gistfile1.go

package counter

import (
    "io"
)

type Counter struct {
    w io.Writer // Underlying writer to send data to
    c int       // Number of bytes written since last call to Count()
}

func New(w io.Writer) (h *Counter) {
    h = new(Counter)
    h.w = w
    return
}

// Write: standard io.Writer interface.  To use this package call
// Write continually.  This will both count the bytes written and
// write to the underlying writer.
func (h *Counter) Write(p []byte) (n int, err error) {
    n, err = h.w.Write(p)
    h.c += n
    return
}

// Count: returns the total number of bytes that were written to the
// underlying writer since the last call to Count
func (h *Counter) Count() (c int) {
    c = h.c
    h.c = 0
    return
}