base64 encoding
static const std::wstring sc_Base64Chars = L"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789 + /";
std::wstring Base64Encode(const std::wstring &data)
{
std::wstring result;
size_t input_size = data.size();
int padding = (3 - input_size % 3) % 3;
size_t output_size = 4 * (input_size + padding) / 3;
result.resize(output_size);
auto input = data.c_str();
auto output = &result[0];
for (size_t i = 0, j = 0; i < input_size;)
{
uint32_t octet_a = i < input_size ? static_cast<unsigned char>(input[i++]) : 0;
uint32_t octet_b = i < input_size ? static_cast<unsigned char>(input[i++]) : 0;
uint32_t octet_c = i < input_size ? static_cast<unsigned char>(input[i++]) : 0;
uint32_t triple = (octet_a << 0x10) + (octet_b << 0x08) + octet_c;
output[j++] = sc_Base64Chars[(triple >> 3 * 6) & 0x3F];
output[j++] = sc_Base64Chars[(triple >> 2 * 6) & 0x3F];
output[j++] = sc_Base64Chars[(triple >> 1 * 6) & 0x3F];
output[j++] = sc_Base64Chars[(triple >> 0 * 6) & 0x3F];
}
for (int i = 0; i < padding; ++i)
{
output[output_size - 1 - i] = '=';
}
return result;
}
Base64 decoding
std::wstring Base64Decode(const std::wstring &data)
{
std::wstring result;
size_t input_size = data.size();
if (input_size % 4 != 0)
{
return result;
}
auto input = data.c_str();
std::vector<uint8_t> tmp(input_size);
for (size_t i = 0; i < input_size; ++i)
{
if (isspace(input[i]) || input[i] == '=')
{
continue;
}
size_t pos = sc_Base64Chars.find(input[i]);
if (pos == std::wstring::npos)
{
return result;
}
tmp[i] = pos;
}
size_t padding = 0;
if (input[input_size - 1] == '=')
{
++padding;
}
if (input[input_size - 2] == '=')
{
++padding;
}
size_t output_size = 3 * (input_size / 4) - padding;
result.resize(output_size);
auto output = &result[0];
for (size_t i = 0, j = 0; i < input_size;)
{
uint32_t sextet_a = tmp[i++];
uint32_t sextet_b = tmp[i++];
uint32_t sextet_c = tmp[i++];
uint32_t sextet_d = tmp[i++];
uint32_t triple = (sextet_a << 3 * 6) + (sextet_b << 2 * 6) + (sextet_c << 1 * 6) + (sextet_d << 0 * 6);
output[j++] = static_cast<unsigned char>((triple >> 2 * 8) & 0xFF);
output[j++] = static_cast<unsigned char>((triple >> 1 * 8) & 0xFF);
output[j++] = static_cast<unsigned char>((triple >> 0 * 8) & 0xFF);
}
return result;
}