I have a sized byte array that I got after doing md5.Sum().
data := []byte("testing")
var pass string
var b [16]byte
b = md5.Sum(data)
pass = string(b)
I get the error:
cannot convert b (type [16]byte) to type string
-
6I'd like to point out that creating a password like that without any kind of salt is extremely insecure and a bad idea.OneOfOne– OneOfOne2014-09-27 18:54:16 +00:00Commented Sep 27, 2014 at 18:54
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8 Answers
You can refer to it as a slice:
pass = string(b[:])
1 Comment
Phil
this does an allocation as it copies
b's data into the new stringA little late but keep in mind that using string(b[:]) will print mostly invalid characters.
If you're trying to get a hex representation of it like php you can use something like:
data := []byte("testing")
b := md5.Sum(data)
//this is mostly invalid characters
fmt.Println(string(b[:]))
pass := hex.EncodeToString(b[:])
fmt.Println(pass)
// or
pass = fmt.Sprintf("%x", b)
fmt.Println(pass)
5 Comments
Nikhil Wagh
@OneOfOne are you sure this is the correct way to it. I got this at the output when I run the playground script you provided.
�+�QYI��O�+��Uu ae2b1fca515949e5d54fb22b8ed95575 ae2b1fca515949e5d54fb22b8ed95575
OneOfOne
@NikhilWagh that is correct, the first print is gonna be the raw checksum, not print-friendly, the other 2 will be the checksum converted to hex.
pkaramol
Why does this
fmt.Println(string(b[:])) prints "mostly invalid data" ?
ChrisG
This is the correct answer to receive a md5 hash string. Everything else is not helpful.. requires:
import "encoding/hex"it can be solved by this
pass = fmt.Sprintf("%x", b)
or
import "encoding/base64"
pass = base64.StdEncoding.EncodeToString(b[:])
this will encoding it to base64 string
3 Comments
Ali
This is the correct answer in many cases, not the accepted answer
rickchristie
Thank you for reminding me that
[n]byte means array and []byte means slice!
guettli
Could you please explain why you use base64 here? The question does not mention base64.
Update 02/01/2023
Per this, unsafe: add StringData, String, SliceData, the reflect.StringHeader and reflect.SliceHeader may be deprecated in Go 1.20. And the unsafe.StringData, unsafe.String, and unsafe.SliceData will replace them, refer to 1.20 release note
The
unsafepackage defines three new functionsSliceData,String, andStringData. Along with Go 1.17's Slice, these functions now provide the complete ability to construct and deconstruct slice and string values, without depending on their exact representation.
func String2Bytes(s string) []byte {
if s == "" {
return nil
}
return unsafe.Slice(unsafe.StringData(s), len(s))
}
func Bytes2String(b []byte) string {
if len(b) == 0 {
return ""
}
return unsafe.String(unsafe.SliceData(b), len(b))
}
Before Go 1.20
func Bytes2StrImp(b []byte) string {
sliceHeader := (*reflect.SliceHeader)(unsafe.Pointer(&b))
var s string
sh := (*reflect.StringHeader)(unsafe.Pointer(&s))
sh.Data = sliceHeader.Data
sh.Len = sliceHeader.Len
return s
}
The above solution converts the byte array to string through Pointer operation. The string(b[:]) will do a new string object and copy data from the byte array to the string.
Benchmark result with string(b[:])
func Bytes2StrRaw(b []byte) string {
return string(b[:])
}
BenchmarkBytes2StrRaw-12 275305142 4.40 ns/op
BenchmarkBytes2StrImp-12 1000000000 0.315 ns/op
Although there are some simple answers here, I want to give one more efficient solution
func Bytes2StrImp(b []byte) string{
sliceHeader := (*reflect.SliceHeader)(unsafe.Pointer(&b))
sh := reflect.StringHeader{
Data: sliceHeader.Data,
Len: sliceHeader.Len,
}
return *(*string)(unsafe.Pointer(&sh)) // go vet error possible misuse reflect.StringHeader
}
5 Comments
rednafi
Care to explain what is happening there and why is it so much faster?
Duncan Harris
This code violates recommendations at golang.org/pkg/unsafe/#Pointer: "In general, reflect.SliceHeader and reflect.StringHeader should be used only as *reflect.SliceHeader and *reflect.StringHeader pointing at actual slices or strings, never as plain structs. A program should not declare or allocate variables of these struct types."
Duncan Harris
go vet also complains about thi in current version, e.g. try in the playground: play.golang.org/p/G6rRGp8jwtWDuncan Harris
Correct code: play.golang.org/p/Lh28f4HF_W9
zangw
@RedowanDelowar, the answer was updated. Hope I make myself clearly
Not for printing hex-encoded strings, but in the general case when the [size]byte array may contain invalid UTF-8 sequence(s), then according to this answer they can be converted into valid UTF-8 using
s := string([]rune(string(b[:])))
package main
import (
"fmt"
"unicode/utf8"
)
func main() {
b := [1]byte{0xff}
s := string(b[:])
fmt.Println(s, []byte(s), utf8.Valid([]byte(s)))
// Output: � [255] false
s = string([]rune(string(b[:])))
fmt.Println(s, []byte(s), utf8.Valid([]byte(s)))
// Output: � [239 191 189] true
}
Comments
I found these comments really unhelpful because they assume OP just wants a literal string of the []byte.... but if you were like me and need utf8 decoded bytes as a string you can use this:
import "unicode/utf8"
func bytesToUtf8(b []byte) string {
var myString = "";
for i := 1; i <= len(b); i++ {
r, _ := utf8.DecodeRune(b[i-1:i])
myString += string(r)
}
return myString
}
var uselessBytes := []byte{123,34,...}
helpfulUtf8String := bytesToUtf8(uselessBytes)
