package execenv

import (
	"crypto/sha256"
	"encoding/hex"
	"hash"
	"io"
)

type shaWriter struct{ h hash.Hash }

func sha256New() shaWriter { return shaWriter{h: sha256.New()} }

func (s shaWriter) Sum() string { return hex.EncodeToString(s.h.Sum(nil)) }

// Write 满足 io.Writer，便于 fileSHA256 之外的流式哈希。
func (s shaWriter) Write(p []byte) (int, error) { return s.h.Write(p) }

// 确认 shaWriter 可传给 io.Copy。
var _ io.Writer = shaWriter{}