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[wifi] Replace std::stable_sort with insertion sort to save 2.4KB flash (#10037)

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J. Nick Koston 2025-08-03 16:19:24 -10:00 committed by GitHub
parent 9aad0733ef
commit ef372eeeb7
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1 changed files with 50 additions and 24 deletions
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74
esphome/components/wifi/wifi_component.cpp
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@ -505,6 +505,54 @@ void WiFiComponent::start_scanning() {
this->state_ = WIFI_COMPONENT_STATE_STA_SCANNING;
}
// Helper function for WiFi scan result comparison
// Returns true if 'a' should be placed before 'b' in the sorted order
[[nodiscard]] inline static bool wifi_scan_result_is_better(const WiFiScanResult &a, const WiFiScanResult &b) {
// Matching networks always come before non-matching
if (a.get_matches() && !b.get_matches())
return true;
if (!a.get_matches() && b.get_matches())
return false;
if (a.get_matches() && b.get_matches()) {
// For APs with the same SSID, always prefer stronger signal
// This helps with mesh networks and multiple APs
if (a.get_ssid() == b.get_ssid()) {
return a.get_rssi() > b.get_rssi();
}
// For different SSIDs, check priority first
if (a.get_priority() != b.get_priority())
return a.get_priority() > b.get_priority();
// If priorities are equal, prefer stronger signal
return a.get_rssi() > b.get_rssi();
}
// Both don't match - sort by signal strength
return a.get_rssi() > b.get_rssi();
}
// Helper function for insertion sort of WiFi scan results
// Using insertion sort instead of std::stable_sort saves flash memory
// by avoiding template instantiations (std::rotate, std::stable_sort, lambdas)
// IMPORTANT: This sort is stable (preserves relative order of equal elements)
static void insertion_sort_scan_results(std::vector<WiFiScanResult> &results) {
const size_t size = results.size();
for (size_t i = 1; i < size; i++) {
// Make a copy to avoid issues with move semantics during comparison
WiFiScanResult key = results[i];
int32_t j = i - 1;
// Move elements that are worse than key to the right
// For stability, we only move if key is strictly better than results[j]
while (j >= 0 && wifi_scan_result_is_better(key, results[j])) {
results[j + 1] = results[j];
j--;
}
results[j + 1] = key;
}
}
void WiFiComponent::check_scanning_finished() {
if (!this->scan_done_) {
if (millis() - this->action_started_ > 30000) {
@ -535,30 +583,8 @@ void WiFiComponent::check_scanning_finished() {
}
}
std::stable_sort(this->scan_result_.begin(), this->scan_result_.end(),
[](const WiFiScanResult &a, const WiFiScanResult &b) {
// return true if a is better than b
if (a.get_matches() && !b.get_matches())
return true;
if (!a.get_matches() && b.get_matches())
return false;
if (a.get_matches() && b.get_matches()) {
// For APs with the same SSID, always prefer stronger signal
// This helps with mesh networks and multiple APs
if (a.get_ssid() == b.get_ssid()) {
return a.get_rssi() > b.get_rssi();
}
// For different SSIDs, check priority first
if (a.get_priority() != b.get_priority())
return a.get_priority() > b.get_priority();
// If priorities are equal, prefer stronger signal
return a.get_rssi() > b.get_rssi();
}
return a.get_rssi() > b.get_rssi();
});
// Sort scan results using insertion sort for better memory efficiency
insertion_sort_scan_results(this->scan_result_);
for (auto &res : this->scan_result_) {
char bssid_s[18];