restic/backend/writer.go

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package backend
import (
"hash"
"io"
)
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// HashingWriter wraps an io.Writer to hashes all data that is written to it.
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type HashingWriter struct {
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w io.Writer
h hash.Hash
size int
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}
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// NewHashAppendWriter wraps the writer w and feeds all data written to the hash h.
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func NewHashingWriter(w io.Writer, h hash.Hash) *HashingWriter {
return &HashingWriter{
h: h,
w: io.MultiWriter(w, h),
}
}
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// Write wraps the write method of the underlying writer and also hashes all data.
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func (h *HashingWriter) Write(p []byte) (int, error) {
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n, err := h.w.Write(p)
h.size += n
return n, err
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}
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// Sum returns the hash of all data written so far.
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func (h *HashingWriter) Sum(d []byte) []byte {
return h.h.Sum(d)
}
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// Size returns the number of bytes written to the underlying writer.
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func (h *HashingWriter) Size() int {
return h.size
}