clean up and document the telopt table stuff

README

@@ -53,19 +53,60 @@ interface.
 
 IIa. Initialization
 
- struct telnet_t;
-   This structure represents the state of the TELNET protocol for a
-   single connection.  Each connection utilizing TELNET must have its
-   own telnet_t structure, which is passed to all libtelnet API
-   calls.
+ Using libtelnet requires the initialization of a telnet_t structure
+ which stores all current state for a single TELNET connection.
 
- void telnet_init(telnet_t *telnet, telnet_event_handler_t handler,
-     unsigned char flags, void *user_data);
+ Initializing a telnet_t structure requires several pieces of data.
+ One of these is the telopt support table, which specifies which
+ TELNET options your application supports both locally and remotely.
+ This table is comprised of telnet_telopt_t structures, one for each
+ supported option.  Each entry specifies the option supported,
+ whether the option is supported locally or remotely.
+
+  struct telnet_telopt_t {
+    short telopt;
+    unsigned char us;
+    unsigned char him;
+  };
+
+ The us field denotes whether your application supporst the telopt
+ locally.  It should be set to TELNET_WILL if you support it and to
+ TELNET_WONT if you don't.  The him field denotes whether the telopt
+ is supported on the remote end, and should be TELNET_DO if yes and
+ TELNET_DONT if not.
+
+ When definition the telopt table you must include an end marker
+ entry, which is simply an entry with telopt set to -1.  For
+ example:
+
+  static const telnet_telopt_t my_telopts[] = {
+    { TELNET_TELOPT_ECHO,      TELNET_WILL, TELNET_DONT },
+    { TELNET_TELOPT_TTYPE,     TELNET_WILL, TELNET_DONT },
+    { TELNET_TELOPT_COMPRESS2, TELNET_WONT, TELNET_DO   },
+    { TELNET_TELOPT_ZMP,       TELNET_WONT, TELNET_DO   },
+    { TELNET_TELOPT_MSSP,      TELNET_WONT, TELNET_DO   },
+    { TELNET_TELOPT_BINARY,    TELNET_WILL, TELNET_DO   },
+    { TELNET_TELOPT_NAWS,      TELNET_WILL, TELNET_DONT },
+    { -1, 0, 0 }
+  };
+ 
+ If you need to dynamically alter supported options on a
+ per-connection basis then you may use a different tables
+ (dynamically allocated if necessary) per call to telnet_init() or
+ you share a single constant table like the above example between
+ all connections if you support a fixed set of options.  Most
+ applications will support only a fixed set of options.
+
+ void telnet_init(telnet_t *telnet, const telnet_telopts_t *telopts,
+     telnet_event_handler_t handler, unsigned char flags,
+     void *user_data);
    The telnet_init() function is responsible for initializing the
    data in a telnet_t structure.  It must be called immediately after
    establishing a connection and before any other libtelnet API calls
    are made.
 
+   The telopts field is the telopt support table as described above.
+
    The handler parameter must be a function matching the
    telnet_event_handler_t definition.  More information about events
    can be found in section IId.

libtelnet.c

@@ -188,9 +188,16 @@ static INLINE int _check_telopt(telnet_t *telnet, unsigned char telopt,
 		return 0;
 
 	/* loop unti found or end marker (us and him both 0) */
-	for (i = 0; telnet->telopts[i].telopt != -1; ++i)
-		if (telnet->telopts[i].telopt == telopt)
-			return us ? telnet->telopts[i].us : telnet->telopts[i].him;
+	for (i = 0; telnet->telopts[i].telopt != -1; ++i) {
+		if (telnet->telopts[i].telopt == telopt) {
+			if (us && telnet->telopts[i].us == TELNET_WILL)
+				return 1;
+			else if (!us && telnet->telopts[i].him == TELNET_DO)
+				return 1;
+			else
+				return 0;
+		}
+	}
 
 	/* not found, so not supported */
 	return 0;

libtelnet.h

@@ -24,7 +24,6 @@ typedef struct telnet_telopt_t telnet_telopt_t;
 #define TELNET_WONT 252
 #define TELNET_WILL 251
 #define TELNET_SB 250
-#define TELNET_SB 250
 #define TELNET_GA 249
 #define TELNET_EL 248
 #define TELNET_EC 247
@@ -153,8 +152,9 @@ typedef void (*telnet_event_handler_t)(telnet_t *telnet,
 
 /* telopt support table element; use telopt of -1 for end marker */
 struct telnet_telopt_t {
-	short telopt;
-	short us:1, him:1;
+	short telopt; /* one of the TELOPT codes or -1 */
+	unsigned char us; /* TELNET_WILL or TELNET_WONT */
+	unsigned char him; /* TELNET_DO or TELNET_DONT */
 };
 
 /* state tracker */

telnet-chatd.c

@@ -29,6 +29,11 @@
 #define MAX_USERS 64
 #define LINEBUFFER_SIZE 256
 
+const telnet_telopt_t telopts[] = {
+	{ TELNET_TELOPT_COMPRESS2,	TELNET_WILL, TELNET_DONT },
+	{ -1, 0, 0 }
+};
+
 struct user_t {
 	char *name;
 	int sock;
@@ -291,7 +296,8 @@ int main(int argc, char **argv) {
 
 			/* init, welcome */
 			users[i].sock = rs;
-			telnet_init(&users[i].telnet, 0, _event_handler, 0, &users[i]);
+			telnet_init(&users[i].telnet, telopts, _event_handler, 0,
+					&users[i]);
 			telnet_negotiate(&users[i].telnet, TELNET_WILL,
 					TELNET_TELOPT_COMPRESS2);
 			telnet_printf(&users[i].telnet, "Enter name: ");

telnet-client.c

@@ -33,9 +33,9 @@ static telnet_t telnet;
 static int do_echo;
 
 static const telnet_telopt_t telopts[] = {
-	{ TELNET_TELOPT_ECHO, 0, 1 },
- 	{ TELNET_TELOPT_COMPRESS2, 0, 1 },
-	{ TELNET_TELOPT_TTYPE, 1, 0 },
+	{ TELNET_TELOPT_ECHO,		TELNET_WONT, TELNET_DO   },
+	{ TELNET_TELOPT_COMPRESS2,	TELNET_WONT, TELNET_DO   },
+	{ TELNET_TELOPT_TTYPE,		TELNET_WILL, TELNET_DONT },
 	{ -1, 0, 0 }
 };