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Add base64 encoders and decoders

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This commit is contained in:
Mark Haines 2015-06-15 17:48:09 +01:00
parent 026e4394bb
commit 7cdde73560
3 changed files with 191 additions and 0 deletions
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35
include/axolotl/base64.hh Normal file
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#ifndef AXOLOLT_BASE64_HH_
#define AXOLOLT_BASE64_HH_
#include <cstddef>
#include <cstdint>
namespace axolotl {
std::size_t encode_base64_length(
std::size_t input_length
);
void encode_base64(
std::uint8_t const * input, std::size_t input_length,
std::uint8_t * output
);
std::size_t decode_base64_length(
std::size_t input_length
);
void decode_base64(
std::uint8_t const * input, std::size_t input_length,
std::uint8_t * output
);
} // namespace axolotl
#endif /* AXOLOLT_BASE64_HH_ */

118
src/base64.cpp Normal file
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#include "axolotl/base64.hh"
namespace {
static const std::uint8_t ENCODE_BASE64[64] = {
0x41, 0x42, 0x43, 0x44, 0x45, 0x46, 0x47, 0x48,
0x49, 0x4A, 0x4B, 0x4C, 0x4D, 0x4E, 0x4F, 0x50,
0x51, 0x52, 0x53, 0x54, 0x55, 0x56, 0x57, 0x58,
0x59, 0x5A, 0x61, 0x62, 0x63, 0x64, 0x65, 0x66,
0x67, 0x68, 0x69, 0x6A, 0x6B, 0x6C, 0x6D, 0x6E,
0x6F, 0x70, 0x71, 0x72, 0x73, 0x74, 0x75, 0x76,
0x77, 0x78, 0x79, 0x7A, 0x30, 0x31, 0x32, 0x33,
0x34, 0x35, 0x36, 0x37, 0x38, 0x39, 0x2B, 0x2F,
};
static const std::uint8_t E = -1;
static const std::uint8_t DECODE_BASE64[128] = {
/* 0x0 0x1 0x2 0x3 0x4 0x5 0x6 0x7 0x8 0x9 0xA 0xB 0xC 0xD 0xE 0xF */
E, E, E, E, E, E, E, E, E, E, E, E, E, E, E, E,
E, E, E, E, E, E, E, E, E, E, E, E, E, E, E, E,
E, E, E, E, E, E, E, E, E, E, E, 62, E, E, E, 63,
52, 53, 54, 55, 56, 57, 58, 59, 60, 61, E, E, E, E, E, E,
E, 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, E, E, E, E, E,
E, 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, E, E, E, E, E,
};
} // namespace
std::size_t axolotl::encode_base64_length(
std::size_t input_length
) {
return 4 * ((input_length + 2) / 3) + (input_length + 2) % 3 - 2;
}
void axolotl::encode_base64(
std::uint8_t const * input, std::size_t input_length,
std::uint8_t * output
) {
std::uint8_t const * end = input + (input_length / 3) * 3;
std::uint8_t const * pos = input;
while (pos != end) {
unsigned value = pos[0];
value <<= 8; value |= pos[1];
value <<= 8; value |= pos[2];
pos += 3;
output[3] = ENCODE_BASE64[value & 0x3F];
value >>= 6; output[2] = ENCODE_BASE64[value & 0x3F];
value >>= 6; output[1] = ENCODE_BASE64[value & 0x3F];
value >>= 6; output[0] = ENCODE_BASE64[value];
output += 4;
}
unsigned remainder = input + input_length - pos;
if (remainder) {
unsigned value = pos[0];
if (remainder == 2) {
value <<= 8; value |= pos[1];
value <<= 2;
output[2] = ENCODE_BASE64[value & 0x3F];
value >>= 6;
} else {
value <<= 4;
}
output[1] = ENCODE_BASE64[value & 0x3F];
value >>= 6;
output[0] = ENCODE_BASE64[value];
}
}
std::size_t axolotl::decode_base64_length(
std::size_t input_length
) {
if (input_length % 4 == 1) {
return std::size_t(-1);
} else {
return 3 * ((input_length + 2) / 4) + (input_length + 2) % 4 - 2;
}
}
void axolotl::decode_base64(
std::uint8_t const * input, std::size_t input_length,
std::uint8_t * output
) {
std::uint8_t const * end = input + (input_length / 4) * 4;
std::uint8_t const * pos = input;
while (pos != end) {
unsigned value = DECODE_BASE64[pos[0] & 0x7F];
value <<= 6; value |= DECODE_BASE64[pos[1] & 0x7F];
value <<= 6; value |= DECODE_BASE64[pos[2] & 0x7F];
value <<= 6; value |= DECODE_BASE64[pos[3] & 0x7F];
pos += 4;
output[2] = value;
value >>= 8; output[1] = value;
value >>= 8; output[0] = value;
output += 3;
}
unsigned remainder = input + input_length - pos;
if (remainder) {
unsigned value = DECODE_BASE64[pos[0] & 0x7F];
value <<= 6; value |= DECODE_BASE64[pos[1] & 0x7F];
if (remainder == 3) {
value <<= 6; value |= DECODE_BASE64[pos[2] & 0x7F];
value >>= 2;
output[1] = value;
value >>= 8;
} else {
value >>= 4;
}
output[0] = value;
}
}

38
tests/test_base64.cpp Normal file
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#include "axolotl/base64.hh"
#include "unittest.hh"
int main() {
{ /* Base64 encode test */
TestCase test_case("Base64 encode test");
std::uint8_t input[] = "Hello World";
std::uint8_t expected_output[] = "SGVsbG8gV29ybGQ";
std::size_t input_length = sizeof(input) - 1;
std::size_t output_length = axolotl::encode_base64_length(input_length);
assert_equals(std::size_t(15), output_length);
std::uint8_t output[output_length];
axolotl::encode_base64(input, input_length, output);
assert_equals(expected_output, output, output_length);
}
{ /* Base64 decode test */
TestCase test_case("Base64 decode test");
std::uint8_t input[] = "SGVsbG8gV29ybGQ";
std::uint8_t expected_output[] = "Hello World";
std::size_t input_length = sizeof(input) - 1;
std::size_t output_length = axolotl::decode_base64_length(input_length);
assert_equals(std::size_t(11), output_length);
std::uint8_t output[output_length];
axolotl::decode_base64(input, input_length, output);
assert_equals(expected_output, output, output_length);
}
}