Team2890/allwpilib
4
0
Fork 0
mirror of https://github.com/wpilibsuite/allwpilib synced 2026-06-22 01:11:42 +00:00
Code Issues Packages Projects Releases Wiki Activity

Change UidVector to be LRU with a reuse threshold. (#29)

Browse Source 
This keeps indexes from being instantly reused and reduces the risk of
accidentally using an old index.

Also change erase and emplace_back to return 0-based instead of 1-based
indexes.

This is a breaking change, but a noisy one due to the template parameter
change.
This commit is contained in:
Peter Johnson
2017-09-06 19:54:58 -07:00
committed by GitHub
parent c3f7c85f8a
commit 041563f8ea
1 changed files with 18 additions and 11 deletions
Download Patch File Download Diff File Expand all files Collapse all files

29
src/main/native/include/support/UidVector.h
View File

@@ -14,44 +14,51 @@ namespace wpi {
// Vector which provides an integrated freelist for removal and reuse of
// individual elements.
template <typename T>
// @tparam T element type; must be default-constructible and evaluate in
// boolean context to false when "empty"
// @tparam reuse_threshold how many free elements to store up before starting
// to recycle them
template <typename T, typename std::vector<T>::size_type reuse_threshold>
class UidVector {
public:
typedef typename std::vector<T>::size_type size_type;
bool empty() const { return m_active_count == 0; }
size_type size() const { return m_vector.size(); }
T& operator[](size_type i) { return m_vector[i]; }
const T& operator[](size_type i) const { return m_vector[i]; }
// Add a new T to the vector. If there are elements on the freelist,
// reuses the last one; otherwise adds to the end of the vector.
// Returns the resulting element index (+1).
// Returns the resulting element index.
template <class... Args>
unsigned int emplace_back(Args&&... args) {
unsigned int uid;
if (m_free.empty()) {
size_type emplace_back(Args&&... args) {
size_type uid;
if (m_free.size() < reuse_threshold) {
uid = m_vector.size();
m_vector.emplace_back(std::forward<Args>(args)...);
} else {
uid = m_free.back();
m_free.pop_back();
uid = m_free.front();
m_free.erase(m_free.begin());
m_vector[uid] = T(std::forward<Args>(args)...);
}
return uid + 1;
++m_active_count;
return uid;
}
// Removes the identified element by replacing it with a default-constructed
// one. The element is added to the freelist for later reuse.
void erase(unsigned int uid) {
--uid;
void erase(size_type uid) {
if (uid >= m_vector.size() || !m_vector[uid]) return;
m_free.push_back(uid);
m_vector[uid] = T();
--m_active_count;
}
private:
std::vector<T> m_vector;
std::vector<unsigned int> m_free;
std::vector<size_type> m_free;
size_type m_active_count{0};
};
} // namespace wpi