Compute hash of a resource at a URL

main-progress.go

package main

import (
	"crypto/md5"
	"crypto/sha1"
	"crypto/sha256"
	"crypto/sha512"
	"crypto/tls"
	"encoding/hex"
	"flag"
	"fmt"
	"hash"
	"io"
	"net/http"
	"os"

	log "github.com/sirupsen/logrus"
)

// PassThru wraps an existing io.Reader.
//
// It simply forwards the Read() call, while displaying
// the results from individual calls to it.
type PassThru struct {
	io.Reader
	total    int64 // Total # of bytes transferred
	length   int64 // Expected length
	progress float64
}

func main() {
	alg := flag.String("a", "SHA256", "algorithm to use (defaults to SHA256)")
	url := flag.String("u", "", "URL of file to hash")
	skip := flag.Bool("s", false, "skip SSL verification")

	flag.Parse()

	if *url == "" {
		log.Fatalf("No URL specified")
	}

	var hasher hash.Hash

	switch *alg {
	case "MD5":
		hasher = md5.New()
	case "SHA1":
		hasher = sha1.New()
	case "SHA256":
		hasher = sha256.New()
	case "SHA512":
		hasher = sha512.New()
	default:
		log.Fatalf("Unsupported algorithm: %s", *alg)
	}

	tr := &http.Transport{
		TLSClientConfig: &tls.Config{InsecureSkipVerify: *skip},
	}
	client := &http.Client{Transport: tr}

	response, e := client.Get(*url)

	if e != nil {
		log.Fatal(e)
	}

	defer response.Body.Close()

	readerpt := &PassThru{Reader: response.Body, length: response.ContentLength}

	if _, err := io.Copy(hasher, readerpt); err != nil {
		log.Fatalf("Error hashing URL: %v", err)
	}

	result := hex.EncodeToString(hasher.Sum(nil))

	fmt.Printf("%s", result)

}

// Read 'overrides' the underlying io.Reader's Read method.
// This is the one that will be called by io.Copy(). We simply
// use it to keep track of byte counts and then forward the call.
func (pt *PassThru) Read(p []byte) (int, error) {
	n, err := pt.Reader.Read(p)
	if n > 0 {
		pt.total += int64(n)
		percentage := float64(pt.total) / float64(pt.length) * float64(100)
		i := int(percentage / float64(10))
		is := fmt.Sprintf("%v", i)
		if percentage-pt.progress > 2 {
			fmt.Fprintf(os.Stderr, is)
			pt.progress = percentage
		}
	}

	return n, err
}

main.go

package main

import (
	"crypto/md5"
	"crypto/sha1"
	"crypto/sha256"
	"crypto/sha512"
	"crypto/tls"
	"encoding/hex"
	"flag"
	"fmt"
	"hash"
	"io"
	"net/http"

	log "github.com/sirupsen/logrus"
)

func main() {
	alg := flag.String("a", "SHA256", "algorithm to use (defaults to SHA256)")
	url := flag.String("u", "", "URL of file to hash")
	skip := flag.Bool("s", false, "skip SSL verification")

	flag.Parse()

	if *url == "" {
		log.Fatalf("No URL specified")
	}

	var hasher hash.Hash

	switch *alg {
	case "MD5":
		hasher = md5.New()
	case "SHA1":
		hasher = sha1.New()
	case "SHA256":
		hasher = sha256.New()
	case "SHA512":
		hasher = sha512.New()
	default:
		log.Fatalf("Unsupported algorithm: %s", *alg)
	}

	tr := &http.Transport{
		TLSClientConfig: &tls.Config{InsecureSkipVerify: *skip},
	}
	client := &http.Client{Transport: tr}

	response, e := client.Get(*url)

	if e != nil {
		log.Fatal(e)
	}

	defer response.Body.Close()

	if _, err := io.Copy(hasher, response.Body); err != nil {
		log.Fatalf("Error hashing URL: %v", err)
	}

	result := hex.EncodeToString(hasher.Sum(nil))

	fmt.Printf("%s", result)

}