include/pub_tool_hashtable.h

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/*--- A hash table implementation.            pub_tool_hashtable.h ---*/
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/*
   This file is part of Valgrind, a dynamic binary instrumentation
   framework.

   Copyright (C) 2005-2013 Nicholas Nethercote
      njn@valgrind.org

   This program is free software; you can redistribute it and/or
   modify it under the terms of the GNU General Public License as
   published by the Free Software Foundation; either version 2 of the
   License, or (at your option) any later version.

   This program is distributed in the hope that it will be useful, but
   WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software
   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
   02111-1307, USA.

   The GNU General Public License is contained in the file COPYING.
*/

#ifndef __PUB_TOOL_HASHTABLE_H
#define __PUB_TOOL_HASHTABLE_H

#include "pub_tool_basics.h"   // VG_ macro

/* Generic type for a separately-chained hash table.  Via a kind of dodgy
   C-as-C++ style inheritance, tools can extend the VgHashNode type, so long
   as the first two fields match the sizes of these two fields.  Requires
   a bit of casting by the tool. */

// Problems with this data structure:
// - Separate chaining gives bad cache behaviour.  Hash tables with linear
//   probing give better cache behaviour.

typedef
   struct _VgHashNode {
      struct _VgHashNode * next;
      UWord              key;
   }
   VgHashNode;

typedef struct _VgHashTable VgHashTable;

/* Make a new table.  Allocates the memory with VG_(calloc)(), so can
   be freed with VG_(free)().  The table starts small but will
   periodically be expanded.  This is transparent to the users of this
   module. The function never returns NULL. */
extern VgHashTable *VG_(HT_construct) ( const HChar* name );

/* Count the number of nodes in a table. */
extern Int VG_(HT_count_nodes) ( const VgHashTable *table );

/* Add a node to the table.  Duplicate keys are permitted. */
extern void VG_(HT_add_node) ( VgHashTable *t, void* node );

/* Looks up a VgHashNode by key in the table.  
 * Returns NULL if not found.  If entries
 * with duplicate keys are present, the most recently-added of the dups will
 * be returned, but it's probably better to avoid dups altogether. */
extern void* VG_(HT_lookup) ( const VgHashTable *table, UWord key );

/* Removes a VgHashNode by key from the table.  Returns NULL if not found. */
extern void* VG_(HT_remove) ( VgHashTable *table, UWord key );

typedef Word  (*HT_Cmp_t) ( const void* node1, const void* node2 );

/* Same as VG_(HT_lookup) and VG_(HT_remove), but allowing a part of or
   the full element to be compared for equality, not only the key.
   The typical use for the below function is to store a hash value of the
   element in the key, and have the comparison function checking for equality
   of the full element data.
   Attention about the comparison function:
    * It must *not* compare the 'next' pointer.
    * when comparing the rest of the node, if the node data contains holes
      between components, either the node memory should be fully initialised
      (e.g. allocated using VG_(calloc)) or each component should be compared
       individually. */
extern void* VG_(HT_gen_lookup) ( const VgHashTable *table, const void* node,
                                  HT_Cmp_t cmp );
extern void* VG_(HT_gen_remove) ( VgHashTable *table, const void* node,
                                  HT_Cmp_t cmp );

/* Output detailed usage/collision statistics.
   cmp will be used to verify if 2 elements with the same key are equal.
   Use NULL cmp if the hash table elements are only to be compared by key. */
extern void VG_(HT_print_stats) ( const VgHashTable *table, HT_Cmp_t cmp );

/* Allocates a suitably-sized array, copies pointers to all the hashtable
   elements into it, then returns both the array and the size of it.  The
   array must be freed with VG_(free). If the hashtable is empty, the
   function returns NULL and assigns *nelems = 0. */
extern VgHashNode** VG_(HT_to_array) ( const VgHashTable *table,
                                       /*OUT*/ UInt* n_elems );

/* Reset the table's iterator to point to the first element. */
extern void VG_(HT_ResetIter) ( VgHashTable *table );

/* Return the element pointed to by the iterator and move on to the
   next one.  Returns NULL if the last one has been passed, or if
   HT_ResetIter() has not been called previously.  Asserts if the
   table has been modified (HT_add_node, HT_remove) since
   HT_ResetIter.  This guarantees that callers cannot screw up by
   modifying the table whilst iterating over it (and is necessary to
   make the implementation safe; specifically we must guarantee that
   the table will not get resized whilst iteration is happening.
   Since resizing only happens as a result of calling HT_add_node,
   disallowing HT_add_node during iteration should give the required
   assurance. */
extern void* VG_(HT_Next) ( VgHashTable *table );

/* Destroy a table and deallocates the memory used by the nodes using
   freenode_fn.*/
extern void VG_(HT_destruct) ( VgHashTable *table, void(*freenode_fn)(void*) );


#endif   // __PUB_TOOL_HASHTABLE_H

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/*--- end                                                          ---*/
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