dense_hash_map.h
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- // Copyright (c) 2005, Google Inc.
- // All rights reserved.
- //
- // Redistribution and use in source and binary forms, with or without
- // modification, are permitted provided that the following conditions are
- // met:
- //
- // * Redistributions of source code must retain the above copyright
- // notice, this list of conditions and the following disclaimer.
- // * Redistributions in binary form must reproduce the above
- // copyright notice, this list of conditions and the following disclaimer
- // in the documentation and/or other materials provided with the
- // distribution.
- // * Neither the name of Google Inc. nor the names of its
- // contributors may be used to endorse or promote products derived from
- // this software without specific prior written permission.
- //
- // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
- // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
- // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
- // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
- // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
- // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
- // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
- // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
- // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
- // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
- // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
- // ----
- // Author: Craig Silverstein
- //
- // This is just a very thin wrapper over densehashtable.h, just
- // like sgi stl's stl_hash_map is a very thin wrapper over
- // stl_hashtable. The major thing we define is operator[], because
- // we have a concept of a data_type which stl_hashtable doesn't
- // (it only has a key and a value).
- //
- // NOTE: this is exactly like sparse_hash_map.h, with the word
- // "sparse" replaced by "dense", except for the addition of
- // set_empty_key().
- //
- // YOU MUST CALL SET_EMPTY_KEY() IMMEDIATELY AFTER CONSTRUCTION.
- //
- // Otherwise your program will die in mysterious ways.
- //
- // In other respects, we adhere mostly to the STL semantics for
- // hash-map. One important exception is that insert() invalidates
- // iterators entirely. On the plus side, though, erase() doesn't
- // invalidate iterators at all, or even change the ordering of elements.
- //
- // Here are a few "power user" tips:
- //
- // 1) set_deleted_key():
- // If you want to use erase() you must call set_deleted_key(),
- // in addition to set_empty_key(), after construction.
- // The deleted and empty keys must differ.
- //
- // 2) resize(0):
- // When an item is deleted, its memory isn't freed right
- // away. This allows you to iterate over a hashtable,
- // and call erase(), without invalidating the iterator.
- // To force the memory to be freed, call resize(0).
- //
- // Guide to what kind of hash_map to use:
- // (1) dense_hash_map: fastest, uses the most memory
- // (2) sparse_hash_map: slowest, uses the least memory
- // (3) hash_map (STL): in the middle
- // Typically I use sparse_hash_map when I care about space and/or when
- // I need to save the hashtable on disk. I use hash_map otherwise. I
- // don't personally use dense_hash_map ever; the only use of
- // dense_hash_map I know of is to work around malloc() bugs in some
- // systems (dense_hash_map has a particularly simple allocation scheme).
- //
- // - dense_hash_map has, typically, a factor of 2 memory overhead (if your
- // data takes up X bytes, the hash_map uses X more bytes in overhead).
- // - sparse_hash_map has about 2 bits overhead per entry.
- // - sparse_hash_map can be 3-7 times slower than the others for lookup and,
- // especially, inserts. See time_hash_map.cc for details.
- //
- // See /usr/(local/)?doc/sparsehash-0.1/dense_hash_map.html
- // for information about how to use this class.
- #ifndef _DENSE_HASH_MAP_H_
- #define _DENSE_HASH_MAP_H_
- #include "sparseconfig.h"
- #include <stdio.h> // for FILE * in read()/write()
- #include <algorithm> // for the default template args
- #include <functional> // for equal_to
- #include <memory> // for alloc<>
- #include <utility> // for pair<>
- #include HASH_FUN_H // defined in sparseconfig.h
- #include "densehashtable.h"
- _START_GOOGLE_NAMESPACE_
- using STL_NAMESPACE::pair;
- template <class Key, class T,
- class HashFcn = HASH_NAMESPACE::hash<Key>,
- class EqualKey = STL_NAMESPACE::equal_to<Key>,
- class Alloc = STL_NAMESPACE::allocator<T> >
- class dense_hash_map {
- private:
- // Apparently select1st is not stl-standard, so we define our own
- struct SelectKey {
- const Key& operator()(const pair<const Key, T>& p) const {
- return p.first;
- }
- };
- // The actual data
- typedef dense_hashtable<pair<const Key, T>, Key, HashFcn,
- SelectKey, EqualKey, Alloc> ht;
- ht rep;
- public:
- typedef typename ht::key_type key_type;
- typedef T data_type;
- typedef T mapped_type;
- typedef typename ht::value_type value_type;
- typedef typename ht::hasher hasher;
- typedef typename ht::key_equal key_equal;
- typedef typename ht::size_type size_type;
- typedef typename ht::difference_type difference_type;
- typedef typename ht::pointer pointer;
- typedef typename ht::const_pointer const_pointer;
- typedef typename ht::reference reference;
- typedef typename ht::const_reference const_reference;
- typedef typename ht::iterator iterator;
- typedef typename ht::const_iterator const_iterator;
- // Iterator functions
- iterator begin() { return rep.begin(); }
- iterator end() { return rep.end(); }
- const_iterator begin() const { return rep.begin(); }
- const_iterator end() const { return rep.end(); }
- // Accessor functions
- hasher hash_funct() const { return rep.hash_funct(); }
- key_equal key_eq() const { return rep.key_eq(); }
- // Constructors
- explicit dense_hash_map(size_type n = 0,
- const hasher& hf = hasher(),
- const key_equal& eql = key_equal())
- : rep(n, hf, eql) { }
- template <class InputIterator>
- dense_hash_map(InputIterator f, InputIterator l,
- size_type n = 0,
- const hasher& hf = hasher(),
- const key_equal& eql = key_equal()) {
- rep.insert(f, l);
- }
- // We use the default copy constructor
- // We use the default operator=()
- // We use the default destructor
- void clear() { rep.clear(); }
- // This clears the hash map without resizing it down to the minimum
- // bucket count, but rather keeps the number of buckets constant
- void clear_no_resize() { rep.clear_no_resize(); }
- void swap(dense_hash_map& hs) { rep.swap(hs.rep); }
- // Functions concerning size
- size_type size() const { return rep.size(); }
- size_type max_size() const { return rep.max_size(); }
- bool empty() const { return rep.empty(); }
- size_type bucket_count() const { return rep.bucket_count(); }
- size_type max_bucket_count() const { return rep.max_bucket_count(); }
- void resize(size_type hint) { rep.resize(hint); }
- // Lookup routines
- iterator find(const key_type& key) { return rep.find(key); }
- const_iterator find(const key_type& key) const { return rep.find(key); }
- data_type& operator[](const key_type& key) { // This is our value-add!
- iterator it = find(key);
- if (it != end()) {
- return it->second;
- } else {
- return insert(value_type(key, data_type())).first->second;
- }
- }
- size_type count(const key_type& key) const { return rep.count(key); }
- pair<iterator, iterator> equal_range(const key_type& key) {
- return rep.equal_range(key);
- }
- pair<const_iterator, const_iterator> equal_range(const key_type& key) const {
- return rep.equal_range(key);
- }
- // Insertion routines
- pair<iterator, bool> insert(const value_type& obj) { return rep.insert(obj); }
- template <class InputIterator>
- void insert(InputIterator f, InputIterator l) { rep.insert(f, l); }
- void insert(const_iterator f, const_iterator l) { rep.insert(f, l); }
- // required for std::insert_iterator; the passed-in iterator is ignored
- iterator insert(iterator, const value_type& obj) { return insert(obj).first; }
- // Deletion and empty routines
- // THESE ARE NON-STANDARD! I make you specify an "impossible" key
- // value to identify deleted and empty buckets. You can change the
- // deleted key as time goes on, or get rid of it entirely to be insert-only.
- void set_empty_key(const key_type& key) { // YOU MUST CALL THIS!
- rep.set_empty_key(value_type(key, data_type())); // rep wants a value
- }
- void set_deleted_key(const key_type& key) {
- rep.set_deleted_key(value_type(key, data_type())); // rep wants a value
- }
- void clear_deleted_key() { rep.clear_deleted_key(); }
- // These are standard
- size_type erase(const key_type& key) { return rep.erase(key); }
- void erase(iterator it) { rep.erase(it); }
- void erase(iterator f, iterator l) { rep.erase(f, l); }
- // Comparison
- bool operator==(const dense_hash_map& hs) const { return rep == hs.rep; }
- bool operator!=(const dense_hash_map& hs) const { return rep != hs.rep; }
- // I/O -- this is an add-on for writing metainformation to disk
- bool write_metadata(FILE *fp) { return rep.write_metadata(fp); }
- bool read_metadata(FILE *fp) { return rep.read_metadata(fp); }
- bool write_nopointer_data(FILE *fp) { return rep.write_nopointer_data(fp); }
- bool read_nopointer_data(FILE *fp) { return rep.read_nopointer_data(fp); }
- };
- // We need a global swap as well
- template <class Key, class T, class HashFcn, class EqualKey, class Alloc>
- inline void swap(dense_hash_map<Key, T, HashFcn, EqualKey, Alloc>& hm1,
- dense_hash_map<Key, T, HashFcn, EqualKey, Alloc>& hm2) {
- hm1.swap(hm2);
- }
- _END_GOOGLE_NAMESPACE_
- #endif /* _DENSE_HASH_MAP_H_ */