restic/backend/hashing_reader.go

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2015-02-11 18:20:45 +00:00
package backend
import (
"hash"
"io"
)
type HashReader struct {
r io.Reader
h hash.Hash
sum []byte
closed bool
}
func NewHashReader(r io.Reader, h hash.Hash) *HashReader {
return &HashReader{
h: h,
r: io.TeeReader(r, h),
sum: make([]byte, 0, h.Size()),
}
}
func (h *HashReader) Read(p []byte) (n int, err error) {
if !h.closed {
n, err = h.r.Read(p)
if err == io.EOF {
h.closed = true
h.sum = h.h.Sum(h.sum)
} else if err != nil {
return
}
}
if h.closed {
// output hash
r := len(p) - n
if r > 0 {
c := copy(p[n:], h.sum)
h.sum = h.sum[c:]
n += c
err = nil
}
if len(h.sum) == 0 {
err = io.EOF
}
}
return
}