Add config component with hostname setting

components/config/config.h

@@ -0,0 +1,54 @@
+/*
+ * SPDX-License-Identifier: AGPL-3.0-only
+ * Copyright (c) Camden Dixie O'Brien
+ */
+
+#ifndef CONFIG_H
+#define CONFIG_H
+
+#include <stddef.h>
+
+#define MAX_HOSTNAME_SIZE 32
+
+/**
+ * Callback type for consumers of string settings.
+ */
+typedef void (*ConfigStringCallback)(const char *value);
+
+/**
+ * Initialize the configuration module.
+ *
+ * If there is a saved configuration, it will be loaded. Otherwise,
+ * the default configuration will be loaded and saved.
+ */
+void config_init();
+
+/**
+ * Set the device's hostname.
+ *
+ * The argument should be a null-terminated string. If the maximum
+ * length is exceeded, the value will still be used, but will be
+ * truncated.
+ */
+void config_set_hostname(const char *hostname);
+
+/**
+ * Write the device's hostname into the given buffer.
+ *
+ * The length of the hostname is returned. If the value's size exceeds
+ * the size of the buffer, nothing will be written to the buffer but
+ * the length is still returned.
+ */
+size_t config_get_hostname(char *buffer, size_t buffer_size);
+
+/**
+ * Add a callback for hostname updates.
+ *
+ * The function specified in the argument will be invoked whenever a
+ * the hostname is updated, with the new value as its argument. The
+ * 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);
+
+#endif