This improves https://offsec.almond.consulting/super-magic-hash.html

blog_benchmark_test.go

package main

import (
	"crypto/sha256"
	"encoding/hex"
	"fmt"
	"math/rand"
	"regexp"
	"testing"
	"time"
)

var re = regexp.MustCompile(`^0+e\d*$`)

const letterBytes = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789&~#'{([-|_@)]=}+$*!:;,?./"

func hash_sha224(password string) string {
	h := sha256.New224()
	h.Write([]byte(password))
	bs := h.Sum(nil)
	hash := fmt.Sprintf("%x\n", bs)
	return string(hash)
}

var src = rand.NewSource(time.Now().UnixNano())

const (
	letterIdxBits = 6                    // 6 bits to represent a letter index
	letterIdxMask = 1<<letterIdxBits - 1 // All 1-bits, as many as letterIdxBits
	letterIdxMax  = 63 / letterIdxBits   // # of letter indices fitting in 63 bits
)

func rand_3(b []byte) {
	n := len(b)
	for i, cache, remain := n-1, src.Int63(), letterIdxMax; i >= 0; {
		if remain == 0 {
			cache, remain = src.Int63(), letterIdxMax
		}
		if idx := int(cache & letterIdxMask); idx < len(letterBytes) {
			b[i] = letterBytes[idx]
			i--
		}
		cache >>= letterIdxBits
		remain--
	}
}

func Parse_2(h []byte) bool {
	if h[0] == 0 || h[0] == 14 { //check whether the hash starts by 00 or 0e
		for _, x := range h[1:] {
			switch x { //all unexpected bytes return false (https://ascii.cl/conversion.htm)
			case
				10, 11, 12, 13, 15, //0A to 0F
				26, 27, 28, 29, 31, //1A to 1F
				42, 43, 44, 45, 47, //2A to 2F
				58, 59, 60, 61, 63, //3A to 3F
				74, 75, 76, 77, 79, //4A to 4F
				90, 91, 92, 93, 95, //5A to 5F
				106, 107, 108, 109, 111, //6A to 6F
				122, 123, 124, 125, 127, //7A to 7F
				138, 139, 140, 141, 143, //8A to 8F
				154, 155, 156, 157, 159, //9A to 9F
				160, 161, 162, 163, 164, 165, 166, 167, 168, 169, 170, 171, 172, 173, 174, 175, //A0 to AF
				176, 177, 178, 179, 180, 181, 182, 183, 184, 185, 186, 187, 188, 189, 190, 191, //B0 to BF
				192, 193, 194, 195, 196, 197, 198, 199, 200, 201, 202, 203, 204, 205, 206, 207, //C0 to CF
				208, 209, 210, 211, 212, 213, 214, 215, 216, 217, 218, 219, 220, 221, 222, 223, //D0 to DF
				234, 235, 236, 237, 238, 239, //EA to EF
				240, 241, 242, 243, 244, 245, 246, 247, 248, 249, 250, 251, 252, 253, 254, 255: //F0 to FF
				return false
			}
		}
	} else {
		return false
	}
	return true
}

// BenchmarkParse_6-4   	10175305	       561 ns/op	       0 B/op	       0 allocs/op
func BenchmarkParse_6(b *testing.B) {
	h := sha256.New224()
	r := make([]byte, 8)
	sum := make([]byte, 0, 28)
	for n := 0; n < b.N; n++ {
		sum = sum[:0]
		rand_3(r)
		h.Reset()
		h.Write(r)
		sum = h.Sum(sum)
		if Parse_2(sum) && re.FindString(hex.EncodeToString(sum)) != "" {
			//Unexpected hashes like 0e0e34567890123456789012345678901234567890123456789012 could pass the Parse_3 function so for these rare cases we can use the slow regexp check
			fmt.Println(string(r))
			fmt.Println(hex.EncodeToString(sum))
			fmt.Println("")
		}
	}
}