gecko-dev/string/public/nsPrintfCString.h

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 * The contents of this file are subject to the Mozilla Public
 * License Version 1.1 (the "License"); you may not use this file
 * except in compliance with the License. You may obtain a copy of
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 * 
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 * IS" basis, WITHOUT WARRANTY OF ANY KIND, either express or
 * implied. See the License for the specific language governing
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 * The Original Code is mozilla.org code.
 * 
 * The Initial Developer of the Original Code is Netscape
 * Communications Corporation.  Portions created by Netscape are 
 * Copyright (C) 1994-2000 Netscape Communications Corporation.  All
 * Rights Reserved.
 * 
 * Original Author:
 *   Scott Collins <scc@mozilla.org>
 *
 * Contributor(s):
 * 
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 * terms of the GNU General Public License Version 2 or later (the
 * "GPL"), in which case the provisions of the GPL are applicable 
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 * GPL.
 */

#ifndef nsPrintfCString_h___
#define nsPrintfCString_h___
 
#ifndef nsAFlatString_h___
#include "nsAFlatString.h"
#endif


  /**
   * |nsPrintfCString| lets you use a formated |printf| string as an |const nsACString|.
   *
   *   myCStr += nsPrintfCString("%f", 13.917);
   *     // ...a general purpose substitute for |AppendFloat|
   *
   * For longer patterns, you'll want to use the constructor that takes a length
   *
   *   nsPrintfCString(128, "%f, %f, %f, %f, %f, %f, %f, %i, %f", x, y, z, 3.2, j, k, l, 3, 3.1);
   *
   * Exceding the default size (which you must specify in the constructor, it is not determined)
   * causes an allocation, so avoid that.  If your formatted string exceeds the allocated space, it is
   * cut off at the size of the buffer, no error is reported (and no out-of-bounds writing occurs).
   * This class is intended to be useful for numbers and short
   * strings, not arbitrary formatting of other strings (e.g., with %s).  There is currently no
   * wide version of this class, since wide |printf| is not generally available.  That means
   * to get a wide version of your formatted data, you must, e.g.,
   *
   *   CopyASCIItoUCS2(nsPrintfCString("%f", 13.917"), myStr);
   *
   * That's another good reason to avoid this class for anything but numbers ... as strings can be
   * much more efficiently handled with |NS_LITERAL_[C]STRING| and |nsLiteral[C]String|.
   */

class NS_COM nsPrintfCString
    : public nsAFlatCString
  {
    enum { kLocalBufferSize=15 };
      // ought to be large enough for most things ... a |long long| needs at most 20 (so you'd better ask)
      //  pinkerton suggests 7.  We should measure and decide what's appropriate


    public:
      explicit nsPrintfCString( const char_type* format, ... );
      nsPrintfCString( size_t n, const char_type* format, ...);
     ~nsPrintfCString();

      virtual PRUint32 Length() const;

    protected:
      virtual const char_type* GetReadableFragment( const_fragment_type&, nsFragmentRequest, PRUint32 ) const;
      virtual       char_type* GetWritableFragment(       fragment_type&, nsFragmentRequest, PRUint32 ) { return 0; }

    private:
      char_type* mStart;
      PRUint32   mLength;
      char_type  mLocalBuffer[ kLocalBufferSize + 1 ];
  };

#endif // !defined(nsPrintfCString_h___)