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// Copyright (c) 2005, Google Inc. |
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// All rights reserved. |
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// |
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// Redistribution and use in source and binary forms, with or without |
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// modification, are permitted provided that the following conditions are |
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// met: |
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// |
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// * Redistributions of source code must retain the above copyright |
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// notice, this list of conditions and the following disclaimer. |
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// * Redistributions in binary form must reproduce the above |
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// copyright notice, this list of conditions and the following disclaimer |
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// in the documentation and/or other materials provided with the |
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// distribution. |
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// * Neither the name of Google Inc. nor the names of its |
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// contributors may be used to endorse or promote products derived from |
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// this software without specific prior written permission. |
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// |
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// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS |
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// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT |
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// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR |
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// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT |
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// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, |
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// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT |
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// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, |
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// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY |
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// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
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// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE |
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// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
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|
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// --- |
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// Author: Craig Silverstein |
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// |
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// This is just a very thin wrapper over sparsehashtable.h, just |
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// like sgi stl's stl_hash_map is a very thin wrapper over |
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// stl_hashtable. The major thing we define is operator[], because |
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// we have a concept of a data_type which stl_hashtable doesn't |
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// (it only has a key and a value). |
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// |
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// We adhere mostly to the STL semantics for hash-map. One important |
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// exception is that insert() invalidates iterators entirely. On the |
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// plus side, though, delete() doesn't invalidate iterators at all, or |
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// even change the ordering of elements. |
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// |
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// Here are a few "power user" tips: |
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// |
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// 1) set_deleted_key(): |
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// Unlike STL's hash_map, if you want to use erase() you |
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// must call set_deleted_key() after construction. |
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// |
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// 2) resize(0): |
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// When an item is deleted, its memory isn't freed right |
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// away. This is what allows you to iterate over a hashtable |
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// and call erase() without invalidating the iterator. |
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// To force the memory to be freed, call resize(0). |
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// |
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// 3) set_resizing_parameters(0.0, 0.8): |
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// Setting the shrink_resize_percent to 0.0 guarantees |
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// that the hash table will never shrink. |
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// |
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// Guide to what kind of hash_map to use: |
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// (1) dense_hash_map: fastest, uses the most memory |
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// (2) sparse_hash_map: slowest, uses the least memory |
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// (3) hash_map (STL): in the middle |
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// Typically I use sparse_hash_map when I care about space and/or when |
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// I need to save the hashtable on disk. I use hash_map otherwise. I |
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// don't personally use dense_hash_map ever; the only use of |
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// dense_hash_map I know of is to work around malloc() bugs in some |
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// systems (dense_hash_map has a particularly simple allocation scheme). |
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// |
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// - dense_hash_map has, typically, a factor of 2 memory overhead (if your |
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// data takes up X bytes, the hash_map uses X more bytes in overhead). |
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// - sparse_hash_map has about 2 bits overhead per entry. |
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// - sparse_hash_map can be 3-7 times slower than the others for lookup and, |
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// especially, inserts. See time_hash_map.cc for details. |
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// |
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// See /usr/(local/)?doc/sparsehash-0.1/sparse_hash_map.html |
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// for information about how to use this class. |
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|
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#ifndef _SPARSE_HASH_MAP_H_ |
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#define _SPARSE_HASH_MAP_H_ |
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|
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#include <google/sparsehash/sparseconfig.h> |
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#include <stdio.h> // for FILE * in read()/write() |
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#include <algorithm> // for the default template args |
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#include <functional> // for equal_to |
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#include <memory> // for alloc<> |
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#include <utility> // for pair<> |
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#include HASH_FUN_H // defined in config.h |
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#include <google/sparsehash/sparsehashtable.h> |
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_START_GOOGLE_NAMESPACE_ |
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|
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using STL_NAMESPACE::pair; |
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|
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template <class Key, class T, |
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class HashFcn = SPARSEHASH_HASH<Key>, // defined in sparseconfig.h |
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class EqualKey = STL_NAMESPACE::equal_to<Key>, |
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class Alloc = STL_NAMESPACE::allocator<T> > |
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class sparse_hash_map { |
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private: |
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// Apparently select1st is not stl-standard, so we define our own |
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struct SelectKey { |
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const Key& operator()(const pair<const Key, T>& p) const { |
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return p.first; |
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} |
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}; |
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|
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// The actual data |
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typedef sparse_hashtable<pair<const Key, T>, Key, HashFcn, |
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SelectKey, EqualKey, Alloc> ht; |
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ht rep; |
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|
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public: |
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typedef typename ht::key_type key_type; |
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typedef T data_type; |
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typedef T mapped_type; |
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typedef typename ht::value_type value_type; |
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typedef typename ht::hasher hasher; |
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typedef typename ht::key_equal key_equal; |
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|
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typedef typename ht::size_type size_type; |
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typedef typename ht::difference_type difference_type; |
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typedef typename ht::pointer pointer; |
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typedef typename ht::const_pointer const_pointer; |
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typedef typename ht::reference reference; |
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typedef typename ht::const_reference const_reference; |
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|
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typedef typename ht::iterator iterator; |
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typedef typename ht::const_iterator const_iterator; |
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|
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// Iterator functions |
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iterator begin() { return rep.begin(); } |
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iterator end() { return rep.end(); } |
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const_iterator begin() const { return rep.begin(); } |
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const_iterator end() const { return rep.end(); } |
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// Accessor functions |
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hasher hash_funct() const { return rep.hash_funct(); } |
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key_equal key_eq() const { return rep.key_eq(); } |
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|
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// Constructors |
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explicit sparse_hash_map(size_type expected_max_items_in_table = 0, |
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const hasher& hf = hasher(), |
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const key_equal& eql = key_equal()) |
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: rep(expected_max_items_in_table, hf, eql) { } |
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template <class InputIterator> |
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sparse_hash_map(InputIterator f, InputIterator l, |
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size_type expected_max_items_in_table = 0, |
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const hasher& hf = hasher(), |
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const key_equal& eql = key_equal()) |
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: rep(expected_max_items_in_table, hf, eql) { |
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rep.insert(f, l); |
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} |
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// We use the default copy constructor |
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// We use the default operator=() |
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// We use the default destructor |
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void clear() { rep.clear(); } |
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void swap(sparse_hash_map& hs) { rep.swap(hs.rep); } |
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// Functions concerning size |
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size_type size() const { return rep.size(); } |
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size_type max_size() const { return rep.max_size(); } |
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bool empty() const { return rep.empty(); } |
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size_type bucket_count() const { return rep.bucket_count(); } |
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size_type max_bucket_count() const { return rep.max_bucket_count(); } |
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void resize(size_type hint) { rep.resize(hint); } |
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void set_resizing_parameters(float shrink, float grow) { |
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return rep.set_resizing_parameters(shrink, grow); |
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} |
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// Lookup routines |
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iterator find(const key_type& key) { return rep.find(key); } |
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const_iterator find(const key_type& key) const { return rep.find(key); } |
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data_type& operator[](const key_type& key) { // This is our value-add! |
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iterator it = find(key); |
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if (it != end()) { |
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return it->second; |
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} else { |
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return insert(value_type(key, data_type())).first->second; |
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} |
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} |
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size_type count(const key_type& key) const { return rep.count(key); } |
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pair<iterator, iterator> equal_range(const key_type& key) { |
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return rep.equal_range(key); |
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} |
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pair<const_iterator, const_iterator> equal_range(const key_type& key) const { |
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return rep.equal_range(key); |
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} |
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// Insertion routines |
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pair<iterator, bool> insert(const value_type& obj) { return rep.insert(obj); } |
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template <class InputIterator> |
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void insert(InputIterator f, InputIterator l) { rep.insert(f, l); } |
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void insert(const_iterator f, const_iterator l) { rep.insert(f, l); } |
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// required for std::insert_iterator; the passed-in iterator is ignored |
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iterator insert(iterator, const value_type& obj) { return insert(obj).first; } |
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// Deletion routines |
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// THESE ARE NON-STANDARD! I make you specify an "impossible" key |
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// value to identify deleted buckets. You can change the key as |
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// time goes on, or get rid of it entirely to be insert-only. |
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void set_deleted_key(const key_type& key) { |
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rep.set_deleted_key(value_type(key, data_type())); // rep wants a value |
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} |
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void clear_deleted_key() { rep.clear_deleted_key(); } |
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// These are standard |
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size_type erase(const key_type& key) { return rep.erase(key); } |
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void erase(iterator it) { rep.erase(it); } |
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void erase(iterator f, iterator l) { rep.erase(f, l); } |
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// Comparison |
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bool operator==(const sparse_hash_map& hs) const { return rep == hs.rep; } |
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bool operator!=(const sparse_hash_map& hs) const { return rep != hs.rep; } |
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// I/O -- this is an add-on for writing metainformation to disk |
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bool write_metadata(FILE *fp) { return rep.write_metadata(fp); } |
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bool read_metadata(FILE *fp) { return rep.read_metadata(fp); } |
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bool write_nopointer_data(FILE *fp) { return rep.write_nopointer_data(fp); } |
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bool read_nopointer_data(FILE *fp) { return rep.read_nopointer_data(fp); } |
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}; |
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// We need a global swap as well |
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template <class Key, class T, class HashFcn, class EqualKey, class Alloc> |
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inline void swap(sparse_hash_map<Key, T, HashFcn, EqualKey, Alloc>& hm1, |
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sparse_hash_map<Key, T, HashFcn, EqualKey, Alloc>& hm2) { |
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hm1.swap(hm2); |
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} |
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_END_GOOGLE_NAMESPACE_ |
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|
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#endif /* _SPARSE_HASH_MAP_H_ */ |
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