func (s *Stack) IterateBackward(handler func(depth int, header io.Reader, body io.Reader) bool) error {
	s.guard.Lock()
	defer s.guard.Unlock()
	if s.depth == 0 {
		return nil
	}
	file, err := s.getFile()
	if err != nil {
		return err
	}
	defer file.Seek(0, os.SEEK_END)
	var (
		currentBlock       fileBlock // Current block description
		currentBlockOffset uint64    // Current block offset from begining of file
	)
	currentBlock = s.currentBlock
	currentBlockOffset = uint64(s.currentBlockPos)
	depth := s.depth
	for {
		body := io.NewSectionReader(file, int64(currentBlock.DataPoint), int64(currentBlock.DataSize))
		header := io.NewSectionReader(file, int64(currentBlock.HeaderPoint), int64(currentBlock.HeaderSize))
		// invoke block processor
		if handler != nil && !handler(depth, header, body) {
			return nil
		}
		if currentBlock.PrevBlock > currentBlockOffset {
			log.Printf("Danger back-ref link: prev block %v has greater index then current %v", currentBlock.PrevBlock, currentBlockOffset)
		}

		depth--
		if currentBlock.PrevBlock == currentBlockOffset {
			// First block has prev block = 0
			break
		}
		currentBlockOffset = currentBlock.PrevBlock
		currentBlock, err = readBlockAt(file, int64(currentBlock.PrevBlock))
		if err != nil {
			return err
		}
	}
	if depth != 0 {
		log.Println("Broker back path detected at", depth, "depth index")
	}
	return nil
}
func (s *Stack) IterateBackward(handler func(depth int, header io.Reader, body io.Reader) bool) error {
	s.guard.Lock()
	defer s.guard.Unlock()
	if s.depth == 0 {
		return nil
	}
	file, err := s.getFile()
	if err != nil {
		return err
	}
	defer file.Seek(0, os.SEEK_END)
	var (
		currentBlock       fileBlock 
		currentBlockOffset uint64    
	)
	currentBlock = s.currentBlock
	currentBlockOffset = uint64(s.currentBlockPos)
	depth := s.depth
	for {
		body := io.NewSectionReader(file, int64(currentBlock.DataPoint), int64(currentBlock.DataSize))
		header := io.NewSectionReader(file, int64(currentBlock.HeaderPoint), int64(currentBlock.HeaderSize))
		
		if handler != nil && !handler(depth, header, body) {
			return nil
		}
		if currentBlock.PrevBlock > currentBlockOffset {
			log.Printf("Danger back-ref link: prev block %v has greater index then current %v", currentBlock.PrevBlock, currentBlockOffset)
		}

		depth--
		if currentBlock.PrevBlock == currentBlockOffset {
			
			break
		}
		currentBlockOffset = currentBlock.PrevBlock
		currentBlock, err = readBlockAt(file, int64(currentBlock.PrevBlock))
		if err != nil {
			return err
		}
	}
	if depth != 0 {
		log.Println("Broker back path detected at", depth, "depth index")
	}
	return nil
}
func ( s * Stack ) IterateBackward ( handler func ( depth int , header io . Reader , body io . Reader ) bool ) error { s . guard . Lock ( ) defer s . guard . Unlock ( ) if s . depth == 0 { return nil } file , err := s . getFile ( ) if err != nil { return err } defer file . Seek ( 0 , os . SEEK_END ) var ( currentBlock fileBlock // Current block description currentBlockOffset uint64 // Current block offset from begining of file ) currentBlock = s . currentBlock currentBlockOffset = uint64 ( s . currentBlockPos ) depth := s . depth for { body := io . NewSectionReader ( file , int64 ( currentBlock . DataPoint ) , int64 ( currentBlock . DataSize ) ) header := io . NewSectionReader ( file , int64 ( currentBlock . HeaderPoint ) , int64 ( currentBlock . HeaderSize ) ) // invoke block processor if handler != nil && ! handler ( depth , header , body ) { return nil } if currentBlock . PrevBlock > currentBlockOffset { log . Printf ( " " , currentBlock . PrevBlock , currentBlockOffset ) } depth -- if currentBlock . PrevBlock == currentBlockOffset { // First block has prev block = 0 break } currentBlockOffset = currentBlock . PrevBlock currentBlock , err = readBlockAt ( file , int64 ( currentBlock . PrevBlock ) ) if err != nil { return err } } if depth != 0 { log . Println ( " " , depth , " " ) } return nil }
// IterateBackward - iterate over hole stack segment-by-segment from end to begining
IterateBackward - iterate over hole stack segment - by - segment from end to begining