packer-cn/vendor/github.com/aws/aws-sdk-go/service/s3/content_md5.go

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package s3
import (
"crypto/md5"
"encoding/base64"
"io"
"github.com/aws/aws-sdk-go/aws/awserr"
"github.com/aws/aws-sdk-go/aws/request"
)
// contentMD5 computes and sets the HTTP Content-MD5 header for requests that
// require it.
func contentMD5(r *request.Request) {
h := md5.New()
// hash the body. seek back to the first position after reading to reset
// the body for transmission. copy errors may be assumed to be from the
// body.
_, err := io.Copy(h, r.Body)
if err != nil {
r.Error = awserr.New("ContentMD5", "failed to read body", err)
return
}
_, err = r.Body.Seek(0, 0)
if err != nil {
r.Error = awserr.New("ContentMD5", "failed to seek body", err)
return
}
// encode the md5 checksum in base64 and set the request header.
sum := h.Sum(nil)
sum64 := make([]byte, base64.StdEncoding.EncodedLen(len(sum)))
base64.StdEncoding.Encode(sum64, sum)
r.HTTPRequest.Header.Set("Content-MD5", string(sum64))
}