Base64 decode data: Difference between revisions
(Scala contribution added.) |
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To err is human, but to really foul things up you need a computer. |
To err is human, but to really foul things up you need a computer. |
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-- Paul R. Ehrlich</pre> |
-- Paul R. Ehrlich</pre> |
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=={{header|Factor}}== |
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<lang factor>USING: base64 io strings ; |
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"VG8gZXJyIGlzIGh1bWFuLCBidXQgdG8gcmVhbGx5IGZvdWwgdGhpbmdzIHVwIHlvdSBuZWVkIGEgY29tcHV0ZXIuCiAgICAtLVBhdWwgUi5FaHJsaWNo" |
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base64> >string print</lang> |
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{{out}} |
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<pre> |
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To err is human, but to really foul things up you need a computer. |
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--Paul R.Ehrlich |
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</pre> |
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=={{header|Go}}== |
=={{header|Go}}== |
Revision as of 12:44, 13 August 2019
You are encouraged to solve this task according to the task description, using any language you may know.
See Base64 encode data.
Now write a program that takes the output of the Base64 encode data task as input and regenerate the original file.
When working on the VBA implementation I found several 'solutions' on the net, including one from the software maker himself, that showed output with incorrect padding. Obviously with incorrect padding in the output you can not decode correctly to the original file again.
C
<lang c>#include <stdio.h>
- include <stdlib.h>
typedef unsigned char ubyte; const ubyte BASE64[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
int findIndex(const ubyte val) {
if ('A' <= val && val <= 'Z') { return val - 'A'; } if ('a' <= val && val <= 'z') { return val - 'a' + 26; } if ('0' <= val && val <= '9') { return val - '0' + 52; } if (val == '+') { return 62; } if (val == '/') { return 63; } return -1;
}
int decode(const ubyte source[], ubyte sink[]) {
const size_t length = strlen(source); const ubyte *it = source; const ubyte *end = source + length; int acc;
if (length % 4 != 0) { return 1; }
while (it != end) { const ubyte b1 = *it++; const ubyte b2 = *it++; const ubyte b3 = *it++; // might be the first padding byte const ubyte b4 = *it++; // might be the first or second padding byte
const int i1 = findIndex(b1); const int i2 = findIndex(b2);
acc = i1 << 2; // six bits came from the first byte acc |= i2 >> 4; // two bits came from the first byte *sink++ = acc; // output the first byte
if (b3 != '=') { const int i3 = findIndex(b3);
acc = (i2 & 0xF) << 4; // four bits came from the second byte acc += i3 >> 2; // four bits came from the second byte *sink++ = acc; // output the second byte
if (b4 != '=') { const int i4 = findIndex(b4);
acc = (i3 & 0x3) << 6; // two bits came from the third byte acc |= i4; // six bits came from the third byte *sink++ = acc; // output the third byte } } }
*sink = '\0'; // add the sigil for end of string return 0;
}
int main() {
ubyte data[] = "VG8gZXJyIGlzIGh1bWFuLCBidXQgdG8gcmVhbGx5IGZvdWwgdGhpbmdzIHVwIHlvdSBuZWVkIGEgY29tcHV0ZXIuCiAgICAtLVBhdWwgUi5FaHJsaWNo"; ubyte decoded[1024];
printf("%s\n\n", data); decode(data, decoded); printf("%s\n\n", decoded);
return 0;
}</lang>
- Output:
VG8gZXJyIGlzIGh1bWFuLCBidXQgdG8gcmVhbGx5IGZvdWwgdGhpbmdzIHVwIHlvdSBuZWVkIGEgY29tcHV0ZXIuCiAgICAtLVBhdWwgUi5FaHJsaWNo To err is human, but to really foul things up you need a computer. --Paul R.Ehrlich
C++
<lang cpp>#include <algorithm>
- include <iostream>
- include <string>
- include <vector>
typedef unsigned char ubyte; const auto BASE64 = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
std::vector<ubyte> encode(const std::vector<ubyte>& source) {
auto it = source.cbegin(); auto end = source.cend();
std::vector<ubyte> sink; while (it != end) { auto b1 = *it++; int acc;
sink.push_back(BASE64[b1 >> 2]); // first output (first six bits from b1)
acc = (b1 & 0x3) << 4; // last two bits from b1 if (it != end) { auto b2 = *it++; acc |= (b2 >> 4); // first four bits from b2
sink.push_back(BASE64[acc]); // second output
acc = (b2 & 0xF) << 2; // last four bits from b2 if (it != end) { auto b3 = *it++; acc |= (b3 >> 6); // first two bits from b3
sink.push_back(BASE64[acc]); // third output sink.push_back(BASE64[b3 & 0x3F]); // fouth output (final six bits from b3) } else { sink.push_back(BASE64[acc]); // third output sink.push_back('='); // fourth output (1 byte padding) } } else { sink.push_back(BASE64[acc]); // second output sink.push_back('='); // third output (first padding byte) sink.push_back('='); // fourth output (second padding byte) } } return sink;
}
int findIndex(ubyte val) {
if ('A' <= val && val <= 'Z') { return val - 'A'; } if ('a' <= val && val <= 'z') { return val - 'a' + 26; } if ('0' <= val && val <= '9') { return val - '0' + 52; } if ('+' == val) { return 62; } if ('/' == val) { return 63; } return -1;
}
std::vector<ubyte> decode(const std::vector<ubyte>& source) {
if (source.size() % 4 != 0) { throw new std::runtime_error("Error in size to the decode method"); }
auto it = source.cbegin(); auto end = source.cend();
std::vector<ubyte> sink; while (it != end) { auto b1 = *it++; auto b2 = *it++; auto b3 = *it++; // might be first padding byte auto b4 = *it++; // might be first or second padding byte
auto i1 = findIndex(b1); auto i2 = findIndex(b2); int acc;
acc = i1 << 2; // six bits came from the first byte acc |= i2 >> 4; // two bits came from the first byte
sink.push_back(acc); // output the first byte
if (b3 != '=') { auto i3 = findIndex(b3);
acc = (i2 & 0xF) << 4; // four bits came from the second byte acc |= i3 >> 2; // four bits came from the second byte
sink.push_back(acc); // output the second byte
if (b4 != '=') { auto i4 = findIndex(b4);
acc = (i3 & 0x3) << 6; // two bits came from the third byte acc |= i4; // six bits came from the third byte
sink.push_back(acc); // output the third byte } } } return sink;
}
int main() {
using namespace std;
string data = "VG8gZXJyIGlzIGh1bWFuLCBidXQgdG8gcmVhbGx5IGZvdWwgdGhpbmdzIHVwIHlvdSBuZWVkIGEgY29tcHV0ZXIuCiAgICAtLVBhdWwgUi5FaHJsaWNo"; vector<ubyte> datav{ begin(data), end(data) }; cout << data << "\n\n";
auto decoded = decode(datav); std::for_each(cbegin(decoded), cend(decoded), [](char c) { cout << c; }); cout << '\n';
return 0;
}</lang>
- Output:
VG8gZXJyIGlzIGh1bWFuLCBidXQgdG8gcmVhbGx5IGZvdWwgdGhpbmdzIHVwIHlvdSBuZWVkIGEgY29tcHV0ZXIuCiAgICAtLVBhdWwgUi5FaHJsaWNo To err is human, but to really foul things up you need a computer. --Paul R.Ehrlich
D
<lang d>import std.base64; import std.stdio;
void main() {
auto data = "VG8gZXJyIGlzIGh1bWFuLCBidXQgdG8gcmVhbGx5IGZvdWwgdGhpbmdzIHVwIHlvdSBuZWVkIGEgY29tcHV0ZXIuCiAgICAtLSBQYXVsIFIuIEVocmxpY2g="; writeln(data); writeln;
auto decoded = cast(char[])Base64.decode(data); writeln(decoded);
}</lang>
- Output:
VG8gZXJyIGlzIGh1bWFuLCBidXQgdG8gcmVhbGx5IGZvdWwgdGhpbmdzIHVwIHlvdSBuZWVkIGEgY29tcHV0ZXIuCiAgICAtLSBQYXVsIFIuIEVocmxpY2g= To err is human, but to really foul things up you need a computer. -- Paul R. Ehrlich
Factor
<lang factor>USING: base64 io strings ;
"VG8gZXJyIGlzIGh1bWFuLCBidXQgdG8gcmVhbGx5IGZvdWwgdGhpbmdzIHVwIHlvdSBuZWVkIGEgY29tcHV0ZXIuCiAgICAtLVBhdWwgUi5FaHJsaWNo" base64> >string print</lang>
- Output:
To err is human, but to really foul things up you need a computer. --Paul R.Ehrlich
Go
As images can no longer be uploaded to RC, I've encoded and decoded a string rather than the Rosetta Code icon. <lang go>package main
import (
"encoding/base64" "fmt"
)
func main() {
msg := "Rosetta Code Base64 decode data task" fmt.Println("Original :", msg) encoded := base64.StdEncoding.EncodeToString([]byte(msg)) fmt.Println("\nEncoded :", encoded) decoded, err := base64.StdEncoding.DecodeString(encoded) if err != nil { fmt.Println(err) return } fmt.Println("\nDecoded :", string(decoded))
}</lang>
- Output:
Original : Rosetta Code Base64 decode data task Encoded : Um9zZXR0YSBDb2RlIEJhc2U2NCBkZWNvZGUgZGF0YSB0YXNr Decoded : Rosetta Code Base64 decode data task
Haskell
Simple implementation that decodes an ASCII string. <lang haskell>--Decodes Base64 to ASCII import qualified Data.Map.Strict as Map (Map, lookup, fromList) import Data.Maybe (fromJust, listToMaybe, mapMaybe) import Numeric (readInt, showIntAtBase) import Data.Char (chr, digitToInt) import Data.List.Split (chunksOf)
byteToASCII :: String -> String byteToASCII = map chr . decoder
--generates list of bytes (represented by Int) decoder :: String -> [Int] decoder =
map readBin . takeWhile (\x -> length x == 8) . chunksOf 8 . concatMap toBin . mapMaybe (`Map.lookup` table) . filter (/= '=')
--turns decimal into a list of char that represents a binary number toBin :: Int -> String toBin n = leftPad $ showIntAtBase 2 ("01" !!) n ""
--this adds all the zeros to the left that showIntAtBase omitted leftPad :: String -> String leftPad a = replicate (6 - length a) '0' ++ a
--turns list of '0' and '1' into list of 0 and 1 readBin :: String -> Int readBin = fromJust . fmap fst . listToMaybe . readInt 2 (`elem` "01") digitToInt
--lookup list for the sextets table :: Map.Map Char Int table =
Map.fromList $ zip "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/" [0 ..]
main :: IO () main =
putStrLn $ byteToASCII "VG8gZXJyIGlzIGh1bWFuLCBidXQgdG8gcmVhbGx5IGZvdWwgdGhpbmdzIHVwIHlvdSBuZWVkIGEgY29tcHV0ZXIuCi0tIFBhdWwgUi4gRWhybGljaA=="</lang>
- Output:
To err is human, but to really foul things up you need a computer. -- Paul R. Ehrlich
or in terms of Data.ByteString.Base64:
<lang haskell>{-# LANGUAGE OverloadedStrings #-}
import qualified Data.ByteString.Base64 as Base64 (decode, encode) import qualified Data.ByteString.Char8 as B (putStrLn)
main :: IO () main = do
B.putStrLn $ Base64.encode "To err is human, but to really foul things up you need a computer.\n-- Paul R. Ehrlich" B.putStrLn "\n-->\n" either print B.putStrLn $ Base64.decode "VG8gZXJyIGlzIGh1bWFuLCBidXQgdG8gcmVhbGx5IGZvdWwgdGhpbmdzIHVwIHlvdSBuZWVkIGEgY29tcHV0ZXIuCi0tIFBhdWwgUi4gRWhybGljaA=="</lang>
- Output:
VG8gZXJyIGlzIGh1bWFuLCBidXQgdG8gcmVhbGx5IGZvdWwgdGhpbmdzIHVwIHlvdSBuZWVkIGEgY29tcHV0ZXIuCi0tIFBhdWwgUi4gRWhybGljaA== --> To err is human, but to really foul things up you need a computer. -- Paul R. Ehrlich
Jsish
See Base64_encode_data#Jsish for base64.jsi.
<lang javascript>/* Base64 decode, in Jsish */ var data = exec('jsish base64.jsi', {retAll:true}).data; // or use File.read('stdin'); var icon = Util.base64(data, true); File.write('rosetta-favicon.ico', icon);</lang>
Julia
Using an IOBuffer here, though not really needed to decode a string, shows how we could pipe a network stream or file though Julia's builtin Base64 decoder. <lang julia>using Base64
io = IOBuffer()
iob64_decode = Base64DecodePipe(io)
write(io, "VG8gZXJyIGlzIGh1bWFuLCBidXQgdG8gcmVhbGx5IGZvdWwgdGhpbmdzIHVwIHlvdSBuZWVkIGEgY29tcHV0ZXIuCiAgICAtLVBhdWwgUi5FaHJsaWNo")
seekstart(io)
println(String(read(iob64_decode)))
</lang>
- Output:
To err is human, but to really foul things up you need a computer. --Paul R.Ehrlich
Kotlin
<lang scala>import java.util.Base64
fun main() {
val data = "VG8gZXJyIGlzIGh1bWFuLCBidXQgdG8gcmVhbGx5IGZvdWwgdGhpbmdzIHVwIHlvdSBuZWVkIGEgY29tcHV0ZXIuCiAgICAtLSBQYXVsIFIuIEVocmxpY2g=" val decoder = Base64.getDecoder() val decoded = decoder.decode(data) val decodedStr = String(decoded, Charsets.UTF_8) println(decodedStr)
}</lang>
- Output:
To err is human, but to really foul things up you need a computer. -- Paul R. Ehrlich
Mathematica
<lang Mathematica>ImportString[
"VG8gZXJyIGlzIGh1bWFuLCBidXQgdG8gcmVhbGx5IGZvdWwgdGhpbmdzIHVwIHlvdSBuZWVkIGEgY29tcHV0ZXIuCiAgICAtLVBhdWwgUi5FaHJsaWNo", "Base64"
]</lang>
- Output:
To err is human, but to really foul things up you need a computer. -- Paul R. Ehrlich
OCaml
We continue from the same toplevel session from the previous page:
# let plain = Base64.decode_exn enc;; val plain : string = "\000\000\001\000\002\000\016\016\000\000\000\000\000\000h\005\000\000&\000"... (* string length 3638; truncated *)
Perl
The MIME::Base64 module is to be preferred, but this works too. <lang perl>sub decode_base64 {
my($d) = @_; $d =~ tr!A-Za-z0-9+/!!cd; $d =~ s/=+$//; $d =~ tr!A-Za-z0-9+/! -_!; my $r = ; while( $d =~ /(.{1,60})/gs ){ my $len = chr(32 + length($1)*3/4); $r .= unpack("u", $len . $1 ); } $r;
}
$data = <<EOD; J1R3YXMgYnJpbGxpZywgYW5kIHRoZSBzbGl0aHkgdG92ZXMKRGlkIGd5cmUgYW5kIGdpbWJsZSBp biB0aGUgd2FiZToKQWxsIG1pbXN5IHdlcmUgdGhlIGJvcm9nb3ZlcywKQW5kIHRoZSBtb21lIHJh dGhzIG91dGdyYWJlLgo= EOD
print decode_base64($data) . "\n";</lang>
- Output:
'Twas brillig, and the slithy toves Did gyre and gimble in the wabe: All mimsy were the borogoves, And the mome raths outgrabe.
Perl 6
<lang perl6>my $e64 = ' VG8gZXJyIGlzIGh1bWFuLCBidXQgdG8gcmVhbGx5IGZvdWwgdGhpbmdzIHVwIHlvdSBuZWVkIGEgY2 9tcHV0ZXIuCiAgICAtLSBQYXVsIFIuIEVocmxpY2g= ';
my @base64map = flat 'A' .. 'Z', 'a' .. 'z', ^10, '+', '/'; my %base64 is default(0) = @base64map.pairs.invert;
sub base64-decode-slow ($enc) {
my $buf = Buf.new; for $enc.subst(/\s/, , :g).comb(4) -> $chunck { $buf.append: |(sprintf "%06d%06d%06d%06d", |$chunck.comb.map: {%base64{$_}.base(2)}).comb(8).map: {:2($_)}; } $buf
}
say 'Slow:'; say base64-decode-slow($e64).decode('utf8');
- Of course, the above routine is slow and is only for demonstration purposes.
- For real code you should use a module, which is MUCH faster and heavily tested.
say "\nFast:"; use Base64::Native; say base64-decode($e64).decode('utf8');</lang>
- Output:
Slow: To err is human, but to really foul things up you need a computer. -- Paul R. Ehrlich Fast: To err is human, but to really foul things up you need a computer. -- Paul R. Ehrlich
Phix
<lang Phix>include builtins\base64.e string s = "Rosetta Code Base64 decode data task" string e = encode_base64(s) ?e ?decode_base64(e)</lang>
- Output:
"Um9zZXR0YSBDb2RlIEJhc2U2NCBkZWNvZGUgZGF0YSB0YXNr" "Rosetta Code Base64 decode data task"
PicoLisp
<lang PicoLisp>(setq *Char64
`'(chop "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/" ) )
(de decode64 (S)
(let S (chop S) (pack (make (while S (let (A (dec (index (++ S) *Char64)) B (dec (index (++ S) *Char64)) C (dec (index (++ S) *Char64)) D (dec (index (++ S) *Char64)) ) (link (char (| (>> -2 A) (>> 4 B))) ) (and C (link (char (| (>> -4 (& B 15)) (>> 2 C)) ) ) D (link (char (| (>> -6 (& C 3)) D)) ) ) ) ) ) ) ) )
(prinl (decode64 "VG8gZXJyIGlzIGh1bWFuLCBidXQgdG8gcmVhbGx5IGZvdWwgdGhpbmdzIHVwIHlvdSBuZWVkIGEgY29tcHV0ZXIuCiAgICAtLVBhdWwgUi5FaHJsaWNo"))</lang>
- Output:
To err is human, but to really foul things up you need a computer. --Paul R.Ehrlich
Ruby
<lang ruby>require 'base64'
perl6_example =' VG8gZXJyIGlzIGh1bWFuLCBidXQgdG8gcmVhbGx5IGZvdWwgdGhpbmdzIHVwIHlvdSBuZWVkIGEgY2 9tcHV0ZXIuCiAgICAtLSBQYXVsIFIuIEVocmxpY2g= ' puts Base64.decode64 perl6_example</lang>
- Output:
To err is human, but to really foul things up you need a computer. -- Paul R. Ehrlich
Rust
<lang rust>use std::str;
const INPUT: &str = "VG8gZXJyIGlzIGh1bWFuLCBidXQgdG8gcmVhbGx5IGZvdWwgdGhpbmdzIHVwIHlvdSBuZWVkIGEgY29tcHV0ZXIuCiAgICAtLVBhdWwgUi5FaHJsaWNo"; const UPPERCASE_OFFSET: i8 = -65; const LOWERCASE_OFFSET: i8 = 26 - 97; const NUM_OFFSET: i8 = 52 - 48;
fn main() {
println!("Input: {}", INPUT);
let result = INPUT.chars() .filter(|&ch| ch != '=') //Filter '=' chars .map(|ch| { //Map char values using Base64 Characters Table let ascii = ch as i8; let convert = match ch { '0' ... '9' => ascii + NUM_OFFSET, 'a' ... 'z' => ascii + LOWERCASE_OFFSET, 'A' ... 'Z' => ascii + UPPERCASE_OFFSET, '+' => 62, '/' => 63, _ => panic!("Not a valid base64 encoded string") }; format!("{:#08b}", convert)[2..].to_string() //convert indices to binary format and remove the two first digits }) .collect::<String>() //concatenate the resulting binary values .chars() .collect::<Vec<char>>() .chunks(8) //split into 8 character chunks .map(|chunk| { let num_str = chunk.iter().collect::<String>(); usize::from_str_radix(&num_str, 2).unwrap() as u8 //convert the binary string into its u8 value }) .collect::<Vec<_>>();
let result = str::from_utf8(&result).unwrap(); //convert into UTF-8 string
println!("Output: {}", result);
}</lang>
- Output:
Input: VG8gZXJyIGlzIGh1bWFuLCBidXQgdG8gcmVhbGx5IGZvdWwgdGhpbmdzIHVwIHlvdSBuZWVkIGEgY29tcHV0ZXIuCiAgICAtLVBhdWwgUi5FaHJsaWNo Output: To err is human, but to really foul things up you need a computer. --Paul R.Ehrlich
Scala
- Output:
Best seen in running your browser either by ScalaFiddle (ES aka JavaScript, non JVM) or Scastie (remote JVM).
<lang Scala>import java.util.Base64
object Base64Decode extends App {
def text2BinaryDecoding(encoded: String): String = { val decoded = Base64.getDecoder.decode(encoded) new String(decoded, "UTF-8") }
def data = "VG8gZXJyIGlzIGh1bWFuLCBidXQgdG8gcmVhbGx5IGZvdWwgdGhpbmdzIHVwIHlvdSBuZWVkIGEgY29tcHV0ZXIuCiAgICAtLSBQYXVsIFIuIEVocmxpY2g="
println(text2BinaryDecoding(data))
}</lang>
Seed7
The Seed7 library encoding.s7i defines the functions toBase64 and fromBase64.
<lang seed7>$ include "seed7_05.s7i";
include "gethttp.s7i"; include "encoding.s7i";
const proc: main is func
local var string: original is ""; var string: encoded is ""; begin original := getHttp("rosettacode.org/favicon.ico"); encoded := toBase64(original); writeln("Is the Rosetta Code icon the same (byte for byte) encoded then decoded: " <& fromBase64(encoded) = original); end func;</lang>
- Output:
Is the Rosetta Code icon the same (byte for byte) encoded then decoded: TRUE
Sidef
<lang ruby>var data = <<'EOT' VG8gZXJyIGlzIGh1bWFuLCBidXQgdG8gcmVhbGx5IGZvdWwgdGhpbmdzIHVwIHlvdSBuZWVkIGEgY2 9tcHV0ZXIuCiAgICAtLSBQYXVsIFIuIEVocmxpY2g= EOT
say data.decode_base64</lang>
- Output:
To err is human, but to really foul things up you need a computer. -- Paul R. Ehrlich
zkl
Using shared libraries for cURL and message hashing: <lang zkl>var [const] MsgHash=Import("zklMsgHash"), Curl=Import("zklCurl");
icon:=Curl().get("http://rosettacode.org/favicon.ico"); //-->(Data(4,331),693,0) icon=icon[0][icon[1],*]; // remove header iconEncoded:=MsgHash.base64encode(icon); iconDecoded:=MsgHash.base64decode(iconEncoded); File("rosettaCodeIcon.ico","wb").write(iconDecoded); # eyeball checking says good println("Is the Rosetta Code icon the same (byte for byte) encoded then decoded: ",
icon==iconDecoded);</lang>
- Output:
Is the Rosetta Code icon the same (byte for byte) encoded then decoded: True
- Text based test:
<lang zkl>msg,b64 := "Rosetta Code Base64 decode data task", MsgHash.base64encode(msg); println("Original: %s\nEncoded: %s\nBytes: %s\nDecoded: %s"
.fmt(msg, b64.text, b64.bytes().apply("toString",16).concat(","), MsgHash.base64decode(b64).text));</lang>
Original: Rosetta Code Base64 decode data task Encoded: Um9zZXR0YSBDb2RlIEJhc2U2NCBkZWNvZGUgZGF0YSB0YXNr Bytes: 55,6d,39,7a,5a,58,52,30,59,53,42,44,62,32,52,6c,49,45,4a,68,63,32,55,32,4e,43,42,6b,5a,57,4e,76,5a,47,55,67,5a,47,46,30,59,53,42,30,59,58,4e,72,a Decoded: Rosetta Code Base64 decode data task