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@tomykaira
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C++ single header base64 decode/encoder for C++ 11 and above.
#ifndef _MACARON_BASE64_H_
#define _MACARON_BASE64_H_
/**
* The MIT License (MIT)
* Copyright (c) 2016-2024 tomykaira
*
* Permission is hereby granted, free of charge, to any person obtaining
* a copy of this software and associated documentation files (the
* "Software"), to deal in the Software without restriction, including
* without limitation the rights to use, copy, modify, merge, publish,
* distribute, sublicense, and/or sell copies of the Software, and to
* permit persons to whom the Software is furnished to do so, subject to
* the following conditions:
*
* The above copyright notice and this permission notice shall be
* included in all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
* LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
* OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
* WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
*/
#include <cstdint>
#include <string>
namespace macaron {
class Base64 {
public:
static std::string Encode(const std::string &data) {
static constexpr char sEncodingTable[] = {
'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M',
'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z',
'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm',
'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z',
'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '+', '/'};
size_t in_len = data.size();
size_t out_len = 4 * ((in_len + 2) / 3);
std::string ret(out_len, '\0');
size_t i;
char *p = const_cast<char *>(ret.c_str());
for (i = 0; in_len > 2 && i < in_len - 2; i += 3) {
*p++ = sEncodingTable[(data[i] >> 2) & 0x3F];
*p++ = sEncodingTable[((data[i] & 0x3) << 4) |
((int)(data[i + 1] & 0xF0) >> 4)];
*p++ = sEncodingTable[((data[i + 1] & 0xF) << 2) |
((int)(data[i + 2] & 0xC0) >> 6)];
*p++ = sEncodingTable[data[i + 2] & 0x3F];
}
if (i < in_len) {
*p++ = sEncodingTable[(data[i] >> 2) & 0x3F];
if (i == (in_len - 1)) {
*p++ = sEncodingTable[((data[i] & 0x3) << 4)];
*p++ = '=';
} else {
*p++ = sEncodingTable[((data[i] & 0x3) << 4) |
((int)(data[i + 1] & 0xF0) >> 4)];
*p++ = sEncodingTable[((data[i + 1] & 0xF) << 2)];
}
*p++ = '=';
}
return ret;
}
static std::string Decode(const std::string &input, std::string &out) {
static constexpr unsigned char kDecodingTable[] = {
64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64,
64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64,
64, 64, 64, 64, 64, 64, 64, 62, 64, 64, 64, 63, 52, 53, 54, 55, 56, 57,
58, 59, 60, 61, 64, 64, 64, 64, 64, 64, 64, 0, 1, 2, 3, 4, 5, 6,
7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24,
25, 64, 64, 64, 64, 64, 64, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36,
37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 64, 64, 64,
64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64,
64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64,
64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64,
64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64,
64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64,
64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64,
64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64,
64, 64, 64, 64};
size_t in_len = input.size();
if (in_len % 4 != 0)
return "Input data size is not a multiple of 4";
size_t out_len = in_len / 4 * 3;
if (in_len >= 1 && input[in_len - 1] == '=')
out_len--;
if (in_len >= 2 && input[in_len - 2] == '=')
out_len--;
out.resize(out_len);
for (size_t i = 0, j = 0; i < in_len;) {
uint32_t a = input[i] == '='
? 0 & i++
: kDecodingTable[static_cast<int>(input[i++])];
uint32_t b = input[i] == '='
? 0 & i++
: kDecodingTable[static_cast<int>(input[i++])];
uint32_t c = input[i] == '='
? 0 & i++
: kDecodingTable[static_cast<int>(input[i++])];
uint32_t d = input[i] == '='
? 0 & i++
: kDecodingTable[static_cast<int>(input[i++])];
uint32_t triple =
(a << 3 * 6) + (b << 2 * 6) + (c << 1 * 6) + (d << 0 * 6);
if (j < out_len)
out[j++] = (triple >> 2 * 8) & 0xFF;
if (j < out_len)
out[j++] = (triple >> 1 * 8) & 0xFF;
if (j < out_len)
out[j++] = (triple >> 0 * 8) & 0xFF;
}
return "";
}
};
} // namespace macaron
#endif /* _MACARON_BASE64_H_ */
#include <cstdint>
#include <iostream>
#include <vector>
#include "Base64.h"
int test(const std::string &data) {
std::string out;
auto b64 = macaron::Base64::Encode(data);
auto error = macaron::Base64::Decode(b64, out);
if (!error.empty()) {
std::cout << "Error: " << error << std::endl;
return 1;
}
if (data == out) {
std::cout << "OK: " << out << std::endl;
} else {
std::cout << "Wrong: " << data << ", " << b64 << ", " << out << std::endl;
}
return 0;
}
int main() {
test("hello");
test("");
test("1");
test("22");
test("333");
test("4444");
return 0;
}
@zdj1414
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zdj1414 commented Aug 12, 2022

when the input data length is 1, it will be crashed.

static std::string Encode(const std::string data) {
    static constexpr char sEncodingTable[] = {
      'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H',
      'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P',
      'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X',
      'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f',
      'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n',
      'o', 'p', 'q', 'r', 's', 't', 'u', 'v',
      'w', 'x', 'y', 'z', '0', '1', '2', '3',
      '4', '5', '6', '7', '8', '9', '+', '/'
    };

    size_t in_len = data.size();
    size_t out_len = 4 * ((in_len + 2) / 3);
    std::string ret(out_len, '\0');
    size_t i = 0;
    char *p = const_cast<char*>(ret.c_str());

    if (in_len >= 2) {
      for (i = 0; i < in_len - 2; i += 3) {
        *p++ = sEncodingTable[(data[i] >> 2) & 0x3F];
        *p++ = sEncodingTable[((data[i] & 0x3) << 4) | ((int) (data[i + 1] & 0xF0) >> 4)];
        *p++ = sEncodingTable[((data[i + 1] & 0xF) << 2) | ((int) (data[i + 2] & 0xC0) >> 6)];
        *p++ = sEncodingTable[data[i + 2] & 0x3F];
      }
    }

    if (i < in_len) {
      *p++ = sEncodingTable[(data[i] >> 2) & 0x3F];
      if (i == (in_len - 1)) {
        *p++ = sEncodingTable[((data[i] & 0x3) << 4)];
        *p++ = '=';
      }
      else {
        *p++ = sEncodingTable[((data[i] & 0x3) << 4) | ((int) (data[i + 1] & 0xF0) >> 4)];
        *p++ = sEncodingTable[((data[i + 1] & 0xF) << 2)];
      }
      *p++ = '=';
    }

    return ret;
  }

@29654761
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29654761 commented Mar 2, 2023

I fixed this:

size_t i=0; // init i=0
char* p = const_cast<char*>(ret.c_str());
if (in_len >= 2) { // skip when in_len less than 2
for (i = 0; i < in_len - 2; i += 3) {
*p++ = sEncodingTable[(data[i] >> 2) & 0x3F];
*p++ = sEncodingTable[((data[i] & 0x3) << 4) | ((int)(data[i + 1] & 0xF0) >> 4)];
*p++ = sEncodingTable[((data[i + 1] & 0xF) << 2) | ((int)(data[i + 2] & 0xC0) >> 6)];
*p++ = sEncodingTable[data[i + 2] & 0x3F];
}
}

@joneeky
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joneeky commented Jan 6, 2024

I think the Encode method should be like this:
static std::string Encode(const char *data, size_t in_len )

Because chat* to std::string may lost some data. The std::string ended by '\0'.
Yes, than I can use the func to encode a image data.

@tomykaira
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Author

Everyone, thank you very much for the discussions.
I fixed pointed bugs and version dependent behavior.

This is just a small example for Base64 encoding/decoding. Feel free to adapt it to your needs, like handling binary data 😄

@Bang1338
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omg this gist is still alive

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