晋太元中，武陵人捕鱼为业。缘溪行，忘路之远近。忽逢桃花林，夹岸数百步，中无杂树，芳草鲜美，落英缤纷。渔人甚异之，复前行，欲穷其林。 　　林尽水源，便得一山，山有小口，仿佛若有光。便舍船，从口入。初极狭，才通人。复行数十步，豁然开朗。土地平旷，屋舍俨然，有良田、美池、桑竹之属。阡陌交通，鸡犬相闻。其中往来种作，男女衣着，悉如外人。黄发垂髫，并怡然自乐。 　　见渔人，乃大惊，问所从来。具答之。便要还家，设酒杀鸡作食。村中闻有此人，咸来问讯。自云先世避秦时乱，率妻子邑人来此绝境，不复出焉，遂与外人间隔。问今是何世，乃不知有汉，无论魏晋。此人一一为具言所闻，皆叹惋。余人各复延至其家，皆出酒食。停数日，辞去。此中人语云：“不足为外人道也。”(间隔 一作：隔绝) 　　既出，得其船，便扶向路，处处志之。及郡下，诣太守，说如此。太守即遣人随其往，寻向所志，遂迷，不复得路。 　　南阳刘子骥，高尚士也，闻之，欣然规往。未果，寻病终。后遂无问津者。 sh-3ll

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/*
   Copyright (c) 2020, MariaDB Corporation.

   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; version 2 of the License.

   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, write to the Free Software
   Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1335  USA */

#pragma once

#include <cassert>
#include <cstring>

#ifdef _MSC_VER
template <std::size_t Alignment, class T>
static inline T my_assume_aligned(T ptr)
{
  assert(reinterpret_cast<size_t>(ptr) % Alignment == 0);
  __assume(reinterpret_cast<size_t>(ptr) % Alignment == 0);
  return ptr;
}
#else
template <std::size_t Alignment, class T>
static inline T my_assume_aligned(T ptr)
{
  assert(reinterpret_cast<size_t>(ptr) % Alignment == 0);
  return static_cast<T>(__builtin_assume_aligned(ptr, Alignment));
}
#endif

template <std::size_t Alignment>
inline void *memcpy_aligned(void *dest, const void *src, size_t n)
{
  static_assert(Alignment && !(Alignment & (Alignment - 1)), "power of 2");

  return std::memcpy(my_assume_aligned<Alignment>(dest),
                     my_assume_aligned<Alignment>(src), n);
}
template <std::size_t Alignment>
inline void *memmove_aligned(void *dest, const void *src, size_t n)
{
  static_assert(Alignment && !(Alignment & (Alignment - 1)), "power of 2");

  return std::memmove(my_assume_aligned<Alignment>(dest),
                      my_assume_aligned<Alignment>(src), n);
}
template <std::size_t Alignment>
inline int memcmp_aligned(const void *s1, const void *s2, size_t n)
{
  static_assert(Alignment && !(Alignment & (Alignment - 1)), "power of 2");

  return std::memcmp(my_assume_aligned<Alignment>(s1),
                     my_assume_aligned<Alignment>(s2), n);
}
template <std::size_t Alignment>
inline void *memset_aligned(void *s, int c, size_t n)
{
  static_assert(Alignment && !(Alignment & (Alignment - 1)), "power of 2");

  return std::memset(my_assume_aligned<Alignment>(s), c, n);
}