gcc/inchash.h

   1 /* An incremental hash abstract data type.
   2    Copyright (C) 2014 Free Software Foundation, Inc.
   3
   4 This file is part of GCC.
   5
   6 GCC is free software; you can redistribute it and/or modify it under
   7 the terms of the GNU General Public License as published by the Free
   8 Software Foundation; either version 3, or (at your option) any later
   9 version.
  10
  11 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
  12 WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13 FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14 for more details.
  15
  16 You should have received a copy of the GNU General Public License
  17 along with GCC; see the file COPYING3.  If not see
  18 <http://www.gnu.org/licenses/>.  */
  19
  20 #ifndef INCHASH_H
  21 #define INCHASH_H 1
  22
  23 #include "config.h"
  24 #include "system.h"
  25 #include "coretypes.h"
  26 #include "hashtab.h"
  27
  28 /* This file implements an incremential hash function ADT, to be used
  29    by code that incrementially hashes a lot of unrelated data
  30    (not in a single memory block) into a single value. The goal
  31    is to make it easy to plug in efficient hash algorithms.
  32    Currently it just implements the plain old jhash based
  33    incremental hash from gcc's tree.c.  */
  34
  35 extern hashval_t iterative_hash_host_wide_int (HOST_WIDE_INT, hashval_t);
  36 extern hashval_t iterative_hash_hashval_t (hashval_t, hashval_t);
  37
  38 class inchash
  39 {
  40  public:
  41
  42   /* Start incremential hashing, optionally with SEED.  */
  43   inchash (hashval_t seed = 0)
  44   {
  45     val = seed;
  46     bits = 0;
  47   }
  48
  49   /* End incremential hashing and provide the final value.  */
  50   hashval_t end ()
  51   {
  52     return val;
  53   }
  54
  55   /* Add unsigned value V.  */
  56   void add_int (unsigned v)
  57   {
  58     val = iterative_hash_hashval_t (v, val);
  59   }
  60
  61   /* Add HOST_WIDE_INT value V.  */
  62   void add_wide_int (HOST_WIDE_INT v)
  63   {
  64     val = iterative_hash_host_wide_int (v, val);
  65   }
  66
  67   /* Hash in pointer PTR.  */
  68   void add_ptr (void *ptr)
  69   {
  70     add (&ptr, sizeof (ptr));
  71   }
  72
  73   /* Add a memory block DATA with size LEN.  */
  74   void add (const void *data, size_t len)
  75   {
  76     val = iterative_hash (data, len, val);
  77   }
  78
  79   /* Merge hash value OTHER.  */
  80   void merge_hash (hashval_t other)
  81   {
  82     val = iterative_hash_hashval_t (other, val);
  83   }
  84
  85   /* Hash in state from other inchash OTHER.  */
  86   void merge (inchash &other)
  87   {
  88     merge_hash (other.val);
  89   }
  90
  91   /* Support for accumulating boolean flags */
  92
  93   void add_flag (bool flag)
  94   {
  95     bits = (bits << 1) | flag;
  96   }
  97
  98   void commit_flag ()
  99   {
 100     add_int (bits);
 101     bits = 0;
 102   }
 103
 104   /* Support for commutative hashing. Add A and B in a defined order
 105      based on their value. This is useful for hashing commutative
 106      expressions, so that A+B and B+A get the same hash.  */
 107
 108   void add_commutative (inchash &a, inchash &b)
 109   {
 110     if (a.end() > b.end())
 111       {
 112         merge (b);
 113         merge (a);
 114       }
 115     else
 116       {
 117         merge (a);
 118         merge (b);
 119       }
 120   }
 121
 122  private:
 123   hashval_t val;
 124   unsigned bits;
 125 };
 126
 127 #define add_object(o) add (&(o), sizeof (o))
 128
 129 #endif