# Base64 decode string to byte array

**URL:** <https://community.particle.io/t/base64-decode-string-to-byte-array/10456>\
**Category:** Firmware\
**Created:** [March 6, 2015, 9:39pm UTC](https://community.particle.io/t/base64-decode-string-to-byte-array/10456 "2015-03-06T21:39:04Z")\
**Posts on this page:** 3\
**Page:** 1

<div class="post-metadata">

**Author:** ![IOTrav](https://sea2.discourse-cdn.com/flex026/user_avatar/community.particle.io/iotrav/32/7707_2.png) [@IOTrav](https://community.particle.io/u/IOTrav)\
**Post date:** [March 6, 2015, 9:39pm UTC](https://community.particle.io/t/base64-decode-string-to-byte-array/10456/1 "2015-03-06T21:39:04Z")

</div>

I feel like I have exhausted every resource online trying to find a routine to decode a Base64 encoded String. I need a method I can pass a String to and have it return something like an unsiged char[] or other form of byte array. Does anyone have anything?

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<div class="post-metadata">

**Author:** ![ScruffR](https://sea2.discourse-cdn.com/flex026/user_avatar/community.particle.io/scruffr/32/6952_2.png) [@ScruffR](https://community.particle.io/u/ScruffR)\
**Post date:** [March 6, 2015, 10:34pm UTC](https://community.particle.io/t/base64-decode-string-to-byte-array/10456/2 "2015-03-06T22:34:18Z")

</div>

What about this 10 second Google search?

[http://www.adp-gmbh.ch/cpp/common/base64.html](http://www.adp-gmbh.ch/cpp/common/base64.html)

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<div class="post-metadata">

**Author:** ![IOTrav](https://sea2.discourse-cdn.com/flex026/user_avatar/community.particle.io/iotrav/32/7707_2.png) [@IOTrav](https://community.particle.io/u/IOTrav)\
**Post date:** [March 6, 2015, 11:08pm UTC](https://community.particle.io/t/base64-decode-string-to-byte-array/10456/3 "2015-03-06T23:08:57Z")

</div>

Hi @ScruffR,

That decode method returns a string. I need to return an unsigned char array so I can get null bytes. That was the problem.

Here is my new working code:

```
void aes_client::base64_decode(const char *data, size_t input_length, size_t *output_length, unsigned char* outputData) {

    if (decoding_table == NULL) build_decoding_table();

    if (input_length % 4 != 0) return;

    int inputLength = input_length / 4 * 3;

// *output_length = input_length / 4 * 3;
    if (data[input_length - 1] == '=') (inputLength)--;
    if (data[input_length - 2] == '=') (inputLength)--;

    unsigned char t[(size_t)inputLength];
// unsigned char *decoded_data = t;
// if (decoded_data == NULL) return;

    for (int i = 0, j = 0; i < input_length;) {

        uint32_t sextet_a = data[i] == '=' ? 0 & i++ : decoding_table[data[i++]];
        uint32_t sextet_b = data[i] == '=' ? 0 & i++ : decoding_table[data[i++]];
        uint32_t sextet_c = data[i] == '=' ? 0 & i++ : decoding_table[data[i++]];
        uint32_t sextet_d = data[i] == '=' ? 0 & i++ : decoding_table[data[i++]];

        uint32_t triple = (sextet_a << 3 * 6)
        + (sextet_b << 2 * 6)
        + (sextet_c << 1 * 6)
        + (sextet_d << 0 * 6);

        if (j < inputLength) t[j++] = (triple >> 2 * 8) & 0xFF;
        if (j < inputLength) t[j++] = (triple >> 1 * 8) & 0xFF;
        if (j < inputLength) t[j++] = (triple >> 0 * 8) & 0xFF;
    }

    memcpy(outputData, t, inputLength);
}
```