Initial revision.

utils/TerraSync/Makefile.am

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+bin_PROGRAMS = terrasync
+
+terrasync_SOURCES = terrasync.cxx
+
+terrasync_LDADD = -lplibnet -lplibul

utils/TerraSync/README.txt

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+TerraSync
+=========
+
+Usage:
+
+    terrasync -p <port> [ -s <rsync_source> ] -d <rsync_dest>
+
+Example:
+
+    $ fgfs --atlas=socket,out,1,localhost,5500,udp --fg-scenery=/data1/Scenery-0.7.9
+    $ nice terrasync -p 5500 -d /data1/Scenery-0.7.9
+
+Requirements:
+
+    - rsync util installed in your path.
+    - mkdir util installed in your path.
+
+TerraSync is a utility that is intended to run as a light weight
+background process.  It's purpose is to monitor the position of a
+FlightGear flight and pre-fetch scenery tiles from a remote server
+based on the current FlightGear position.
+
+This allows you to do a base install of FlightGear with no add on
+scenery.  Now just go and fly anywhere.  Scenery is fetched "just in
+time" and accumulated on your HD so it is already there next time you
+fly.  You can fly anywhere and essentially just the scenery you need
+is auto-installed as you fly.
+
+Terrasync runs as a separate process and expects the --atlas=port
+format to be sent from fgfs.  The fgfs output tells the terrasync util
+where FlightGear is currently flying.  Terrasync will then issue the
+appropriate commands to rsync the surrounding areas to your local
+scenery directory.  The user need to choose a port for
+FlightGear->TerraSync communication and then specify the server
+location and destation scenery tree.
+
+As you fly, terrasync will periodically refresh and pull any new
+scenery tiles that you need for your position from the server.
+
+This also works if the scenery on the scenery server is updated.
+Rsync will pull any missing files, or any updated files.
+
+There is a chicken/egg problem when you first start up in a brand new
+area.  FlightGear is expecting the scenery to be there *now* but it
+may not have been fetched yet.  I suppose without making a more
+complex protocol, the user will need to be aware of this.  The user
+could restart flightgear after the initial rsync completes, and then
+after that everything should be good, assuming the flight track is
+"continuous" and the user has the necessary bandwidth to keep up with
+flight speeds.
+
+Final notes:
+
+I have set up an initial scenery server at
+baron.flightgear.org::Scenery-0.7.9.  This is the 0.7.9 vintage
+scenery with airports rebuilt to include lighting.  Alex Perry also
+has a partial rsync server, but I don't know it's current status.
+William Riley has rebuilt the entire world, but the tiles are zipped
+in 10x10 degree chunks on on a relatively low bandwidth connection.
+There are aspects of the 0.7.9 scenery I like including the quality of
+the terrain, but William scenery has roads and streams which is also
+nice.

utils/TerraSync/terrasync.cxx

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+// terrasync.cxx -- "JIT" scenery fetcher
+//
+// Written by Curtis Olson, started November 2002.
+//
+// Copyright (C) 2002  Curtis L. Olson  - curt@flightgear.org
+//
+// This program is free software; you can redistribute it and/or
+// modify it under the terms of the GNU General Public License as
+// published by the Free Software Foundation; either version 2 of the
+// License, or (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful, but
+// WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+// General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program; if not, write to the Free Software
+// Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+//
+// $Id$
+
+
+#include <stdlib.h>             // atoi() atof() abs() system()
+
+#include <simgear/compiler.h>
+
+#include STL_IOSTREAM
+#include STL_STRING
+
+#include <plib/netSocket.h>
+#include <plib/ul.h>
+
+#include <simgear/bucket/newbucket.hxx>
+
+SG_USING_STD(string);
+SG_USING_STD(cout);
+SG_USING_STD(endl);
+
+
+static string server = "baron.flightgear.org";
+static string source_module = "Scenery-0.7.9";
+static string source_base = server + (string)"::" + source_module;
+static string dest_base = "/dest/scenery/dir";
+
+
+// display usage
+static void usage( const string& prog ) {
+    cout << "Usage: " << prog
+         << " -p <port> [ -s <rsync_source> ] -d <rsync_dest>" << endl;
+}
+
+
+// parse message
+static void parse_message( const string &msg, int *lat, int *lon ) {
+    double dlat, dlon;
+    string text = msg;
+
+    // find GGA string and advance to start of lat
+    string::size_type pos = text.find( "$GPGGA" );
+    string tmp = text.substr( pos + 7 );
+    pos = text.find( "," );
+    tmp = tmp.substr( pos + 1 );
+    // cout << "-> " << tmp << endl;
+
+    // find lat then advance to start of hemisphere
+    pos = tmp.find( "," );
+    string lats = tmp.substr( 0, pos );
+    dlat = atof( lats.c_str() ) / 100.0;
+    tmp = tmp.substr( pos + 1 );
+
+    // find N/S hemisphere and advance to start of lon
+    if ( tmp.substr( 0, 1 ) == "S" ) {
+        dlat = -dlat;
+    }
+    pos = tmp.find( "," );
+    tmp = tmp.substr( pos + 1 );
+
+    // find lon
+    pos = tmp.find( "," );
+    string lons = tmp.substr( 0, pos );
+    dlon = atof( lons.c_str() ) / 100.0;
+    tmp = tmp.substr( pos + 1 );
+
+    // find E/W hemisphere and advance to start of lon
+    if ( tmp.substr( 0, 1 ) == "W" ) {
+        dlon = -dlon;
+    }
+
+    if ( dlat < 0 ) {
+        *lat = (int)dlat - 1;
+    } else {
+        *lat = (int)dlat;
+    }
+
+    if ( dlon < 0 ) {
+        *lon = (int)dlon - 1;
+    } else {
+        *lon = (int)dlon;
+    }
+}
+
+
+// sync area
+static void sync_area( int lat, int lon ) {
+    char NS, EW;
+    int baselat, baselon;
+
+    if ( lat < 0 ) {
+        int base = (int)(lat / 10);
+        if ( lat == base * 10 ) {
+            baselat = base * 10;
+        } else {
+            baselat = (base - 1) * 10;
+        }
+        NS = 's';
+    } else {
+        baselat = (int)(lat / 10) * 10;
+        NS = 'n';
+    }
+    if ( lon < 0 ) {
+        int base = (int)(lon / 10);
+        if ( lon == base * 10 ) {
+            baselon = base * 10;
+        } else {
+            baselon = (base - 1) * 10;
+        }
+        EW = 'w';
+    } else {
+        baselon = (int)(lon / 10) * 10;
+        EW = 'e';
+    }
+
+    char command[512];
+
+    // make container directory
+    char container_dir[512];
+    snprintf( container_dir, 512, "%s/%c%03d%c%02d",
+              dest_base.c_str(), EW, abs(baselon), NS, abs(baselat) );
+    snprintf( command, 512, "mkdir -p %s", container_dir );
+    cout << command << endl;
+    system( command );
+
+    char dir[512];
+    snprintf( dir, 512, "%c%03d%c%02d/%c%03d%c%02d",
+              EW, abs(baselon), NS, abs(baselat),
+              EW, abs(lon), NS, abs(lat) );
+
+    snprintf( command, 512,
+              "rsync --verbose --archive --delete --perms --owner --group %s/%s/ %s/%s",
+              source_base.c_str(), dir, dest_base.c_str(), dir );
+    cout << command << endl;
+    system( command );
+}
+
+
+// sync areas
+static void sync_areas( int lat, int lon, int lat_dir, int lon_dir ) {
+    // do current 1x1 degree area first
+    sync_area( lat, lon );
+
+    if ( lat_dir == 0 && lon_dir == 0 ) {
+        // now do surrounding 8 1x1 degree areas.
+        for ( int i = lat - 1; i <= lat + 1; ++i ) {
+            for ( int j = lon - 1; j <= lon + 1; ++j ) {
+                if ( i != lat || j != lon ) {
+                    sync_area( i, j );
+                }
+            }
+        }
+    } else {
+        if ( lat_dir != 0 ) {
+            sync_area( lat + lat_dir, lon );
+            sync_area( lat + lat_dir, lon - 1 );
+            sync_area( lat + lat_dir, lon + 1 );
+        }
+        if ( lon_dir != 0 ) {
+            sync_area( lat, lon + lon_dir );
+            sync_area( lat - 1, lon + lon_dir );
+            sync_area( lat + 1, lon + lon_dir );
+        }
+    }
+}
+
+
+int main( int argc, char **argv ) {
+    int port = 5501;
+    char host[256] = "";        // accept messages from anyone
+
+    // parse arguments
+    int i = 1;
+    while ( i < argc ) {
+        if ( (string)argv[i] == "-p" ) {
+            ++i;
+            port = atoi( argv[i] );
+        } else if ( (string)argv[i] == "-s" ) {
+            ++i;
+            source_base = argv[i];
+        } else if ( (string)argv[i] == "-d" ) {
+            ++i;
+            dest_base = argv[i];
+        } else {
+            usage( argv[0] );
+            exit(-1);        
+        }
+        ++i;
+    }
+
+    // Must call this before any other net stuff
+    netInit( &argc,argv );
+
+    netSocket s;
+
+    if ( ! s.open( false ) ) {  // open a UDP socket
+        printf("error opening socket\n");
+        return -1;
+    }
+
+    s.setBlocking( false );
+
+    if ( s.bind( host, port ) == -1 ) {
+        printf("error binding to port %d\n", port);
+        return -1;
+    }
+
+    char msg[256];
+    int maxlen = 256;
+    int len;
+    int lat, lon;
+    int last_lat = -9999;
+    int last_lon = -9999;
+    bool recv_msg = false;
+
+    while ( true ) {
+        recv_msg = false;
+        while ( (len = s.recv(msg, maxlen, 0)) >= 0 ) {
+            msg[len] = '\0';
+            recv_msg = true;
+
+            parse_message( msg, &lat, &lon );
+            cout << "pos = " << lat << "," << lon << endl;
+        }
+
+        if ( recv_msg ) {
+            if ( lat != last_lat || lon != last_lon ) {
+                int lat_dir, lon_dir, dist;
+                if ( last_lat == -9999 || last_lon == -9999 ) {
+                    lat_dir = lon_dir = 0;
+                } else {
+                    dist = lat - last_lat;
+                    if ( dist != 0 ) {
+                        lat_dir = dist / abs(dist);
+                    } else {
+                        lat_dir = 0;
+                    }
+                    dist = lon - last_lon;
+                    if ( dist != 0 ) {
+                        lon_dir = dist / abs(dist);
+                    } else {
+                        lon_dir = 0;
+                    }
+                }
+                cout << "lat = " << lat << " lon = " << lon << endl;
+                cout << "lat_dir = " << lat_dir << " " << " lon_dir = " << lon_dir << endl;
+                sync_areas( lat, lon, lat_dir, lon_dir );
+            }
+
+            last_lat = lat;
+            last_lon = lon;
+        }
+
+        ulSleep( 1 );
+    }
+        
+    return 0;
+}