Restructure config module for easier addition of items

components/config/config.c

@@ -15,28 +15,28 @@
 #define TAG "Config"
 
 #define NAMESPACE "config"
-#define MAX_CONSUMERS 8
+#define MAX_CALLBACKS 8
 
-#define DEFAULT_HOSTNAME "bedside-clock"
+typedef enum {
-#define HOSTNAME_KEY "hostname"
+	HOSTNAME,
+	ITEM_COUNT,
+} ItemIndex;
 
 typedef struct {
-	char hostname[MAX_HOSTNAME_SIZE];
+	const char *id;
-} Config;
+	const char *default_value;
+	char value[CONFIG_MAX_VALUE_SIZE];
+	struct {
+		ConfigCallback funcs[MAX_CALLBACKS];
+		unsigned count;
+	} callbacks;
+} Item;
 
-typedef struct {
+static Item state[ITEM_COUNT] = {
-	ConfigStringCallback callbacks[MAX_CONSUMERS];
+	[HOSTNAME] = { .id = "hostname", .default_value = "bedside-clock" },
-	unsigned count;
+};
-} StringConsumers;
 
-typedef struct {
+static bool load(ItemIndex item)
-	Config config;
-	StringConsumers hostname_consumers;
-} State;
-
-static State state;
-
-static bool load_hostname()
 {
 	esp_err_t error;
 
@@ -49,10 +49,12 @@ static bool load_hostname()
 		return false;
 	}
 
-	size_t size = MAX_HOSTNAME_SIZE;
+	size_t size = CONFIG_MAX_VALUE_SIZE;
-	error = nvs_get_str(handle, HOSTNAME_KEY, state.config.hostname, &size);
+	error = nvs_get_str(handle, state[item].id, state[item].value, &size);
 	if (error != ESP_OK) {
-		ESP_LOGE(TAG, "Error loading hostname from storage: %04x", error);
+		ESP_LOGE(
+		    TAG, "Error loading %s from storage: %04x", state[item].id,
+		    error);
 		nvs_close(handle);
 		return false;
 	}
@@ -61,7 +63,7 @@ static bool load_hostname()
 	return true;
 }
 
-static void save_hostname()
+static void save(ItemIndex item)
 {
 	esp_err_t error;
 
@@ -74,9 +76,11 @@ static void save_hostname()
 		return;
 	}
 
-	error = nvs_set_str(handle, HOSTNAME_KEY, state.config.hostname);
+	error = nvs_set_str(handle, state[item].id, state[item].value);
 	if (error != ESP_OK) {
-		ESP_LOGE(TAG, "Error loading hostname from storage: %04x", error);
+		ESP_LOGE(
+		    TAG, "Error loading %s from storage: %04x", state[item].id,
+		    error);
 		nvs_close(handle);
 		return;
 	}
@@ -88,6 +92,58 @@ static void save_hostname()
 	nvs_close(handle);
 }
 
+static void set(ItemIndex item, const char *value)
+{
+	if (value == NULL) {
+		ESP_LOGW(
+		    TAG, "Attempt to set %s to null pointer; ignored",
+		    state[item].id);
+		return;
+	}
+
+	size_t len = strlen(value);
+	if (len >= CONFIG_MAX_VALUE_SIZE) {
+		ESP_LOGW(
+		    TAG, "%s value \"%s\" exceeds maximum size; truncated",
+		    state[item].id, value);
+		len = CONFIG_MAX_VALUE_SIZE - 1;
+	}
+
+	memcpy(state[item].value, value, len);
+	state[item].value[len] = '\0';
+
+	save(item);
+	for (unsigned i = 0; i < state[item].callbacks.count; ++i)
+		state[item].callbacks.funcs[i](state[item].value);
+}
+
+static size_t get(ItemIndex item, char *buffer, size_t buffer_size)
+{
+	size_t len = strlen(state[item].value);
+	if (len < buffer_size) {
+		memcpy(buffer, state[item].value, len);
+		buffer[len] = '\0';
+	}
+	return len;
+}
+
+static void add_callback(ItemIndex item, ConfigCallback callback)
+{
+	if (callback == NULL) {
+		ESP_LOGW(
+		    TAG, "Attempt to add null callback for %s; ignored",
+		    state[item].id);
+	} else if (state[item].callbacks.count >= MAX_CALLBACKS) {
+		ESP_LOGE(
+		    TAG, "Max callbacks exceeded for %s; callback discarded",
+		    state[item].id);
+	} else {
+		const unsigned pos = state[item].callbacks.count;
+		state[item].callbacks.funcs[pos] = callback;
+		++state[item].callbacks.count;
+	}
+}
+
 void config_init()
 {
 	esp_err_t error;
@@ -104,56 +160,25 @@ void config_init()
 		FATAL();
 	}
 
-	memset(&state, 0, sizeof(state));
+	for (ItemIndex item = (ItemIndex)0; item < ITEM_COUNT; ++item) {
-
+		if (!load(item)) {
-	if (!load_hostname()) {
+			set(item, state[item].default_value);
-		config_set_hostname(DEFAULT_HOSTNAME);
+			save(item);
-		save_hostname();
+		}
 	}
 }
 
 void config_set_hostname(const char *hostname)
 {
-	if (hostname == NULL) {
+	set(HOSTNAME, hostname);
-		ESP_LOGW(TAG, "Null pointer passed to %s(); ignored", __func__);
-		return;
-	}
-	size_t len = strlen(hostname);
-	if (len >= MAX_HOSTNAME_SIZE) {
-		ESP_LOGW(
-		    TAG, "Hostname \"%s\" exceeds maximum size; truncated",
-		    hostname);
-		len = MAX_HOSTNAME_SIZE - 1;
-	}
-
-	memcpy(state.config.hostname, hostname, len);
-	state.config.hostname[len] = '\0';
-
-	save_hostname();
-
-	for (unsigned i = 0; i < state.hostname_consumers.count; ++i)
-		state.hostname_consumers.callbacks[i](state.config.hostname);
 }
 
 size_t config_get_hostname(char *buffer, size_t buffer_size)
 {
-	size_t len = strlen(state.config.hostname);
+	return get(HOSTNAME, buffer, buffer_size);
-	if (len < buffer_size) {
-		memcpy(buffer, state.config.hostname, len);
-		buffer[len] = '\0';
-	}
-	return len;
 }
 
-void config_add_hostname_consumer(ConfigStringCallback callback)
+void config_add_hostname_callback(ConfigCallback callback)
 {
-	if (callback == NULL) {
+	add_callback(HOSTNAME, callback);
-	} else if (state.hostname_consumers.count >= MAX_CONSUMERS) {
-		ESP_LOGE(
-		    TAG, "Max consumers exceeded for hostname; callback discarded");
-	} else {
-		state.hostname_consumers.callbacks[state.hostname_consumers.count]
-		    = callback;
-		++state.hostname_consumers.count;
-	}
 }

components/config/config.h

@@ -8,12 +8,12 @@
 
 #include <stddef.h>
 
-#define MAX_HOSTNAME_SIZE 32
+#define CONFIG_MAX_VALUE_SIZE 32U
 
 /**
- * Callback type for consumers of string settings.
+ * Callback type for config updates
  */
-typedef void (*ConfigStringCallback)(const char *value);
+typedef void (*ConfigCallback)(const char *value);
 
 /**
  * Initialize the configuration module.
@@ -21,7 +21,7 @@ typedef void (*ConfigStringCallback)(const char *value);
  * If there is a saved configuration, it will be loaded. Otherwise,
  * the default configuration will be loaded and saved.
  */
-void config_init();
+void config_init(void);
 
 /**
  * Set the device's hostname.
@@ -49,6 +49,6 @@ size_t config_get_hostname(char *buffer, size_t buffer_size);
  * lifetime of the passed argument will be static, but the value may
  * be modified once the callback returns.
  */
-void config_add_hostname_callback(ConfigStringCallback callback);
+void config_add_hostname_callback(ConfigCallback callback);
 
 #endif