/[thuban]/branches/WIP-pyshapelib-bramz/Thuban/Model/resource.py
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trunk/thuban/Thuban/Model/resource.py revision 709 by jonathan, Wed Apr 23 08:45:44 2003 UTC branches/WIP-pyshapelib-bramz/Thuban/Model/resource.py revision 2734 by bramz, Thu Mar 1 12:42:59 2007 UTC
# Line 5  Line 5 
5  # This program is free software under the GPL (>=v2)  # This program is free software under the GPL (>=v2)
6  # Read the file COPYING coming with Thuban for details.  # Read the file COPYING coming with Thuban for details.
7    
8    """Handle resources loaded from files such as projections"""
9    
10    __version__ = "$Revision$"
11    # $Source$
12    # $Id$
13    
14    
15  import os  import os
16    import os.path
17    import weakref
18    import traceback
19    
20  import Thuban  import Thuban
21  from Thuban.Model.load import XMLReader  from Thuban import _
22  from Thuban.Model.save import XMLWriter  
23    from Thuban.Lib.fileutil import get_application_dir
24    
25    from Thuban.Model.xmlreader import XMLReader
26    from Thuban.Model.xmlwriter import XMLWriter
27  from Thuban.Model.proj import Projection, ProjFile  from Thuban.Model.proj import Projection, ProjFile
28    from xml.sax import SAXParseException
29    
30  projdir = \  projdir = \
31          os.path.join(Thuban.__path__[0], os.pardir, "Resources", "Projections")          os.path.join(Thuban.__path__[0], os.pardir, "Resources", "Projections")
32    
 usrdir  = os.path.expanduser("~/.thuban")  
33    
34  PROJ_EXT = ".proj"  PROJ_EXT = ".proj"
35    
36  def ReadProjFile(filename):  # Determine the status of GDAL support. If GDAL is supported
37      """Read a single .proj file and return a ProjFile object."""  # gdal_support_status will be set to the empty string, otherwise to a
38    # string with information why it isn't supported
39      projs = []  #
40    # GDAL is supported if we can import both the thuban specific gdalwarp
41    # module and the GDAL python bindings.
42    for _module in ("gdalwarp", "gdal"):
43      try:      try:
44            __import__(_module)
45        except ImportError, val:
46            gdal_support_status = (_("No GDAL support because module '%s'"
47                                     " cannot be imported. Python exception: '%s'")
48                                   % (_module, str(val)))
49            break
50    else:
51        gdal_support_status = ""
52    
53    def has_gdal_support():
54        return gdal_support_status == ""
55    
56    
57    projfile_cache = weakref.WeakValueDictionary()
58    
59    def clear_proj_file_cache():
60        """Clear the cache of ProjFile objects maintained by read_proj_file.
61    
62        This function is probably only useful for the test suite.
63        """
64        projfile_cache.clear()
65    
66    def read_proj_file(filename):
67        """Read a .proj file and return a ProjFile object and warnings
68    
69        The return value is a tuple with the ProjFile object and a list of
70        strings with warnings messages that might have been generated by the
71        proj file parser.
72    
73        The objects returned cached so that reading the same file
74        (identified by its absolute name) several times yields the same
75        ProjFile object. The cache uses weak references so the objects will
76        be removed from the cache once the last reference an object in the
77        cache is removed.
78    
79        Raises IOError if the file cannot be opened, OSError if the file
80        cannot be read and SAXParseException if the file is not valid XML.
81        """
82        filename = os.path.abspath(filename)
83        if filename in projfile_cache:
84            return projfile_cache[filename], []
85        else:
86          handler = ProjFileReader()          handler = ProjFileReader()
87          handler.read(filename)          handler.read(filename)
88          pf = handler.GetProjFile()          proj_file = handler.GetProjFile()
89      except OSError:          projfile_cache[filename] = proj_file
90          pass          return proj_file, handler.GetWarnings()
91    
92    def write_proj_file(pf):
93        """Write a single .proj file
94    
95      return pf      Raises IOError if the file cannot be written.
96        """
97    
 def WriteProjFile(pf):  
98      saver = ProjFileSaver(pf)      saver = ProjFileSaver(pf)
99      saver.write(pf.GetFileName())      saver.write(pf.GetFilename())
100    
101  def GetProjFiles(dir):  #
102      """Read all .proj files in the given directory and  # Constants for the get_system_proj_file function
103      return a list of ProjFile objects.  #
104      """  
105    # The default projection file with a few predefined projections
106    DEFAULT_PROJ_FILE = "defaults.proj"
107    
108    # The epsg projections.
109    EPSG_PROJ_FILE = "epsg.proj"
110    
111    # Deprecated EPSG projections.
112    EPSG_DEPRECATED_PROJ_FILE = "epsg-deprecated.proj"
113    
114    def get_system_proj_file(filename):
115        """Return the projections from the indicated file and a list with warnings
116    
117      list = []      The filename argument should be the name of a file in the directory
118        with Thuban's default projection files (Resources/Projections/). If
119        possible callers should not use hardwired string literal for the
120        name to avoid unnecessary duplication. Instead they should use one
121        of the predefined constants, currently DEFAULT_PROJ_FILE,
122        EPSG_PROJ_FILE or EPSG_DEPRECATED_PROJ_FILE.
123    
124        The return value is a tuple with the projections in a ProjFile
125        object and a list of strings with warning messages. The warnings
126        list is usually empty but may contain messages about ignored errors.
127    
128        If the file could could not be opened return an empty projection
129        file object set to store data in the indicated default file.
130        """
131        fullname = os.path.join(projdir, filename)
132      try:      try:
133          for file in filter(lambda s: s.endswith(PROJ_EXT), os.listdir(dir)):          return read_proj_file(fullname)
134              filename = os.path.join(dir, file)      except (OSError, IOError, SAXParseException), val:
135              list.append(ReadProjFile(filename))          msg = _('Could not read "%s": %s') % (fullname, str(val))
136      except OSError:          return ProjFile(fullname), [msg]
137          pass  
138    def get_user_proj_file():
139      return list      """Return the user's projections and a list with warnings
140    
141  def GetSystemProjFiles():      The projections read from the user's thuban projection file (usually
142      """Return a list of ProjFile objects from files that are      in ~/.thuban/user.proj). The return value is a tuple with the
143      supplied by Thuban.      projections in a ProjFile object and a list of strings with warning
144        messages. The warnings list is usually empty but may contain
145        messages about ignored errors.
146    
147        If the file could could not be opened return an empty projection
148        file object set to store data in the default file.
149      """      """
150      return GetProjFiles(projdir)      usrdir  = get_application_dir()
151        filename = os.path.join(usrdir, "user.proj")
152        try:
153            return read_proj_file(filename)
154        except (OSError, IOError, SAXParseException), val:
155            msg = _('Could not read "%s": %s') % (filename, str(val))
156            return ProjFile(filename), [msg]
157    
 def GetUserProjFiles():  
     """Return a list of ProjFile objects from files that are user-defined."""  
     return GetProjFiles(usrdir)  
158    
159  class ProjFileReader(XMLReader):  class ProjFileReader(XMLReader):
160    
161      def __init__(self):      def __init__(self):
162          XMLReader.__init__(self)          XMLReader.__init__(self)
163          self.__pf = ProjFile("")          self.projfile = ProjFile("")
164            self.warnings = []
165    
166          XMLReader.AddDispatchers(self,          XMLReader.AddDispatchers(self,
167              {'projection': ("start_projection", "end_projection"),              {'projection': ("start_projection", "end_projection"),
168               'parameter':  ("start_parameter", None)})               'parameter':  ("start_parameter", None)})
169                
170      def read(self, file_or_filename):      def read(self, file_or_filename):
171          XMLReader.read(self, file_or_filename)          XMLReader.read(self, file_or_filename)
172    
173          self.__pf.SetFileName(XMLReader.GetFileName(self))          self.projfile.SetFilename(XMLReader.GetFilename(self))
174            
175      def start_projection(self, name, qname, attrs):      def start_projection(self, name, qname, attrs):
176          self.params = []          self.params = []
177          self.name = attrs.get((None, 'name'), "Unknown")          name = self.encode(attrs.get((None, 'name')))
178            if name is None:
179                name = _("Unknown")
180            self.name = name
181            self.epsg = self.encode(attrs.get((None, 'epsg')))
182    
183      def end_projection(self, name, qname):      def end_projection(self, name, qname):
184          self.__pf.Add(Projection(self.params, self.name))          try:
185                proj = Projection(self.params, self.name, epsg = self.epsg)
186            except IOError, val:
187                self.warnings.append(_('Error in projection "%s": %s')
188                                     % (self.name, str(val)))
189            else:
190                self.projfile.Add(proj)
191    
192      def start_parameter(self, name, qname, attrs):      def start_parameter(self, name, qname, attrs):
193          s = attrs.get((None, 'value'))          s = attrs.get((None, 'value'))
# Line 88  class ProjFileReader(XMLReader): Line 195  class ProjFileReader(XMLReader):
195          self.params.append(s)          self.params.append(s)
196    
197      def GetProjFile(self):      def GetProjFile(self):
198          return self.__pf          return self.projfile
199    
200        def GetWarnings(self):
201            """Return the list of warning messages that may have been produced"""
202            return self.warnings
203    
204    
205  class ProjFileSaver(XMLWriter):  class ProjFileSaver(XMLWriter):
# Line 100  class ProjFileSaver(XMLWriter): Line 211  class ProjFileSaver(XMLWriter):
211      def write(self, file_or_filename):      def write(self, file_or_filename):
212          XMLWriter.write(self, file_or_filename)          XMLWriter.write(self, file_or_filename)
213    
214          self.write_header("projfile", "thuban.dtd")          self.write_header("projectionlist", "projfile.dtd")
215          self.write_projfile(self.__pf)          self.write_projfile(self.__pf)
216          self.close()          self.close()
217    
# Line 109  class ProjFileSaver(XMLWriter): Line 220  class ProjFileSaver(XMLWriter):
220          self.open_element("projectionlist")          self.open_element("projectionlist")
221    
222          for p in pf.GetProjections():          for p in pf.GetProjections():
223              self.open_element("projection", {"name": p.GetName()})              attrs = {"name": p.GetName()}
224                if p.EPSGCode():
225                    attrs["epsg"] = p.EPSGCode()
226                self.open_element("projection", attrs)
227    
228              for param in p.GetAllParameters():              for param in p.GetAllParameters():
229                  self.write_element("parameter", {"value": param})                  self.write_element("parameter", {"value": param})
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