Function getFileScanner

io.go:743–777

get suitable scanner(compressed or not)

(fn string)

// get suitable scanner(compressed or not)
func getFileScanner(fn string) (*bufio.Scanner, error) {
	info, err := os.Stat(fn)
	if err != nil {
		return nil, err
	}
	//check if fn is a directory
	if info.IsDir() {
		return nil, errors.New(fn + " is a directory")
	}

	file, err := os.Open(fn)
	if err != nil {
		return nil, err
	}

	var scanner *bufio.Scanner
	//if input is a gzip file
	if strings.HasSuffix(fn, ".gz") {
		gzCont, err := gzip.NewReader(file)
		if err != nil {
			return nil, err
		}
		scanner = bufio.NewScanner(gzCont)
	} else {
		scanner = bufio.NewScanner(file)
	}

	//increase buffer size for large files and long lines
	//default is 64KB, we set to 1MB for better performance
	const maxScanTokenSize = 1024 * 1024
	buf := make([]byte, maxScanTokenSize)
	scanner.Buffer(buf, maxScanTokenSize)

	return scanner, nil
}

// check columns that should be displayed
func getVisCol(showNumL, hideNumL []int, colLen int) ([]int, error) {