Line data    Source code

       1              : // Copyright (C) 2020-2026 Free Software Foundation, Inc.
       2              : 
       3              : // This file is part of GCC.
       4              : 
       5              : // GCC is free software; you can redistribute it and/or modify it under
       6              : // the terms of the GNU General Public License as published by the Free
       7              : // Software Foundation; either version 3, or (at your option) any later
       8              : // version.
       9              : 
      10              : // GCC is distributed in the hope that it will be useful, but WITHOUT ANY
      11              : // WARRANTY; without even the implied warranty of MERCHANTABILITY or
      12              : // FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
      13              : // for more details.
      14              : 
      15              : // You should have received a copy of the GNU General Public License
      16              : // along with GCC; see the file COPYING3.  If not see
      17              : // <http://www.gnu.org/licenses/>.
      18              : #include "rust-system.h"
      19              : 
      20              : #ifndef RUST_FNV_HASH_H
      21              : #define RUST_FNV_HASH_H
      22              : 
      23              : namespace Rust {
      24              : namespace Hash {
      25              : 
      26              : const uint64_t offset128Lower = 0x62b821756295c58d;
      27              : const uint64_t offset128Higher = 0x6c62272e07bb0142;
      28              : const uint64_t prime128Lower = 0x13b;
      29              : const uint64_t prime128Shift = 24;
      30              : 
      31              : // ported from https://github.com/golang/go/blob/master/src/hash/fnv/fnv.go
      32              : class FNV128
      33              : {
      34              : public:
      35        29690 :   FNV128 () { reset (); }
      36              : 
      37        29690 :   void reset ()
      38              :   {
      39        29690 :     buf[0] = offset128Higher;
      40        29690 :     buf[1] = offset128Lower;
      41              :   }
      42              : 
      43        29690 :   void write (const unsigned char *in, size_t len)
      44              :   {
      45      2412378 :     for (size_t i = 0; i < len; i++)
      46              :       {
      47      2382688 :         unsigned char c = in[i];
      48              : 
      49              :         // https://stackoverflow.com/questions/28868367/getting-the-high-part-of-64-bit-integer-multiplication
      50      2382688 :         uint64_t a = prime128Lower;
      51      2382688 :         uint64_t b = buf[1];
      52              : 
      53      2382688 :         uint64_t a_lo = (uint32_t) a;
      54      2382688 :         uint64_t a_hi = a >> 32;
      55      2382688 :         uint64_t b_lo = (uint32_t) b;
      56      2382688 :         uint64_t b_hi = b >> 32;
      57              : 
      58      2382688 :         uint64_t a_x_b_hi = a_hi * b_hi;
      59      2382688 :         uint64_t a_x_b_mid = a_hi * b_lo;
      60      2382688 :         uint64_t b_x_a_mid = b_hi * a_lo;
      61      2382688 :         uint64_t a_x_b_lo = a_lo * b_lo;
      62              : 
      63      2382688 :         uint64_t carry_bit
      64              :           = ((uint64_t) (uint32_t) a_x_b_mid + (uint64_t) (uint32_t) b_x_a_mid
      65      2382688 :              + (a_x_b_lo >> 32))
      66              :             >> 32;
      67              : 
      68      2382688 :         uint64_t multhi
      69      2382688 :           = a_x_b_hi + (a_x_b_mid >> 32) + (b_x_a_mid >> 32) + carry_bit;
      70              : 
      71      2382688 :         uint64_t s0 = multhi;                 // high
      72      2382688 :         uint64_t s1 = prime128Lower * buf[1]; // low
      73              : 
      74      2382688 :         s0 += buf[1] << (prime128Shift + prime128Lower * buf[0]);
      75              : 
      76              :         // Update the values
      77      2382688 :         buf[1] = s1;
      78      2382688 :         buf[0] = s0;
      79      2382688 :         buf[1] ^= (uint64_t) c;
      80              :       }
      81        29690 :   }
      82              : 
      83        29690 :   void sum (uint64_t *hi, uint64_t *lo) const
      84              :   {
      85        29690 :     *hi = buf[0];
      86        29690 :     *lo = buf[1];
      87              :   }
      88              : 
      89              : private:
      90              :   uint64_t buf[2];
      91              : };
      92              : 
      93              : } // namespace Hash
      94              : } // namespace Rust
      95              : 
      96              : #endif // RUST_FNV_HASH_H