restic/internal/hashing/writer.go

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package hashing
import (
"hash"
"io"
)
// Writer transparently hashes all data while writing it to the underlying writer.
type Writer struct {
w io.Writer
h hash.Hash
}
// NewWriter wraps the writer w and feeds all data written to the hash h.
func NewWriter(w io.Writer, h hash.Hash) *Writer {
return &Writer{
h: h,
w: w,
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}
}
// Write wraps the write method of the underlying writer and also hashes all data.
func (h *Writer) Write(p []byte) (int, error) {
// write the data to the underlying writing
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n, err := h.w.Write(p)
// according to the interface documentation, Write() on a hash.Hash never
// returns an error.
_, hashErr := h.h.Write(p[:n])
if hashErr != nil {
panic(hashErr)
}
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return n, err
}
// Sum returns the hash of all data written so far.
func (h *Writer) Sum(d []byte) []byte {
return h.h.Sum(d)
}