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base64.cpp
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#include <base64.hpp>
namespace base64
{
bool base64_encode(const std::string &input, std::string &output)
{
// This is left as a raw array (and not a range checked std::array) under
// the suspicion that the optimizer is not smart enough to remove the range
// checks that would be done below if at were called. As is, this array is
// 64 bytes long, which should be greater than the max of 0b00111111 when
// indexed NOLINT calls below are to silence clang-tidy about this
// TODO(ed) this requires further investigation if a more safe method could
// be used without performance impact.
static const char encoding_data[] =
"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
size_t input_length = input.size();
// allocate space for output string
output.clear();
output.reserve(((input_length + 2) / 3) * 4);
// for each 3-bytes sequence from the input, extract 4 6-bits sequences and
// encode using
// encoding_data lookup table.
// if input do not contains enough chars to complete 3-byte sequence,use pad
// char '='
for (size_t i = 0; i < input_length; i++)
{
int base64code0 = 0;
int base64code1 = 0;
int base64code2 = 0;
int base64code3 = 0;
base64code0 = (input[i] >> 2) & 0x3f; // 1-byte 6 bits
output += encoding_data[base64code0]; // NOLINT
base64code1 = (input[i] << 4) & 0x3f; // 1-byte 2 bits +
if (++i < input_length)
{
base64code1 |= (input[i] >> 4) & 0x0f; // 2-byte 4 bits
output += encoding_data[base64code1]; // NOLINT
base64code2 = (input[i] << 2) & 0x3f; // 2-byte 4 bits +
if (++i < input_length)
{
base64code2 |= (input[i] >> 6) & 0x03; // 3-byte 2 bits
base64code3 = input[i] & 0x3f; // 3-byte 6 bits
output += encoding_data[base64code2]; // NOLINT
output += encoding_data[base64code3]; // NOLINT
}
else
{
output += encoding_data[base64code2]; // NOLINT
output += '=';
}
}
else
{
output += encoding_data[base64code1]; // NOLINT
output += '=';
output += '=';
}
}
return true;
}
bool base64_decode(const std::string &input, std::string &output)
{
static const char nop = -1;
// See note on encoding_data[] in above function
static const char decoding_data[] = {
nop, nop, nop, nop, nop, nop, nop, nop, nop, nop, nop, nop, nop, nop,
nop, nop, nop, nop, nop, nop, nop, nop, nop, nop, nop, nop, nop, nop,
nop, nop, nop, nop, nop, nop, nop, nop, nop, nop, nop, nop, nop, nop,
nop, 62, nop, nop, nop, 63, 52, 53, 54, 55, 56, 57, 58, 59,
60, 61, nop, nop, nop, nop, nop, nop, nop, 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, nop, nop, nop, nop, nop, nop, 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, nop, nop, nop,
nop, nop, nop, nop, nop, nop, nop, nop, nop, nop, nop, nop, nop, nop,
nop, nop, nop, nop, nop, nop, nop, nop, nop, nop, nop, nop, nop, nop,
nop, nop, nop, nop, nop, nop, nop, nop, nop, nop, nop, nop, nop, nop,
nop, nop, nop, nop, nop, nop, nop, nop, nop, nop, nop, nop, nop, nop,
nop, nop, nop, nop, nop, nop, nop, nop, nop, nop, nop, nop, nop, nop,
nop, nop, nop, nop, nop, nop, nop, nop, nop, nop, nop, nop, nop, nop,
nop, nop, nop, nop, nop, nop, nop, nop, nop, nop, nop, nop, nop, nop,
nop, nop, nop, nop, nop, nop, nop, nop, nop, nop, nop, nop, nop, nop,
nop, nop, nop, nop, nop, nop, nop, nop, nop, nop, nop, nop, nop, nop,
nop, nop, nop, nop};
size_t input_length = input.size();
// allocate space for output string
output.clear();
output.reserve(((input_length + 2) / 3) * 4);
// for each 4-bytes sequence from the input, extract 4 6-bits sequences by
// droping first two bits
// and regenerate into 3 8-bits sequences
for (size_t i = 0; i < input_length; i++)
{
char base64code0;
char base64code1;
char base64code2 = 0; // initialized to 0 to suppress warnings
char base64code3;
base64code0 = decoding_data[static_cast<int>(input[i])]; // NOLINT
if (base64code0 == nop)
{ // non base64 character
return false;
}
if (!(++i < input_length))
{ // we need at least two input bytes for first
// byte output
return false;
}
base64code1 = decoding_data[static_cast<int>(input[i])]; // NOLINT
if (base64code1 == nop)
{ // non base64 character
return false;
}
output +=
static_cast<char>((base64code0 << 2) | ((base64code1 >> 4) & 0x3));
if (++i < input_length)
{
char c = input[i];
if (c == '=')
{ // padding , end of input
return (base64code1 & 0x0f) == 0;
}
base64code2 = decoding_data[static_cast<int>(input[i])]; // NOLINT
if (base64code2 == nop)
{ // non base64 character
return false;
}
output += static_cast<char>(((base64code1 << 4) & 0xf0) |
((base64code2 >> 2) & 0x0f));
}
if (++i < input_length)
{
char c = input[i];
if (c == '=')
{ // padding , end of input
return (base64code2 & 0x03) == 0;
}
base64code3 = decoding_data[static_cast<int>(input[i])]; // NOLINT
if (base64code3 == nop)
{ // non base64 character
return false;
}
output +=
static_cast<char>((((base64code2 << 6) & 0xc0) | base64code3));
}
}
return true;
}
} // namespace base64