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// This code is in the public domain -- Ignacio Castaño <castano@gmail.com>
#pragma once
#ifndef NV_CORE_HASHMAP_H
#define NV_CORE_HASHMAP_H
/*
HashMap based on Thatcher Ulrich <tu@tulrich.com> container, donated to the Public Domain.
I'd like to do something to reduce the amount of code generated with this template. The type of
U is largely irrelevant to the generated code, except for calls to constructors and destructors,
but the combination of all T and U pairs, generate a large amounts of code.
HashMap is not used in NVTT, so it could be removed from the repository.
*/
#include "Memory.h"
#include "Debug.h"
#include "ForEach.h"
#include "Hash.h"
namespace nv
{
class Stream;
/** Thatcher Ulrich's hash table.
*
* Hash table, linear probing, internal chaining. One
* interesting/nice thing about this implementation is that the table
* itself is a flat chunk of memory containing no pointers, only
* relative indices. If the key and value types of the hash contain
* no pointers, then the hash can be serialized using raw IO. Could
* come in handy.
*
* Never shrinks, unless you explicitly clear() it. Expands on
* demand, though. For best results, if you know roughly how big your
* table will be, default it to that size when you create it.
*/
template<typename T, typename U, typename H = Hash<T>, typename E = Equal<T> >
class NVCORE_CLASS HashMap
{
NV_FORBID_COPY(HashMap);
public:
/// Default ctor.
HashMap() : entry_count(0), size_mask(-1), table(NULL) { }
/// Ctor with size hint.
explicit HashMap(int size_hint) : entry_count(0), size_mask(-1), table(NULL) { setCapacity(size_hint); }
/// Dtor.
~HashMap() { clear(); }
void set(const T& key, const U& value);
void add(const T& key, const U& value);
bool remove(const T& key);
void clear();
bool isEmpty() const;
bool get(const T& key, U* value = NULL, T* other_key = NULL) const;
bool contains(const T & key) const;
int size() const;
int count() const;
int capacity() const;
void checkExpand();
void resize(int n);
void setCapacity(int new_size);
// Behaves much like std::pair.
struct Entry
{
int next_in_chain; // internal chaining for collisions
uint hash_value; // avoids recomputing. Worthwhile?
T key;
U value;
Entry() : next_in_chain(-2) {}
Entry(const Entry& e) : next_in_chain(e.next_in_chain), hash_value(e.hash_value), key(e.key), value(e.value) {}
Entry(const T& k, const U& v, int next, int hash) : next_in_chain(next), hash_value(hash), key(k), value(v) {}
bool isEmpty() const { return next_in_chain == -2; }
bool isEndOfChain() const { return next_in_chain == -1; }
bool isTombstone() const { return hash_value == TOMBSTONE_HASH; }
void clear() {
key.~T(); // placement delete
value.~U(); // placement delete
next_in_chain = -2;
hash_value = ~TOMBSTONE_HASH;
}
void makeTombstone() {
key.~T();
value.~U();
hash_value = TOMBSTONE_HASH;
}
};
// HashMap enumerator.
typedef int PseudoIndex;
PseudoIndex start() const { PseudoIndex i = 0; findNext(i); return i; }
bool isDone(const PseudoIndex & i) const { nvDebugCheck(i <= size_mask+1); return i == size_mask+1; };
void advance(PseudoIndex & i) const { nvDebugCheck(i <= size_mask+1); i++; findNext(i); }
#if NV_NEED_PSEUDOINDEX_WRAPPER
Entry & operator[]( const PseudoIndexWrapper & i ) {
Entry & e = entry(i(this));
nvDebugCheck(e.isTombstone() == false);
return e;
}
const Entry & operator[]( const PseudoIndexWrapper & i ) const {
const Entry & e = entry(i(this));
nvDebugCheck(e.isTombstone() == false);
return e;
}
#else
Entry & operator[](const PseudoIndex & i) {
Entry & e = entry(i);
nvDebugCheck(e.isTombstone() == false);
return e;
}
const Entry & operator[](const PseudoIndex & i) const {
const Entry & e = entry(i);
nvDebugCheck(e.isTombstone() == false);
return e;
}
#endif
// By default we serialize the key-value pairs compactl y.
template<typename _T, typename _U, typename _H, typename _E>
friend Stream & operator<< (Stream & s, HashMap<_T, _U, _H, _E> & map);
// This requires more storage, but saves us from rehashing the elements.
template<typename _T, typename _U, typename _H, typename _E>
friend Stream & rawSerialize(Stream & s, HashMap<_T, _U, _H, _E> & map);
/// Swap the members of this vector and the given vector.
template<typename _T, typename _U, typename _H, typename _E>
friend void swap(HashMap<_T, _U, _H, _E> & a, HashMap<_T, _U, _H, _E> & b);
private:
static const uint TOMBSTONE_HASH = (uint) -1;
uint compute_hash(const T& key) const;
// Find the index of the matching entry. If no match, then return -1.
int findIndex(const T& key) const;
// Return the index of the newly cleared element.
int removeTombstone(int index);
// Helpers.
Entry & entry(int index);
const Entry & entry(int index) const;
void setRawCapacity(int new_size);
// Move the enumerator to the next valid element.
void findNext(PseudoIndex & i) const;
int entry_count;
int size_mask;
Entry * table;
};
} // nv namespace
#endif // NV_CORE_HASHMAP_H
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