369 lines
16 KiB
Text
369 lines
16 KiB
Text
// 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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// This is just a very thin wrapper over densehashtable.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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// NOTE: this is exactly like sparse_hash_map.h, with the word
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// "sparse" replaced by "dense", except for the addition of
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// set_empty_key().
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//
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// YOU MUST CALL SET_EMPTY_KEY() IMMEDIATELY AFTER CONSTRUCTION.
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//
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// Otherwise your program will die in mysterious ways. (Note if you
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// use the constructor that takes an InputIterator range, you pass in
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// the empty key in the constructor, rather than after. As a result,
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// this constructor differs from the standard STL version.)
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//
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// In other respects, we adhere mostly to the STL semantics for
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// hash-map. One important exception is that insert() may invalidate
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// iterators entirely -- STL semantics are that insert() may reorder
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// iterators, but they all still refer to something valid in the
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// hashtable. Not so for us. Likewise, insert() may invalidate
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// pointers into the hashtable. (Whether insert invalidates iterators
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// and pointers depends on whether it results in a hashtable resize).
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// On the plus side, delete() doesn't invalidate iterators or pointers
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// at all, or 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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// If you want to use erase() you *must* call set_deleted_key(),
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// in addition to set_empty_key(), after construction.
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// The deleted and empty keys must differ.
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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 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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// For tr1 compatibility, this can also be called as rehash(0).
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//
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// 3) min_load_factor(0.0)
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// Setting the minimum load factor to 0.0 guarantees that
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// the hash table will never shrink.
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//
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// Roughly speaking:
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// (1) dense_hash_map: fastest, uses the most memory unless entries are small
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// (2) sparse_hash_map: slowest, uses the least memory
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// (3) hash_map / unordered_map (STL): in the middle
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//
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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_set ever; some people use it for
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// small sets with lots of lookups.
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//
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// - dense_hash_map has, typically, about 78% memory overhead (if your
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// data takes up X bytes, the hash_map uses .78X more bytes in overhead).
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// - sparse_hash_map has about 4 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-*/dense_hash_map.html
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// for information about how to use this class.
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#ifndef _DENSE_HASH_MAP_H_
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#define _DENSE_HASH_MAP_H_
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#include <sparsehash/internal/sparseconfig.h>
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#include <algorithm> // needed by stl_alloc
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#include <functional> // for equal_to<>, select1st<>, etc
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#include <memory> // for alloc
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#include <utility> // for pair<>
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#include <sparsehash/internal/densehashtable.h> // IWYU pragma: export
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#include <sparsehash/internal/libc_allocator_with_realloc.h>
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#include HASH_FUN_H // for hash<>
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_START_GOOGLE_NAMESPACE_
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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 = std::equal_to<Key>,
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class Alloc = libc_allocator_with_realloc<std::pair<const Key, T> > >
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class dense_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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typedef const Key& result_type;
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const Key& operator()(const std::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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struct SetKey {
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void operator()(std::pair<const Key, T>* value, const Key& new_key) const {
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*const_cast<Key*>(&value->first) = new_key;
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// It would be nice to clear the rest of value here as well, in
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// case it's taking up a lot of memory. We do this by clearing
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// the value. This assumes T has a zero-arg constructor!
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value->second = T();
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}
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};
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// For operator[].
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struct DefaultValue {
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std::pair<const Key, T> operator()(const Key& key) {
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return std::make_pair(key, T());
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}
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};
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// The actual data
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typedef dense_hashtable<std::pair<const Key, T>, Key, HashFcn, SelectKey,
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SetKey, EqualKey, Alloc> ht;
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ht rep;
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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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typedef Alloc allocator_type;
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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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typedef typename ht::iterator iterator;
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typedef typename ht::const_iterator const_iterator;
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typedef typename ht::local_iterator local_iterator;
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typedef typename ht::const_local_iterator const_local_iterator;
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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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// These come from tr1's unordered_map. For us, a bucket has 0 or 1 elements.
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local_iterator begin(size_type i) { return rep.begin(i); }
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local_iterator end(size_type i) { return rep.end(i); }
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const_local_iterator begin(size_type i) const { return rep.begin(i); }
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const_local_iterator end(size_type i) const { return rep.end(i); }
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// Accessor functions
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allocator_type get_allocator() const { return rep.get_allocator(); }
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hasher hash_funct() const { return rep.hash_funct(); }
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hasher hash_function() const { return hash_funct(); }
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key_equal key_eq() const { return rep.key_eq(); }
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// Constructors
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explicit dense_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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const allocator_type& alloc = allocator_type())
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: rep(expected_max_items_in_table, hf, eql, SelectKey(), SetKey(), alloc) {
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}
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template <class InputIterator>
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dense_hash_map(InputIterator f, InputIterator l,
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const key_type& empty_key_val,
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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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const allocator_type& alloc = allocator_type())
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: rep(expected_max_items_in_table, hf, eql, SelectKey(), SetKey(), alloc) {
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set_empty_key(empty_key_val);
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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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// This clears the hash map without resizing it down to the minimum
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// bucket count, but rather keeps the number of buckets constant
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void clear_no_resize() { rep.clear_no_resize(); }
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void swap(dense_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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// These are tr1 methods. bucket() is the bucket the key is or would be in.
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size_type bucket_size(size_type i) const { return rep.bucket_size(i); }
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size_type bucket(const key_type& key) const { return rep.bucket(key); }
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float load_factor() const {
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return size() * 1.0f / bucket_count();
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}
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float max_load_factor() const {
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float shrink, grow;
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rep.get_resizing_parameters(&shrink, &grow);
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return grow;
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}
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void max_load_factor(float new_grow) {
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float shrink, grow;
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rep.get_resizing_parameters(&shrink, &grow);
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rep.set_resizing_parameters(shrink, new_grow);
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}
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// These aren't tr1 methods but perhaps ought to be.
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float min_load_factor() const {
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float shrink, grow;
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rep.get_resizing_parameters(&shrink, &grow);
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return shrink;
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}
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void min_load_factor(float new_shrink) {
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float shrink, grow;
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rep.get_resizing_parameters(&shrink, &grow);
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rep.set_resizing_parameters(new_shrink, grow);
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}
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// Deprecated; use min_load_factor() or max_load_factor() instead.
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void set_resizing_parameters(float shrink, float grow) {
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rep.set_resizing_parameters(shrink, grow);
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}
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void resize(size_type hint) { rep.resize(hint); }
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void rehash(size_type hint) { resize(hint); } // the tr1 name
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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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// If key is in the hashtable, returns find(key)->second,
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// otherwise returns insert(value_type(key, T()).first->second.
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// Note it does not create an empty T unless the find fails.
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return rep.template find_or_insert<DefaultValue>(key).second;
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}
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size_type count(const key_type& key) const { return rep.count(key); }
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std::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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std::pair<const_iterator, const_iterator> equal_range(const key_type& key)
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const {
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return rep.equal_range(key);
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}
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// Insertion routines
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std::pair<iterator, bool> insert(const value_type& obj) {
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return rep.insert(obj);
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}
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template <class InputIterator> void insert(InputIterator f, InputIterator l) {
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rep.insert(f, l);
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}
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void insert(const_iterator f, const_iterator l) {
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rep.insert(f, l);
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}
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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) {
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return insert(obj).first;
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}
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// Deletion and empty routines
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// THESE ARE NON-STANDARD! I make you specify an "impossible" key
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// value to identify deleted and empty buckets. You can change the
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// deleted key as time goes on, or get rid of it entirely to be insert-only.
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void set_empty_key(const key_type& key) { // YOU MUST CALL THIS!
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rep.set_empty_key(value_type(key, data_type())); // rep wants a value
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}
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key_type empty_key() const {
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return rep.empty_key().first; // rep returns a value
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}
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void set_deleted_key(const key_type& key) { rep.set_deleted_key(key); }
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void clear_deleted_key() { rep.clear_deleted_key(); }
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key_type deleted_key() const { return rep.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 dense_hash_map& hs) const { return rep == hs.rep; }
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bool operator!=(const dense_hash_map& hs) const { return rep != hs.rep; }
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// I/O -- this is an add-on for writing hash map to disk
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//
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// For maximum flexibility, this does not assume a particular
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// file type (though it will probably be a FILE *). We just pass
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// the fp through to rep.
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// If your keys and values are simple enough, you can pass this
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// serializer to serialize()/unserialize(). "Simple enough" means
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// value_type is a POD type that contains no pointers. Note,
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// however, we don't try to normalize endianness.
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typedef typename ht::NopointerSerializer NopointerSerializer;
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// serializer: a class providing operator()(OUTPUT*, const value_type&)
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// (writing value_type to OUTPUT). You can specify a
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// NopointerSerializer object if appropriate (see above).
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// fp: either a FILE*, OR an ostream*/subclass_of_ostream*, OR a
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// pointer to a class providing size_t Write(const void*, size_t),
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// which writes a buffer into a stream (which fp presumably
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// owns) and returns the number of bytes successfully written.
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// Note basic_ostream<not_char> is not currently supported.
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template <typename ValueSerializer, typename OUTPUT>
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bool serialize(ValueSerializer serializer, OUTPUT* fp) {
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return rep.serialize(serializer, fp);
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}
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// serializer: a functor providing operator()(INPUT*, value_type*)
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// (reading from INPUT and into value_type). You can specify a
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// NopointerSerializer object if appropriate (see above).
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// fp: either a FILE*, OR an istream*/subclass_of_istream*, OR a
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// pointer to a class providing size_t Read(void*, size_t),
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// which reads into a buffer from a stream (which fp presumably
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// owns) and returns the number of bytes successfully read.
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// Note basic_istream<not_char> is not currently supported.
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// NOTE: Since value_type is std::pair<const Key, T>, ValueSerializer
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// may need to do a const cast in order to fill in the key.
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template <typename ValueSerializer, typename INPUT>
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bool unserialize(ValueSerializer serializer, INPUT* fp) {
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return rep.unserialize(serializer, fp);
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}
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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(dense_hash_map<Key, T, HashFcn, EqualKey, Alloc>& hm1,
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dense_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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#endif /* _DENSE_HASH_MAP_H_ */
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