// 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.
// ---
//
// 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 dense_hash_map<>
// or dense_hash_set<> instead.
// You can change the following below:
// HT_OCCUPANCY_PCT -- how full before we double size
// HT_EMPTY_PCT -- how empty before we halve size
// HT_MIN_BUCKETS -- default smallest bucket size
//
// You can also change enlarge_factor (which defaults to
// HT_OCCUPANCY_PCT), and shrink_factor (which defaults to
// HT_EMPTY_PCT) with set_resizing_parameters().
//
// How to decide what values to use?
// shrink_factor's default of .4 * OCCUPANCY_PCT, is probably good.
// HT_MIN_BUCKETS is probably unnecessary since you can specify
// (indirectly) the starting number of buckets at construct-time.
// For enlarge_factor, 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_factor -- 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_
#include <sparsehash/internal/sparseconfig.h>
#include <assert.h>
#include <stdio.h> // for FILE, fwrite, fread
#include <algorithm> // For swap(), eg
#include <iterator> // For iterator tags
#include <limits> // for numeric_limits
#include <memory> // For uninitialized_fill
#include <utility> // for pair
#include <sparsehash/internal/hashtable-common.h>
#include <sparsehash/internal/libc_allocator_with_realloc.h>
#include <sparsehash/type_traits.h>
#include <stdexcept> // For length_error
_START_GOOGLE_NAMESPACE_
namespace base { // just to make google->opensource transition easier
using GOOGLE_NAMESPACE::true_type;
using GOOGLE_NAMESPACE::false_type;
using GOOGLE_NAMESPACE::integral_constant;
using GOOGLE_NAMESPACE::is_same;
using GOOGLE_NAMESPACE::remove_const;
}
// The probing method
// Linear probing
// #define JUMP_(key, num_probes) ( 1 )
// Quadratic probing
#define JUMP_(key, num_probes) ( num_probes )
// 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.
// Must inherit from unary_function, or at least have a
// result_type enum indicating the return type of operator().
// 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.
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 {
private:
typedef typename A::template rebind<V>::other value_alloc_type;
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 std::forward_iterator_tag iterator_category; // very little defined!
typedef V value_type;
typedef typename value_alloc_type::difference_type difference_type;
typedef typename value_alloc_type::size_type size_type;
typedef typename value_alloc_type::reference reference;
typedef typename value_alloc_type::pointer 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 {
private:
typedef typename A::template rebind<V>::other value_alloc_type;
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 std::forward_iterator_tag iterator_category; // very little defined!
typedef V value_type;
typedef typename value_alloc_type::difference_type difference_type;
typedef typename value_alloc_type::size_type size_type;
typedef typename value_alloc_type::const_reference reference;
typedef typename value_alloc_type::const_pointer 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()
: ht(NULL), pos(pointer()), end(pointer()) { }
// 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 {
private:
typedef typename Alloc::template rebind<Value>::other value_alloc_type;
public:
typedef Key key_type;
typedef Value value_type;
typedef HashFcn hasher;
typedef EqualKey key_equal;
typedef Alloc allocator_type;
typedef typename value_alloc_type::size_type size_type;
typedef typename value_alloc_type::difference_type difference_type;
typedef typename value_alloc_type::reference reference;
typedef typename value_alloc_type::const_reference const_reference;
typedef typename value_alloc_type::pointer pointer;
typedef typename value_alloc_type::const_pointer const_pointer;
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 int HT_OCCUPANCY_PCT; // defined at the bottom of this file
// 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_PCT / 2 or we thrash resizing
static const int HT_EMPTY_PCT; // defined at the bottom of this file
// 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_type 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_type 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.
// We'll just consider bucket n to be the n-th element of the table.
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 settings; }
key_equal key_eq() const { return key_info; }
allocator_type get_allocator() const {
return allocator_type(val_info);
}
// Accessor function for statistics gathering.
int num_table_copies() const { return settings.num_ht_copies(); }
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(pointer dst, const_reference src) {
dst->~value_type(); // delete the old value, if any
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);
}
// Test if the given key is the deleted indicator. Requires
// num_deleted > 0, for correctness of read(), and because that
// guarantees that key_info.delkey is valid.
bool test_deleted_key(const key_type& key) const {
assert(num_deleted > 0);
return equals(key_info.delkey, key);
}
public:
void set_deleted_key(const key_type &key) {
// the empty indicator (if specified) and the deleted indicator
// must be different
assert((!settings.use_empty() || !equals(key, get_key(val_info.emptyval)))
&& "Passed the empty-key to set_deleted_key");
// It's only safe to change what "deleted" means if we purge deleted guys
squash_deleted();
settings.set_use_deleted(true);
key_info.delkey = key;
}
void clear_deleted_key() {
squash_deleted();
settings.set_use_deleted(false);
}
key_type deleted_key() const {
assert(settings.use_deleted()
&& "Must set deleted key before calling deleted_key");
return key_info.delkey;
}
// 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 {
// Invariant: !use_deleted() implies num_deleted is 0.
assert(settings.use_deleted() || num_deleted == 0);
return num_deleted > 0 && test_deleted_key(get_key(table[bucknum]));
}
bool test_deleted(const iterator &it) const {
// Invariant: !use_deleted() implies num_deleted is 0.
assert(settings.use_deleted() || num_deleted == 0);
return num_deleted > 0 && test_deleted_key(get_key(*it));
}
bool test_deleted(const const_iterator &it) const {
// Invariant: !use_deleted() implies num_deleted is 0.
assert(settings.use_deleted() || num_deleted == 0);
return num_deleted > 0 && test_deleted_key(get_key(*it));
}
private:
void check_use_deleted(const char* caller) {
(void)caller; // could log it if the assert failed
assert(settings.use_deleted());
}
// Set it so test_deleted is true. true if object didn't used to be deleted.
bool set_deleted(iterator &it) {
check_use_deleted("set_deleted()");
bool retval = !test_deleted(it);
// &* converts from iterator to value-type.
set_key(&(*it), key_info.delkey);
return retval;
}
// Set it so test_deleted is false. true if object used to be deleted.
bool clear_deleted(iterator &it) {
check_use_deleted("clear_deleted()");
// Happens automatically when we assign something else in its place.
return test_deleted(it);
}
// We also allow to set/clear the deleted bit on a const iterator.
// We allow a const_iterator for the same reason you can delete a
// const pointer: it's convenient, and semantically you can't use
// 'it' after it's been deleted anyway, so its const-ness doesn't
// really matter.
bool set_deleted(const_iterator &it) {
check_use_deleted("set_deleted()");
bool retval = !test_deleted(it);
set_key(const_cast<pointer>(&(*it)), key_info.delkey);
return retval;
}
// Set it so test_deleted is false. true if object used to be deleted.
bool clear_deleted(const_iterator &it) {
check_use_deleted("clear_deleted()");
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(settings.use_empty()); // we always need to know what's empty!
return equals(get_key(val_info.emptyval), get_key(table[bucknum]));
}
bool test_empty(const iterator &it) const {
assert(settings.use_empty()); // we always need to know what's empty!
return equals(get_key(val_info.emptyval), get_key(*it));
}
bool test_empty(const const_iterator &it) const {
assert(settings.use_empty()); // we always need to know what's empty!
return equals(get_key(val_info.emptyval), get_key(*it));
}
private:
void fill_range_with_empty(pointer table_start, pointer table_end) {
std::uninitialized_fill(table_start, table_end, val_info.emptyval);
}
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_reference val) {
// Once you set the empty key, you can't change it
assert(!settings.use_empty() && "Calling set_empty_key multiple times");
// The deleted indicator (if specified) and the empty indicator
// must be different.
assert((!settings.use_deleted() || !equals(get_key(val), key_info.delkey))
&& "Setting the empty key the same as the deleted key");
settings.set_use_empty(true);
set_value(&val_info.emptyval, val);
assert(!table); // must set before first use
// num_buckets was set in constructor even though table was NULL
table = val_info.allocate(num_buckets);
assert(table);
fill_range_with_empty(table, table + num_buckets);
}
// TODO(user): return a key_type rather than a value_type
value_type empty_key() const {
assert(settings.use_empty());
return val_info.emptyval;
}
// FUNCTIONS CONCERNING SIZE
public:
size_type size() const { return num_elements - num_deleted; }
size_type max_size() const { return val_info.max_size(); }
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);
// Used after a string of deletes. Returns true if we actually shrunk.
// TODO(csilvers): take a delta so we can take into account inserts
// done after shrinking. Maybe make part of the Settings class?
bool 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);
bool retval = false;
// 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.
const size_type num_remain = num_elements - num_deleted;
const size_type shrink_threshold = settings.shrink_threshold();
if (shrink_threshold > 0 && num_remain < shrink_threshold &&
bucket_count() > HT_DEFAULT_STARTING_BUCKETS) {
const float shrink_factor = settings.shrink_factor();
size_type sz = bucket_count() / 2; // find how much we should shrink
while (sz > HT_DEFAULT_STARTING_BUCKETS &&
num_remain < sz * shrink_factor) {
sz /= 2; // stay a power of 2
}
dense_hashtable tmp(*this, sz); // Do the actual resizing
swap(tmp); // now we are tmp
retval = true;
}
settings.set_consider_shrink(false); // because we just considered it
return retval;
}
// 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"
// Returns true if we actually resized, false if size was already ok.
bool resize_delta(size_type delta) {
bool did_resize = false;
if ( settings.consider_shrink() ) { // see if lots of deletes happened
if ( maybe_shrink() )
did_resize = true;
}
if (num_elements >=
(std::numeric_limits<size_type>::max)() - delta) {
throw std::length_error("resize overflow");
}
if ( bucket_count() >= HT_MIN_BUCKETS &&
(num_elements + delta) <= settings.enlarge_threshold() )
return did_resize; // 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 = settings.min_buckets(num_elements + delta, 0);
if ( needed_size <= bucket_count() ) // we have enough buckets
return did_resize;
size_type resize_to =
settings.min_buckets(num_elements - num_deleted + delta, bucket_count());
if (resize_to < needed_size && // may double resize_to
resize_to < (std::numeric_limits<size_type>::max)() / 2) {
// This situation means that we have enough deleted elements,
// that once we purge them, we won't actually have needed to
// grow. But we may want to grow anyway: if we just purge one
// element, say, we'll have to grow anyway next time we
// insert. Might as well grow now, since we're already going
// through the trouble of copying (in order to purge the
// deleted elements).
const size_type target =
static_cast<size_type>(settings.shrink_size(resize_to*2));
if (num_elements - num_deleted + delta >= target) {
// Good, we won't be below the shrink threshhold even if we double.
resize_to *= 2;
}
}
dense_hashtable tmp(*this, resize_to);
swap(tmp); // now we are tmp
return true;
}
// We require table be not-NULL and empty before calling this.
void resize_table(size_type /*old_size*/, size_type new_size,
base::true_type) {
table = val_info.realloc_or_die(table, new_size);
}
void resize_table(size_type old_size, size_type new_size, base::false_type) {
val_info.deallocate(table, old_size);
table = val_info.allocate(new_size);
}
// 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_to_size(settings.min_buckets(ht.size(), min_buckets_wanted));
// 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()
&& "Hashtable is full: an error in key_equal<> or hash<>");
}
set_value(&table[bucknum], *it); // copies the value to here
num_elements++;
}
settings.inc_num_ht_copies();
}
// 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 num_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 ( settings.consider_shrink() || req_elements == 0 )
maybe_shrink();
if ( req_elements > num_elements )
resize_delta(req_elements - num_elements);
}
// Get and change the value of shrink_factor and enlarge_factor. 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 = settings.shrink_factor();
*grow = settings.enlarge_factor();
}
void set_resizing_parameters(float shrink, float grow) {
settings.set_resizing_parameters(shrink, grow);
settings.reset_thresholds(bucket_count());
}
// 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(),
const Alloc& alloc = Alloc())
: settings(hf),
key_info(ext, set, eql),
num_deleted(0),
num_elements(0),
num_buckets(expected_max_items_in_table == 0
? HT_DEFAULT_STARTING_BUCKETS
: settings.min_buckets(expected_max_items_in_table, 0)),
val_info(alloc_impl<value_alloc_type>(alloc)),
table(NULL) {
// 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
settings.reset_thresholds(bucket_count());
}
// 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)
: settings(ht.settings),
key_info(ht.key_info),
num_deleted(0),
num_elements(0),
num_buckets(0),
val_info(ht.val_info),
table(NULL) {
if (!ht.settings.use_empty()) {
// If use_empty isn't set, copy_from will crash, so we do our own copying.
assert(ht.empty());
num_buckets = settings.min_buckets(ht.size(), min_buckets_wanted);
settings.reset_thresholds(bucket_count());
return;
}
settings.reset_thresholds(bucket_count());
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
if (!ht.settings.use_empty()) {
assert(ht.empty());
dense_hashtable empty_table(ht); // empty table with ht's thresholds
this->swap(empty_table);
return *this;
}
settings = ht.settings;
key_info = ht.key_info;
set_value(&val_info.emptyval, ht.val_info.emptyval);
// copy_from() calls clear and sets num_deleted to 0 too
copy_from(ht, HT_MIN_BUCKETS);
// we purposefully don't copy the allocator, which may not be copyable
return *this;
}
~dense_hashtable() {
if (table) {
destroy_buckets(0, num_buckets);
val_info.deallocate(table, num_buckets);
}
}
// Many STL algorithms use swap instead of copy constructors
void swap(dense_hashtable& ht) {
std::swap(settings, ht.settings);
std::swap(key_info, ht.key_info);
std::swap(num_deleted, ht.num_deleted);
std::swap(num_elements, ht.num_elements);
std::swap(num_buckets, ht.num_buckets);
{ value_type tmp; // for annoying reasons, swap() doesn't work
set_value(&tmp, val_info.emptyval);
set_value(&val_info.emptyval, ht.val_info.emptyval);
set_value(&ht.val_info.emptyval, tmp);
}
std::swap(table, ht.table);
settings.reset_thresholds(bucket_count()); // also resets consider_shrink
ht.settings.reset_thresholds(ht.bucket_count());
// we purposefully don't swap the allocator, which may not be swap-able
}
private:
void clear_to_size(size_type new_num_buckets) {
if (!table) {
table = val_info.allocate(new_num_buckets);
} else {
destroy_buckets(0, num_buckets);
if (new_num_buckets != num_buckets) { // resize, if necessary
typedef base::integral_constant<bool,
base::is_same<value_alloc_type,
libc_allocator_with_realloc<value_type> >::value>
realloc_ok;
resize_table(num_buckets, new_num_buckets, realloc_ok());
}
}
assert(table);
fill_range_with_empty(table, table + new_num_buckets);
num_elements = 0;
num_deleted = 0;
num_buckets = new_num_buckets; // our new size
settings.reset_thresholds(bucket_count());
}
public:
// It's always nice to be able to clear a table without deallocating it
void clear() {
// If the table is already empty, and the number of buckets is
// already as we desire, there's nothing to do.
const size_type new_num_buckets = settings.min_buckets(0, 0);
if (num_elements == 0 && new_num_buckets == num_buckets) {
return;
}
clear_to_size(new_num_buckets);
}
// 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 (num_elements > 0) {
assert(table);
destroy_buckets(0, num_buckets);
fill_range_with_empty(table, table + num_buckets);
}
// don't consider to shrink before another erase()
settings.reset_thresholds(bucket_count());
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
std::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 std::pair<size_type,size_type>(ILLEGAL_BUCKET, bucknum);
else
return std::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 std::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()
&& "Hashtable is full: an error in key_equal<> or hash<>");
}
}
public:
iterator find(const key_type& key) {
if ( size() == 0 ) return end();
std::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();
std::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 {
std::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 {
std::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.
std::pair<iterator,iterator> equal_range(const key_type& key) {
iterator pos = find(key); // either an iterator or end
if (pos == end()) {
return std::pair<iterator,iterator>(pos, pos);
} else {
const iterator startpos = pos++;
return std::pair<iterator,iterator>(startpos, pos);
}
}
std::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 std::pair<const_iterator,const_iterator>(pos, pos);
} else {
const const_iterator startpos = pos++;
return std::pair<const_iterator,const_iterator>(startpos, pos);
}
}
// INSERTION ROUTINES
private:
// Private method used by insert_noresize and find_or_insert.
iterator insert_at(const_reference obj, size_type pos) {
if (size() >= max_size()) {
throw std::length_error("insert overflow");
}
if ( test_deleted(pos) ) { // just replace if it's been del.
// shrug: shouldn't need to be const.
const_iterator delpos(this, table + pos, table + num_buckets, false);
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], obj);
return iterator(this, table + pos, table + num_buckets, false);
}
// If you know *this is big enough to hold obj, use this routine
std::pair<iterator, bool> insert_noresize(const_reference obj) {
// First, double-check we're not inserting delkey or emptyval
assert((!settings.use_empty() || !equals(get_key(obj),
get_key(val_info.emptyval)))
&& "Inserting the empty key");
assert((!settings.use_deleted() || !equals(get_key(obj), key_info.delkey))
&& "Inserting the deleted key");
const std::pair<size_type,size_type> pos = find_position(get_key(obj));
if ( pos.first != ILLEGAL_BUCKET) { // object was already there
return std::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
return std::pair<iterator,bool>(insert_at(obj, pos.second), true);
}
}
// Specializations of insert(it, it) depending on the power of the iterator:
// (1) Iterator supports operator-, resize before inserting
template <class ForwardIterator>
void insert(ForwardIterator f, ForwardIterator l, std::forward_iterator_tag) {
size_t dist = std::distance(f, l);
if (dist >= (std::numeric_limits<size_type>::max)()) {
throw std::length_error("insert-range overflow");
}
resize_delta(static_cast<size_type>(dist));
for ( ; dist > 0; --dist, ++f) {
insert_noresize(*f);
}
}
// (2) 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);
}
public:
// This is the normal insert routine, used by the outside world
std::pair<iterator, bool> insert(const_reference 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());
}
// DefaultValue is a functor that takes a key and returns a value_type
// representing the default value to be inserted if none is found.
template <class DefaultValue>
value_type& find_or_insert(const key_type& key) {
// First, double-check we're not inserting emptykey or delkey
assert((!settings.use_empty() || !equals(key, get_key(val_info.emptyval)))
&& "Inserting the empty key");
assert((!settings.use_deleted() || !equals(key, key_info.delkey))
&& "Inserting the deleted key");
const std::pair<size_type,size_type> pos = find_position(key);
DefaultValue default_value;
if ( pos.first != ILLEGAL_BUCKET) { // object was already there
return table[pos.first];
} else if (resize_delta(1)) { // needed to rehash to make room
// Since we resized, we can't use pos, so recalculate where to insert.
return *insert_noresize(default_value(key)).first;
} else { // no need to rehash, insert right here
return *insert_at(default_value(key), pos.second);
}
}
// DELETION ROUTINES
size_type erase(const key_type& key) {
// First, double-check we're not trying to erase delkey or emptyval.
assert((!settings.use_empty() || !equals(key, get_key(val_info.emptyval)))
&& "Erasing the empty key");
assert((!settings.use_deleted() || !equals(key, key_info.delkey))
&& "Erasing the deleted 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;
settings.set_consider_shrink(true); // will think about shrink after next insert
return 1; // because we deleted one thing
} else {
return 0; // because we deleted nothing
}
}
// We return the iterator past the deleted item.
void erase(iterator pos) {
if ( pos == end() ) return; // sanity check
if ( set_deleted(pos) ) { // true if object has been newly deleted
++num_deleted;
settings.set_consider_shrink(true); // will think about shrink after next insert
}
}
void erase(iterator f, iterator l) {
for ( ; f != l; ++f) {
if ( set_deleted(f) ) // should always be true
++num_deleted;
}
settings.set_consider_shrink(true); // will think about shrink after next insert
}
// We allow you to erase a const_iterator just like we allow you to
// erase an iterator. This is in parallel to 'delete': you can delete
// a const pointer just like a non-const pointer. The logic is that
// you can't use the object after it's erased anyway, so it doesn't matter
// if it's const or not.
void erase(const_iterator pos) {
if ( pos == end() ) return; // sanity check
if ( set_deleted(pos) ) { // true if object has been newly deleted
++num_deleted;
settings.set_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;
}
settings.set_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.
private:
// Every time the disk format changes, this should probably change too
typedef unsigned long MagicNumberType;
static const MagicNumberType MAGIC_NUMBER = 0x13578642;
public:
// I/O -- this is an add-on for writing hash table to disk
//
// INPUT and OUTPUT must be either a FILE, *or* a C++ stream
// (istream, ostream, etc) *or* a class providing
// Read(void*, size_t) and Write(const void*, size_t)
// (respectively), which writes a buffer into a stream
// (which the INPUT/OUTPUT instance presumably owns).
typedef sparsehash_internal::pod_serializer<value_type> NopointerSerializer;
// ValueSerializer: a functor. operator()(OUTPUT*, const value_type&)
template <typename ValueSerializer, typename OUTPUT>
bool serialize(ValueSerializer serializer, OUTPUT *fp) {
squash_deleted(); // so we don't have to worry about delkey
if ( !sparsehash_internal::write_bigendian_number(fp, MAGIC_NUMBER, 4) )
return false;
if ( !sparsehash_internal::write_bigendian_number(fp, num_buckets, 8) )
return false;
if ( !sparsehash_internal::write_bigendian_number(fp, num_elements, 8) )
return false;
// Now write a bitmap of non-empty buckets.
for ( size_type i = 0; i < num_buckets; i += 8 ) {
unsigned char bits = 0;
for ( int bit = 0; bit < 8; ++bit ) {
if ( i + bit < num_buckets && !test_empty(i + bit) )
bits |= (1 << bit);
}
if ( !sparsehash_internal::write_data(fp, &bits, sizeof(bits)) )
return false;
for ( int bit = 0; bit < 8; ++bit ) {
if ( bits & (1 << bit) ) {
if ( !serializer(fp, table[i + bit]) ) return false;
}
}
}
return true;
}
// INPUT: anything we've written an overload of read_data() for.
// ValueSerializer: a functor. operator()(INPUT*, value_type*)
template <typename ValueSerializer, typename INPUT>
bool unserialize(ValueSerializer serializer, INPUT *fp) {
assert(settings.use_empty() && "empty_key not set for read");
clear(); // just to be consistent
MagicNumberType magic_read;
if ( !sparsehash_internal::read_bigendian_number(fp, &magic_read, 4) )
return false;
if ( magic_read != MAGIC_NUMBER ) {
return false;
}
size_type new_num_buckets;
if ( !sparsehash_internal::read_bigendian_number(fp, &new_num_buckets, 8) )
return false;
clear_to_size(new_num_buckets);
if ( !sparsehash_internal::read_bigendian_number(fp, &num_elements, 8) )
return false;
// Read the bitmap of non-empty buckets.
for (size_type i = 0; i < num_buckets; i += 8) {
unsigned char bits;
if ( !sparsehash_internal::read_data(fp, &bits, sizeof(bits)) )
return false;
for ( int bit = 0; bit < 8; ++bit ) {
if ( i + bit < num_buckets && (bits & (1 << bit)) ) { // not empty
if ( !serializer(fp, &table[i + bit]) ) return false;
}
}
}
return true;
}
private:
template <class A>
class alloc_impl : public A {
public:
typedef typename A::pointer pointer;
typedef typename A::size_type size_type;
// Convert a normal allocator to one that has realloc_or_die()
alloc_impl(const A& a) : A(a) { }
// realloc_or_die should only be used when using the default
// allocator (libc_allocator_with_realloc).
pointer realloc_or_die(pointer /*ptr*/, size_type /*n*/) {
fprintf(stderr, "realloc_or_die is only supported for "
"libc_allocator_with_realloc\n");
exit(1);
return NULL;
}
};
// A template specialization of alloc_impl for
// libc_allocator_with_realloc that can handle realloc_or_die.
template <class A>
class alloc_impl<libc_allocator_with_realloc<A> >
: public libc_allocator_with_realloc<A> {
public:
typedef typename libc_allocator_with_realloc<A>::pointer pointer;
typedef typename libc_allocator_with_realloc<A>::size_type size_type;
alloc_impl(const libc_allocator_with_realloc<A>& a)
: libc_allocator_with_realloc<A>(a) { }
pointer realloc_or_die(pointer ptr, size_type n) {
pointer retval = this->reallocate(ptr, n);
if (retval == NULL) {
fprintf(stderr, "sparsehash: FATAL ERROR: failed to reallocate "
"%lu elements for ptr %p", static_cast<unsigned long>(n), ptr);
exit(1);
}
return retval;
}
};
// Package allocator with emptyval to eliminate memory needed for
// the zero-size allocator.
// If new fields are added to this class, we should add them to
// operator= and swap.
class ValInfo : public alloc_impl<value_alloc_type> {
public:
typedef typename alloc_impl<value_alloc_type>::value_type value_type;
ValInfo(const alloc_impl<value_alloc_type>& a)
: alloc_impl<value_alloc_type>(a), emptyval() { }
ValInfo(const ValInfo& v)
: alloc_impl<value_alloc_type>(v), emptyval(v.emptyval) { }
value_type emptyval; // which key marks unused entries
};
// Package functors with another class to eliminate memory needed for
// zero-size functors. Since ExtractKey and hasher's operator() might
// have the same function signature, they must be packaged in
// different classes.
struct Settings :
sparsehash_internal::sh_hashtable_settings<key_type, hasher,
size_type, HT_MIN_BUCKETS> {
explicit Settings(const hasher& hf)
: sparsehash_internal::sh_hashtable_settings<key_type, hasher,
size_type, HT_MIN_BUCKETS>(
hf, HT_OCCUPANCY_PCT / 100.0f, HT_EMPTY_PCT / 100.0f) {}
};
// Packages ExtractKey and SetKey functors.
class KeyInfo : public ExtractKey, public SetKey, public EqualKey {
public:
KeyInfo(const ExtractKey& ek, const SetKey& sk, const EqualKey& eq)
: ExtractKey(ek),
SetKey(sk),
EqualKey(eq) {
}
// We want to return the exact same type as ExtractKey: Key or const Key&
typename ExtractKey::result_type get_key(const_reference v) const {
return ExtractKey::operator()(v);
}
void set_key(pointer v, const key_type& k) const {
SetKey::operator()(v, k);
}
bool equals(const key_type& a, const key_type& b) const {
return EqualKey::operator()(a, b);
}
// Which key marks deleted entries.
// TODO(csilvers): make a pointer, and get rid of use_deleted (benchmark!)
typename base::remove_const<key_type>::type delkey;
};
// Utility functions to access the templated operators
size_type hash(const key_type& v) const {
return settings.hash(v);
}
bool equals(const key_type& a, const key_type& b) const {
return key_info.equals(a, b);
}
typename ExtractKey::result_type get_key(const_reference v) const {
return key_info.get_key(v);
}
void set_key(pointer v, const key_type& k) const {
key_info.set_key(v, k);
}
private:
// Actual data
Settings settings;
KeyInfo key_info;
size_type num_deleted; // how many occupied buckets are marked deleted
size_type num_elements;
size_type num_buckets;
ValInfo val_info; // holds emptyval, and also the allocator
pointer table;
};
// 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, via
// max_load_factor() and/or set_resizing_parameters().
template <class V, class K, class HF, class ExK, class SetK, class EqK, class A>
const int dense_hashtable<V,K,HF,ExK,SetK,EqK,A>::HT_OCCUPANCY_PCT = 50;
// How empty we let the table get before we resize lower.
// It should be less than OCCUPANCY_PCT / 2 or we thrash resizing.
template <class V, class K, class HF, class ExK, class SetK, class EqK, class A>
const int dense_hashtable<V,K,HF,ExK,SetK,EqK,A>::HT_EMPTY_PCT
= static_cast<int>(0.4 *
dense_hashtable<V,K,HF,ExK,SetK,EqK,A>::HT_OCCUPANCY_PCT);
_END_GOOGLE_NAMESPACE_
#endif /* _DENSEHASHTABLE_H_ */