/[thuban]/branches/WIP-pyshapelib-bramz/Thuban/Model/resource.py
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revision 709 by jonathan, Wed Apr 23 08:45:44 2003 UTC revision 1933 by bh, Tue Nov 11 16:37:53 2003 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    
19  import Thuban  import Thuban
20  from Thuban.Model.load import XMLReader  from Thuban import _
21  from Thuban.Model.save import XMLWriter  
22    from Thuban.Lib.fileutil import get_application_dir
23    
24    from Thuban.Model.xmlreader import XMLReader
25    from Thuban.Model.xmlwriter import XMLWriter
26  from Thuban.Model.proj import Projection, ProjFile  from Thuban.Model.proj import Projection, ProjFile
27    from xml.sax import SAXParseException
28    
29  projdir = \  projdir = \
30          os.path.join(Thuban.__path__[0], os.pardir, "Resources", "Projections")          os.path.join(Thuban.__path__[0], os.pardir, "Resources", "Projections")
31    
 usrdir  = os.path.expanduser("~/.thuban")  
32    
33  PROJ_EXT = ".proj"  PROJ_EXT = ".proj"
34    
35  def ReadProjFile(filename):  has_gdal_support = lambda: False
36      """Read a single .proj file and return a ProjFile object."""  try:
37        # first try to see if our extension module is there. if it
38        # wasn't even compiled, we obviously don't have gdal support.
39        import gdalwarp
40    
41        # now try to import the python extension. if this doesn't
42        # exist then we can't do anything.
43        import gdal
44    
45        """Return True if the gdal library is available."""
46        has_gdal_support = lambda: True
47    except ImportError:
48        pass
49    
50      projs = []  projfile_cache = weakref.WeakValueDictionary()
51      try:  
52    def clear_proj_file_cache():
53        """Clear the cache of ProjFile objects maintained by read_proj_file.
54    
55        This function is probably only useful for the test suite.
56        """
57        projfile_cache.clear()
58    
59    def read_proj_file(filename):
60        """Read a .proj file and return a ProjFile object and warnings
61    
62        The return value is a tuple with the ProjFile object and a list of
63        strings with warnings messages that might have been generated by the
64        proj file parser.
65    
66        The objects returned cached so that reading the same file
67        (identified by its absolute name) several times yields the same
68        ProjFile object. The cache uses weak references so the objects will
69        be removed from the cache once the last reference an object in the
70        cache is removed.
71    
72        Raises IOError if the file cannot be opened, OSError if the file
73        cannot be read and SAXParseException if the file is not valid XML.
74        """
75        filename = os.path.abspath(filename)
76        if filename in projfile_cache:
77            return projfile_cache[filename], []
78        else:
79          handler = ProjFileReader()          handler = ProjFileReader()
80          handler.read(filename)          handler.read(filename)
81          pf = handler.GetProjFile()          proj_file = handler.GetProjFile()
82      except OSError:          projfile_cache[filename] = proj_file
83          pass          return proj_file, handler.GetWarnings()
84    
85      return pf  def write_proj_file(pf):
86        """Write a single .proj file
87    
88        Raises IOError if the file cannot be written.
89        """
90    
 def WriteProjFile(pf):  
91      saver = ProjFileSaver(pf)      saver = ProjFileSaver(pf)
92      saver.write(pf.GetFileName())      saver.write(pf.GetFilename())
93    
 def GetProjFiles(dir):  
     """Read all .proj files in the given directory and  
     return a list of ProjFile objects.  
     """  
94    
95      list = []  # Constants for the get_system_proj_file function
96    DEFAULT_PROJ_FILE = "defaults.proj"
97    EPSG_PROJ_FILE = "epsg.proj"
98    
99    def get_system_proj_file(filename):
100        """Return the projections from the indicated file and a list with warnings
101    
102        The filename argument should be the name of a file in the directory
103        with Thuban's default projection files (Resources/Projections/). If
104        possible callers should not use hardwired string literal for the
105        name to avoid unnecessary duplication. Instead they should use one
106        of the predefined constants, currently DEFAULT_PROJ_FILE or
107        EPSG_PROJ_FILE.
108    
109        The return value is a tuple with the projections in a ProjFile
110        object and a list of strings with warning messages. The warnings
111        list is usually empty but may contain messages about ignored errors.
112    
113        If the file could could not be opened return an empty projection
114        file object set to store data in the indicated default file.
115        """
116        fullname = os.path.join(projdir, filename)
117      try:      try:
118          for file in filter(lambda s: s.endswith(PROJ_EXT), os.listdir(dir)):          return read_proj_file(fullname)
119              filename = os.path.join(dir, file)      except (OSError, IOError, SAXParseException), val:
120              list.append(ReadProjFile(filename))          msg = _('Could not read "%s": %s') % (fullname, str(val))
121      except OSError:          return ProjFile(fullname), [msg]
122          pass  
123    def get_user_proj_file():
124      return list      """Return the user's projections and a list with warnings
125    
126  def GetSystemProjFiles():      The projections read from the user's thuban projection file (usually
127      """Return a list of ProjFile objects from files that are      in ~/.thuban/user.proj). The return value is a tuple with the
128      supplied by Thuban.      projections in a ProjFile object and a list of strings with warning
129        messages. The warnings list is usually empty but may contain
130        messages about ignored errors.
131    
132        If the file could could not be opened return an empty projection
133        file object set to store data in the default file.
134      """      """
135      return GetProjFiles(projdir)      usrdir  = get_application_dir()
136        filename = os.path.join(usrdir, "user.proj")
137        try:
138            return read_proj_file(filename)
139        except (OSError, IOError, SAXParseException), val:
140            msg = _('Could not read "%s": %s') % (filename, str(val))
141            return ProjFile(filename), [msg]
142    
 def GetUserProjFiles():  
     """Return a list of ProjFile objects from files that are user-defined."""  
     return GetProjFiles(usrdir)  
143    
144  class ProjFileReader(XMLReader):  class ProjFileReader(XMLReader):
145    
146      def __init__(self):      def __init__(self):
147          XMLReader.__init__(self)          XMLReader.__init__(self)
148          self.__pf = ProjFile("")          self.projfile = ProjFile("")
149            self.warnings = []
150    
151          XMLReader.AddDispatchers(self,          XMLReader.AddDispatchers(self,
152              {'projection': ("start_projection", "end_projection"),              {'projection': ("start_projection", "end_projection"),
153               'parameter':  ("start_parameter", None)})               'parameter':  ("start_parameter", None)})
154                
155      def read(self, file_or_filename):      def read(self, file_or_filename):
156          XMLReader.read(self, file_or_filename)          XMLReader.read(self, file_or_filename)
157    
158          self.__pf.SetFileName(XMLReader.GetFileName(self))          self.projfile.SetFilename(XMLReader.GetFilename(self))
159            
160      def start_projection(self, name, qname, attrs):      def start_projection(self, name, qname, attrs):
161          self.params = []          self.params = []
162          self.name = attrs.get((None, 'name'), "Unknown")          name = self.encode(attrs.get((None, 'name')))
163            if name is None:
164                name = _("Unknown")
165            self.name = name
166            self.epsg = self.encode(attrs.get((None, 'epsg')))
167    
168      def end_projection(self, name, qname):      def end_projection(self, name, qname):
169          self.__pf.Add(Projection(self.params, self.name))          try:
170                proj = Projection(self.params, self.name, epsg = self.epsg)
171            except IOError, val:
172                self.warnings.append(_('Error in projection "%s": %s')
173                                     % (self.name, str(val)))
174            else:
175                self.projfile.Add(proj)
176    
177      def start_parameter(self, name, qname, attrs):      def start_parameter(self, name, qname, attrs):
178          s = attrs.get((None, 'value'))          s = attrs.get((None, 'value'))
# Line 88  class ProjFileReader(XMLReader): Line 180  class ProjFileReader(XMLReader):
180          self.params.append(s)          self.params.append(s)
181    
182      def GetProjFile(self):      def GetProjFile(self):
183          return self.__pf          return self.projfile
184    
185        def GetWarnings(self):
186            """Return the list of warning messages that may have been produced"""
187            return self.warnings
188    
189    
190  class ProjFileSaver(XMLWriter):  class ProjFileSaver(XMLWriter):
# Line 100  class ProjFileSaver(XMLWriter): Line 196  class ProjFileSaver(XMLWriter):
196      def write(self, file_or_filename):      def write(self, file_or_filename):
197          XMLWriter.write(self, file_or_filename)          XMLWriter.write(self, file_or_filename)
198    
199          self.write_header("projfile", "thuban.dtd")          self.write_header("projectionlist", "projfile.dtd")
200          self.write_projfile(self.__pf)          self.write_projfile(self.__pf)
201          self.close()          self.close()
202    
# Line 109  class ProjFileSaver(XMLWriter): Line 205  class ProjFileSaver(XMLWriter):
205          self.open_element("projectionlist")          self.open_element("projectionlist")
206    
207          for p in pf.GetProjections():          for p in pf.GetProjections():
208              self.open_element("projection", {"name": p.GetName()})              attrs = {"name": p.GetName()}
209                if p.EPSGCode():
210                    attrs["epsg"] = p.EPSGCode()
211                self.open_element("projection", attrs)
212    
213              for param in p.GetAllParameters():              for param in p.GetAllParameters():
214                  self.write_element("parameter", {"value": param})                  self.write_element("parameter", {"value": param})
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