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diff --git a/Runtime/Utilities/densehashtable.h b/Runtime/Utilities/densehashtable.h new file mode 100644 index 0000000..763bce1 --- /dev/null +++ b/Runtime/Utilities/densehashtable.h @@ -0,0 +1,899 @@ +// 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 +// +// How to decide what values to use? +// HT_EMPTY_FLT'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 HT_OCCUPANCY_FLT, 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 +// +// -- HT_OCCUPANCY_FLT -- 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 ) + + +// Hashtable class, used to implement the hashed associative containers +// hash_set and hash_map. + +//#include <google/sparsehash/sparseconfig.h> +//#include <Assert.h> +#include "LogAssert.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 "type_traits.h" // for true_type, integral_constant, etc. + +using std::pair; + +template <class Value, class Key, class HashFcn, + class ExtractKey, class EqualKey, class Alloc> +class dense_hashtable; + +template <class V, class K, class HF, class ExK, class EqK, class A> +struct dense_hashtable_iterator; + +template <class V, class K, class HF, class ExK, 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 EqK, class A> +struct dense_hashtable_iterator { + public: + typedef dense_hashtable_iterator<V,K,HF,ExK,EqK,A> iterator; + typedef dense_hashtable_const_iterator<V,K,HF,ExK,EqK,A> const_iterator; + + typedef std::forward_iterator_tag iterator_category; + typedef V value_type; + typedef std::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,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,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 EqK, class A> +struct dense_hashtable_const_iterator { + public: + typedef dense_hashtable_iterator<V,K,HF,ExK,EqK,A> iterator; + typedef dense_hashtable_const_iterator<V,K,HF,ExK,EqK,A> const_iterator; + + typedef std::forward_iterator_tag iterator_category; + typedef V value_type; + typedef std::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,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,EqK,A> *ht; + pointer pos, end; +}; + +template <class Value, class Key, class HashFcn, + class ExtractKey, 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 std::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, EqualKey, Alloc> + iterator; + + typedef dense_hashtable_const_iterator<Value, Key, HashFcn, + ExtractKey, EqualKey, Alloc> + const_iterator; + + // 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 + static const float HT_OCCUPANCY_FLT; // = 0.8; + + // How empty we let the table get before we resize lower. + // (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 = 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);} + + // ACCESSOR FUNCTIONS for the things we templatize on, basically + hasher hash_funct() const { return hash; } + key_equal key_eq() const { return equals; } + + // 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. + private: + 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 value_type &val) { + // the empty indicator (if specified) and the deleted indicator + // must be different + Assert(!use_empty || !equals(get_key(val), get_key(emptyval))); + // It's only safe to change what "deleted" means if we purge deleted guys + squash_deleted(); + use_deleted = true; + set_value(&delval, val); + } + 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(get_key(delval), get_key(table[bucknum]))); + } + bool test_deleted(const iterator &it) const { + return (use_deleted && num_deleted > 0 && + equals(get_key(delval), get_key(*it))); + } + bool test_deleted(const const_iterator &it) const { + return (use_deleted && num_deleted > 0 && + equals(get_key(delval), 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_value(const_cast<value_type*>(&(*it)), delval); + 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 + std::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), get_key(delval))); + 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 = _Alval.allocate(num_buckets); + 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; } + + 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 * HT_OCCUPANCY_FLT ) + 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 ( (num_elements-num_deleted) < shrink_threshold && + bucket_count() > HT_MIN_BUCKETS ) { + size_type sz = bucket_count() / 2; // find how much we should shrink + while ( sz > HT_MIN_BUCKETS && + (num_elements - num_deleted) < sz * HT_EMPTY_FLT ) + 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, size_type min_buckets_wanted = 0) { + if ( consider_shrink ) // see if lots of deletes happened + maybe_shrink(); + if ( bucket_count() > min_buckets_wanted && + (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, + min_buckets_wanted); + if ( needed_size > bucket_count() ) { // we don't have enough buckets + const size_type resize_to = min_size(num_elements - num_deleted + delta, + min_buckets_wanted); + 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, dense_hash_map_traits::true_type) { + value_type* new_table = _Alval.allocate(resize_to); + Assert(new_table); + if(table) + { + std::uninitialized_copy(table, table + num_buckets, new_table); + _Alval.deallocate(table, num_buckets); + } + fill_range_with_empty(new_table + num_buckets, new_table + resize_to); + table = new_table; + Assert(table); + } + + // 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, dense_hash_map_traits::false_type) { + value_type* new_table = _Alval.allocate(resize_to); + Assert(new_table); + std::uninitialized_copy(table, table + std::min(num_buckets,resize_to), new_table); + fill_range_with_empty(new_table + num_buckets, new_table + resize_to); + destroy_buckets(0, num_buckets); + _Alval.deallocate(table, num_buckets); + 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 = 0) { + 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 dense_hash_map_traits::integral_constant<bool, + (dense_hash_map_traits::has_trivial_copy<value_type>::value && + dense_hash_map_traits::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, 0); + } + + + // 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 n = 0, + const HashFcn& hf = HashFcn(), + const EqualKey& eql = EqualKey(), + const ExtractKey& ext = ExtractKey()) + : hash(hf), equals(eql), get_key(ext), num_deleted(0), + use_deleted(false), use_empty(false), + delval(), emptyval(), + table(NULL), num_buckets(min_size(0, n)), 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 = 0) + : hash(ht.hash), equals(ht.equals), get_key(ht.get_key), num_deleted(0), + use_deleted(ht.use_deleted), use_empty(ht.use_empty), + delval(ht.delval), emptyval(ht.emptyval), + 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; + use_deleted = ht.use_deleted; + use_empty = ht.use_empty; + set_value(&delval, ht.delval); + set_value(&emptyval, ht.emptyval); + copy_from(ht); // sets num_deleted to 0 too + return *this; + } + + ~dense_hashtable() { + if (table) { + destroy_buckets(0, num_buckets); + _Alval.deallocate(table, num_buckets); + } + } + + // Many STL algorithms use swap instead of copy constructors + void swap(dense_hashtable& ht) { + std::swap(hash, ht.hash); + std::swap(equals, ht.equals); + std::swap(get_key, ht.get_key); + std::swap(num_deleted, ht.num_deleted); + std::swap(use_deleted, ht.use_deleted); + std::swap(use_empty, ht.use_empty); + { value_type tmp; // for annoying reasons, swap() doesn't work + set_value(&tmp, delval); + set_value(&delval, ht.delval); + set_value(&ht.delval, tmp); + } + { value_type tmp; // for annoying reasons, swap() doesn't work + set_value(&tmp, emptyval); + set_value(&emptyval, ht.emptyval); + set_value(&ht.emptyval, tmp); + } + std::swap(table, ht.table); + std::swap(num_buckets, ht.num_buckets); + std::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); + + size_type old_bucket_count = num_buckets; + num_buckets = min_size(0,0); // our new size + reset_thresholds(); + value_type* new_table = _Alval.allocate(num_buckets); + Assert(new_table); + if(table) + _Alval.deallocate(table, old_bucket_count); + table = new_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); + } + + // 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) { + const iterator pos = find(key); // either an iterator or end + return pair<iterator,iterator>(pos, pos); + } + pair<const_iterator,const_iterator> equal_range(const key_type& key) const { + const const_iterator pos = find(key); // either an iterator or end + return pair<iterator,iterator>(pos, 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) { + 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 std::iterator_traits<InputIterator>::iterator_category()); + } + + // Iterator supports operator-, resize before inserting + template <class ForwardIterator> + void insert(ForwardIterator f, ForwardIterator l, + std::forward_iterator_tag) { + size_type n = std::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, + std::input_iterator_tag) { + for ( ; f != l; ++f) + insert(*f); + } + + + // DELETION ROUTINES + size_type erase(const key_type& key) { + 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); + } + + + private: + // The actual data + hasher hash; // required by hashed_associative_container + key_equal equals; + ExtractKey get_key; + size_type num_deleted; // how many occupied buckets are marked deleted + bool use_deleted; // false until delval has been set + bool use_empty; // you must do this before you start + value_type delval; // which key marks deleted entries + value_type emptyval; // which key marks unused entries + value_type *table; + size_type num_buckets; + size_type num_elements; + size_type shrink_threshold; // num_buckets * HT_EMPTY_FLT + size_type enlarge_threshold; // num_buckets * HT_OCCUPANCY_FLT + bool consider_shrink; // true if we should try to shrink before next insert + + Alloc _Alval; // allocator object for value_type + + void reset_thresholds() { + enlarge_threshold = static_cast<size_type>(num_buckets*HT_OCCUPANCY_FLT); + shrink_threshold = static_cast<size_type>(num_buckets*HT_EMPTY_FLT); + 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 EqK, class A> +inline void swap(dense_hashtable<V,K,HF,ExK,EqK,A> &x, + dense_hashtable<V,K,HF,ExK,EqK,A> &y) { + x.swap(y); +} + +#undef JUMP_ + +template <class V, class K, class HF, class ExK, class EqK, class A> +const typename dense_hashtable<V,K,HF,ExK,EqK,A>::size_type + dense_hashtable<V,K,HF,ExK,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 +template <class V, class K, class HF, class ExK, class EqK, class A> +const float dense_hashtable<V,K,HF,ExK,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 EqK, class A> +const float dense_hashtable<V,K,HF,ExK,EqK,A>::HT_EMPTY_FLT = 0.4f * +dense_hashtable<V,K,HF,ExK,EqK,A>::HT_OCCUPANCY_FLT; + +#endif /* _DENSEHASHTABLE_H_ */ |