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[http_server] Cache parameter child pointer for O(1) lookup fallback #4

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[http_server] Cache parameter child pointer for O(1) lookup fallback #4

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22 changes: 11 additions & 11 deletions libraries/http_server/http_server/dynamic_routing_table.hh
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Original file line number Diff line number Diff line change
Expand Up @@ -53,7 +53,12 @@ template <typename V> struct drt_node {
std::string_view k = r.substr(s, c - s);

if (children_.find(k) == children_.end()) {
children_[k] = pool_.allocate(pool_);
auto* child = pool_.allocate(pool_);
children_[k] = child;
// Cache the parameter child pointer for O(1) lookup in find()
if (k.size() > 4 and k[0] == '{' and k[1] == '{' and
k[k.size() - 2] == '}' and k[k.size() - 1] == '}')
param_child_ = child;
}
return children_[k]->find_or_create(r, c);
}
Expand Down Expand Up @@ -100,20 +105,15 @@ template <typename V> struct drt_node {
return it2;
}

{
// if one child is a url param {{param_name}}, choose it
for (const auto& kv : children_) {
auto name = kv.first;
if (name.size() > 4 and name[0] == '{' and name[1] == '{' and
name[name.size() - 2] == '}' and name[name.size() - 1] == '}')
return kv.second->find(r, c);
}
return end();
}
// O(1) fallback to cached parameter child instead of O(n) linear scan
if (param_child_)
return param_child_->find(r, c);
return end();
}

V v_;
std::unordered_map<std::string_view, drt_node*> children_;
drt_node* param_child_ = nullptr; // cached {{param}} child for O(1) lookup
drt_node_pool<drt_node>& pool_;
};

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