QSort for CStringArray

Environment: Tested on VC5

These three routines can be used to perform a qsort on a CStringArray.  It is a fairly simple hack, but still a hack.  It sure is fast, though.


// first, declare these somewhere
void SortStringArray (CStringArray& ar, BOOL bDescending);
int CompareDescending(const void *a, const void *b);
int CompareAscending(const void *a, const void *b);

// put something in your CString array
  CStringArray bob;
  bob.Add("Are");
  bob.Add("You");
  bob.Add("Talking");
  bob.Add("To");
  bob.Add("Me?");

// sort it
  SortStringArray(bob, TRUE);

// here's the code!

//////////////////////////////////////////////////////////////////////////
int CompareAscending(const void *a, const void *b)
{
  CString *pA = (CString*)a;
  CString *pB = (CString*)b;
  return (pA->Compare(*pB));
}

//////////////////////////////////////////////////////////////////////////
int CompareDescending(const void *a, const void *b)
{
  CString *pA = (CString*)a;
  CString *pB = (CString*)b;
  return (-1 * (pA->Compare(*pB)));
}

//////////////////////////////////////////////////////////////////////////
void SortStringArray (CStringArray& csa, BOOL bDescending)
{
  int iArraySize = csa.GetSize();
  if (iArraySize <= 0)
     return;

  int iCSSize = sizeof (CString*);
  void* pArrayStart = (void *)&csa[0];

  if (bDescending)
     qsort (pArrayStart, iArraySize, iCSSize, CompareDescending);
  else
     qsort (pArrayStart, iArraySize, iCSSize, CompareAscending);
}



Comments

  • Case sensitivity added...

    Posted by Legacy on 01/26/2000 12:00am

    Originally posted by: Troels

    //////////////////////////////////////////////////////////////////////////
    inline int StringArray_Compare(const void* a, const void* b, BOOL bCaseSensitive)
    {
    LPCTSTR pA = ((CString*)a)->operator LPCTSTR();
    LPCTSTR pB = ((CString*)b)->operator LPCTSTR();
    return bCaseSensitive ? _tcscmp(pA, pB) : _tcsicmp(pA, pB);
    }
    static int __cdecl StringArray_CompareAscending (const void* a, const void* b)
    {
    return StringArray_Compare(a, b, FALSE);
    }
    static int __cdecl StringArray_CompareDescending (const void* a, const void* b)
    {
    return StringArray_Compare(a, b, FALSE) * -1;
    }
    static int __cdecl StringArray_CompareAscending_Case (const void* a, const void* b)
    {
    return StringArray_Compare(a, b, TRUE);
    }
    static int __cdecl StringArray_CompareDescending_Case(const void* a, const void* b)
    {
    return StringArray_Compare(a, b, TRUE) * -1;
    }
    //////////////////////////////////////////////////////////////////////////
    int StringArray_Sort(CStringArray* pas, BOOL bCaseSensitive, BOOL bAscending)
    {
    const int count = pas->GetSize();
    qsort(pas->GetData(), count, sizeof(CString*),
    bAscending ? (bCaseSensitive ? StringArray_CompareAscending_Case : StringArray_CompareAscending )
    : (bCaseSensitive ? StringArray_CompareDescending_Case : StringArray_CompareDescending));
    return count;
    }
    //////////////////////////////////////////////////////////////////////////

    Reply
  • 1. Case insensitive sorting and 2. missing parameter error is not an error

    Posted by Legacy on 07/27/1999 12:00am

    Originally posted by: Will Mainwaring

    1.
    
    To sort the array without case considerstions, replace
    "pA->Compare(*pB)" with
    "pA->CompareNoCase(*pB)"

    2.
    The Compare function is not missing parameters, as it is a function pointer. qsort uses elements of the array passed in as void parameters to the Compare...() function.

    The error that this guy has reported is probably due to declaring the 3 functions in his class definition:
    void CMyClass::SortStringArray(...)
    As they are C functions, not C++ functions, you must use:
    void SortStringArray(...)
    Check the help in VC on the "__cdecl" keyword for C -> C++ compatibility.

    Reply
  • Compare function is missing parameters

    Posted by Legacy on 07/07/1999 12:00am

    Originally posted by: Tim Hodgson

    Ex: qsort (pArrayStart, iArraySize, iCSSize, CompareDescending);

    CompareDescending is missing parameters to make this code work.

    Anyone know what should go there?

    Reply
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