/**

* SPDX-License-Identifier: GPL-2.0-or-later

*

* This file is part of osm2pgsql (https://osm2pgsql.org/).

*

* Copyright (C) 2006-2026 by the osm2pgsql developer community.

* For a full list of authors see the git log.

*/

#include "hex.hpp"

#include <array>

#include <cassert>

#include <stdexcept>

namespace util {

void encode_hex(std::string const &input, std::string *output)

{

assert(output);

constexpr char const *const LOOKUP_HEX = "0123456789ABCDEF";

for (auto const c : input) {

unsigned int const num = static_cast<unsigned char>(c);

(*output) += LOOKUP_HEX[(num >> 4U) & 0xfU];

(*output) += LOOKUP_HEX[num & 0xfU];

}

}

std::string encode_hex(std::string const &input)

{

std::string result;

result.reserve(input.size() * 2);

encode_hex(input, &result);

return result;

}

namespace {

constexpr std::array<char, 256> HEX_TABLE = {

0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,

0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,

0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,

0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 0, 0, 0, 0, 0, 0,

0, 10, 11, 12, 13, 14, 15, 0, 0, 0, 0, 0, 0, 0, 0, 0,

0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,

0, 10, 11, 12, 13, 14, 15, 0, 0, 0, 0, 0, 0, 0, 0, 0,

};

} // anonymous namespace

unsigned char decode_hex_char(char c) noexcept

{

// NOLINTNEXTLINE(cppcoreguidelines-pro-bounds-constant-array-index)

return HEX_TABLE[static_cast<std::size_t>(static_cast<unsigned char>(c))];

}

std::string decode_hex(std::string_view hex_string)

{

if (hex_string.size() % 2 != 0) {

throw std::runtime_error{"Invalid wkb: Not a valid hex string"};

}

std::string wkb;

wkb.reserve(hex_string.size() / 2);

// NOLINTNEXTLINE(llvm-qualified-auto, readability-qualified-auto)

for (auto hex = hex_string.cbegin(); hex != hex_string.cend();) {

unsigned int const c = decode_hex_char(*hex++);

wkb += static_cast<char>((c << 4U) | decode_hex_char(*hex++));

}

return wkb;

}

} // namespace util