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 namespace inchash
  39 {
  40
  41 class hash
  42 {
  43  public:
  44
  45   /* Start incremential hashing, optionally with SEED.  */
  46   hash (hashval_t seed = 0)
  47   {
  48     val = seed;
  49     bits = 0;
  50   }
  51
  52   /* End incremential hashing and provide the final value.  */
  53   hashval_t end ()
  54   {
  55     return val;
  56   }
  57
  58   /* Add unsigned value V.  */
  59   void add_int (unsigned v)
  60   {
  61     val = iterative_hash_hashval_t (v, val);
  62   }
  63
  64   /* Add HOST_WIDE_INT value V.  */
  65   void add_wide_int (HOST_WIDE_INT v)
  66   {
  67     val = iterative_hash_host_wide_int (v, val);
  68   }
  69
  70   /* Hash in pointer PTR.  */
  71   void add_ptr (void *ptr)
  72   {
  73     add (&ptr, sizeof (ptr));
  74   }
  75
  76   /* Add a memory block DATA with size LEN.  */
  77   void add (const void *data, size_t len)
  78   {
  79     val = iterative_hash (data, len, val);
  80   }
  81
  82   /* Merge hash value OTHER.  */
  83   void merge_hash (hashval_t other)
  84   {
  85     val = iterative_hash_hashval_t (other, val);
  86   }
  87
  88   /* Hash in state from other inchash OTHER.  */
  89   void merge (hash &other)
  90   {
  91     merge_hash (other.val);
  92   }
  93
  94   template<class T> void add_object(T &obj)
  95   {
  96     add (&obj, sizeof(T));
  97   }
  98
  99   /* Support for accumulating boolean flags */
 100
 101   void add_flag (bool flag)
 102   {
 103     bits = (bits << 1) | flag;
 104   }
 105
 106   void commit_flag ()
 107   {
 108     add_int (bits);
 109     bits = 0;
 110   }
 111
 112   /* Support for commutative hashing. Add A and B in a defined order
 113      based on their value. This is useful for hashing commutative
 114      expressions, so that A+B and B+A get the same hash.  */
 115
 116   void add_commutative (hash &a, hash &b)
 117   {
 118     if (a.end() > b.end())
 119       {
 120         merge (b);
 121         merge (a);
 122       }
 123     else
 124       {
 125         merge (a);
 126         merge (b);
 127       }
 128   }
 129
 130  private:
 131   hashval_t val;
 132   unsigned bits;
 133 };
 134
 135 }
 136
 137 #endif