1 files changed, 186 insertions, 0 deletions
diff --git a/sublab_project/matekarte/osmux.py b/sublab_project/matekarte/osmux.py
new file mode 100644
index 0000000..69cefe5
--- /dev/null
+++ b/sublab_project/matekarte/osmux.py
@@ -0,0 +1,186 @@
+'''
+
+OSMux - A query multiplexer for the Overpass OpenStreetMap-API
+
+Version 2011-10-22
+
+(c) 2011 - Conrad Hoffmann <ch@bitfehler.net>
+
+This software is public domain and comes without warranty of any kind.
+
+This script splits queries for large areas into several smaller bounding boxes, sends them to them
+to the server and merges the results into a single file (the result for the original query).
+
+Additionally, ways are returned as nodes, so they can be displayed in map overlays. Actually, for
+a matching way the script returns the first node of the way - but with all the tags that were
+originally attached to the way.
+
+Basic usage instructions available via the --help switch.
+
+See http://code.bitfehler.net/osmux for more details.
+
+'''
+
+from __future__ import print_function
+
+from os import close
+from os import remove
+from sys import stderr
+from time import sleep
+from tempfile import mkstemp
+from argparse import ArgumentParser
+import xml.etree.ElementTree as etree
+
+try:
+    from urllib.request import urlretrieve
+except ImportError:
+    from urllib import urlretrieve
+
+QUERY_TEMPLATE = 'http://www.overpass-api.de/api/xapi?%s[bbox=%f,%f,%f,%f][%s=%s]'
+
+def log(msg):
+    ''' Print a message to the console, unless the 'quiet' flag was set. '''
+
+    if 'params' not in globals():
+        return
+
+    if not params.quiet:
+        print(msg)
+
+def extract(xmlfile, tagname):
+    ''' Extract nodes from a query result.
+
+    Regular nodes are just added to the result. For ways, the ways tags are copied to the first
+    node of the way and this first node is added to the result.
+
+    '''
+    tree = etree.parse(xmlfile)
+    root = tree.getroot()
+    result = {}
+    nodes = {}
+
+    for child in root:
+        if child.tag == 'node':
+            # Save all nodes in this temp structure, if we are parsing ways we need them later on.
+            nodes[child.attrib['id']] = child
+            # If the node also contains the tag we are looking for, add it to the result.
+            for tag in child:
+                if tag.attrib['k'] == tagname:
+                    result[child.attrib['id']] = child
+        elif child.tag == 'way':
+            # Create a new custom node that contains all of the ways tags and add it to result. If
+            # a way is returned, it must contain the tag we are looking for, so no need to check.
+            node = nodes[child[0].attrib['ref']]
+            for sub in child:
+                if sub.tag == 'tag':
+                    etree.SubElement(node, 'tag', sub.attrib)
+            result[node.attrib['id']] = node
+        elif child.tag == 'remark':
+            # This usually means the query timed out or ran out of memory.
+            print('Potential error: %s' % child.text, file=stderr)
+
+    return result
+
+def osmux(tag, north, south, east, west, value='*', pause=1, step=1.0):
+    (handle, tmpfile) = mkstemp(suffix='.xml', prefix='osm')
+    close(handle)
+    log("Using temporary file %s, step %f and pause %d." % (tmpfile, step, pause))
+
+    result = {}
+
+    cur_lat = south
+    cur_lon = west
+
+    while cur_lat < north:
+
+        # While we are in this loop, there are more squares to fetch.
+
+        # We know which square to go for, get its bbox:
+        bbox_lon = [cur_lon, min(cur_lon + step, east)]
+        bbox_lat = [cur_lat, min(cur_lat + step, north)]
+
+        nquery = QUERY_TEMPLATE % ('node', bbox_lon[0], bbox_lat[0], bbox_lon[1], bbox_lat[1], tag, value)
+        wquery = QUERY_TEMPLATE % ('way', bbox_lon[0], bbox_lat[0], bbox_lon[1], bbox_lat[1], tag, value)
+
+        log("Fetching %s" % nquery)
+        urlretrieve(nquery, tmpfile)
+        result.update(extract(tmpfile, tag))
+
+        log("Fetching %s" % wquery)
+        urlretrieve(wquery, tmpfile)
+        result.update(extract(tmpfile, tag))
+
+        # Calculate the next sub-bbox:
+        if cur_lon + step < east:
+            # Proceed with next square in current "row":
+            cur_lon += step
+        else:
+            # Reset longitude, continue with next "row", if any:
+            cur_lon = west
+            cur_lat += step
+
+        # Wait a moment - might help the server.
+        sleep(pause)
+
+
+    log("Removing temporary data file...")
+    remove(tmpfile)
+
+    log("Generating data...")
+    buffer_ = (('''<?xml version='1.0' encoding='UTF-8'?>
+<osm version="0.6" generator="OSMux (http://code.bitfehler.net/osmux">
+    <bound box="%f,%f,%f,%f" origin="Osmosis SNAPSHOT-rexported"/>
+''' % (west, south, east, north)).encode('utf-8'))
+    for nid in result:
+        node = result[nid]
+        buffer_ += etree.tostring(node, encoding='utf-8')
+    buffer_ += '</osm>'.encode('utf-8')
+    return buffer_
+
+if __name__ == '__main__':
+    # Parse command line arguments.
+    parser = ArgumentParser(description='Generate an OpenLayers OSM file using the Overpass API.',
+            epilog='See http://code.bitfehler.net for more details.')
+    parser.add_argument('-q', '--quiet', dest='quiet', action='store_true', help='suppress progress messages')
+    parser.add_argument('-S', '--step', dest='step', metavar='D', default=1.0, type=float, help='split into steps of D degrees')
+    parser.add_argument('-p', '--pause', dest='pause', metavar='P', default=1, type=int, help='pause for P seconds between requests to reduce server load (default: 1, must be >= 0)')
+    parser.add_argument('-t', '--tag', dest='tag', metavar='<tag>', type=str, required=True, help='return only elements with this tag')
+    parser.add_argument('-v', '--value', dest='value', metavar='<value>', default='*', type=str, help='return only elements with this value (omit for \'*\')')
+    parser.add_argument('-s', '--south', dest='south', metavar='S', type=float, required=True, help='latitude of the southern border of the bounding box')
+    parser.add_argument('-w', '--west', dest='west', metavar='W', type=float, required=True, help='longitude of the western border of the bounding box')
+    parser.add_argument('-n', '--north', dest='north', metavar='N', type=float, required=True, help='latitude of the northern border of the bounding box')
+    parser.add_argument('-e', '--east', dest='east', metavar='E', type=float, required=True, help='longitude of the eastern border of the bounding box')
+    parser.add_argument('outfile', metavar='<output file>', type=str, help='the output file for the merged OSM data')
+    params = parser.parse_args()
+
+    # Sanity checks for the arguments.
+    if params.pause < 0:
+        print('Value for --pause must be >= 0. Exiting.', file=stderr)
+        exit(1)
+    if params.step <= 0:
+        print('Value for --pause must be > 0. Exiting.', file=stderr)
+        exit(1)
+    try:
+        open(params.outfile, mode='ab')
+    except IOError as e:
+        (errno, strerror) = e.args
+        print('Failed to open output file for writing: %s. Exiting.' % strerror, file=stderr)
+        exit(1)
+    if min(params.south, params.north) != params.south:
+        print('Value for --south must be less then --north. Use negative numbers for southern hemisphere. Exiting.', file=stderr)
+        exit(1)
+    if min(params.east, params.west) != params.west:
+        print('Value for --west must be less then --east. Use e.g. --east 187.5 if you need to cover the 180th meridian. Exiting.', file=stderr)
+        exit(1)
+
+    buffer_ = osmux(params.tag,
+          params.north,
+          params.south,
+          params.east,
+          params.west,
+          value=params.value,
+          pause=params.pause,
+          step=params.step)
+
+    with open(params.outfile, mode='wb') as outfile:
+        outfile.write(buffer_)