Microsoft KB Archive/216858

= How to use the quick-sort function to sort MFC CArray-derived classes on the MFC and Visual C++ run-time library =

Article ID: 216858

Article Last Modified on 1/21/2006

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APPLIES TO


 * Microsoft Visual C++ 5.0 Enterprise Edition
 * Microsoft Visual C++ 6.0 Enterprise Edition
 * Microsoft Visual C++ 5.0 Professional Edition
 * Microsoft Visual C++ 6.0 Professional Edition
 * Microsoft Visual C++ 6.0 Standard Edition
 * Microsoft Visual C++ .NET 2003 Standard Edition
 * Microsoft Visual C++ .NET 2002 Standard Edition
 * Microsoft Visual C++ 2005 Express Edition

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This article was previously published under Q216858



SUMMARY
Note Microsoft Visual C++ .NET (2002) supports both the managed code model that is provided by the Microsoft .NET Framework and the unmanaged native Microsoft Windows code model. The information in this article applies to unmanaged Visual C++ code only.

Note Microsoft Visual C++ 2005 supports both the managed code model that is provided by the Microsoft .NET Framework and the unmanaged native Microsoft Windows code model.

This article shows you how to quick-sort an MFC CArray-derived class. The code below depends only on the MFC and Visual C++ run-time library.



MORE INFORMATION
The Visual C++ run-time library (MSVCRT) implements the quick-sort function, qsort, as follows: void qsort( void *base, size_t num, size_t width, int (__cdecl *compare )(const void *elem1, const void *elem2 ) ); The following example shows you how to use this function to sort an MFC CArray class. Although the following example uses a CString array, you can easily customize for other MFC CArray-derived classes, such as CByteArray, CDWordArray, CObArray, CPtrArray, CUintArray, and CWordArray.

Steps to implement sorting
  Derive your array data class from one of the CArray-derived classes. In our example, we use CStringArray as the base class for our class. The following is the declaration in the header file: class CSortableStringArray : public CStringArray { public: protected: };                         To the public section of your class add the following function: void Sort(STRINGCOMPAREFN pfnCompare = Compare);   To the protected section of your class add the following static function: static int __cdecl Compare(const CString * pstr1, const CString * pstr2);   Now add the following two type defs above the declaration of your class. These typedefs later help us in passing pointers of the two functions that we declared in steps 2 and 3 to the Visual C++ run-time's qsort function: typedef int (__cdecl *GENERICCOMPAREFN)(const void * elem1, const void * elem2); typedef int (__cdecl *STRINGCOMPAREFN)(const CString * elem1, const CString * elem2);   In your .cpp file, implement the two functions that you declared earlier: // // SortableStringArray.cpp //

int CSortableStringArray::Compare(const CString * pstr1, const CString * pstr2) {   ASSERT(pstr1); ASSERT(pstr2); return pstr1->Compare(*pstr2); }

void CSortableStringArray::Sort(STRINGCOMPAREFN pfnCompare /*= CSortedStringArray::Compare */) {   CString * prgstr = GetData; qsort(prgstr,GetSize,sizeof(CString),(GENERICCOMPAREFN)pfnCompare); }                       

That is it. Now let's look at the contents of the entire file: // // SortableStringArray.h //

typedef int (__cdecl *GENERICCOMPAREFN)(const void * elem1, const void * elem2); typedef int (__cdecl *STRINGCOMPAREFN)(const CString * elem1, const CString * elem2);

class CSortableStringArray : public CStringArray { public: void Sort(STRINGCOMPAREFN pfnCompare = Compare);

protected: static int __cdecl Compare(const CString * pstr1, const CString * pstr2); };

// // SortableStringArray.cpp //


 * 1) include "SortableStringArray.h"

int CSortableStringArray::Compare(const CString * pstr1, const CString * pstr2) {   ASSERT(pstr1); ASSERT(pstr2); return pstr1->Compare(*pstr2); }

void CSortableStringArray::Sort(STRINGCOMPAREFN pfnCompare /*= CSortedStringArray::Compare */) {   CString * prgstr = GetData; qsort(prgstr,GetSize,sizeof(CString),(GENERICCOMPAREFN)pfnCompare); } To use the array in your code, just declare it and call the Sort function. The following example uses this array: srand( (unsigned)time( NULL ) ); // Generate seed for rand. CSortableStringArray arr; CString str; for (int i=0; i< 1000;i++) {       str.Format("%6d", rand);// Get a random number string. arr.Add(str); TRACE("%s\n", (LPCTSTR)str); }   long ltim=GetTickCount; arr.Sort; for (i=0; i< 1000;i++) {       TRACE("%s\n", (LPCTSTR)arr[i]); }

TRACE("Time took= %li\n", GetTickCount-ltim); Note To implement a CArray type other than CString, just derive your class from the other array types and modify the Sort and the Compare functions accordingly.

Note Quick Sort is a more efficient mechanism of sorting than the bubble sort used in the Microsoft Knowledge Base article, "How to Sort a CStringArray in MFC" (Q120961)

