Murmur3 comparison and test fixtures

hashtopic.py

#!/usr/bin/env python3

import mmh3
import json
import base64


def topic_hash(name):
    hash = mmh3.hash128(name.encode('utf-8'), signed=False).to_bytes(16, byteorder='big', signed=False)
    hash = hash[8:] + hash[:8]
    return base64.urlsafe_b64encode(hash).decode('utf-8').strip("=")


def main():
    with open("topichash.json", "r") as f:
        fixture = json.load(f)

        for name, expected in fixture.items():
            actual = topic_hash(name)
            if actual == expected:
                print(name, expected, actual)


if __name__ == "__main__":
    main()

main.go

package main

import (
	"encoding/base64"
	"encoding/json"
	"fmt"
	"log"
	"os"

	"github.com/spaolacci/murmur3"
)

var topicNames = []string{
	"testing.topics.topica",
	"testing.topics.topicb",
	"testing.topics.topicc",
	"noaa-alerts",
	"chocolate-covered-espresso-beans",
}

func topicHash(topicName string) string {
	hash := murmur3.New128()
	hash.Write([]byte(topicName))
	return base64.RawURLEncoding.EncodeToString(hash.Sum(nil))
}

func checkTopicHash(topicHash string) error {
	sum, err := base64.RawURLEncoding.DecodeString(topicHash)
	if err != nil {
		return err
	}

	if len(sum) != 16 {
		return fmt.Errorf("expected length 16 sum not length %d", len(sum))
	}
	return nil
}

func main() {
	fixture := make(map[string]string)
	for _, name := range topicNames {
		fixture[name] = topicHash(name)

		if err := checkTopicHash(fixture[name]); err != nil {
			log.Fatal(err)
		}
	}

	// Write fixture to disk
	f, err := os.Create("topichash.json")
	if err != nil {
		log.Fatal(err)
	}
	defer f.Close()

	encoder := json.NewEncoder(f)
	encoder.SetIndent("", "  ")
	if err := encoder.Encode(fixture); err != nil {
		log.Fatal(err)
	}
}

topichash.json

{
  "chocolate-covered-espresso-beans": "cLHSo2nCBxyOezviLM5gwg",
  "noaa-alerts": "MRpILJErB6vKZROR6H9JiA",
  "testing.topics.topica": "IdTcxHgZmlLM8oBj_YytLw",
  "testing.topics.topicb": "F7x4fhbO4EhHVNDmBjMRIQ",
  "testing.topics.topicc": "YuxuzM--ndLwlQX0kqnOBw"
}