How to decode a string encoded by C# Convert.ToBase64String in python 3

Question

The c# server side:

[HttpGet("{id}")]
public ActionResult Get(int id)
{
    var user = new User
    {
        Id = id,
        Name = $"User{id}"
    };

     using(var ms = new MemoryStream())
     {
         ProtoBuf.Serializer.Serialize(ms, user);
         var bytes = ms.ToArray();
         var str = Convert.ToBase64String(bytes);
         return Json(str);
     }
 }

the python client side:

async def foo():
    async with ClientSession() as session:
        async with session.get("http://localhost:57968/api/values/5") as response:
            json = await response.json()
            # how to get the bytes created by the server
            person = Person.create_from_bytes(bs)

How to get the raw bytes array created by the server using ProtoBuf.Serializer.Serialize(ms, user); in the python client.

If i do not wrap the raw byte array with base64:

Update: I worked it out in the python client side like this:

json = await response.json()
bs = json.encode("ascii")
b64 = base64.b64decode(bs)
person = Person.create_from_bytes(b64)
print(f"{person.id} {person.name}")

minor tip: var bytes = ms.GetBuffer(); var str = Convert.ToBase64String(bytes, 0, (int)ms.Length); - avoids an extra array alloc/copy; as for the base-64 decode: isn't that just base64.b64decode(yourString) ? or possibly this? stackoverflow.com/questions/39209872/… ? What does Person.create_from_bytes take as input? have you already unwrapped the json? i.e. what is bs? — Marc Gravell
– Marc Gravell, Commented Jun 22, 2017 at 10:30
@MarcGravell In python3,base64.b64decode can not take string as parameter. — HongyanShen
– HongyanShen, Commented Jun 22, 2017 at 10:50
@mjwills if the intent is to talk protobuf, then ... that's OK too; I would perhaps question the decision to wrap it as base-64 in json rather than just raw bytes in the http response, but: it is OK to use things that aren't json — Marc Gravell
– Marc Gravell, Commented Jun 22, 2017 at 10:53
@code_farmer did you try the other link I suggested? also: to emphasize: base-64 costs bandwidth; if possible, I would recommend a raw http binary payload here, not base-64 inside json — Marc Gravell
– Marc Gravell, Commented Jun 22, 2017 at 10:53

HongyanShen · Accepted Answer · 2017-06-22 12:59:10Z

1

Finally, i worked it out in the client side by using:

json = await response.json()
bs = json.encode("ascii")
b64 = base64.b64decode(bs)
person = Person.create_from_bytes(b64)
print(f"{person.id} {person.name}")

answered Jun 22, 2017 at 12:59

HongyanShen

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Comments

Breno Medeiros de Oliveira · Accepted Answer · 2020-01-09 18:36:48Z

I had some time to develop this Solution for Python3.7, considering as example:

'''        Argument =   [110, 13, 46, 136, 95, 66, 92, 132, 109, 217, 58, 112, 43, 8, 145, 
                         42, 233, 98, 40, 139, 165, 228, 52, 9, 89, 175, 146, 103, 227, 238, 233, 190, 
                         78, 175, 242, 224, 202, 138, 248, 103, 114, 98, 199, 252, 80, 86, 61, 174]
            return =    'bg0uiF9CXIRt2TpwKwiRKuliKIul5DQJWa+SZ+Pu6b5Or/Lgyor4Z3Jix/xQVj2u' 
'''

Like this:

import base64
import numpy as np


# Do the same as Convert.ToBase64String() from C#
def ConvertToBase64String(encrypted):
    return (base64.b64encode(textoUnicodeToUtf8Literal(("".join([chr(item) for item in np.array(encrypted, dtype=np.uint8)]))).encode('ISO-8859-1'))).decode()

# Do the oposite of Convert.ToBase64String() from C#
def ConvertToStringBase64(encrypted):
    return np.frombuffer(base64.b64decode(encrypted.encode()), np.uint8)


def textoUnicodeToUtf8Literal(encodando):
    return encodando.replace("\xc2\x80", r'\x80').replace("\xc2\x81", r'\x81').replace("\xc2\x82", r'\x82')\
        .replace("\xc2\x83", r'\x83').replace("\xc2\x84", r'\x84').replace("\xc2\x85", r'\x85')\
        .replace("\xc2\x86", r'\x86').replace("\xc2\x87", r'\x87').replace("\xc2\x88", r'\x88')\
        .replace("\xc2\x89", r'\x89').replace("\xc2\x8a", r'\x8A').replace("\xc2\x8b", r'\x8B')\
        .replace("\xc2\x8c", r'\x8C').replace("\xc2\x8d", r'\x8D').replace("\xc2\x8e", r'\x8E')\
        .replace("\xc2\x8f", r'\x8F').replace("\xc2\x90", r'\x90').replace("\xc2\x91", r'\x91')\
        .replace("\xc2\x92", r'\x92').replace("\xc2\x93", r'\x93').replace("\xc2\x94", r'\x94')\
        .replace("\xc2\x95", r'\x95').replace("\xc2\x96", r'\x96').replace("\xc2\x97", r'\x97')\
        .replace("\xc2\x98", r'\x98').replace("\xc2\x99", r'\x99').replace("\xc2\x9a", r'\x9A')\
        .replace("\xc2\x9b", r'\x9B').replace("\xc2\x9c", r'\x9C').replace("\xc2\x9d", r'\x9D')\
        .replace("\xc2\x9e", r'\x9E').replace("\xc2\x9f", r'\x9F').replace("\xc2\xa0", r'\xA0')\
        .replace("\xc2\xa1", r'\xA1').replace("\xc2\xa2", r'\xA2').replace("\xc2\xa3", r'\xA3')\
        .replace("\xc2\xa4", r'\xA4').replace("\xc2\xa5", r'\xA5').replace("\xc2\xa6", r'\xA6')\
        .replace("\xc2\xa7", r'\xA7').replace("\xc2\xa8", r'\xA8').replace("\xc2\xa9", r'\xA9')\
        .replace("\xc2\xaa", r'\xAA').replace("\xc2\xab", r'\xAB').replace("\xc2\xac", r'\xAC')\
        .replace("\xc2\xad", r'\xAD').replace("\xc2\xae", r'\xAE').replace("\xc2\xaf", r'\xAF')\
        .replace("\xc2\xb0", r'\xB0').replace("\xc2\xb1", r'\xB1').replace("\xc2\xb2", r'\xB2')\
        .replace("\xc2\xb3", r'\xB3').replace("\xc2\xb4", r'\xB4').replace("\xc2\xb5", r'\xB5')\
        .replace("\xc2\xb6", r'\xB6').replace("\xc2\xb7", r'\xB7').replace("\xc2\xb8", r'\xB8')\
        .replace("\xc2\xb9", r'\xB9').replace("\xc2\xba", r'\xBA').replace("\xc2\xbb", r'\xBB')\
        .replace("\xc2\xbc", r'\xBC').replace("\xc2\xbd", r'\xBD').replace("\xc2\xbe", r'\xBE')\
        .replace("\xc2\xbf", r'\xBF').replace("\xc3\x80", r'\xC0').replace("\xc3\x81", r'\xC1')\
        .replace("\xc3\x82", r'\xC2').replace("\xc3\x83", r'\xC3').replace("\xc3\x84", r'\xC4')\
        .replace("\xc3\x85", r'\xC5').replace("\xc3\x86", r'\xC6').replace("\xc3\x87", r'\xC7')\
        .replace("\xc3\x88", r'\xC8').replace("\xc3\x89", r'\xC9').replace("\xc3\x8a", r'\xCA')\
        .replace("\xc3\x8b", r'\xCB').replace("\xc3\x8c", r'\xCC').replace("\xc3\x8d", r'\xCD')\
        .replace("\xc3\x8e", r'\xCE').replace("\xc3\x8f", r'\xCF').replace("\xc3\x90", r'\xD0')\
        .replace("\xc3\x91", r'\xD1').replace("\xc3\x92", r'\xD2').replace("\xc3\x93", r'\xD3')\
        .replace("\xc3\x94", r'\xD4').replace("\xc3\x95", r'\xD5').replace("\xc3\x96", r'\xD6')\
        .replace("\xc3\x97", r'\xD7').replace("\xc3\x98", r'\xD8').replace("\xc3\x99", r'\xD9')\
        .replace("\xc3\x9a", r'\xDA').replace("\xc3\x9b", r'\xDB').replace("\xc3\x9c", r'\xDC')\
        .replace("\xc3\x9d", r'\xDD').replace("\xc3\x9e", r'\xDE').replace("\xc3\x9f", r'\xDF')\
        .replace("\xc3\xa0", r'\xE0').replace("\xc3\xa1", r'\xE1').replace("\xc3\xa2", r'\xE2')\
        .replace("\xc3\xa3", r'\xE3').replace("\xc3\xa4", r'\xE4').replace("\xc3\xa5", r'\xE5')\
        .replace("\xc3\xa6", r'\xE6').replace("\xc3\xa7", r'\xE7').replace("\xc3\xa8", r'\xE8')\
        .replace("\xc3\xa9", r'\xE9').replace("\xc3\xaa", r'\xEA').replace("\xc3\xab", r'\xEB')\
        .replace("\xc3\xac", r'\xEC').replace("\xc3\xad", r'\xED').replace("\xc3\xae", r'\xEE')\
        .replace("\xc3\xaf", r'\xEF').replace("\xc3\xb0", r'\xF0').replace("\xc3\xb1", r'\xF1')\
        .replace("\xc3\xb2", r'\xF2').replace("\xc3\xb3", r'\xF3').replace("\xc3\xb4", r'\xF4')\
        .replace("\xc3\xb5", r'\xF5').replace("\xc3\xb6", r'\xF6').replace("\xc3\xb7", r'\xF7')\
        .replace("\xc3\xb8", r'\xF8').replace("\xc3\xb9", r'\xF9').replace("\xc3\xba", r'\xFA')\
        .replace("\xc3\xbb", r'\xFB').replace("\xc3\xbc", r'\xFC').replace("\xc3\xbd", r'\xFD')\
        .replace("\xc3\xbe", r'\xFE').replace("\xc3\xbf", r'\xFF')

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