common/capstr.c

   1 /***********************************************************************
   2  Freeciv - Copyright (C) 1996 - A Kjeldberg, L Gregersen, P Unold
   3    This program is free software; you can redistribute it and/or modify
   4    it under the terms of the GNU General Public License as published by
   5    the Free Software Foundation; either version 2, or (at your option)
   6    any later version.
   7
   8    This program is distributed in the hope that it will be useful,
   9    but WITHOUT ANY WARRANTY; without even the implied warranty of
  10    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  11    GNU General Public License for more details.
  12 ***********************************************************************/
  13
  14 #ifdef HAVE_CONFIG_H
  15 #include <fc_config.h>
  16 #endif
  17
  18 #include <stdlib.h>             /* getenv() */
  19
  20 /* utility */
  21 #include "support.h"
  22
  23 /* common */
  24 #include "connection.h"         /* MAX_LEN_CAPSTR */
  25
  26 #include "capstr.h"
  27
  28 static char our_capability_internal[MAX_LEN_CAPSTR];
  29 const char * const our_capability = our_capability_internal;
  30
  31 /* Capabilities: original author: Mitch Davis (mjd@alphalink.com.au)
  32  *
  33  * The capability string is a string clients and servers trade to find
  34  * out if they can talk to each other, and using which protocol version,
  35  * and which features and behaviors to expect.  The string is a list of
  36  * words, separated by whitespace and/or commas, where each word indicates
  37  * a capability that this version of Freeciv understands.
  38  * If a capability word is mandatory, it should start with a "+".
  39  *
  40  * eg, #define CAPABILITY "+1.6, MapScroll, +AutoSettlers"
  41  *
  42  * Client and server functions can test these strings for a particular
  43  * capability by calling the functions in capability.c
  44  *
  45  * Each executable has a string our_capability (above), which gives the
  46  * capabilities of the running executable.  This is normally initialised
  47  * with CAPABILITY, but can be changed at run-time by setting the
  48  * FREECIV_CAPS environment variable, though that is probably mainly
  49  * useful for testing purposes.
  50  *
  51  * For checking the connections of other executables, each
  52  * "struct connection" has a capability string, which gives the
  53  * capability of the executable at the other end of the connection.
  54  * So for the client, the capability of the server is in
  55  * client.conn.capability, and for the server, the capabilities of
  56  * connected clients are in player_by_number(i)->conn.capability
  57  * The client now also knows the capabilities of other clients,
  58  * via player_by_number(i)->conn.capability.
  59  *
  60  * Note the connection struct is a parameter to the functions to send and
  61  * receive packets, which may be convenient for adjusting how a packet is
  62  * sent or interpreted based on the capabilities of the connection.
  63  *
  64  * At the time of a major release, the capability string may be
  65  * simplified; eg, the example string above could be replaced by "+1.7".
  66  * (This should probably only happen if a mandatory capability has
  67  * been introduced since the previous release.)
  68  * Whoever makes such a change has responsibility to search the Freeciv
  69  * code, and look for places where people are using has_capability.
  70  * If you're taking a capability out of the string, because now every
  71  * client and server supports it, then you should take out the
  72  * if (has_capability()) code so that this code is always executed.
  73  *
  74  * (The savefile and ruleset files have strings which are used similarly,
  75  * and checked by the same has_capability function, but the strings there
  76  * are not directly related to the capability strings discussed here.)
  77  *
  78  * The actual capability string is now defined in fc_version.
  79  */
  80
  81 /**************************************************************************
  82   Setup our internal network capability string.
  83 **************************************************************************/
  84 void init_our_capability(void)
  85 {
  86   const char *s;
  87
  88   s = getenv("FREECIV_CAPS");
  89   if (!s) {
  90     s = NETWORK_CAPSTRING;
  91   }
  92   sz_strlcpy(our_capability_internal, s);
  93 }