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#ifndef _APPEND_VECTOR_H
#define _APPEND_VECTOR_H
#include "mmap_allocator.h"
#include <vector>
#include <queue>
// Tilemaker collects OutputObjects in a list that
// - spills to disk
// - only gets appended to
//
// Vector is great for linear access, but resizes cause expensive disk I/O to
// copy elements.
//
// Deque is great for growing without disk I/O, but it allocates in blocks of 512,
// which is inefficient for linear access.
//
// Instead, we author a limited vector-of-vectors class that allocates in bigger chunks,
// to get the best of both worlds.
#define APPEND_VECTOR_SIZE 8192
namespace AppendVectorNS {
template <class T>
class AppendVector {
public:
struct Iterator {
using iterator_category = std::random_access_iterator_tag;
using difference_type = std::ptrdiff_t;
using value_type = T;
using pointer = T*;
using reference = T&;
Iterator(AppendVector<T>& appendVector, uint16_t vec, uint16_t offset):
appendVector(&appendVector), vec(vec), offset(offset) {}
Iterator():
appendVector(nullptr), vec(0), offset(0) {}
bool operator<(const Iterator& other) const {
if (vec < other.vec)
return true;
if (vec > other.vec)
return false;
return offset < other.offset;
}
bool operator>=(const Iterator& other) const {
return !(*this < other);
}
Iterator operator-(int delta) const {
int64_t absolute = vec * APPEND_VECTOR_SIZE + offset;
absolute -= delta;
return Iterator(*appendVector, absolute / APPEND_VECTOR_SIZE, absolute % APPEND_VECTOR_SIZE);
}
Iterator operator+(int delta) const {
int64_t absolute = vec * APPEND_VECTOR_SIZE + offset;
absolute += delta;
return Iterator(*appendVector, absolute / APPEND_VECTOR_SIZE, absolute % APPEND_VECTOR_SIZE);
}
bool operator==(const Iterator& other) const {
return appendVector == other.appendVector && vec == other.vec && offset == other.offset;
}
bool operator!=(const Iterator& other) const {
return !(*this == other);
}
std::ptrdiff_t operator-(const Iterator& other) const {
int64_t absolute = vec * APPEND_VECTOR_SIZE + offset;
int64_t otherAbsolute = other.vec * APPEND_VECTOR_SIZE + other.offset;
return absolute - otherAbsolute;
}
reference operator*() const {
auto& vector = appendVector->vecs[vec];
auto& el = vector[offset];
return el;
}
pointer operator->() const {
auto& vector = appendVector->vecs[vec];
auto& el = vector[offset];
return ⪙
}
Iterator& operator+= (int delta) {
int64_t absolute = vec * APPEND_VECTOR_SIZE + offset;
absolute += delta;
vec = absolute / APPEND_VECTOR_SIZE;
offset = absolute % APPEND_VECTOR_SIZE;
return *this;
}
Iterator& operator-= (int delta) {
int64_t absolute = vec * APPEND_VECTOR_SIZE + offset;
absolute -= delta;
vec = absolute / APPEND_VECTOR_SIZE;
offset = absolute % APPEND_VECTOR_SIZE;
return *this;
}
// Prefix increment
Iterator& operator++() {
offset++;
if (offset == APPEND_VECTOR_SIZE) {
offset = 0;
vec++;
}
return *this;
}
// Postfix increment
Iterator operator++(int) { Iterator tmp = *this; ++(*this); return tmp; }
// Prefix decrement
Iterator& operator--() {
if (offset > 0) {
offset--;
} else {
vec--;
offset = APPEND_VECTOR_SIZE - 1;
}
return *this;
}
// Postfix decrement
Iterator operator--(int) { Iterator tmp = *this; --(*this); return tmp; }
private:
mutable AppendVector<T>* appendVector;
int32_t vec, offset;
};
AppendVector():
count(0),
vecs(1) {
}
void clear() {
count = 0;
vecs.clear();
vecs.push_back(std::vector<T, mmap_allocator<T>>());
vecs.back().reserve(APPEND_VECTOR_SIZE);
}
size_t size() const {
return count;
}
T& operator [](int idx) {
auto& vec = vecs[idx / APPEND_VECTOR_SIZE];
auto& el = vec[idx % APPEND_VECTOR_SIZE];
return el;
}
Iterator begin() {
return Iterator(*this, 0, 0);
}
Iterator end() {
return Iterator(*this, vecs.size() - 1, count % APPEND_VECTOR_SIZE);
}
void push_back(const T& el) {
if (vecs.back().capacity() == 0)
vecs.back().reserve(APPEND_VECTOR_SIZE);
vecs.back().push_back(el);
if (vecs.back().size() == vecs.back().capacity()) {
vecs.push_back(std::vector<T, mmap_allocator<T>>());
vecs.back().reserve(APPEND_VECTOR_SIZE);
}
count++;
}
size_t count;
std::deque<std::vector<T, mmap_allocator<T>>> vecs;
};
}
#undef APPEND_VECTOR_SIZE
#endif
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