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#include <Common/formatIPv6.h>
#include <base/hex.h>
#include <Common/StringUtils/StringUtils.h>
#include <base/range.h>
#include <array>
#include <algorithm>
namespace DB
{
/** Further we want to generate constexpr array of strings with sizes from sequence of unsigned ints [0..N)
* in order to use this arrey for fast conversion of unsigned integers to strings
*/
namespace detail
{
template <unsigned... digits>
struct ToChars
{
static const char value[];
static const size_t size;
};
template <unsigned... digits>
constexpr char ToChars<digits...>::value[] = {('0' + digits)..., 0};
template <unsigned... digits>
constexpr size_t ToChars<digits...>::size = sizeof...(digits);
template <unsigned rem, unsigned... digits>
struct Decompose : Decompose<rem / 10, rem % 10, digits...> {};
template <unsigned... digits>
struct Decompose<0, digits...> : ToChars<digits...> {};
template <>
struct Decompose<0> : ToChars<0> {};
template <unsigned num>
struct NumToString : Decompose<num> {};
template <class T, T... ints>
consteval std::array<std::pair<const char *, size_t>, sizeof...(ints)> str_make_array_impl(std::integer_sequence<T, ints...>)
{
return std::array<std::pair<const char *, size_t>, sizeof...(ints)> { std::pair<const char *, size_t> {NumToString<ints>::value, NumToString<ints>::size}... };
}
}
/** str_make_array<N>() - generates static array of std::pair<const char *, size_t> for numbers [0..N), where:
* first - null-terminated string representing number
* second - size of the string as would returned by strlen()
*/
template <size_t N>
consteval std::array<std::pair<const char *, size_t>, N> str_make_array()
{
return detail::str_make_array_impl(std::make_integer_sequence<int, N>{});
}
/// This will generate static array of pair<const char *, size_t> for [0..255] at compile time
extern constexpr auto one_byte_to_string_lookup_table = str_make_array<256>();
/// integer logarithm, return ceil(log(value, base)) (the smallest integer greater or equal than log(value, base)
static constexpr UInt32 intLog(const UInt32 value, const UInt32 base, const bool carry)
{
return value >= base ? 1 + intLog(value / base, base, value % base || carry) : value % base > 1 || carry;
}
/// Print integer in desired base, faster than sprintf.
/// NOTE This is not the best way. See https://github.com/miloyip/itoa-benchmark
/// But it doesn't matter here.
template <UInt32 base, typename T>
static void printInteger(char *& out, T value)
{
if (value == 0)
*out++ = '0';
else
{
constexpr size_t buffer_size = sizeof(T) * intLog(256, base, false);
char buf[buffer_size];
auto ptr = buf;
while (value > 0)
{
*ptr = hexDigitLowercase(value % base);
++ptr;
value /= base;
}
/// Copy to out reversed.
while (ptr != buf)
{
--ptr;
*out = *ptr;
++out;
}
}
}
void formatIPv6(const unsigned char * src, char *& dst, uint8_t zeroed_tail_bytes_count)
{
struct { Int64 base, len; } best{-1, 0}, cur{-1, 0};
std::array<UInt16, IPV6_BINARY_LENGTH / sizeof(UInt16)> words{};
/** Preprocess:
* Copy the input (bytewise) array into a wordwise array.
* Find the longest run of 0x00's in src[] for :: shorthanding. */
for (const auto i : collections::range(0, IPV6_BINARY_LENGTH - zeroed_tail_bytes_count))
words[i / 2] |= src[i] << ((1 - (i % 2)) << 3);
for (const auto i : collections::range(0, words.size()))
{
if (words[i] == 0)
{
if (cur.base == -1)
{
cur.base = i;
cur.len = 1;
}
else
cur.len++;
}
else
{
if (cur.base != -1)
{
if (best.base == -1 || cur.len > best.len)
best = cur;
cur.base = -1;
}
}
}
if (cur.base != -1)
{
if (best.base == -1 || cur.len > best.len)
best = cur;
}
if (best.base != -1 && best.len < 2)
best.base = -1;
/// Format the result.
for (const size_t i : collections::range(0, words.size()))
{
/// Are we inside the best run of 0x00's?
if (best.base != -1)
{
size_t best_base = static_cast<size_t>(best.base);
if (i >= best_base && i < (best_base + best.len))
{
if (i == best_base)
*dst++ = ':';
continue;
}
}
/// Are we following an initial run of 0x00s or any real hex?
if (i != 0)
*dst++ = ':';
/// Is this address an encapsulated IPv4?
if (i == 6 && best.base == 0 && (best.len == 6 || (best.len == 5 && words[5] == 0xffffu)))
{
uint8_t ipv4_buffer[IPV4_BINARY_LENGTH] = {0};
memcpy(ipv4_buffer, src + 12, IPV4_BINARY_LENGTH);
// Due to historical reasons formatIPv4() takes ipv4 in BE format, but inside ipv6 we store it in LE-format.
#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
std::reverse(std::begin(ipv4_buffer), std::end(ipv4_buffer));
#endif
formatIPv4(ipv4_buffer, dst, std::min(zeroed_tail_bytes_count, static_cast<uint8_t>(IPV4_BINARY_LENGTH)), "0");
// formatIPv4 has already added a null-terminator for us.
return;
}
printInteger<16>(dst, words[i]);
}
/// Was it a trailing run of 0x00's?
if (best.base != -1 && static_cast<size_t>(best.base) + static_cast<size_t>(best.len) == words.size())
*dst++ = ':';
*dst++ = '\0';
}
}
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