gecko-dev/xpcom/ds/nsReadableUtils.cpp

/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/*
 * 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
 * the License at http://www.mozilla.org/MPL/
 * 
 * Software distributed under the License is distributed on an "AS
 * IS" basis, WITHOUT WARRANTY OF ANY KIND, either express or
 * implied. See the License for the specific language governing
 * rights and limitations under the License.
 * 
 * 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) 2000 Netscape Communications Corporation. All
 * Rights Reserved.
 *
 * Original Author:
 *   Scott Collins <scc@mozilla.org>
 *
 * Contributor(s):
 */

#include "nsReadableUtils.h"
#include "nsMemory.h"





  /**
   * A character sink that performs a |reinterpret_cast| style conversion between character types.
   */
template <class FromCharT, class ToCharT>
class LossyConvertEncoding
  {
    public:
      typedef FromCharT value_type;
 
      typedef FromCharT input_type;
      typedef ToCharT   output_type;

    public:
      LossyConvertEncoding( output_type* aDestination ) : mDestination(aDestination) { }

      PRUint32
      write( const input_type* aSource, PRUint32 aSourceLength )
        {
          const input_type* done_writing = aSource + aSourceLength;
          while ( aSource < done_writing )
            *mDestination++ = (output_type)(*aSource++);  // use old-style cast to mimic old |ns[C]String| behavior
          return aSourceLength;
        }

      void
      write_terminator()
        {
          *mDestination = output_type(0);
        }

    private:
      output_type* mDestination;
  };



  /**
   * A helper function that allocates a buffer of the desired character type big enough to hold a copy of the supplied string (plus a zero terminator).
   *
   * @param aSource an string you will eventually be making a copy of
   * @return a new buffer (of the type specified by the second parameter) which you must free with |nsMemory::Free|.
   *
   */
template <class FromCharT, class ToCharT>
inline
ToCharT*
AllocateStringCopy( const basic_nsAReadableString<FromCharT>& aSource, ToCharT* )
  {
    return NS_STATIC_CAST(ToCharT*, nsMemory::Alloc((aSource.Length()+1) * sizeof(ToCharT)));
  }


char*
ToNewCString( const nsAReadableString& aSource )
  {
    char* result = AllocateStringCopy(aSource, (char*)0);
    copy_string(aSource.BeginReading(), aSource.EndReading(), LossyConvertEncoding<PRUnichar, char>(result)).write_terminator();
    return result;
  }

char*
ToNewCString( const nsAReadableCString& aSource )
  {
    // no conversion needed, just allocate a buffer of the correct length and copy into it

    char* result = AllocateStringCopy(aSource, (char*)0);
    *copy_string(aSource.BeginReading(), aSource.EndReading(), result) = char(0);
    return result;
  }

PRUnichar*
ToNewUnicode( const nsAReadableString& aSource )
  {
    // no conversion needed, just allocate a buffer of the correct length and copy into it

    PRUnichar* result = AllocateStringCopy(aSource, (PRUnichar*)0);
    *copy_string(aSource.BeginReading(), aSource.EndReading(), result) = PRUnichar(0);
    return result;
  }

PRUnichar*
ToNewUnicode( const nsAReadableCString& aSource )
  {
    PRUnichar* result = AllocateStringCopy(aSource, (PRUnichar*)0);
    copy_string(aSource.BeginReading(), aSource.EndReading(), LossyConvertEncoding<char, PRUnichar>(result)).write_terminator();
    return result;
  }

PRBool
IsASCII( const nsAReadableString& aString )
  {
    static const PRUnichar NOT_ASCII = PRUnichar(~0x007F);


    // Don't want to use |copy_string| for this task, since we can stop at the first non-ASCII character

    typedef nsAReadableString::const_iterator iterator;
    iterator iter = aString.BeginReading();
    iterator done_reading = aString.EndReading();

      // for each chunk of |aString|...
    while ( iter != done_reading )
      {
        iterator::difference_type chunk_size = iter.size_forward();
        const PRUnichar* c = iter.get();
        const PRUnichar* chunk_end = c + chunk_size;

          // for each character in this chunk...
        while ( c < chunk_end )
          if ( *c++ & NOT_ASCII )
            return PR_FALSE;

        iter += chunk_size;
      }

    return PR_TRUE;
  }