// Copyright (c) 2015-2021 MinIO, Inc.//// This file is part of MinIO Object Storage stack//// This program is free software: you can redistribute it and/or modify// it under the terms of the GNU Affero General Public License as published by// the Free Software Foundation, either version 3 of the License, or// (at your option) any later version.//// This program is distributed in the hope that it will be useful// but WITHOUT ANY WARRANTY; without even the implied warranty of// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the// GNU Affero General Public License for more details.//// You should have received a copy of the GNU Affero General Public License// along with this program.  If not, see <http://www.gnu.org/licenses/>. package main import (	"bufio"	"bytes"	"encoding/binary"	"flag"	"fmt"	"hash/crc32"	"io/ioutil"	"log"	"os"	"strings" 	"github.com/dchest/siphash"	"github.com/google/uuid") // hashes the key returning an integer based on the input algorithm.// This function currently supports// - SIPMODfunc sipHashMod(key string, cardinality int, id [16]byte) int {	if cardinality <= 0 {		return -1	}	// use the faster version as per siphash docs	// https://github.com/dchest/siphash#usage	k0, k1 := binary.LittleEndian.Uint64(id[0:8]), binary.LittleEndian.Uint64(id[8:16])	sum64 := siphash.Hash(k0, k1, []byte(key))	return int(sum64 % uint64(cardinality))} // hashOrder - hashes input key to return consistent// hashed integer slice. Returned integer order is salted// with an input key. This results in consistent order.// NOTE: collisions are fine, we are not looking for uniqueness// in the slices returned.func hashOrder(key string, cardinality int) []int {	if cardinality <= 0 {		// Returns an empty int slice for cardinality < 0.		return nil	} 	nums := make([]int, cardinality)	keyCrc := crc32.Checksum([]byte(key), crc32.IEEETable) 	start := int(keyCrc % uint32(cardinality))	for i := 1; i <= cardinality; i++ {		nums[i-1] = 1 + ((start + i) % cardinality)	}	return nums} var (	file, object, deploymentID, prefix string	setCount, shards                   int	verbose                            bool) func main() {	flag.StringVar(&file, "file", "", "Read all objects from file, newline separated")	flag.StringVar(&prefix, "prefix", "", "Add prefix to all objects")	flag.StringVar(&object, "object", "", "Select an object")	flag.StringVar(&deploymentID, "deployment-id", "", "MinIO deployment ID, obtained from 'format.json'")	flag.IntVar(&setCount, "set-count", 0, "Total set count")	flag.IntVar(&shards, "shards", 0, "Total shards count")	flag.BoolVar(&verbose, "v", false, "Display all objects") 	flag.Parse() 	if deploymentID == "" {		log.Fatalln("deployment ID is mandatory")	} 	if setCount == 0 {		log.Fatalln("set count cannot be zero")	} 	id := uuid.MustParse(deploymentID) 	if file != "" {		distrib := make([][]string, setCount)		b, err := ioutil.ReadFile(file)		if err != nil {			log.Fatalln(err)		}		b = bytes.ReplaceAll(b, []byte("\r"), []byte{})		sc := bufio.NewScanner(bytes.NewBuffer(b))		for sc.Scan() {			object = strings.TrimSpace(sc.Text())			set := sipHashMod(prefix+object, setCount, id)			distrib[set] = append(distrib[set], prefix+object)		}		for set, files := range distrib {			fmt.Println("Set:", set+1, "Objects:", len(files))			if !verbose {				continue			}			for _, s := range files {				fmt.Printf("\t%s\n", s)			}		}		os.Exit(0)	} 	if object == "" {		log.Fatalln("object name is mandatory")	} 	if shards != 0 {		fmt.Println("Erasure distribution for the object", hashOrder(prefix+object, shards))	}	fmt.Println("Erasure setNumber for the object", sipHashMod(prefix+object, setCount, id)+1)}