AP_Menu: dynamically allocate the menu buffers

this saves memory when the menus are not used, and allows for the
commandline and argument limits to be changed

libraries/AP_Menu/AP_Menu.cpp

@@ -17,8 +17,8 @@
 extern const AP_HAL::HAL& hal;
 
 // statics
-char Menu::_inbuf[MENU_COMMANDLINE_MAX];
-Menu::arg Menu::_argv[MENU_ARGS_MAX + 1];
+char *Menu::_inbuf;
+Menu::arg *Menu::_argv;
 AP_HAL::BetterStream *Menu::_port;
 
 
@@ -27,8 +27,14 @@ Menu::Menu(const prog_char *prompt, const Menu::command *commands, uint8_t entri
     _prompt(prompt),
     _commands(commands),
     _entries(entries),
-    _ppfunc(ppfunc)
+    _ppfunc(ppfunc),
+    _commandline_max(MENU_COMMANDLINE_MAX),
+    _args_max(MENU_ARGS_MAX)
 {
+    // the buffers are initially NULL, then they are allocated on
+    // first use
+    _inbuf = NULL;
+    _argv = NULL;
 }
 
 // run the menu
@@ -46,6 +52,8 @@ Menu::run(void)
 		_port = hal.console;
 	}
 
+    _allocate_buffers();
+
     // loop performing commands
     for (;;) {
 
@@ -168,3 +176,34 @@ Menu::_call(uint8_t n, uint8_t argc)
     fn = (func)pgm_read_pointer(&_commands[n].func);
     return(fn(argc, &_argv[0]));
 }
+
+/**
+   set limits on max args and command line length
+*/
+void
+Menu::set_limits(uint8_t commandline_max, uint8_t args_max)
+{
+    if (_inbuf != NULL) {
+        delete[] _inbuf;
+        _inbuf = NULL;
+    }
+    if (_argv != NULL) {
+        delete[] _argv;
+        _argv = NULL;
+    }
+    // remember limits, the buffers will be allocated by allocate_buffers()
+    _commandline_max = commandline_max;
+    _args_max = args_max;
+}
+
+void
+Menu::_allocate_buffers(void)
+{
+    /* only allocate if the buffers are NULL */
+    if (_inbuf == NULL) {
+        _inbuf = new char[_commandline_max];
+    }
+    if (_argv == NULL) {
+        _argv = new arg[_args_max+1];
+    }
+}

libraries/AP_Menu/AP_Menu.h

@@ -103,6 +103,9 @@ public:
     ///
     Menu(const char *prompt, const struct command *commands, uint8_t entries, preprompt ppfunc = 0);
 
+    /// set command line length limit
+    void set_limits(uint8_t commandline_max, uint8_t args_max);
+
     /// menu runner
     void        run(void);
 
@@ -123,8 +126,14 @@ private:
     const uint8_t           _entries;                                                   ///< size of the menu
     const preprompt         _ppfunc;                                                    ///< optional pre-prompt action
 
-    static char             _inbuf[MENU_COMMANDLINE_MAX];       ///< input buffer
-    static arg              _argv[MENU_ARGS_MAX + 1];                   ///< arguments
+    static char             *_inbuf;       ///< input buffer
+    static arg              *_argv;       ///< arguments
+
+    uint8_t                 _commandline_max;
+    uint8_t                 _args_max;
+
+    // allocate inbuf and args buffers
+    void _allocate_buffers(void);
 
 	// port to run on
 	static AP_HAL::BetterStream  *_port;