calculate sha256 file checksum by streaming

[samt42]

What type of PR is this?

/kind feature
change file checksum method to stream calculation in order to run on limited memory machine.

What this PR does / why we need it:

When I initiate the Harbor registry using the kubekey command tool like this:

./kk init registry

It fails with error message "Killed". After debugging step by step, I found the root cause in file cmd/kk/pkg/files/file.go function sha256sum:

func (b *KubeBinary) Download() error {
	for i := 5; i > 0; i-- {
		...
		if err := b.SHA256Check(); err != nil {
		    ...
                }
	}
	return nil
}
// SHA256Check is used to hash checks on downloaded binary. (sha256)
func (b *KubeBinary) SHA256Check() error {
	output, err := sha256sum(b.Path())
        ...
	return nil
}

func sha256sum(path string) (string, error) {
	file, err := os.Open(path)
	if err != nil {
		return "", err
	}
	defer file.Close()

	data, err := io.ReadAll(file)
	if err != nil {
		return "", err
	}
	return fmt.Sprintf("%x", sha256.Sum256(data)), nil
}

In function sha256sum, it read all file content into memory to calculate file checksum. because of that, when running on machine with low memory(only 2GB), process be killed by system because of the memory exhausted.
So I changed it into stream calculation, like this:

func sha256sum(path string) (string, error) {
	file, err := os.Open(path)
	if err != nil {
		return "", err
	}
	defer file.Close()

	hasher := sha256.New()
	if _, err := io.Copy(hasher, file); err != nil {
		return "", err
	}
	return fmt.Sprintf("%x", hasher.Sum(nil)), nil
}

It works fine on my server machine.

[pixiake]

@samt42 Thanks for this contributions !
/lgtm
/approve

[ks-ci-bot]

LGTM label has been added.

Git tree hash: c2cf94e5655e4d0bcfbe0d305e37e70596cd35fb

[ks-ci-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: pixiake, samt42

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