[util] Add big-endian long msg read/write

And improve the generated code as well (ie, use a code sequence that gcc
recognizes and optimizes to a single 32-bit read and a byte-swap).

nq uses big-endian for its packet headers (arg, though it is consistent
with IP, it's not with the rest of quake).

include/QF/msg.h

@@ -37,6 +37,7 @@
 void MSG_WriteByte (sizebuf_t *sb, int c);
 void MSG_WriteShort (sizebuf_t *sb, int c);
 void MSG_WriteLong (sizebuf_t *sb, int c);
+void MSG_WriteLongBE (sizebuf_t *sb, int c);
 void MSG_WriteFloat (sizebuf_t *sb, float f);
 void MSG_WriteString (sizebuf_t *sb, const char *s);
 void MSG_WriteBytes (sizebuf_t *sb, const void *buf, int len);
@@ -108,6 +109,19 @@ int MSG_ReadShort (qmsg_t *msg);
 */
 int MSG_ReadLong (qmsg_t *msg);
 
+/** Read a single big-endian long from the message.
+
+	Advances the read index.
+
+	\param msg		The message from which the long will be read.
+	\return			The signed long value or -1 if already at the end of
+					the message.
+	\note	-1 may be either an error or a value. Check qmsg_t::badread to
+			differentiate the two cases (false for a value).
+	\todo	Fix?
+*/
+int MSG_ReadLongBE (qmsg_t *msg);
+
 /** Read a single little-endian float from the message.
 
 	Advances the read index.

libs/util/msg.c

@@ -80,6 +80,18 @@ MSG_WriteLong (sizebuf_t *sb, int c)
 	*buf = ((unsigned int) c) >> 24;
 }
 
+VISIBLE void
+MSG_WriteLongBE (sizebuf_t *sb, int c)
+{
+	byte	   *buf;
+
+	buf = SZ_GetSpace (sb, 4);
+	*buf++ = ((unsigned int) c) >> 24;
+	*buf++ = (((unsigned int) c) >> 16) & 0xff;
+	*buf++ = (((unsigned int) c) >> 8) & 0xff;
+	*buf = ((unsigned int) c) & 0xff;
+}
+
 VISIBLE void
 MSG_WriteFloat (sizebuf_t *sb, float f)
 {
@@ -269,10 +281,30 @@ MSG_ReadLong (qmsg_t *msg)
 	int         c;
 
 	if (msg->readcount + 4 <= msg->message->cursize) {
-		c = msg->message->data[msg->readcount]
+		byte       *buf = msg->message->data + msg->readcount;
-			+ (msg->message->data[msg->readcount + 1] << 8)
+		c = *buf++;
-			+ (msg->message->data[msg->readcount + 2] << 16)
+		c |= (*buf++) << 8;
-			+ (msg->message->data[msg->readcount + 3] << 24);
+		c |= (*buf++) << 16;
+		c |= (*buf) << 24;
+		msg->readcount += 4;
+		return c;
+	}
+	msg->readcount = msg->message->cursize;
+	msg->badread = true;
+	return -1;
+}
+
+VISIBLE int
+MSG_ReadLongBE (qmsg_t *msg)
+{
+	int         c;
+
+	if (msg->readcount + 4 <= msg->message->cursize) {
+		byte       *buf = msg->message->data + msg->readcount;
+		c = (*buf++) << 24;
+		c |= (*buf++) << 16;
+		c |= (*buf++) << 8;
+		c |= *buf;
 		msg->readcount += 4;
 		return c;
 	}