include/pub_tool_hashtable.h

   1
   2 /*--------------------------------------------------------------------*/
   3 /*--- A hash table implementation.            pub_tool_hashtable.h ---*/
   4 /*--------------------------------------------------------------------*/
   5
   6 /*
   7    This file is part of Valgrind, a dynamic binary instrumentation
   8    framework.
   9
  10    Copyright (C) 2005-2013 Nicholas Nethercote
  11       njn@valgrind.org
  12
  13    This program is free software; you can redistribute it and/or
  14    modify it under the terms of the GNU General Public License as
  15    published by the Free Software Foundation; either version 2 of the
  16    License, or (at your option) any later version.
  17
  18    This program is distributed in the hope that it will be useful, but
  19    WITHOUT ANY WARRANTY; without even the implied warranty of
  20    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  21    General Public License for more details.
  22
  23    You should have received a copy of the GNU General Public License
  24    along with this program; if not, write to the Free Software
  25    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  26    02111-1307, USA.
  27
  28    The GNU General Public License is contained in the file COPYING.
  29 */
  30
  31 #ifndef __PUB_TOOL_HASHTABLE_H
  32 #define __PUB_TOOL_HASHTABLE_H
  33
  34 #include "pub_tool_basics.h"   // VG_ macro
  35
  36 /* Generic type for a separately-chained hash table.  Via a kind of dodgy
  37    C-as-C++ style inheritance, tools can extend the VgHashNode type, so long
  38    as the first two fields match the sizes of these two fields.  Requires
  39    a bit of casting by the tool. */
  40
  41 // Problems with this data structure:
  42 // - Separate chaining gives bad cache behaviour.  Hash tables with linear
  43 //   probing give better cache behaviour.
  44
  45 typedef
  46    struct _VgHashNode {
  47       struct _VgHashNode * next;
  48       UWord              key;
  49    }
  50    VgHashNode;
  51
  52 typedef struct _VgHashTable VgHashTable;
  53
  54 /* Make a new table.  Allocates the memory with VG_(calloc)(), so can
  55    be freed with VG_(free)().  The table starts small but will
  56    periodically be expanded.  This is transparent to the users of this
  57    module. The function never returns NULL. */
  58 extern VgHashTable *VG_(HT_construct) ( const HChar* name );
  59
  60 /* Count the number of nodes in a table. */
  61 extern Int VG_(HT_count_nodes) ( const VgHashTable *table );
  62
  63 /* Add a node to the table.  Duplicate keys are permitted. */
  64 extern void VG_(HT_add_node) ( VgHashTable *t, void* node );
  65
  66 /* Looks up a VgHashNode by key in the table.
  67  * Returns NULL if not found.  If entries
  68  * with duplicate keys are present, the most recently-added of the dups will
  69  * be returned, but it's probably better to avoid dups altogether. */
  70 extern void* VG_(HT_lookup) ( const VgHashTable *table, UWord key );
  71
  72 /* Removes a VgHashNode by key from the table.  Returns NULL if not found. */
  73 extern void* VG_(HT_remove) ( VgHashTable *table, UWord key );
  74
  75 typedef Word  (*HT_Cmp_t) ( const void* node1, const void* node2 );
  76
  77 /* Same as VG_(HT_lookup) and VG_(HT_remove), but allowing a part of or
  78    the full element to be compared for equality, not only the key.
  79    The typical use for the below function is to store a hash value of the
  80    element in the key, and have the comparison function checking for equality
  81    of the full element data.
  82    Attention about the comparison function:
  83     * It must *not* compare the 'next' pointer.
  84     * when comparing the rest of the node, if the node data contains holes
  85       between components, either the node memory should be fully initialised
  86       (e.g. allocated using VG_(calloc)) or each component should be compared
  87        individually. */
  88 extern void* VG_(HT_gen_lookup) ( const VgHashTable *table, const void* node,
  89                                   HT_Cmp_t cmp );
  90 extern void* VG_(HT_gen_remove) ( VgHashTable *table, const void* node,
  91                                   HT_Cmp_t cmp );
  92
  93 /* Output detailed usage/collision statistics.
  94    cmp will be used to verify if 2 elements with the same key are equal.
  95    Use NULL cmp if the hash table elements are only to be compared by key. */
  96 extern void VG_(HT_print_stats) ( const VgHashTable *table, HT_Cmp_t cmp );
  97
  98 /* Allocates a suitably-sized array, copies pointers to all the hashtable
  99    elements into it, then returns both the array and the size of it.  The
 100    array must be freed with VG_(free). If the hashtable is empty, the
 101    function returns NULL and assigns *nelems = 0. */
 102 extern VgHashNode** VG_(HT_to_array) ( const VgHashTable *table,
 103                                        /*OUT*/ UInt* n_elems );
 104
 105 /* Reset the table's iterator to point to the first element. */
 106 extern void VG_(HT_ResetIter) ( VgHashTable *table );
 107
 108 /* Return the element pointed to by the iterator and move on to the
 109    next one.  Returns NULL if the last one has been passed, or if
 110    HT_ResetIter() has not been called previously.  Asserts if the
 111    table has been modified (HT_add_node, HT_remove) since
 112    HT_ResetIter.  This guarantees that callers cannot screw up by
 113    modifying the table whilst iterating over it (and is necessary to
 114    make the implementation safe; specifically we must guarantee that
 115    the table will not get resized whilst iteration is happening.
 116    Since resizing only happens as a result of calling HT_add_node,
 117    disallowing HT_add_node during iteration should give the required
 118    assurance. */
 119 extern void* VG_(HT_Next) ( VgHashTable *table );
 120
 121 /* Destroy a table and deallocates the memory used by the nodes using
 122    freenode_fn.*/
 123 extern void VG_(HT_destruct) ( VgHashTable *table, void(*freenode_fn)(void*) );
 124
 125
 126 #endif   // __PUB_TOOL_HASHTABLE_H
 127
 128 /*--------------------------------------------------------------------*/
 129 /*--- end                                                          ---*/
 130 /*--------------------------------------------------------------------*/