Bad / Missing ending on decoded content

[morgan-wild]

Hi! I'm trying to use your library but I have a problem, probably i use it the bad way.

I encode and decode the same string or array of bytes but I can't obtain the same result.

    char m[] = "'I FINK U FREEKY' by DIE ANTWOORD xxx (Official)";

    Serial.println(m);

    char mBase64[128];

    int base64Length = Base64.encode(mBase64, (char *)m, sizeof(m));

    Serial.println(mBase64);

    int dLength = Base64.decodedLength(mBase64, strlen(mBase64)); 

    char m2[dLength];

    Base64.decode(m2, mBase64, dLength);

    Serial.println(m2);

Result

'I FINK U FREEKY' by DIE ANTWOORD xxx (Official)
J0kgRklOSyBVIEZSRUVLWScgYnkgRElFIEFOVFdPT1JEIHh4eCAoT2ZmaWNpYWwpAA==
'I FINK U FREEKY' by DIE ANTWOORD xx <- Humm?

    char m[] = { 0x57, 0x2a, 0x63, 0x79, 0x3a, 0x9f, 0x76, 0x60, 0x66, 0xcf, 0x50, 0x59, 0x1c, 0x8f, 0x97, 0x49, 0x92, 0xba, 0x71, 0x14, 0x27, 0xb5, 0x2c, 0x6c, 0xf1, 0xa4, 0x7a, 0x4b, 0xc8, 0x13, 0xe6, 0x93 };

    Serial.println(m);

    for (uint8_t i = 0; i < sizeof(m); i++)
    {
        Serial.print(m[i], HEX);
        Serial.print(" ");
    }

    Serial.println();

    char mBase64[128];

    int base64Length = Base64.encode(mBase64, (char *)m, sizeof(m));

    Serial.println(mBase64);

    int dLength = Base64.decodedLength(mBase64, strlen(mBase64)); 

    char m2[dLength];

    Base64.decode(m2, mBase64, dLength);

    for (uint8_t i = 0; i < sizeof(m2); i++)
    {
        Serial.print(m2[i], HEX);
        Serial.print(" ");
    }

Result

57 2A 63 79 3A 9F 76 60 66 CF 50 59 1C 8F 97 49 92 BA 71 14 27 B5 2C 6C F1 A4 7A 4B C8 13 E6 93 
VypjeTqfdmBmz1BZHI+XSZK6cRQntSxs8aR6S8gT5pM=
57 2A 63 79 3A 9F 76 60 66 CF 50 59 1C 8F 97 49 92 BA 71 14 27 B5 2C 6C 0 A5 A5 A5 A5 A5 A5 A5  <- Humm?

Same exercice using another library (densaugeo/base64@^1.4.0):

    char m[] = "'I FINK U FREEKY' by DIE ANTWOORD xxx (Official)";

    Serial.println(m);

    char mBase64[128];

    int base64_length = encode_base64((unsigned char *)m, sizeof(m), (unsigned char *)mBase64);

    Serial.println(mBase64);

    char m2[128];

    int decoded_length = decode_base64((unsigned char *)mBase64, (unsigned char *) m2);

    Serial.println(m2);

Result

'I FINK U FREEKY' by DIE ANTWOORD xxx (Official)
J0kgRklOSyBVIEZSRUVLWScgYnkgRElFIEFOVFdPT1JEIHh4eCAoT2ZmaWNpYWwpAA==
'I FINK U FREEKY' by DIE ANTWOORD xxx (Official) <- OK!

    char m[] = { 0x57, 0x2a, 0x63, 0x79, 0x3a, 0x9f, 0x76, 0x60, 0x66, 0xcf, 0x50, 0x59, 0x1c, 0x8f, 0x97, 0x49, 0x92, 0xba, 0x71, 0x14, 0x27, 0xb5, 0x2c, 0x6c, 0xf1, 0xa4, 0x7a, 0x4b, 0xc8, 0x13, 0xe6, 0x93 };

    for (uint8_t i = 0; i < sizeof(m); i++)
    {
        Serial.print(m[i], HEX);
        Serial.print(" ");
    }

    Serial.println();

    char mBase64[128];

    int base64_length = encode_base64((unsigned char *)m, sizeof(m), (unsigned char *)mBase64);

    Serial.println(mBase64);

    char m2[128];

    int decoded_length = decode_base64((unsigned char *)mBase64, (unsigned char *) m2);

    for (uint8_t i = 0; i < decoded_length; i++)
    {
        Serial.print(m2[i], HEX);
        Serial.print(" ");
    }

Result

57 2A 63 79 3A 9F 76 60 66 CF 50 59 1C 8F 97 49 92 BA 71 14 27 B5 2C 6C F1 A4 7A 4B C8 13 E6 93
VypjeTqfdmBmz1BZHI+XSZK6cRQntSxs8aR6S8gT5pM=
57 2A 63 79 3A 9F 76 60 66 CF 50 59 1C 8F 97 49 92 BA 71 14 27 B5 2C 6C F1 A4 7A 4B C8 13 E6 93 <- OK!

The encoding part looks fine, I have the same result with both libraries and I checked it with an online tool.

But there is something bad on the decoding side.

Any idea?

[agdl]

The [decode function's third parameter inputLength should be the length of the Base64 encoded string, not the expected decoded length.

The issues in your code are:

For strings: Use strlen(m) instead of sizeof(m) to avoid encoding the null terminator
For decode function: Pass strlen(mBase64) (the encoded string length) instead of dLength (the decoded length)
Here's how your corrected code should look:

For the string example:

char m[] = "'I FINK U FREEKY' by DIE ANTWOORD xxx (Official)";
Serial.println(m);

char mBase64[128];
int base64Length = Base64.encode(mBase64, m, strlen(m)); // Use strlen() not sizeof()

Serial.println(mBase64);

int dLength = Base64.decodedLength(mBase64, strlen(mBase64)); 
char m2[dLength];

Base64.decode(m2, mBase64, strlen(mBase64)); // Pass encoded string length, not decoded length

Serial.println(m2);

For the byte array example:

char m[] = { 0x57, 0x2a, 0x63, 0x79, 0x3a, 0x9f, 0x76, 0x60, 0x66, 0xcf, 0x50, 0x59, 0x1c, 0x8f, 0x97, 0x49, 0x92, 0xba, 0x71, 0x14, 0x27, 0xb5, 0x2c, 0x6c, 0xf1, 0xa4, 0x7a, 0x4b, 0xc8, 0x13, 0xe6, 0x93 };

// For byte arrays, sizeof() is correct since there's no null terminator issue
char mBase64[128];
int base64Length = Base64.encode(mBase64, m, sizeof(m));

Serial.println(mBase64);

int dLength = Base64.decodedLength(mBase64, strlen(mBase64)); 
char m2[dLength];

Base64.decode(m2, mBase64, strlen(mBase64)); // Pass encoded string length

for (uint8_t i = 0; i < dLength; i++) // Use dLength for the loop limit
{
    Serial.print(m2[i], HEX);
    Serial.print(" ");
}