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#include <llmr/util/clip_ids.hpp>
#include <llmr/map/tile.hpp>
#include <llmr/util/math.hpp>
#include <list>
#include <vector>
#include <bitset>
#include <cassert>
#include <iostream>
#include <algorithm>
namespace llmr {
struct TileHierarchy {
TileHierarchy(Tile::ID id, std::list<TileHierarchy> &&children)
: id(id), children(std::move(children)) {}
const Tile::ID id;
ClipID clip;
std::list<TileHierarchy> children;
};
std::list<TileHierarchy> partition(std::forward_list<Tile::ID> &&array) {
if (array.empty()) {
// We don't have to update the clipping mask because there are no tiles
// anyway.
return {};
}
int8_t minZ = array.begin()->z;
std::list<TileHierarchy> result;
std::forward_list<Tile::ID> remainder;
auto remainder_it = remainder.before_begin();
while (!array.empty()) {
const Tile::ID id = array.front();
array.pop_front();
if (id.z == minZ) {
std::forward_list<Tile::ID> children;
auto children_it = children.before_begin();
array.remove_if([&id, &children, &children_it](const Tile::ID &child) {
if (child.isChildOf(id)) {
children_it = children.insert_after(children_it, child);
return true;
} else {
return false;
}
});
result.emplace_back(id, partition(std::move(children)));
} else {
remainder_it = remainder.insert_after(remainder_it, id);
}
}
// Concatenate the remainder.
if (!remainder.empty()) {
result.splice(result.begin(), partition(std::move(remainder)));
}
return result;
}
uint8_t prefix(std::list<TileHierarchy> &array, TileHierarchy *parent = nullptr) {
if (array.empty()) {
return 0;
}
bool all_children_are_immediate = true;
uint8_t max_child_prefix_length = 0;
struct Huffman {
explicit Huffman(int prefix_length, TileHierarchy *item)
: prefix_length(prefix_length), children(1, item) {}
uint8_t prefix_length;
std::vector<TileHierarchy *> children;
};
// Create a temporary structure that we use for sorting the prefix tree.
std::list<Huffman> huffman;
std::transform(array.begin(), array.end(), std::back_inserter(huffman), [parent, &all_children_are_immediate, &max_child_prefix_length](TileHierarchy &item) {
uint8_t prefix_length = prefix(item.children, &item);
if (prefix_length > max_child_prefix_length) {
max_child_prefix_length = prefix_length;
}
if (!parent || item.id.z != parent->id.z + 1) {
all_children_are_immediate = false;
}
return Huffman { prefix_length + 1, &item };
});
while (huffman.size() > 1) {
huffman.sort([](const Huffman &a, const Huffman &b) {
return a.prefix_length < b.prefix_length;
});
Huffman &first = *huffman.begin();
Huffman &second = *(++huffman.begin());
assert(&first != &second);
// Prefix with 0
std::for_each(first.children.begin(), first.children.end(), [](TileHierarchy *child) {
child->clip.mask >>= 1;
child->clip.mask.set(7, false); // noop
child->clip.length++;
});
first.prefix_length++;
// Prefix with 1
std::for_each(second.children.begin(), second.children.end(), [](TileHierarchy *child) {
child->clip.mask >>= 1;
child->clip.mask.set(7, true);
child->clip.length++;
});
second.prefix_length++;
second.children.insert(second.children.end(), first.children.begin(), first.children.end());
second.prefix_length = first.prefix_length + second.prefix_length;
// Remove the first child as we've just merged it into the second version.
huffman.erase(huffman.begin());
}
uint8_t prefix_length = 0;
// Filter out all-zero bits
bool filter_zero = !all_children_are_immediate || array.size() != 4;
for (TileHierarchy &item : array) {
if (filter_zero && !item.clip.mask.any()) {
// Make sure we don't have a prefix that is all zeros.
// item.clip.mask |= (0x80 >> item.length);
item.clip.mask.set(7 - item.clip.length);
item.clip.length++;
}
if (item.clip.length > prefix_length) {
prefix_length = item.clip.length;
}
}
return max_child_prefix_length + prefix_length;
}
void propagate(std::map<Tile::ID, ClipID> &mapping, std::list<TileHierarchy> &array, const ClipID &parent = ClipID{}) {
for (auto &item : array) {
item.clip.mask >>= parent.length;
item.clip.mask |= parent.mask;
item.clip.length += parent.length;
#if defined(DEBUG)
auto result = mapping.emplace(item.id, item.clip);
assert("Tried to insert a duplicate item" && result.second == true);
#else
mapping.emplace(item.id, item.clip);
#endif
propagate(mapping, item.children, const_cast<const ClipID &>(item.clip));
};
}
void updateClipIDs(const std::list<Tile *> &array) {
std::forward_list<Tile::ID> ids;
std::transform(array.begin(), array.end(), std::front_inserter(ids), [](Tile *item) {
return item->id;
});
const std::map<Tile::ID, ClipID> mapping = computeClipIDs(ids);
std::for_each(array.begin(), array.end(), [&mapping](Tile *item) {
auto it = mapping.find(item->id);
if (it != mapping.end()) {
item->clip = it->second;
} else {
item->clip = ClipID {};
}
});
}
std::map<Tile::ID, ClipID> computeClipIDs(std::forward_list<Tile::ID> array) {
// Sort by zoom level and make sure that we don't have duplicate elements.
array.sort();
array.unique();
std::list<TileHierarchy> hierarchy = partition(std::move(array));
prefix(hierarchy);
std::map<Tile::ID, ClipID> mapping;
propagate(mapping, hierarchy);
return mapping;
}
}
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