type;

  explicit nsTGetterCopies_CharT(nsTSubstring_CharT& aStr)
    : mString(aStr)
    , mData(nullptr)
  {
  }

  ~nsTGetterCopies_CharT()
  {
    mString.Adopt(mData); // OK if mData is null
  }

  operator char_type**()
  {
    return &mData;
  }

private:
  nsTSubstring_CharT& mString;
  char_type* mData;
};

inline nsTGetterCopies_CharT
getter_Copies(nsTSubstring_CharT& aString)
{
  return nsTGetterCopies_CharT(aString);
}


/**
 * nsTAdoptingString extends nsTXPIDLString such that:
 *
 * (1) Adopt given string on construction or assignment, i.e. take
 * the value of what's given, and make what's given forget its
 * value. Note that this class violates constness in a few
 * places. Be careful!
 */
class nsTAdoptingString_CharT : public nsTXPIDLString_CharT
{
public:

  typedef nsTAdoptingString_CharT self_type;

public:

  explicit nsTAdoptingString_CharT()
  {
  }
  explicit nsTAdoptingString_CharT(char_type* aStr,
                                   size_type aLength = size_type(-1))
  {
    Adopt(aStr, aLength);
  }

  // copy-constructor required to adopt on copy. Note that this
  // will violate the constness of |aStr| in the operator=()
  // call. |aStr| will be truncated as a side-effect of this
  // constructor.
  nsTAdoptingString_CharT(const self_type& aStr)
    : nsTXPIDLString_CharT()
  {
    *this = aStr;
  }

  // |operator=| does not inherit, so we must define our own
  self_type& operator=(const substring_type& aStr)
  {
    Assign(aStr);
    return *this;
  }
  self_type& operator=(const substring_tuple_type& aTuple)
  {
    Assign(aTuple);
    return *this;
  }

  // Adopt(), if possible, when assigning to a self_type&. Note
  // that this violates the constness of aStr, aStr is always
  // truncated when this operator is called.
  self_type& operator=(const self_type& aStr);

private:
  self_type& operator=(const char_type* aData) = delete;
  self_type& operator=(char_type* aData) = delete;
};