func readColonFile()

in internal/resources/utils/user/user.go [123:186]
41 lines of code
16 McCabe index (conditional complexity)

func readColonFile(r io.Reader, fn lineFunc, readCols int) (v any, err error) {
	rd := bufio.NewReader(r)

	// Read the file line-by-line.
	for {
		var isPrefix bool
		var wholeLine []byte

		// Read the next line. We do so in chunks (as much as reader's
		// buffer is able to keep), check if we read enough columns
		// already on each step and store final result in wholeLine.
		for {
			var line []byte
			line, isPrefix, err = rd.ReadLine()

			if err != nil {
				// We should return (nil, nil) if EOF is reached
				// without a match.
				if err == io.EOF {
					err = nil
				}
				return nil, err
			}

			// Simple common case: line is short enough to fit in a
			// single reader's buffer.
			if !isPrefix && len(wholeLine) == 0 {
				wholeLine = line
				break
			}

			wholeLine = append(wholeLine, line...)

			// Check if we read the whole line (or enough columns)
			// already.
			if !isPrefix || bytes.Count(wholeLine, []byte{':'}) >= readCols {
				break
			}
		}

		// There's no spec for /etc/passwd or /etc/group, but we try to follow
		// the same rules as the glibc parser, which allows comments and blank
		// space at the beginning of a line.
		wholeLine = bytes.TrimSpace(wholeLine)
		if len(wholeLine) == 0 || wholeLine[0] == '#' {
			continue
		}
		v, err = fn(wholeLine)
		if v != nil || err != nil {
			return
		}

		// If necessary, skip the rest of the line
		for ; isPrefix; _, isPrefix, err = rd.ReadLine() {
			if err != nil {
				// We should return (nil, nil) if EOF is reached without a match.
				if err == io.EOF {
					err = nil
				}
				return nil, err
			}
		}
	}
}