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/*
* Copyright (C) 2008-2019 TrinityCore <https://www.trinitycore.org/>
*
* This program is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License as published by the
* Free Software Foundation; either version 2 of the License, or (at your
* option) any later version.
*
* This program is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
* more details.
*
* You should have received a copy of the GNU General Public License along
* with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#ifndef TRINITY_BASE_ENCODING_HPP
#define TRINITY_BASE_ENCODING_HPP
#include "advstd.h"
#include "Define.h"
#include "Optional.h"
#include <string>
#include <vector>
namespace Trinity
{
namespace Impl
{
template <typename Encoding>
struct GenericBaseEncoding
{
static constexpr std::size_t BITS_PER_CHAR = Encoding::BITS_PER_CHAR;
static constexpr std::size_t PAD_TO = advstd::lcm(8u, BITS_PER_CHAR);
static_assert(BITS_PER_CHAR < 8, "Encoding parameters are invalid");
static constexpr uint8 DECODE_ERROR = Encoding::DECODE_ERROR;
static constexpr char PADDING = Encoding::PADDING;
static constexpr std::size_t EncodedSize(std::size_t size)
{
size *= 8; // bits in input
if (size % PAD_TO) // pad to boundary
size += (PAD_TO - (size % PAD_TO));
return (size / BITS_PER_CHAR);
}
static constexpr std::size_t DecodedSize(std::size_t size)
{
size *= BITS_PER_CHAR; // bits in input
if (size % PAD_TO) // pad to boundary
size += (PAD_TO - (size % PAD_TO));
return (size / 8);
}
static std::string Encode(std::vector<uint8> const& data)
{
auto it = data.begin(), end = data.end();
if (it == end)
return "";
std::string s;
s.reserve(EncodedSize(data.size()));
uint8 bitsLeft = 8; // in current byte
do
{
uint8 thisC = 0;
if (bitsLeft >= BITS_PER_CHAR)
{
bitsLeft -= BITS_PER_CHAR;
thisC = ((*it >> bitsLeft) & ((1 << BITS_PER_CHAR)-1));
if (!bitsLeft)
{
++it;
bitsLeft = 8;
}
}
else
{
thisC = (*it & ((1 << bitsLeft) - 1)) << (BITS_PER_CHAR - bitsLeft);
bitsLeft += (8 - BITS_PER_CHAR);
if ((++it) != end)
thisC |= (*it >> bitsLeft);
}
s.append(1, Encoding::Encode(thisC));
} while (it != end);
while (bitsLeft != 8)
{
if (bitsLeft > BITS_PER_CHAR)
bitsLeft -= BITS_PER_CHAR;
else
bitsLeft += (8 - BITS_PER_CHAR);
s.append(1, PADDING);
}
return s;
}
static Optional<std::vector<uint8>> Decode(std::string const& data)
{
auto it = data.begin(), end = data.end();
if (it == end)
return std::vector<uint8>();
std::vector<uint8> v;
v.reserve(DecodedSize(data.size()));
uint8 currentByte = 0;
uint8 bitsLeft = 8; // in current byte
while ((it != end) && (*it != PADDING))
{
uint8 cur = Encoding::Decode(*(it++));
if (cur == DECODE_ERROR)
return {};
if (bitsLeft > BITS_PER_CHAR)
{
bitsLeft -= BITS_PER_CHAR;
currentByte |= (cur << bitsLeft);
}
else
{
bitsLeft = BITS_PER_CHAR - bitsLeft; // in encoded char
currentByte |= (cur >> bitsLeft);
v.push_back(currentByte);
currentByte = (cur & ((1 << bitsLeft) - 1));
bitsLeft = 8 - bitsLeft; // in byte again
currentByte <<= bitsLeft;
}
}
if (currentByte)
return {}; // decode error, trailing non-zero bits
// process padding
while ((it != end) && (*it == PADDING) && (bitsLeft != 8))
{
if (bitsLeft > BITS_PER_CHAR)
bitsLeft -= BITS_PER_CHAR;
else
bitsLeft += (8 - BITS_PER_CHAR);
++it;
}
// ok, all padding should be consumed, and we should be at end of string
if (it == end)
return v;
// anything else is an error
return {};
}
};
}
}
#endif
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