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  1. template <typename T> 
  2. T reduce2(T v) {
  3.     T k = ((v * 410) >> 12) & 0x000F000F000F000Full;
  4.     return (((v - k * 10) << 8) + k);
  5. }
  6.  
  7. template <typename T>
  8. T reduce4(T v) {
  9.     T k = ((v * 10486) >> 20) & 0xFF000000FFull;
  10.     return reduce2(((v - k * 100) << 16) + (k));
  11. }
  12.  
  13. typedef unsigned long long ull;
  14. inline ull reduce8(ull v) {
  15.     ull k = ((v * 3518437209u) >> 45);
  16.     return reduce4(((v - k * 10000) << 32) + (k));
  17. }
  18.  
  19. template <typename T>
  20. std::string itostr(T o) {
  21.     union {
  22.         char str[16];
  23.         unsigned short u2[8];
  24.         unsigned u4[4];
  25.         unsigned long long u8[2];
  26.     };
  27.  
  28.     unsigned v = o < 0 ? ~o + 1 : o;
  29.  
  30.     u8[0] = (ull(v) * 3518437209u) >> 45;
  31.     u8[0] = (u8[0] * 28147497672ull);
  32.     u8[1] = v - u2[3] * 100000000;
  33.  
  34.     u8[1] = reduce8(u8[1]);
  35.     char* f;
  36.     if (u2[3]) {
  37.         u2[3] = reduce2(u2[3]);
  38.         f = str + 6;
  39.     } else {
  40.         unsigned short* k = u4[2] ? u2 + 4 : u2 + 6;
  41.         f = *k ? (char*)k : (char*)(k + 1);
  42.     }
  43.     if (!*f) f++;
  44.  
  45.     u4[1] |= 0x30303030;
  46.     u4[2] |= 0x30303030;
  47.     u4[3] |= 0x30303030;
  48.     if (o < 0) *--f = '-';
  49.     return std::string(f, (str + 16) - f);
  50. }
  51.  
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https://ideone.com/RWmFQ
language:
C++ (gcc 8.3)
created:
13 years ago
visibility:
secret

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