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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
+//
+// A dense hashtable is a particular implementation of
+// a hashtable: one that is meant to minimize memory allocation.
+// It does this by using an array to store all the data. We
+// steal a value from the key space to indicate "empty" array
+// elements (ie indices where no item lives) and another to indicate
+// "deleted" elements.
+//
+// (Note it is possible to change the value of the delete key
+// on the fly; you can even remove it, though after that point
+// the hashtable is insert_only until you set it again. The empty
+// value however can't be changed.)
+//
+// To minimize allocation and pointer overhead, we use internal
+// probing, in which the hashtable is a single table, and collisions
+// are resolved by trying to insert again in another bucket. The
+// most cache-efficient internal probing schemes are linear probing
+// (which suffers, alas, from clumping) and quadratic probing, which
+// is what we implement by default.
+//
+// Type requirements: value_type is required to be Copy Constructible
+// and Default Constructible. It is not required to be (and commonly
+// isn't) Assignable.
+//
+// You probably shouldn't use this code directly. Use
+// <google/dense_hash_map> or <google/dense_hash_set> instead.
+
+// You can change the following below:
+// HT_OCCUPANCY_FLT -- how full before we double size
+// HT_EMPTY_FLT -- how empty before we halve size
+// HT_MIN_BUCKETS -- default smallest bucket size
+//
+// You can also change enlarge_resize_percent (which defaults to
+// HT_OCCUPANCY_FLT), and shrink_resize_percent (which defaults to
+// HT_EMPTY_FLT) with set_resizing_parameters().
+//
+// How to decide what values to use?
+// shrink_resize_percent's default of .4 * OCCUPANCY_FLT, is probably good.
+// HT_MIN_BUCKETS is probably unnecessary since you can specify
+// (indirectly) the starting number of buckets at construct-time.
+// For enlarge_resize_percent, you can use this chart to try to trade-off
+// expected lookup time to the space taken up. By default, this
+// code uses quadratic probing, though you can change it to linear
+// via _JUMP below if you really want to.
+//
+// From http://www.augustana.ca/~mohrj/courses/1999.fall/csc210/lecture_notes/hashing.html
+// NUMBER OF PROBES / LOOKUP Successful Unsuccessful
+// Quadratic collision resolution 1 - ln(1-L) - L/2 1/(1-L) - L - ln(1-L)
+// Linear collision resolution [1+1/(1-L)]/2 [1+1/(1-L)2]/2
+//
+// -- enlarge_resize_percent -- 0.10 0.50 0.60 0.75 0.80 0.90 0.99
+// QUADRATIC COLLISION RES.
+// probes/successful lookup 1.05 1.44 1.62 2.01 2.21 2.85 5.11
+// probes/unsuccessful lookup 1.11 2.19 2.82 4.64 5.81 11.4 103.6
+// LINEAR COLLISION RES.
+// probes/successful lookup 1.06 1.5 1.75 2.5 3.0 5.5 50.5
+// probes/unsuccessful lookup 1.12 2.5 3.6 8.5 13.0 50.0 5000.0
+
+#ifndef _DENSEHASHTABLE_H_
+#define _DENSEHASHTABLE_H_
+
+// The probing method
+// Linear probing
+// #define JUMP_(key, num_probes) ( 1 )
+// Quadratic-ish probing
+#define JUMP_(key, num_probes) ( num_probes )
+
+
+#include "google/sparsehash/sparseconfig.h"
+#include <assert.h>
+#include <stdio.h>
+#include <stdlib.h> // for abort()
+#include <algorithm> // For swap(), eg
+#include <iostream> // For cerr
+#include <memory> // For uninitialized_fill, uninitialized_copy
+#include <utility> // for pair<>
+#include <iterator> // for facts about iterator tags
+#include "google/type_traits.h" // for true_type, integral_constant, etc.
+
+_START_GOOGLE_NAMESPACE_
+
+using STL_NAMESPACE::pair;
+
+// Hashtable class, used to implement the hashed associative containers
+// hash_set and hash_map.
+
+// Value: what is stored in the table (each bucket is a Value).
+// Key: something in a 1-to-1 correspondence to a Value, that can be used
+// to search for a Value in the table (find() takes a Key).
+// HashFcn: Takes a Key and returns an integer, the more unique the better.
+// ExtractKey: given a Value, returns the unique Key associated with it.
+// SetKey: given a Value* and a Key, modifies the value such that
+// ExtractKey(value) == key. We guarantee this is only called
+// with key == deleted_key or key == empty_key.
+// EqualKey: Given two Keys, says whether they are the same (that is,
+// if they are both associated with the same Value).
+// Alloc: STL allocator to use to allocate memory. Currently ignored.
+
+template <class Value, class Key, class HashFcn,
+ class ExtractKey, class SetKey, class EqualKey, class Alloc>
+class dense_hashtable;
+
+template <class V, class K, class HF, class ExK, class SetK, class EqK, class A>
+struct dense_hashtable_iterator;
+
+template <class V, class K, class HF, class ExK, class SetK, class EqK, class A>
+struct dense_hashtable_const_iterator;
+
+// We're just an array, but we need to skip over empty and deleted elements
+template <class V, class K, class HF, class ExK, class SetK, class EqK, class A>
+struct dense_hashtable_iterator {
+ public:
+ typedef dense_hashtable_iterator<V,K,HF,ExK,SetK,EqK,A> iterator;
+ typedef dense_hashtable_const_iterator<V,K,HF,ExK,SetK,EqK,A> const_iterator;
+
+ typedef STL_NAMESPACE::forward_iterator_tag iterator_category;
+ typedef V value_type;
+ typedef ptrdiff_t difference_type;
+ typedef size_t size_type;
+ typedef V& reference; // Value
+ typedef V* pointer;
+
+ // "Real" constructor and default constructor
+ dense_hashtable_iterator(const dense_hashtable<V,K,HF,ExK,SetK,EqK,A> *h,
+ pointer it, pointer it_end, bool advance)
+ : ht(h), pos(it), end(it_end) {
+ if (advance) advance_past_empty_and_deleted();
+ }
+ dense_hashtable_iterator() { }
+ // The default destructor is fine; we don't define one
+ // The default operator= is fine; we don't define one
+
+ // Happy dereferencer
+ reference operator*() const { return *pos; }
+ pointer operator->() const { return &(operator*()); }
+
+ // Arithmetic. The only hard part is making sure that
+ // we're not on an empty or marked-deleted array element
+ void advance_past_empty_and_deleted() {
+ while ( pos != end && (ht->test_empty(*this) || ht->test_deleted(*this)) )
+ ++pos;
+ }
+ iterator& operator++() {
+ assert(pos != end); ++pos; advance_past_empty_and_deleted(); return *this;
+ }
+ iterator operator++(int) { iterator tmp(*this); ++*this; return tmp; }
+
+ // Comparison.
+ bool operator==(const iterator& it) const { return pos == it.pos; }
+ bool operator!=(const iterator& it) const { return pos != it.pos; }
+
+
+ // The actual data
+ const dense_hashtable<V,K,HF,ExK,SetK,EqK,A> *ht;
+ pointer pos, end;
+};
+
+
+// Now do it all again, but with const-ness!
+template <class V, class K, class HF, class ExK, class SetK, class EqK, class A>
+struct dense_hashtable_const_iterator {
+ public:
+ typedef dense_hashtable_iterator<V,K,HF,ExK,SetK,EqK,A> iterator;
+ typedef dense_hashtable_const_iterator<V,K,HF,ExK,SetK,EqK,A> const_iterator;
+
+ typedef STL_NAMESPACE::forward_iterator_tag iterator_category;
+ typedef V value_type;
+ typedef ptrdiff_t difference_type;
+ typedef size_t size_type;
+ typedef const V& reference; // Value
+ typedef const V* pointer;
+
+ // "Real" constructor and default constructor
+ dense_hashtable_const_iterator(
+ const dense_hashtable<V,K,HF,ExK,SetK,EqK,A> *h,
+ pointer it, pointer it_end, bool advance)
+ : ht(h), pos(it), end(it_end) {
+ if (advance) advance_past_empty_and_deleted();
+ }
+ dense_hashtable_const_iterator() { }
+ // This lets us convert regular iterators to const iterators
+ dense_hashtable_const_iterator(const iterator &it)
+ : ht(it.ht), pos(it.pos), end(it.end) { }
+ // The default destructor is fine; we don't define one
+ // The default operator= is fine; we don't define one
+
+ // Happy dereferencer
+ reference operator*() const { return *pos; }
+ pointer operator->() const { return &(operator*()); }
+
+ // Arithmetic. The only hard part is making sure that
+ // we're not on an empty or marked-deleted array element
+ void advance_past_empty_and_deleted() {
+ while ( pos != end && (ht->test_empty(*this) || ht->test_deleted(*this)) )
+ ++pos;
+ }
+ const_iterator& operator++() {
+ assert(pos != end); ++pos; advance_past_empty_and_deleted(); return *this;
+ }
+ const_iterator operator++(int) { const_iterator tmp(*this); ++*this; return tmp; }
+
+ // Comparison.
+ bool operator==(const const_iterator& it) const { return pos == it.pos; }
+ bool operator!=(const const_iterator& it) const { return pos != it.pos; }
+
+
+ // The actual data
+ const dense_hashtable<V,K,HF,ExK,SetK,EqK,A> *ht;
+ pointer pos, end;
+};
+
+template <class Value, class Key, class HashFcn,
+ class ExtractKey, class SetKey, class EqualKey, class Alloc>
+class dense_hashtable {
+ public:
+ typedef Key key_type;
+ typedef Value value_type;
+ typedef HashFcn hasher;
+ typedef EqualKey key_equal;
+
+ typedef size_t size_type;
+ typedef ptrdiff_t difference_type;
+ typedef value_type* pointer;
+ typedef const value_type* const_pointer;
+ typedef value_type& reference;
+ typedef const value_type& const_reference;
+ typedef dense_hashtable_iterator<Value, Key, HashFcn,
+ ExtractKey, SetKey, EqualKey, Alloc>
+ iterator;
+
+ typedef dense_hashtable_const_iterator<Value, Key, HashFcn,
+ ExtractKey, SetKey, EqualKey, Alloc>
+ const_iterator;
+
+ // These come from tr1. For us they're the same as regular iterators.
+ typedef iterator local_iterator;
+ typedef const_iterator const_local_iterator;
+
+ // How full we let the table get before we resize, by default.
+ // Knuth says .8 is good -- higher causes us to probe too much,
+ // though it saves memory.
+ static const float HT_OCCUPANCY_FLT; // = 0.5;
+
+ // How empty we let the table get before we resize lower, by default.
+ // (0.0 means never resize lower.)
+ // It should be less than OCCUPANCY_FLT / 2 or we thrash resizing
+ static const float HT_EMPTY_FLT; // = 0.4 * HT_OCCUPANCY_FLT
+
+ // Minimum size we're willing to let hashtables be.
+ // Must be a power of two, and at least 4.
+ // Note, however, that for a given hashtable, the initial size is a
+ // function of the first constructor arg, and may be >HT_MIN_BUCKETS.
+ static const size_t HT_MIN_BUCKETS = 4;
+
+ // By default, if you don't specify a hashtable size at
+ // construction-time, we use this size. Must be a power of two, and
+ // at least HT_MIN_BUCKETS.
+ static const size_t HT_DEFAULT_STARTING_BUCKETS = 32;
+
+
+ // ITERATOR FUNCTIONS
+ iterator begin() { return iterator(this, table,
+ table + num_buckets, true); }
+ iterator end() { return iterator(this, table + num_buckets,
+ table + num_buckets, true); }
+ const_iterator begin() const { return const_iterator(this, table,
+ table+num_buckets,true);}
+ const_iterator end() const { return const_iterator(this, table + num_buckets,
+ table+num_buckets,true);}
+
+ // These come from tr1 unordered_map. They iterate over 'bucket' n.
+ // For sparsehashtable, we could consider each 'group' to be a bucket,
+ // I guess, but I don't really see the point. We'll just consider
+ // bucket n to be the n-th element of the sparsetable, if it's occupied,
+ // or some empty element, otherwise.
+ local_iterator begin(size_type i) {
+ return local_iterator(this, table + i, table + i+1, false);
+ }
+ local_iterator end(size_type i) {
+ local_iterator it = begin(i);
+ if (!test_empty(i) && !test_deleted(i))
+ ++it;
+ return it;
+ }
+ const_local_iterator begin(size_type i) const {
+ return const_local_iterator(this, table + i, table + i+1, false);
+ }
+ const_local_iterator end(size_type i) const {
+ const_local_iterator it = begin(i);
+ if (!test_empty(i) && !test_deleted(i))
+ ++it;
+ return it;
+ }
+
+ // ACCESSOR FUNCTIONS for the things we templatize on, basically
+ hasher hash_funct() const { return hash; }
+ key_equal key_eq() const { return equals; }
+
+ private:
+ // Annoyingly, we can't copy values around, because they might have
+ // const components (they're probably pair<const X, Y>). We use
+ // explicit destructor invocation and placement new to get around
+ // this. Arg.
+ void set_value(value_type* dst, const value_type& src) {
+ dst->~value_type();
+ new(dst) value_type(src);
+ }
+
+ void destroy_buckets(size_type first, size_type last) {
+ for ( ; first != last; ++first)
+ table[first].~value_type();
+ }
+
+ // DELETE HELPER FUNCTIONS
+ // This lets the user describe a key that will indicate deleted
+ // table entries. This key should be an "impossible" entry --
+ // if you try to insert it for real, you won't be able to retrieve it!
+ // (NB: while you pass in an entire value, only the key part is looked
+ // at. This is just because I don't know how to assign just a key.)
+ private:
+ void squash_deleted() { // gets rid of any deleted entries we have
+ if ( num_deleted ) { // get rid of deleted before writing
+ dense_hashtable tmp(*this); // copying will get rid of deleted
+ swap(tmp); // now we are tmp
+ }
+ assert(num_deleted == 0);
+ }
+
+ public:
+ void set_deleted_key(const key_type &key) {
+ // the empty indicator (if specified) and the deleted indicator
+ // must be different
+ assert(!use_empty || !equals(key, get_key(emptyval)));
+ // It's only safe to change what "deleted" means if we purge deleted guys
+ squash_deleted();
+ use_deleted = true;
+ delkey = key;
+ }
+ void clear_deleted_key() {
+ squash_deleted();
+ use_deleted = false;
+ }
+
+ // These are public so the iterators can use them
+ // True if the item at position bucknum is "deleted" marker
+ bool test_deleted(size_type bucknum) const {
+ // The num_deleted test is crucial for read(): after read(), the ht values
+ // are garbage, and we don't want to think some of them are deleted.
+ return (use_deleted && num_deleted > 0 &&
+ equals(delkey, get_key(table[bucknum])));
+ }
+ bool test_deleted(const iterator &it) const {
+ return (use_deleted && num_deleted > 0 &&
+ equals(delkey, get_key(*it)));
+ }
+ bool test_deleted(const const_iterator &it) const {
+ return (use_deleted && num_deleted > 0 &&
+ equals(delkey, get_key(*it)));
+ }
+ // Set it so test_deleted is true. true if object didn't used to be deleted
+ // See below (at erase()) to explain why we allow const_iterators
+ bool set_deleted(const_iterator &it) {
+ assert(use_deleted); // bad if set_deleted_key() wasn't called
+ bool retval = !test_deleted(it);
+ // &* converts from iterator to value-type
+ set_key(const_cast<value_type*>(&(*it)), delkey);
+ return retval;
+ }
+ // Set it so test_deleted is false. true if object used to be deleted
+ bool clear_deleted(const_iterator &it) {
+ assert(use_deleted); // bad if set_deleted_key() wasn't called
+ // happens automatically when we assign something else in its place
+ return test_deleted(it);
+ }
+
+ // EMPTY HELPER FUNCTIONS
+ // This lets the user describe a key that will indicate empty (unused)
+ // table entries. This key should be an "impossible" entry --
+ // if you try to insert it for real, you won't be able to retrieve it!
+ // (NB: while you pass in an entire value, only the key part is looked
+ // at. This is just because I don't know how to assign just a key.)
+ public:
+ // These are public so the iterators can use them
+ // True if the item at position bucknum is "empty" marker
+ bool test_empty(size_type bucknum) const {
+ assert(use_empty); // we always need to know what's empty!
+ return equals(get_key(emptyval), get_key(table[bucknum]));
+ }
+ bool test_empty(const iterator &it) const {
+ assert(use_empty); // we always need to know what's empty!
+ return equals(get_key(emptyval), get_key(*it));
+ }
+ bool test_empty(const const_iterator &it) const {
+ assert(use_empty); // we always need to know what's empty!
+ return equals(get_key(emptyval), get_key(*it));
+ }
+
+ private:
+ // You can either set a range empty or an individual element
+ void set_empty(size_type bucknum) {
+ assert(use_empty);
+ set_value(&table[bucknum], emptyval);
+ }
+ void fill_range_with_empty(value_type* table_start, value_type* table_end) {
+ // Like set_empty(range), but doesn't destroy previous contents
+ STL_NAMESPACE::uninitialized_fill(table_start, table_end, emptyval);
+ }
+ void set_empty(size_type buckstart, size_type buckend) {
+ assert(use_empty);
+ destroy_buckets(buckstart, buckend);
+ fill_range_with_empty(table + buckstart, table + buckend);
+ }
+
+ public:
+ // TODO(csilvers): change all callers of this to pass in a key instead,
+ // and take a const key_type instead of const value_type.
+ void set_empty_key(const value_type &val) {
+ // Once you set the empty key, you can't change it
+ assert(!use_empty);
+ // The deleted indicator (if specified) and the empty indicator
+ // must be different.
+ assert(!use_deleted || !equals(get_key(val), delkey));
+ use_empty = true;
+ set_value(&emptyval, val);
+
+ assert(!table); // must set before first use
+ // num_buckets was set in constructor even though table was NULL
+ table = (value_type *) malloc(num_buckets * sizeof(*table));
+ assert(table);
+ fill_range_with_empty(table, table + num_buckets);
+ }
+
+ // FUNCTIONS CONCERNING SIZE
+ public:
+ size_type size() const { return num_elements - num_deleted; }
+ // Buckets are always a power of 2
+ size_type max_size() const { return (size_type(-1) >> 1U) + 1; }
+ bool empty() const { return size() == 0; }
+ size_type bucket_count() const { return num_buckets; }
+ size_type max_bucket_count() const { return max_size(); }
+ size_type nonempty_bucket_count() const { return num_elements; }
+ // These are tr1 methods. Their idea of 'bucket' doesn't map well to
+ // what we do. We just say every bucket has 0 or 1 items in it.
+ size_type bucket_size(size_type i) const {
+ return begin(i) == end(i) ? 0 : 1;
+ }
+
+
+
+ private:
+ // Because of the above, size_type(-1) is never legal; use it for errors
+ static const size_type ILLEGAL_BUCKET = size_type(-1);
+
+ private:
+ // This is the smallest size a hashtable can be without being too crowded
+ // If you like, you can give a min #buckets as well as a min #elts
+ size_type min_size(size_type num_elts, size_type min_buckets_wanted) {
+ size_type sz = HT_MIN_BUCKETS; // min buckets allowed
+ while ( sz < min_buckets_wanted || num_elts >= sz * enlarge_resize_percent )
+ sz *= 2;
+ return sz;
+ }
+
+ // Used after a string of deletes
+ void maybe_shrink() {
+ assert(num_elements >= num_deleted);
+ assert((bucket_count() & (bucket_count()-1)) == 0); // is a power of two
+ assert(bucket_count() >= HT_MIN_BUCKETS);
+
+ // If you construct a hashtable with < HT_DEFAULT_STARTING_BUCKETS,
+ // we'll never shrink until you get relatively big, and we'll never
+ // shrink below HT_DEFAULT_STARTING_BUCKETS. Otherwise, something
+ // like "dense_hash_set<int> x; x.insert(4); x.erase(4);" will
+ // shrink us down to HT_MIN_BUCKETS buckets, which is too small.
+ if (shrink_threshold > 0 &&
+ (num_elements-num_deleted) < shrink_threshold &&
+ bucket_count() > HT_DEFAULT_STARTING_BUCKETS ) {
+ size_type sz = bucket_count() / 2; // find how much we should shrink
+ while ( sz > HT_DEFAULT_STARTING_BUCKETS &&
+ (num_elements - num_deleted) < sz * shrink_resize_percent )
+ sz /= 2; // stay a power of 2
+ dense_hashtable tmp(*this, sz); // Do the actual resizing
+ swap(tmp); // now we are tmp
+ }
+ consider_shrink = false; // because we just considered it
+ }
+
+ // We'll let you resize a hashtable -- though this makes us copy all!
+ // When you resize, you say, "make it big enough for this many more elements"
+ void resize_delta(size_type delta) {
+ if ( consider_shrink ) // see if lots of deletes happened
+ maybe_shrink();
+ if ( bucket_count() > HT_MIN_BUCKETS &&
+ (num_elements + delta) <= enlarge_threshold )
+ return; // we're ok as we are
+
+ // Sometimes, we need to resize just to get rid of all the
+ // "deleted" buckets that are clogging up the hashtable. So when
+ // deciding whether to resize, count the deleted buckets (which
+ // are currently taking up room). But later, when we decide what
+ // size to resize to, *don't* count deleted buckets, since they
+ // get discarded during the resize.
+ const size_type needed_size = min_size(num_elements + delta, 0);
+ if ( needed_size > bucket_count() ) { // we don't have enough buckets
+ const size_type resize_to = min_size(num_elements - num_deleted + delta,
+ 0);
+ dense_hashtable tmp(*this, resize_to);
+ swap(tmp); // now we are tmp
+ }
+ }
+
+ // Increase number of buckets, assuming value_type has trivial copy
+ // constructor and destructor. (Really, we want it to have "trivial
+ // move", because that's what realloc does. But there's no way to
+ // capture that using type_traits, so we pretend that move(x, y) is
+ // equivalent to "x.~T(); new(x) T(y);" which is pretty much
+ // correct, if a bit conservative.)
+ void expand_array(size_t resize_to, true_type) {
+ table = (value_type *) realloc(table, resize_to * sizeof(value_type));
+ assert(table);
+ fill_range_with_empty(table + num_buckets, table + resize_to);
+ }
+
+ // Increase number of buckets, without special assumptions about value_type.
+ // TODO(austern): make this exception safe. Handle exceptions from
+ // value_type's copy constructor.
+ void expand_array(size_t resize_to, false_type) {
+ value_type* new_table =
+ (value_type *) malloc(resize_to * sizeof(value_type));
+ assert(new_table);
+ STL_NAMESPACE::uninitialized_copy(table, table + num_buckets, new_table);
+ fill_range_with_empty(new_table + num_buckets, new_table + resize_to);
+ destroy_buckets(0, num_buckets);
+ free(table);
+ table = new_table;
+ }
+
+ // Used to actually do the rehashing when we grow/shrink a hashtable
+ void copy_from(const dense_hashtable &ht, size_type min_buckets_wanted) {
+ clear(); // clear table, set num_deleted to 0
+
+ // If we need to change the size of our table, do it now
+ const size_type resize_to = min_size(ht.size(), min_buckets_wanted);
+ if ( resize_to > bucket_count() ) { // we don't have enough buckets
+ typedef integral_constant<bool,
+ (has_trivial_copy<value_type>::value &&
+ has_trivial_destructor<value_type>::value)>
+ realloc_ok; // we pretend mv(x,y) == "x.~T(); new(x) T(y)"
+ expand_array(resize_to, realloc_ok());
+ num_buckets = resize_to;
+ reset_thresholds();
+ }
+
+ // We use a normal iterator to get non-deleted bcks from ht
+ // We could use insert() here, but since we know there are
+ // no duplicates and no deleted items, we can be more efficient
+ assert((bucket_count() & (bucket_count()-1)) == 0); // a power of two
+ for ( const_iterator it = ht.begin(); it != ht.end(); ++it ) {
+ size_type num_probes = 0; // how many times we've probed
+ size_type bucknum;
+ const size_type bucket_count_minus_one = bucket_count() - 1;
+ for (bucknum = hash(get_key(*it)) & bucket_count_minus_one;
+ !test_empty(bucknum); // not empty
+ bucknum = (bucknum + JUMP_(key, num_probes)) & bucket_count_minus_one) {
+ ++num_probes;
+ assert(num_probes < bucket_count()); // or else the hashtable is full
+ }
+ set_value(&table[bucknum], *it); // copies the value to here
+ num_elements++;
+ }
+ }
+
+ // Required by the spec for hashed associative container
+ public:
+ // Though the docs say this should be num_buckets, I think it's much
+ // more useful as req_elements. As a special feature, calling with
+ // req_elements==0 will cause us to shrink if we can, saving space.
+ void resize(size_type req_elements) { // resize to this or larger
+ if ( consider_shrink || req_elements == 0 )
+ maybe_shrink();
+ if ( req_elements > num_elements )
+ return resize_delta(req_elements - num_elements);
+ }
+
+ // Get and change the value of shrink_resize_percent and
+ // enlarge_resize_percent. The description at the beginning of this
+ // file explains how to choose the values. Setting the shrink
+ // parameter to 0.0 ensures that the table never shrinks.
+ void get_resizing_parameters(float* shrink, float* grow) const {
+ *shrink = shrink_resize_percent;
+ *grow = enlarge_resize_percent;
+ }
+ void set_resizing_parameters(float shrink, float grow) {
+ assert(shrink >= 0.0);
+ assert(grow <= 1.0);
+ if (shrink > grow/2.0f)
+ shrink = grow / 2.0f; // otherwise we thrash hashtable size
+ shrink_resize_percent = shrink;
+ enlarge_resize_percent = grow;
+ reset_thresholds();
+ }
+
+ // CONSTRUCTORS -- as required by the specs, we take a size,
+ // but also let you specify a hashfunction, key comparator,
+ // and key extractor. We also define a copy constructor and =.
+ // DESTRUCTOR -- needs to free the table
+ explicit dense_hashtable(size_type expected_max_items_in_table = 0,
+ const HashFcn& hf = HashFcn(),
+ const EqualKey& eql = EqualKey(),
+ const ExtractKey& ext = ExtractKey(),
+ const SetKey& set = SetKey())
+ : hash(hf), equals(eql), get_key(ext), set_key(set), num_deleted(0),
+ use_deleted(false), use_empty(false),
+ delkey(), emptyval(), enlarge_resize_percent(HT_OCCUPANCY_FLT),
+ shrink_resize_percent(HT_EMPTY_FLT), table(NULL),
+ num_buckets(expected_max_items_in_table == 0
+ ? HT_DEFAULT_STARTING_BUCKETS
+ : min_size(expected_max_items_in_table, 0)),
+ num_elements(0) {
+ // table is NULL until emptyval is set. However, we set num_buckets
+ // here so we know how much space to allocate once emptyval is set
+ reset_thresholds();
+ }
+
+ // As a convenience for resize(), we allow an optional second argument
+ // which lets you make this new hashtable a different size than ht
+ dense_hashtable(const dense_hashtable& ht,
+ size_type min_buckets_wanted = HT_DEFAULT_STARTING_BUCKETS)
+ : hash(ht.hash), equals(ht.equals),
+ get_key(ht.get_key), set_key(ht.set_key), num_deleted(0),
+ use_deleted(ht.use_deleted), use_empty(ht.use_empty),
+ delkey(ht.delkey), emptyval(ht.emptyval),
+ enlarge_resize_percent(ht.enlarge_resize_percent),
+ shrink_resize_percent(ht.shrink_resize_percent), table(NULL),
+ num_buckets(0), num_elements(0) {
+ reset_thresholds();
+ copy_from(ht, min_buckets_wanted); // copy_from() ignores deleted entries
+ }
+
+ dense_hashtable& operator= (const dense_hashtable& ht) {
+ if (&ht == this) return *this; // don't copy onto ourselves
+ clear();
+ hash = ht.hash;
+ equals = ht.equals;
+ get_key = ht.get_key;
+ set_key = ht.set_key;
+ use_deleted = ht.use_deleted;
+ use_empty = ht.use_empty;
+ delkey = ht.delkey;
+ set_value(&emptyval, ht.emptyval);
+ enlarge_resize_percent = ht.enlarge_resize_percent;
+ shrink_resize_percent = ht.shrink_resize_percent;
+ copy_from(ht, HT_MIN_BUCKETS); // sets num_deleted to 0 too
+ return *this;
+ }
+
+ ~dense_hashtable() {
+ if (table) {
+ destroy_buckets(0, num_buckets);
+ free(table);
+ }
+ }
+
+ // Many STL algorithms use swap instead of copy constructors
+ void swap(dense_hashtable& ht) {
+ STL_NAMESPACE::swap(hash, ht.hash);
+ STL_NAMESPACE::swap(equals, ht.equals);
+ STL_NAMESPACE::swap(get_key, ht.get_key);
+ STL_NAMESPACE::swap(set_key, ht.set_key);
+ STL_NAMESPACE::swap(num_deleted, ht.num_deleted);
+ STL_NAMESPACE::swap(use_deleted, ht.use_deleted);
+ STL_NAMESPACE::swap(use_empty, ht.use_empty);
+ STL_NAMESPACE::swap(enlarge_resize_percent, ht.enlarge_resize_percent);
+ STL_NAMESPACE::swap(shrink_resize_percent, ht.shrink_resize_percent);
+ STL_NAMESPACE::swap(delkey, ht.delkey);
+ { value_type tmp; // for annoying reasons, swap() doesn't work
+ set_value(&tmp, emptyval);
+ set_value(&emptyval, ht.emptyval);
+ set_value(&ht.emptyval, tmp);
+ }
+ STL_NAMESPACE::swap(table, ht.table);
+ STL_NAMESPACE::swap(num_buckets, ht.num_buckets);
+ STL_NAMESPACE::swap(num_elements, ht.num_elements);
+ reset_thresholds();
+ ht.reset_thresholds();
+ }
+
+ // It's always nice to be able to clear a table without deallocating it
+ void clear() {
+ if (table)
+ destroy_buckets(0, num_buckets);
+ num_buckets = min_size(0,0); // our new size
+ reset_thresholds();
+ table = (value_type *) realloc(table, num_buckets * sizeof(*table));
+ assert(table);
+ fill_range_with_empty(table, table + num_buckets);
+ num_elements = 0;
+ num_deleted = 0;
+ }
+
+ // Clear the table without resizing it.
+ // Mimicks the stl_hashtable's behaviour when clear()-ing in that it
+ // does not modify the bucket count
+ void clear_no_resize() {
+ if (table) {
+ set_empty(0, num_buckets);
+ }
+ // don't consider to shrink before another erase()
+ reset_thresholds();
+ num_elements = 0;
+ num_deleted = 0;
+ }
+
+ // LOOKUP ROUTINES
+ private:
+ // Returns a pair of positions: 1st where the object is, 2nd where
+ // it would go if you wanted to insert it. 1st is ILLEGAL_BUCKET
+ // if object is not found; 2nd is ILLEGAL_BUCKET if it is.
+ // Note: because of deletions where-to-insert is not trivial: it's the
+ // first deleted bucket we see, as long as we don't find the key later
+ pair<size_type, size_type> find_position(const key_type &key) const {
+ size_type num_probes = 0; // how many times we've probed
+ const size_type bucket_count_minus_one = bucket_count() - 1;
+ size_type bucknum = hash(key) & bucket_count_minus_one;
+ size_type insert_pos = ILLEGAL_BUCKET; // where we would insert
+ while ( 1 ) { // probe until something happens
+ if ( test_empty(bucknum) ) { // bucket is empty
+ if ( insert_pos == ILLEGAL_BUCKET ) // found no prior place to insert
+ return pair<size_type,size_type>(ILLEGAL_BUCKET, bucknum);
+ else
+ return pair<size_type,size_type>(ILLEGAL_BUCKET, insert_pos);
+
+ } else if ( test_deleted(bucknum) ) {// keep searching, but mark to insert
+ if ( insert_pos == ILLEGAL_BUCKET )
+ insert_pos = bucknum;
+
+ } else if ( equals(key, get_key(table[bucknum])) ) {
+ return pair<size_type,size_type>(bucknum, ILLEGAL_BUCKET);
+ }
+ ++num_probes; // we're doing another probe
+ bucknum = (bucknum + JUMP_(key, num_probes)) & bucket_count_minus_one;
+ assert(num_probes < bucket_count()); // don't probe too many times!
+ }
+ }
+
+ public:
+ iterator find(const key_type& key) {
+ if ( size() == 0 ) return end();
+ pair<size_type, size_type> pos = find_position(key);
+ if ( pos.first == ILLEGAL_BUCKET ) // alas, not there
+ return end();
+ else
+ return iterator(this, table + pos.first, table + num_buckets, false);
+ }
+
+ const_iterator find(const key_type& key) const {
+ if ( size() == 0 ) return end();
+ pair<size_type, size_type> pos = find_position(key);
+ if ( pos.first == ILLEGAL_BUCKET ) // alas, not there
+ return end();
+ else
+ return const_iterator(this, table + pos.first, table+num_buckets, false);
+ }
+
+ // This is a tr1 method: the bucket a given key is in, or what bucket
+ // it would be put in, if it were to be inserted. Shrug.
+ size_type bucket(const key_type& key) const {
+ pair<size_type, size_type> pos = find_position(key);
+ return pos.first == ILLEGAL_BUCKET ? pos.second : pos.first;
+ }
+
+ // Counts how many elements have key key. For maps, it's either 0 or 1.
+ size_type count(const key_type &key) const {
+ pair<size_type, size_type> pos = find_position(key);
+ return pos.first == ILLEGAL_BUCKET ? 0 : 1;
+ }
+
+ // Likewise, equal_range doesn't really make sense for us. Oh well.
+ pair<iterator,iterator> equal_range(const key_type& key) {
+ iterator pos = find(key); // either an iterator or end
+ if (pos == end()) {
+ return pair<iterator,iterator>(pos, pos);
+ } else {
+ const iterator startpos = pos++;
+ return pair<iterator,iterator>(startpos, pos);
+ }
+ }
+ pair<const_iterator,const_iterator> equal_range(const key_type& key) const {
+ const_iterator pos = find(key); // either an iterator or end
+ if (pos == end()) {
+ return pair<const_iterator,const_iterator>(pos, pos);
+ } else {
+ const const_iterator startpos = pos++;
+ return pair<const_iterator,const_iterator>(startpos, pos);
+ }
+ }
+
+
+ // INSERTION ROUTINES
+ private:
+ // If you know *this is big enough to hold obj, use this routine
+ pair<iterator, bool> insert_noresize(const value_type& obj) {
+ // First, double-check we're not inserting delkey or emptyval
+ assert(!use_empty || !equals(get_key(obj), get_key(emptyval)));
+ assert(!use_deleted || !equals(get_key(obj), delkey));
+ const pair<size_type,size_type> pos = find_position(get_key(obj));
+ if ( pos.first != ILLEGAL_BUCKET) { // object was already there
+ return pair<iterator,bool>(iterator(this, table + pos.first,
+ table + num_buckets, false),
+ false); // false: we didn't insert
+ } else { // pos.second says where to put it
+ if ( test_deleted(pos.second) ) { // just replace if it's been del.
+ const_iterator delpos(this, table + pos.second, // shrug:
+ table + num_buckets, false);// shouldn't need const
+ clear_deleted(delpos);
+ assert( num_deleted > 0);
+ --num_deleted; // used to be, now it isn't
+ } else {
+ ++num_elements; // replacing an empty bucket
+ }
+ set_value(&table[pos.second], obj);
+ return pair<iterator,bool>(iterator(this, table + pos.second,
+ table + num_buckets, false),
+ true); // true: we did insert
+ }
+ }
+
+ public:
+ // This is the normal insert routine, used by the outside world
+ pair<iterator, bool> insert(const value_type& obj) {
+ resize_delta(1); // adding an object, grow if need be
+ return insert_noresize(obj);
+ }
+
+ // When inserting a lot at a time, we specialize on the type of iterator
+ template <class InputIterator>
+ void insert(InputIterator f, InputIterator l) {
+ // specializes on iterator type
+ insert(f, l, typename STL_NAMESPACE::iterator_traits<InputIterator>::iterator_category());
+ }
+
+ // Iterator supports operator-, resize before inserting
+ template <class ForwardIterator>
+ void insert(ForwardIterator f, ForwardIterator l,
+ STL_NAMESPACE::forward_iterator_tag) {
+ size_type n = STL_NAMESPACE::distance(f, l); // TODO(csilvers): standard?
+ resize_delta(n);
+ for ( ; n > 0; --n, ++f)
+ insert_noresize(*f);
+ }
+
+ // Arbitrary iterator, can't tell how much to resize
+ template <class InputIterator>
+ void insert(InputIterator f, InputIterator l,
+ STL_NAMESPACE::input_iterator_tag) {
+ for ( ; f != l; ++f)
+ insert(*f);
+ }
+
+
+ // DELETION ROUTINES
+ size_type erase(const key_type& key) {
+ // First, double-check we're not trying to erase delkey or emptyval
+ assert(!use_empty || !equals(key, get_key(emptyval)));
+ assert(!use_deleted || !equals(key, delkey));
+ const_iterator pos = find(key); // shrug: shouldn't need to be const
+ if ( pos != end() ) {
+ assert(!test_deleted(pos)); // or find() shouldn't have returned it
+ set_deleted(pos);
+ ++num_deleted;
+ consider_shrink = true; // will think about shrink after next insert
+ return 1; // because we deleted one thing
+ } else {
+ return 0; // because we deleted nothing
+ }
+ }
+
+ // This is really evil: really it should be iterator, not const_iterator.
+ // But...the only reason keys are const is to allow lookup.
+ // Since that's a moot issue for deleted keys, we allow const_iterators
+ void erase(const_iterator pos) {
+ if ( pos == end() ) return; // sanity check
+ if ( set_deleted(pos) ) { // true if object has been newly deleted
+ ++num_deleted;
+ consider_shrink = true; // will think about shrink after next insert
+ }
+ }
+
+ void erase(const_iterator f, const_iterator l) {
+ for ( ; f != l; ++f) {
+ if ( set_deleted(f) ) // should always be true
+ ++num_deleted;
+ }
+ consider_shrink = true; // will think about shrink after next insert
+ }
+
+
+ // COMPARISON
+ bool operator==(const dense_hashtable& ht) const {
+ if (size() != ht.size()) {
+ return false;
+ } else if (this == &ht) {
+ return true;
+ } else {
+ // Iterate through the elements in "this" and see if the
+ // corresponding element is in ht
+ for ( const_iterator it = begin(); it != end(); ++it ) {
+ const_iterator it2 = ht.find(get_key(*it));
+ if ((it2 == ht.end()) || (*it != *it2)) {
+ return false;
+ }
+ }
+ return true;
+ }
+ }
+ bool operator!=(const dense_hashtable& ht) const {
+ return !(*this == ht);
+ }
+
+
+ // I/O
+ // We support reading and writing hashtables to disk. Alas, since
+ // I don't know how to write a hasher or key_equal, you have to make
+ // sure everything but the table is the same. We compact before writing
+ //
+ // NOTE: These functions are currently TODO. They've not been implemented.
+ bool write_metadata(FILE *fp) {
+ squash_deleted(); // so we don't have to worry about delkey
+ return false; // TODO
+ }
+
+ bool read_metadata(FILE *fp) {
+ num_deleted = 0; // since we got rid before writing
+ assert(use_empty); // have to set this before calling us
+ if (table) free(table); // we'll make our own
+ // TODO: read magic number
+ // TODO: read num_buckets
+ reset_thresholds();
+ table = (value_type *) malloc(num_buckets * sizeof(*table));
+ assert(table);
+ fill_range_with_empty(table, table + num_buckets);
+ // TODO: read num_elements
+ for ( size_type i = 0; i < num_elements; ++i ) {
+ // TODO: read bucket_num
+ // TODO: set with non-empty, non-deleted value
+ }
+ return false; // TODO
+ }
+
+ // If your keys and values are simple enough, we can write them to
+ // disk for you. "simple enough" means value_type is a POD type
+ // that contains no pointers. However, we don't try to normalize
+ // endianness
+ bool write_nopointer_data(FILE *fp) const {
+ for ( const_iterator it = begin(); it != end(); ++it ) {
+ // TODO: skip empty/deleted values
+ if ( !fwrite(&*it, sizeof(*it), 1, fp) ) return false;
+ }
+ return false;
+ }
+
+ // When reading, we have to override the potential const-ness of *it
+ bool read_nopointer_data(FILE *fp) {
+ for ( iterator it = begin(); it != end(); ++it ) {
+ // TODO: skip empty/deleted values
+ if ( !fread(reinterpret_cast<void*>(&(*it)), sizeof(*it), 1, fp) )
+ return false;
+ }
+ return false;
+ }
+
+ private:
+ // The actual data
+ hasher hash; // required by hashed_associative_container
+ key_equal equals;
+ ExtractKey get_key;
+ SetKey set_key;
+ size_type num_deleted; // how many occupied buckets are marked deleted
+ bool use_deleted; // false until delkey has been set
+ bool use_empty; // you must do this before you start
+ // TODO(csilvers): make a pointer, and get rid of use_deleted (benchmark!)
+ key_type delkey; // which key marks deleted entries
+ value_type emptyval; // which key marks unused entries
+ float enlarge_resize_percent; // how full before resize
+ float shrink_resize_percent; // how empty before resize
+ size_type shrink_threshold; // num_buckets * shrink_resize_percent
+ size_type enlarge_threshold; // num_buckets * enlarge_resize_percent
+ value_type *table;
+ size_type num_buckets;
+ size_type num_elements;
+ bool consider_shrink; // true if we should try to shrink before next insert
+
+ void reset_thresholds() {
+ enlarge_threshold = static_cast<size_type>(num_buckets
+ * enlarge_resize_percent);
+ shrink_threshold = static_cast<size_type>(num_buckets
+ * shrink_resize_percent);
+ consider_shrink = false; // whatever caused us to reset already considered
+ }
+};
+
+// We need a global swap as well
+template <class V, class K, class HF, class ExK, class SetK, class EqK, class A>
+inline void swap(dense_hashtable<V,K,HF,ExK,SetK,EqK,A> &x,
+ dense_hashtable<V,K,HF,ExK,SetK,EqK,A> &y) {
+ x.swap(y);
+}
+
+#undef JUMP_
+
+template <class V, class K, class HF, class ExK, class SetK, class EqK, class A>
+const typename dense_hashtable<V,K,HF,ExK,SetK,EqK,A>::size_type
+dense_hashtable<V,K,HF,ExK,SetK,EqK,A>::ILLEGAL_BUCKET;
+
+// How full we let the table get before we resize. Knuth says .8 is
+// good -- higher causes us to probe too much, though saves memory.
+// However, we go with .5, getting better performance at the cost of
+// more space (a trade-off densehashtable explicitly chooses to make).
+// Feel free to play around with different values, though.
+template <class V, class K, class HF, class ExK, class SetK, class EqK, class A>
+const float dense_hashtable<V,K,HF,ExK,SetK,EqK,A>::HT_OCCUPANCY_FLT = 0.5f;
+
+// How empty we let the table get before we resize lower.
+// It should be less than OCCUPANCY_FLT / 2 or we thrash resizing
+template <class V, class K, class HF, class ExK, class SetK, class EqK, class A>
+const float dense_hashtable<V,K,HF,ExK,SetK,EqK,A>::HT_EMPTY_FLT
+ = 0.4f * dense_hashtable<V,K,HF,ExK,SetK,EqK,A>::HT_OCCUPANCY_FLT;
+
+_END_GOOGLE_NAMESPACE_
+
+#endif /* _DENSEHASHTABLE_H_ */