将bufio.Scanner的阅读器包装在bufio.Reader中有什么好处？

Question

I'm using bufio.Scanner, and I'm not sure if I should be giving it a reader wrapped by bufio.Reader.

I.e., where f is an os.File, should I:

scanner := bufio.NewScanner(f)

or

scanner := bufio.NewScanner(bufio.NewReader(f))

Answer 1

From the scan.go source it doesn't look like you need to pass it a *bufio.Reader: it has its own buffer, defaulting to 4K as bufio.Reader's buffers do.

// NewScanner returns a new Scanner to read from r.
// The split function defaults to ScanLines.
func NewScanner(r io.Reader) *Scanner {
    return &Scanner{
        r:            r,
        split:        ScanLines,
        maxTokenSize: MaxScanTokenSize,
        buf:          make([]byte, 4096), // Plausible starting size; needn't be large.
    }
}