Page names kept in RAM: /api/pages 1.8 s -> 1.05 s

Measured on the display with 16 pages: listing the directory took 350 ms,
and every loadPage() first asked LittleFS whether the file exists (26 ms
each) before opening it (25 ms) and reading it (11 ms); drawing all
previews took only 29 ms. The names of the stored pages are now kept
until a page is saved or deleted, and storedPage() looks there instead
of calling exists().

Version 2.19.1, tested on the display over OTA (save, list, delete).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/esp32/config.h

@@ -118,7 +118,7 @@ const uint32_t SETUP_AP_DELAY = 20000;        // open the AP when WiFi fails thi
 const uint32_t WIFI_CONNECT_TIMEOUT = 30000;
 const uint32_t WIFI_RESTART_TIME = 10UL * 60 * 1000;
 
-#define FIRMWARE_VERSION "2.19.0"
+#define FIRMWARE_VERSION "2.19.1"
 
 // Home Assistant device id (do not change: Home Assistant's entities are linked to it)
 const uint8_t HA_DEVICE_ID[] = {0x34, 0x86, 0x5d, 0x3a, 0x08, 0x28};

src/esp32/display/page_store.cpp

@@ -25,9 +25,29 @@ static String path(const char *name)
 	return String(DIR) + "/" + name + EXTENSION;
 }
 
+// The names of the stored pages, kept until a page is saved or deleted: listing the
+// directory takes about 350 ms with 16 pages, and each exists() about 25 ms
+static std::vector<String> names;
+static bool names_valid = false;
+
+static const std::vector<String> &storedPageNames()
+{
+	if (!names_valid)
+	{
+		names = bitmapStorageAvailable() ? storedNames(DIR, EXTENSION) : std::vector<String>();
+		names_valid = true;
+	}
+	return names;
+}
+
 static bool storedPage(const char *name)
 {
-	return bitmapStorageAvailable() && validBitmapName(name) && LittleFS.exists(path(name));
+	if (!bitmapStorageAvailable() || !validBitmapName(name))
+		return false;
+	for (const String &stored : storedPageNames())
+		if (stored == name) // like exists(): the file names are case-sensitive
+			return true;
+	return false;
 }
 
 void pageStoreBegin()
@@ -48,7 +68,7 @@ std::vector<PageInfo> listPages()
 	for (int i = 0; i < builtinPageCount(); i++)
 		if (!storedPage(builtinPageName(i)))
 			list.push_back({builtinPageName(i), true, false});
-	for (const String &name : storedNames(DIR, EXTENSION))
+	for (const String &name : storedPageNames())
 		list.push_back({name, false, builtinPageName(name.c_str()) != nullptr});
 	return list;
 }
@@ -99,7 +119,7 @@ const char *savePage(const char *name, const DynamicPage &page)
 		return error;
 	if (!bitmapStorageAvailable())
 		return "No storage (install the new flash layout over USB, see README)";
-	if (!LittleFS.exists(path(name)) && storedNames(DIR, EXTENSION).size() >= (size_t)MAX_PAGES)
+	if (!storedPage(name) && storedPageNames().size() >= (size_t)MAX_PAGES)
 		return "Too many pages, delete some first";
 
 	StoredPage *stored = new StoredPage;
@@ -112,6 +132,7 @@ const char *savePage(const char *name, const DynamicPage &page)
 		file.close();
 	delete stored;
 	revision++;
+	names_valid = false;
 	return ok ? nullptr : "Could not write the file (storage full?)";
 }
 
@@ -121,7 +142,9 @@ const char *deletePage(const char *name)
 		return "Built-in pages can't be deleted";
 	if (!storedPage(name))
 		return "Page not found";
-	if (!LittleFS.remove(path(name)))
+	bool removed = LittleFS.remove(path(name));
+	names_valid = false;
+	if (!removed)
 		return "Could not delete the file";
 	revision++;
 	return nullptr;
@@ -132,7 +155,9 @@ template <typename F> static String findPage(F uses)
 {
 	DynamicPage *page = new DynamicPage;
 	String found;
-	for (const String &name : storedNames(DIR, EXTENSION))
+	// A copy: loadPage() may list the directory again
+	std::vector<String> list = storedPageNames();
+	for (const String &name : list)
 		if (loadPage(name.c_str(), *page) && uses(*page))
 		{
 			found = name;