1/* An incremental hash abstract data type.
2   Copyright (C) 2014-2015 Free Software Foundation, Inc.
3
4This file is part of GCC.
5
6GCC is free software; you can redistribute it and/or modify it under
7the terms of the GNU General Public License as published by the Free
8Software Foundation; either version 3, or (at your option) any later
9version.
10
11GCC is distributed in the hope that it will be useful, but WITHOUT ANY
12WARRANTY; without even the implied warranty of MERCHANTABILITY or
13FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
14for more details.
15
16You should have received a copy of the GNU General Public License
17along 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
35extern hashval_t iterative_hash_host_wide_int (HOST_WIDE_INT, hashval_t);
36extern hashval_t iterative_hash_hashval_t (hashval_t, hashval_t);
37
38namespace inchash
39{
40
41class 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
138