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#pragma once
//hashset
//
//search: O(1) average; O(n) worst
//insert: O(1) average; O(n) worst
//remove: O(1) average; O(n) worst
//
//requirements:
// auto T::hash() const -> uint;
// auto T::operator==(const T&) const -> bool;
namespace nall {
template<typename T>
struct hashset {
hashset() = default;
hashset(uint length) : length(bit::round(length)) {}
hashset(const hashset& source) { operator=(source); }
hashset(hashset&& source) { operator=(move(source)); }
~hashset() { reset(); }
auto operator=(const hashset& source) -> hashset& {
reset();
if(source.pool) {
for(uint n : range(source.count)) {
insert(*source.pool[n]);
}
}
return *this;
}
auto operator=(hashset&& source) -> hashset& {
reset();
pool = source.pool;
length = source.length;
count = source.count;
source.pool = nullptr;
source.length = 8;
source.count = 0;
return *this;
}
explicit operator bool() const { return count; }
auto capacity() const -> uint { return length; }
auto size() const -> uint { return count; }
auto reset() -> void {
if(pool) {
for(uint n : range(length)) {
if(pool[n]) {
delete pool[n];
pool[n] = nullptr;
}
}
delete pool;
pool = nullptr;
}
length = 8;
count = 0;
}
auto reserve(uint size) -> void {
//ensure all items will fit into pool (with <= 50% load) and amortize growth
size = bit::round(max(size, count << 1));
T** copy = new T*[size]();
if(pool) {
for(uint n : range(length)) {
if(pool[n]) {
uint hash = (*pool[n]).hash() & (size - 1);
while(copy[hash]) if(++hash >= size) hash = 0;
copy[hash] = pool[n];
pool[n] = nullptr;
}
}
}
delete pool;
pool = copy;
length = size;
}
auto find(const T& value) -> maybe<T&> {
if(!pool) return nothing;
uint hash = value.hash() & (length - 1);
while(pool[hash]) {
if(value == *pool[hash]) return *pool[hash];
if(++hash >= length) hash = 0;
}
return nothing;
}
auto insert(const T& value) -> maybe<T&> {
if(!pool) pool = new T*[length]();
//double pool size when load is >= 50%
if(count >= (length >> 1)) reserve(length << 1);
count++;
uint hash = value.hash() & (length - 1);
while(pool[hash]) if(++hash >= length) hash = 0;
pool[hash] = new T(value);
return *pool[hash];
}
auto remove(const T& value) -> bool {
if(!pool) return false;
uint hash = value.hash() & (length - 1);
while(pool[hash]) {
if(value == *pool[hash]) {
delete pool[hash];
pool[hash] = nullptr;
count--;
return true;
}
if(++hash >= length) hash = 0;
}
return false;
}
protected:
T** pool = nullptr;
uint length = 8; //length of pool
uint count = 0; //number of objects inside of the pool
};
}
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