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Decoding base64 without extra allocations


By : David Horne
Date : September 15 2020, 03:00 PM
I wish this help you Why do you have a base64-encoded, immutable string? Converting from []byte to string is wasteful. You should have a base64-encoded, mutable []byte.
For example,
code :
package main

import (
    "encoding/base64"
    "fmt"
)

func main() {
    enc := base64.StdEncoding

    // Test data
    b := make([]byte, 16)
    for i := range b {
        b[i] = byte(i)
    }
    fmt.Println(len(b), b)
    b64 := make([]byte, enc.EncodedLen(len(b)))
    enc.Encode(b64, b)

    // Decode base64 without extra array allocations
    fmt.Printf("%d %q\n", len(b64), b64)
    d := b64
    n, err := enc.Decode(d, b64)
    d = d[:n:n]
    if err != nil {
        panic(err)
    }
    fmt.Println(len(d), d)
}
16 [0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15]
24 "AAECAwQFBgcICQoLDA0ODw=="
16 [0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15]


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Decoding base64 adds extra spaces


By : shadowc
Date : March 29 2020, 07:55 AM
it helps some times I am working in Delphi XE2 I am converting base64 byte array to string using this , You can add one line to get the length you are expecting:
code :
function Base64Decode(const EncodedText: string): TBytes;
var
  DecodedStm: TBytesStream;
  Decoder: TIdDecoderMIME;
begin
  Decoder := TIdDecoderMIME.Create(nil);
  try
    DecodedStm := TBytesStream.Create;
    try
      Decoder.DecodeBegin(DecodedStm);
      Decoder.Decode(EncodedText);
      Decoder.DecodeEnd;
      Result := DecodedStm.Bytes;
      SetLength(Result, DecodedStm.Size);  // add this line
    finally
      DecodedStm.Free;
    end;
  finally
    Decoder.Free;
  end;
end;

Base64 encoding variations? I have base64 encoded data not decoding properly


By : raghu
Date : March 29 2020, 07:55 AM
seems to work fine What I have so far, I probably need more info to decode everything but here it goes:
code :
>>> t = base64.b64decode('AgAOAAAAQQEA3AcKDhIyCNwHCg4SMgyYIzSWoACP1T2TRRw1MTExMDUwMTE2ICAAAAAAAAAAAAAA3AAjU1QsKzAyMjEuMGxiDQo=')
>>> print int(t[9:11][::-1].encode("hex"), 16), int(t[11].encode("hex"), 16), int(t[12].encode("hex"), 16), int(t[13].encode("hex"), 16), int(t[14].encode("hex"), 16), int(t[15].encode("hex"), 16)
2012 10 14 18 50 8

>>> print int(t[16:18][::-1].encode("hex"), 16), int(t[18].encode("hex"), 16), int(t[19].encode("hex"), 16), int(t[20].encode("hex"), 16), int(t[21].encode("hex"), 16), int(t[22].encode("hex"), 16)
2012 10 14 18 50 12
>>> t[23:29][::-1].encode("hex")
'00a096342398'
>>> t[35:47]
'5111050116  '
>>> t[63:72]
'+0221.0lb'

Base64 decoding and writing to file in Python sending Base64-String over cgi.Fieldstorage


By : Fabrice Kakcha Ntich
Date : March 29 2020, 07:55 AM
wish help you to fix your issue If you hand over data via adress bar, + is automatically converted to an empty space. Just string.replace(' ', '+') on the Base64-String and you should be fine.

Do you remove the data:image/jpeg;base64, before decoding Base64 string using C#?


By : Robert
Date : March 29 2020, 07:55 AM
wish help you to fix your issue
do I need to strip off the prefix of data:image/jpeg;base64, and then decode the remainder?

Decoding Base64 in C# sometimes gives incorrect result with one extra padding character


By : Owen James Turner
Date : March 29 2020, 07:55 AM
Hope this helps Looks like this was a bug: https://github.com/dotnet/corefx/issues/30793 It's fixed in .NET Core but still present in .NET Framework up to 4.7.2.
This code should abort with exception instead of printing 1:
code :
using System;

public class Program
{
    public static void Main()
    {
        Console.WriteLine(Convert.FromBase64String("YWE==").Length);
    }
}
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