You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: compressible.go
    path of file: ./repos/podman/vendor/github.com/klauspost/compress
    
    the code of the file until where you have to start completion: package compress

import "math"

// Estimate returns a normalized compressibility estimate of block b.
// Values close to zero are likely uncompressible.
// Values above 0.1 are likely to be compressible.
// Values above 0.5 are 
    
func ShannonEntropyBits(b []byte) int {
	if len(b) == 0 {
		return 0
	}
	var hist [256]int
	for _, c := range b {
		hist[c]++
	}
	shannon := float64(0)
	invTotal := 1.0 / float64(len(b))
	for _, v := range hist[:] {
		if v > 0 {
			n := float64(v)
			shannon += math.Ceil(-math.Log2(n*invTotal) * n)
		}
	}
	return int(math.Ceil(shannon))
}