Win32 file name iteration STL way

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Introduction

Several times I worked with file names, I usually used Win32 API such as ::FindFirstFile.. But it turns out that it's so boring work. Finally, I realized I can use STL's great feature, iterator, to handle file name iteration. That's why I made a simple STL iterator class for file name iteration.

Usage

win32_file_iterator itBegin("c:\\*.*"), itEnd;
std::copy(itBegin, itEnd, ostream_iterator<std::string>(cout, "\n"));

The code above shows the simplest way to use the class. Actually, you can use almost all of STL algorithm, I think..

win32_file_iterator itBegin("c:\\*.*"), itEnd;
std::vector<std::string> vec(itBegin, itEnd);

You also can fill the STL container by using the constructor that takes begin iterator and end iterator.

Actually, win32_file_iterator class' constructor takes three parameters. The first one is the filter string that is for calling ::FindFirstFile function. Second one is the flag that specifies whether dereferenced path is full path or not. For example, if it's true, the returned path string is c:\test\aa.txt, otherwise it'll be aa.txt only. The last parameter is the other flags which specify file attribute. For simplicity, I used Win32 API's FILE_ATTRIBUTE_XXX flags..

If you want to get only directory names, and which is full path, the code will look like this:

win32_file_iterator itBegin("c:\\*", true, FILE_ATTRIBUTE_DIRECTORY);

So easy, huh?

Source

#include <windows.h>
#include <iterator>
#include <string>

class win32_file_iterator : 
 public std::iterator<std::input_iterator_tag, std::string>
{
private:

 class internal_handle_data{
 public:
  internal_handle_data():_h(NULL), _ref(0){}
  void setHandle(HANDLE handle){ _h = handle; }
  HANDLE getHandle(){ return _h; }
  void incRef(){ _ref++; }
  unsigned decRef(){ return --_ref; }
  operator HANDLE(){ return _h; }

 private:
  HANDLE _h;
  unsigned _ref;
 };


public:

 win32_file_iterator(std::string strfilter, bool bFullPath = false, 
   int flag = FILE_ATTRIBUTE_ARCHIVE|FILE_ATTRIBUTE_NORMAL|FILE_ATTRIBUTE_DIRECTORY):
   _bEnd(false), _bFullPath(bFullPath), _flag(flag){
        HANDLE h = ::FindFirstFile(strfilter.c_str(), &_wfd);
  _handle.setHandle(h);
  if(h == INVALID_HANDLE_VALUE){
   _bEnd = true;
  }else{
   _handle.incRef();
   std::string::size_type n1 = strfilter.find_last_of("\\");
   _strroot = strfilter.substr(0,n1+1);
   _chkvalid(_wfd);
  }
 }

 win32_file_iterator():_bEnd(true){}

 win32_file_iterator(win32_file_iterator& rhs){
  
  _handle = rhs._handle;
  _handle.incRef();
  _flag = rhs._flag;
  _bFullPath = rhs._bFullPath;
  _bEnd = rhs._bEnd;
  _wfd = rhs._wfd;
  _strfname = rhs._strfname;
  _strroot = rhs._strroot;  
 }

 ~win32_file_iterator(){
  if(_handle.decRef() == 0 && _handle.getHandle() != NULL ){
   FindClose(_handle);
  }
  
 }

 reference operator*(){
  return _strfname;
 }

 bool operator==(const win32_file_iterator& rhs) const{
  return (_bEnd == rhs._bEnd);
 }

 bool operator!=(const win32_file_iterator& rhs) const{
  return (_bEnd != rhs._bEnd);
 }


 win32_file_iterator& operator++(){
  _findnext();
  return *this;
 }

 win32_file_iterator& operator++(int){
  _findnext();
  return *this;
 }

private:

 void _findnext(){
  BOOL b = ::FindNextFile(_handle, &_wfd);
  if(b){
   _chkvalid(_wfd);
  }else{
   _bEnd = true;
  }
 }

 void _chkvalid(WIN32_FIND_DATA& _wfd){
  if(_wfd.dwFileAttributes & _flag){
   _getval(_wfd);
  }
  else{
   _findnext();
  }
 }

 void _getval(WIN32_FIND_DATA& wfd){
  if(_bFullPath)
   _strfname = _strroot+ wfd.cFileName;
  else
   _strfname = wfd.cFileName;
 }


private:
 int _flag;
 bool _bFullPath;
 bool _bEnd;
 internal_handle_data _handle;
 WIN32_FIND_DATA _wfd;
 std::string _strroot;
 std::string _strfname;
};

Comment

The code might have many terrible bugs. But what I want was to show the way we can use STL like iteration to find filenames. I wish it'll help you. You can use this code in whatever ways you want, comments are welcome..

And also check out boost::filesystem library.. it's well-written but a little bit heavy. It needs an additional DLL, I suppose.

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