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#include "base32.h"
#include <util/generic/yexception.h>
#include <algorithm>
#include <array>
#include <limits>
namespace {
// RFC 4648 Base32 alphabet
//
// A 9 J 18 S 27 3
// 1 B 10 K 19 T 28 4
// 2 C 11 L 20 U 29 5
// 3 D 12 M 21 V 30 6
// 4 E 13 N 22 W 31 7
// 5 F 14 O 23 X
// 6 G 15 P 24 Y
// 7 H 16 Q 25 Z
// 8 I 17 R 26 2 pad =
constexpr std::string_view BASE32_TABLE = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
"234567";
constexpr uint8_t BAD = 0xff;
// clang-format off
constexpr std::array<uint8_t, 256> BASE32_DECODE_TABLE = {{
BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD,
BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD,
BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD,
BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD,
BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD,
0x1a, 0x1b, 0x1c, 0x1d, 0x1e, 0x1f, BAD, BAD, BAD, BAD,
BAD, BAD, BAD, BAD, BAD, 0x0, 0x1, 0x2, 0x3, 0x4,
0x5, 0x6, 0x7, 0x8, 0x9, 0xa, 0xb, 0xc, 0xd, 0xe,
0xf, 0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 0x18,
0x19, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD,
BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD,
BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD,
BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD,
BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD,
BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD,
BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD,
BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD,
BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD,
BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD,
BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD,
BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD,
BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD,
BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD,
BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD,
BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD,
BAD, BAD, BAD, BAD, BAD, BAD,
}};
// clang-format on
char encodeBits(unsigned char sz) {
static_assert(static_cast<size_t>(std::numeric_limits<decltype(sz)>::max()) < BASE32_DECODE_TABLE.size());
return BASE32_TABLE[sz];
}
uint8_t decodeChar(unsigned char ch, bool isStrict) {
if (uint8_t val = BASE32_DECODE_TABLE[ch]; val != BAD) {
return val;
}
if (isStrict) {
ythrow yexception() << "Error during decode symbol from Base32: character is not in Base32 set";
}
return 0;
}
void shiftBitsFrom(unsigned char& dst, const unsigned char& src, size_t i, size_t n) {
unsigned char m = ((src << i) & 0xFF) >> (8 - n);
dst = dst << n;
dst |= m;
}
size_t Base32DecodeImpl(std::string_view src, char* dst, bool isStrict) {
if (src.empty()) {
return 0;
}
size_t dstSize = 0;
size_t bitIndex = 0;
unsigned char byte = 0;
for (auto c = src.cbegin(); c != src.cend(); ++c) {
if (*c == '=') {
Y_ENSURE(
!isStrict || std::all_of(c, src.cend(), [](char pad) { return pad == '='; }),
"Unexpected character after padding");
break;
}
uint8_t octet = decodeChar(*c, isStrict) << 3;
byte = byte | (octet >> bitIndex);
size_t bitsWritten = std::min<size_t>(5, 8 - bitIndex);
if (bitsWritten < 5 || (bitIndex + bitsWritten) == 8) {
dst[dstSize++] = byte;
byte = (octet << bitsWritten);
}
bitIndex = (bitIndex + 5) % 8;
}
// For example, correct encoding of \x00 is
// AA====== (\b0000'0000\b00xx'xxxx), not a
// AAA= (\b0000'0000\b0000'000x)
size_t lastOctetBitsCount = (dstSize * 8) % 5;
size_t expectedBitIndex = (lastOctetBitsCount == 0) ? 0 : 5 - lastOctetBitsCount;
Y_ENSURE(!isStrict || (byte == 0 && bitIndex == expectedBitIndex), "Invalid Base32 string format");
return dstSize;
}
} // namespace
size_t Base32Encode(std::string_view src, char* dst) {
if (src.size() == 0) {
return 0;
}
size_t dstSize = 0;
size_t curInd = 0;
unsigned char c = src[curInd];
unsigned char bitInd = 0;
unsigned char n = 0;
unsigned char ind = 0;
while (curInd < src.size()) {
ind = 0;
unsigned char bitProcessed = 0;
while (bitProcessed < 5) {
n = std::min<unsigned char>(8 - bitInd, 5 - bitProcessed);
shiftBitsFrom(ind, c, bitInd, n);
bitProcessed += n;
if (bitInd + n >= 8) {
++curInd;
if (curInd == src.size()) {
c = 0;
} else {
c = src[curInd];
}
}
bitInd = (bitInd + n) % 8;
}
dst[dstSize++] = encodeBits(ind);
}
const size_t paddingSize = ((8 - (dstSize & 7)) & 7);
for (size_t i = 0; i < paddingSize; ++i) {
dst[dstSize++] = '=';
}
return dstSize;
}
size_t Base32Decode(std::string_view src, char* dst) {
return Base32DecodeImpl(src, dst, /*isStrict*/ false);
}
size_t Base32StrictDecode(std::string_view src, char* dst) {
return Base32DecodeImpl(src, dst, /*isStrict*/ true);
}
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