114 lines
3.6 KiB
C++
114 lines
3.6 KiB
C++
#include "mybase64.hpp"
|
|
|
|
#include <climits>
|
|
#include <cstdint>
|
|
#include <string_view>
|
|
|
|
namespace mybase64
|
|
{
|
|
|
|
static_assert(CHAR_BIT == 8);
|
|
|
|
auto encode(std::string_view const input, char* output) -> void
|
|
{
|
|
static char const* const alphabet =
|
|
"ABCDEFGHIJKLMNOPQRSTUVWXYZ"
|
|
"abcdefghijklmnopqrstuvwxyz"
|
|
"0123456789+/";
|
|
|
|
auto cursor = std::begin(input);
|
|
auto const end = std::end(input);
|
|
|
|
while (end - cursor >= 3)
|
|
{
|
|
uint32_t buffer = uint8_t(*cursor++);
|
|
buffer <<= 8; buffer |= uint8_t(*cursor++);
|
|
buffer <<= 8; buffer |= uint8_t(*cursor++);
|
|
|
|
*output++ = alphabet[(buffer >> 6 * 3) % 64];
|
|
*output++ = alphabet[(buffer >> 6 * 2) % 64];
|
|
*output++ = alphabet[(buffer >> 6 * 1) % 64];
|
|
*output++ = alphabet[(buffer >> 6 * 0) % 64];
|
|
}
|
|
|
|
if (cursor < end)
|
|
{
|
|
uint32_t buffer = uint8_t(*cursor++) << 10;
|
|
if (cursor < end) buffer |= uint8_t(*cursor) << 2;
|
|
|
|
*output++ = alphabet[(buffer >> 12) % 64];
|
|
*output++ = alphabet[(buffer >> 6) % 64];
|
|
*output++ = cursor < end ? alphabet[(buffer % 64)] : '=';
|
|
*output++ = '=';
|
|
}
|
|
*output = '\0';
|
|
}
|
|
|
|
auto decode(std::string_view const input, char* const output, std::size_t* const outlen) -> bool
|
|
{
|
|
static int8_t const alphabet_values[] = {
|
|
-1, -1, -1, -1, -1, -1, -1, -1,
|
|
-1, -1, -1, -1, -1, -1, -1, -1,
|
|
-1, -1, -1, -1, -1, -1, -1, -1,
|
|
-1, -1, -1, -1, -1, -1, -1, -1,
|
|
-1, -1, -1, -1, -1, -1, -1, -1,
|
|
-1, -1, -1, 0x3e, -1, -1, -1, 0x3f,
|
|
0x34, 0x35, 0x36, 0x37, 0x38, 0x39, 0x3a, 0x3b,
|
|
0x3c, 0x3d, -1, -1, -1, -1, -1, -1,
|
|
-1, 0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06,
|
|
0x07, 0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e,
|
|
0x0f, 0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16,
|
|
0x17, 0x18, 0x19, -1, -1, -1, -1, -1,
|
|
-1, 0x1a, 0x1b, 0x1c, 0x1d, 0x1e, 0x1f, 0x20,
|
|
0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27, 0x28,
|
|
0x29, 0x2a, 0x2b, 0x2c, 0x2d, 0x2e, 0x2f, 0x30,
|
|
0x31, 0x32, 0x33, -1, -1, -1, -1, -1,
|
|
-1, -1, -1, -1, -1, -1, -1, -1,
|
|
-1, -1, -1, -1, -1, -1, -1, -1,
|
|
-1, -1, -1, -1, -1, -1, -1, -1,
|
|
-1, -1, -1, -1, -1, -1, -1, -1,
|
|
-1, -1, -1, -1, -1, -1, -1, -1,
|
|
-1, -1, -1, -1, -1, -1, -1, -1,
|
|
-1, -1, -1, -1, -1, -1, -1, -1,
|
|
-1, -1, -1, -1, -1, -1, -1, -1,
|
|
-1, -1, -1, -1, -1, -1, -1, -1,
|
|
-1, -1, -1, -1, -1, -1, -1, -1,
|
|
-1, -1, -1, -1, -1, -1, -1, -1,
|
|
-1, -1, -1, -1, -1, -1, -1, -1,
|
|
-1, -1, -1, -1, -1, -1, -1, -1,
|
|
-1, -1, -1, -1, -1, -1, -1, -1,
|
|
-1, -1, -1, -1, -1, -1, -1, -1,
|
|
-1, -1, -1, -1, -1, -1, -1, -1,
|
|
};
|
|
|
|
uint32_t buffer = 1;
|
|
char* cursor = output;
|
|
|
|
for (char c : input) {
|
|
int8_t const value = alphabet_values[uint8_t(c)];
|
|
if (-1 == value) continue;
|
|
|
|
buffer = (buffer << 6) | value;
|
|
|
|
if (buffer & 1<<6*4) {
|
|
*cursor++ = buffer >> 8*2;
|
|
*cursor++ = buffer >> 8*1;
|
|
*cursor++ = buffer >> 8*0;
|
|
buffer = 1;
|
|
}
|
|
}
|
|
|
|
if (buffer & 1<<6*3) {
|
|
*cursor++ = buffer >> 10;
|
|
*cursor++ = buffer >> 2;
|
|
} else if (buffer & 1<<6*2) {
|
|
*cursor++ = buffer >> 4;
|
|
} else if (buffer & 1<<6*1) {
|
|
return false;
|
|
}
|
|
*outlen = cursor - output;
|
|
return true;
|
|
}
|
|
|
|
} // namespace
|