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path: root/zsig/sum.go
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package zsig

import (
	"hash"
	"io"
)

const (
	Alg       = "SHA512/256"
	BlockSize = 65536
)

// Sum calculates SHA512/256
func Sum(r io.Reader, blockSize int, h hash.Hash) chan []byte {
	c := make(chan []byte, 1)
	if blockSize == 0 {
		blockSize = BlockSize
	}
	go func() {
		defer close(c)
		buf := make([]byte, blockSize)
		for {
			n, err := io.ReadFull(r, buf)
			if err == io.EOF {
				return
			}
			h.Reset()
			h.Write(buf[:n])
			c <- h.Sum(nil)
		}
	}()
	return c
}