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tdlib-fork/tdutils/td/utils/Container.h

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//
// Copyright Aliaksei Levin (levlam@telegram.org), Arseny Smirnov (arseny30@gmail.com) 2014-2019
//
// Distributed under the Boost Software License, Version 1.0. (See accompanying
// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
//
#pragma once
#include "td/utils/common.h"
#include "td/utils/logging.h"
#include <limits>
namespace td {
// 1. Allocates all objects in vector. (but vector never shrinks)
// 2. Id is safe way to reach this object.
// 3. All ids are unique.
// 4. All ids are non-zero.
template <class DataT>
class Container {
public:
using Id = uint64;
DataT *get(Id id) {
int32 slot_id = decode_id(id);
if (slot_id == -1) {
return nullptr;
}
return &slots_[slot_id].data;
}
void erase(Id id) {
int32 slot_id = decode_id(id);
if (slot_id == -1) {
return;
}
release(slot_id);
}
DataT extract(Id id) {
int32 slot_id = decode_id(id);
CHECK(slot_id != -1);
auto res = std::move(slots_[slot_id].data);
release(slot_id);
return res;
}
Id create(DataT &&data = DataT(), uint8 type = 0) {
int32 id = store(std::move(data), type);
return encode_id(id);
}
Id reset_id(Id id) {
int32 slot_id = decode_id(id);
CHECK(slot_id != -1);
inc_generation(slot_id);
return encode_id(slot_id);
}
static uint8 type_from_id(Id id) {
return static_cast<uint8>(id);
}
vector<Id> ids() {
vector<bool> is_bad(slots_.size(), false);
for (auto id : empty_slots_) {
is_bad[id] = true;
}
vector<Id> res;
for (size_t i = 0, n = slots_.size(); i < n; i++) {
if (!is_bad[i]) {
res.push_back(encode_id(static_cast<int32>(i)));
}
}
return res;
}
template <class F>
void for_each(const F &f) {
auto ids = this->ids();
for (auto id : ids) {
f(id, *get(id));
}
}
size_t size() const {
CHECK(empty_slots_.size() <= slots_.size());
return slots_.size() - empty_slots_.size();
}
bool empty() const {
return size() == 0;
}
void clear() {
*this = Container<DataT>();
}
private:
static constexpr uint32 GENERATION_STEP = 1 << 8;
static constexpr uint32 TYPE_MASK = (1 << 8) - 1;
struct Slot {
uint32 generation;
DataT data;
};
vector<Slot> slots_;
vector<int32> empty_slots_;
Id encode_id(int32 id) const {
return (static_cast<uint64>(id) << 32) | slots_[id].generation;
}
int32 decode_id(Id id) const {
int32 slot_id = static_cast<int32>(id >> 32);
uint32 generation = static_cast<uint32>(id);
if (slot_id < 0 || slot_id >= static_cast<int32>(slots_.size())) {
return -1;
}
if (generation != slots_[slot_id].generation) {
return -1;
}
return slot_id;
}
int32 store(DataT &&data, uint8 type) {
int32 pos;
if (!empty_slots_.empty()) {
pos = empty_slots_.back();
empty_slots_.pop_back();
slots_[pos].data = std::move(data);
slots_[pos].generation ^= (slots_[pos].generation & TYPE_MASK) ^ type;
} else {
CHECK(slots_.size() <= static_cast<size_t>(std::numeric_limits<int32>::max()));
pos = static_cast<int32>(slots_.size());
slots_.push_back(Slot{GENERATION_STEP + type, std::move(data)});
}
return pos;
}
void release(int32 id) {
inc_generation(id);
slots_[id].data = DataT();
if (slots_[id].generation & ~TYPE_MASK) { // generation overflow. Can't use this id anymore
empty_slots_.push_back(id);
}
}
void inc_generation(int32 id) {
slots_[id].generation += GENERATION_STEP;
}
};
} // namespace td