Thuban/Model/resource.py

# Copyright (c) 2003 by Intevation GmbH
# Authors:
# Jonathan Coles <[email protected]>
#
# This program is free software under the GPL (>=v2)
# Read the file COPYING coming with Thuban for details.

"""Handle resources loaded from files such as projections"""

__version__ = "$Revision$"
# $Source$
# $Id$


import os
import os.path
import weakref

import Thuban
from Thuban import _

from Thuban.Lib.fileutil import get_application_dir

from Thuban.Model.xmlreader import XMLReader
from Thuban.Model.xmlwriter import XMLWriter
from Thuban.Model.proj import Projection, ProjFile
from xml.sax import SAXParseException

projdir = \
        os.path.join(Thuban.__path__[0], os.pardir, "Resources", "Projections")


PROJ_EXT = ".proj"

has_gdal_support = lambda: False
try:
    # first try to see if our extension module is there. if it 
    # wasn't even compiled, we obviously don't have gdal support.
    import gdalwarp

    # now try to import the python extension. if this doesn't
    # exist then we can't do anything.
    import gdal

    """Return True if the gdal library is available."""
    has_gdal_support = lambda: True
except ImportError:
    pass

projfile_cache = weakref.WeakValueDictionary()

def clear_proj_file_cache():
    """Clear the cache of ProjFile objects maintained by read_proj_file.

    This function is probably only useful for the test suite.
    """
    projfile_cache.clear()

def read_proj_file(filename):
    """Read a .proj file and return a ProjFile object and warnings

    The return value is a tuple with the ProjFile object and a list of
    strings with warnings messages that might have been generated by the
    proj file parser.

    The objects returned cached so that reading the same file
    (identified by its absolute name) several times yields the same
    ProjFile object. The cache uses weak references so the objects will
    be removed from the cache once the last reference an object in the
    cache is removed.

    Raises IOError if the file cannot be opened, OSError if the file
    cannot be read and SAXParseException if the file is not valid XML.
    """
    filename = os.path.abspath(filename)
    if filename in projfile_cache:
        return projfile_cache[filename], []
    else:
        handler = ProjFileReader()
        handler.read(filename)
        proj_file = handler.GetProjFile()
        projfile_cache[filename] = proj_file
        return proj_file, handler.GetWarnings()

def write_proj_file(pf):
    """Write a single .proj file

    Raises IOError if the file cannot be written.
    """

    saver = ProjFileSaver(pf)
    saver.write(pf.GetFilename())


def get_system_proj_file():
    """Return the standard projections and a list with warnings

    The projections read from the default thuban projection file
    (usually in Resources/Projections/defaults.proj). The return value
    is a tuple with the projections in a ProjFile object and a list of
    strings with warning messages. The warnings list is usually empty
    but may contain messages about ignored errors.

    If the file could could not be opened return an empty projection
    file object set to store data in the default file.
    """
    filename = os.path.join(projdir, "defaults.proj")
    try:
        return read_proj_file(filename)
    except (OSError, IOError, SAXParseException), val:
        msg = _('Could not read "%s": %s') % (filename, str(val))
        return ProjFile(filename), [msg]

def get_user_proj_file():
    """Return the user's projections and a list with warnings

    The projections read from the user's thuban projection file (usually
    in ~/.thuban/user.proj). The return value is a tuple with the
    projections in a ProjFile object and a list of strings with warning
    messages. The warnings list is usually empty but may contain
    messages about ignored errors.

    If the file could could not be opened return an empty projection
    file object set to store data in the default file.
    """
    usrdir  = get_application_dir()
    filename = os.path.join(usrdir, "user.proj")
    try:
        return read_proj_file(filename)
    except (OSError, IOError, SAXParseException), val:
        msg = _('Could not read "%s": %s') % (filename, str(val))
        return ProjFile(filename), [msg]


class ProjFileReader(XMLReader):

    def __init__(self):
        XMLReader.__init__(self)
        self.projfile = ProjFile("")
        self.warnings = []

        XMLReader.AddDispatchers(self,
            {'projection': ("start_projection", "end_projection"),
             'parameter':  ("start_parameter", None)})

    def read(self, file_or_filename):
        XMLReader.read(self, file_or_filename)

        self.projfile.SetFilename(XMLReader.GetFilename(self))

    def start_projection(self, name, qname, attrs):
        self.params = []
        name = self.encode(attrs.get((None, 'name')))
        if name is None:
            name = _("Unknown")
        self.name = name
        self.epsg = self.encode(attrs.get((None, 'epsg')))

    def end_projection(self, name, qname):
        try:
            proj = Projection(self.params, self.name, epsg = self.epsg)
        except IOError, val:
            self.warnings.append(_('Error in projection "%s": %s')
                                 % (self.name, str(val)))
        else:
            self.projfile.Add(proj)

    def start_parameter(self, name, qname, attrs):
        s = attrs.get((None, 'value'))
        s = str(s) # we can't handle unicode in proj
        self.params.append(s)

    def GetProjFile(self):
        return self.projfile

    def GetWarnings(self):
        """Return the list of warning messages that may have been produced"""
        return self.warnings


class ProjFileSaver(XMLWriter):

    def __init__(self, pf):
        XMLWriter.__init__(self)
        self.__pf = pf

    def write(self, file_or_filename):
        XMLWriter.write(self, file_or_filename)

        self.write_header("projectionlist", "projfile.dtd")
        self.write_projfile(self.__pf)
        self.close()

    def write_projfile(self, pf):

        self.open_element("projectionlist")

        for p in pf.GetProjections():
            attrs = {"name": p.GetName()}
            if p.EPSGCode():
                attrs["epsg"] = p.EPSGCode()
            self.open_element("projection", attrs)

            for param in p.GetAllParameters():
                self.write_element("parameter", {"value": param})

            self.close_element("projection")

        self.close_element("projectionlist")


1	# Copyright (c) 2003 by Intevation GmbH
2	# Authors:
3	# Jonathan Coles <[email protected]>
4	#
5	# This program is free software under the GPL (>=v2)
6	# 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
16	import os.path
17	import weakref
18
19	import Thuban
20	from Thuban import _
21
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
27	from xml.sax import SAXParseException
28
29	projdir = \
30	os.path.join(Thuban.__path__[0], os.pardir, "Resources", "Projections")
31
32
33	PROJ_EXT = ".proj"
34
35	has_gdal_support = lambda: False
36	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	projfile_cache = weakref.WeakValueDictionary()
51
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()
80	handler.read(filename)
81	proj_file = handler.GetProjFile()
82	projfile_cache[filename] = proj_file
83	return proj_file, handler.GetWarnings()
84
85	def write_proj_file(pf):
86	"""Write a single .proj file
87
88	Raises IOError if the file cannot be written.
89	"""
90
91	saver = ProjFileSaver(pf)
92	saver.write(pf.GetFilename())
93
94
95	def get_system_proj_file():
96	"""Return the standard projections and a list with warnings
97
98	The projections read from the default thuban projection file
99	(usually in Resources/Projections/defaults.proj). The return value
100	is a tuple with the projections in a ProjFile object and a list of
101	strings with warning messages. The warnings list is usually empty
102	but may contain messages about ignored errors.
103
104	If the file could could not be opened return an empty projection
105	file object set to store data in the default file.
106	"""
107	filename = os.path.join(projdir, "defaults.proj")
108	try:
109	return read_proj_file(filename)
110	except (OSError, IOError, SAXParseException), val:
111	msg = _('Could not read "%s": %s') % (filename, str(val))
112	return ProjFile(filename), [msg]
113
114	def get_user_proj_file():
115	"""Return the user's projections and a list with warnings
116
117	The projections read from the user's thuban projection file (usually
118	in ~/.thuban/user.proj). The return value is a tuple with the
119	projections in a ProjFile object and a list of strings with warning
120	messages. The warnings list is usually empty but may contain
121	messages about ignored errors.
122
123	If the file could could not be opened return an empty projection
124	file object set to store data in the default file.
125	"""
126	usrdir = get_application_dir()
127	filename = os.path.join(usrdir, "user.proj")
128	try:
129	return read_proj_file(filename)
130	except (OSError, IOError, SAXParseException), val:
131	msg = _('Could not read "%s": %s') % (filename, str(val))
132	return ProjFile(filename), [msg]
133
134
135	class ProjFileReader(XMLReader):
136
137	def __init__(self):
138	XMLReader.__init__(self)
139	self.projfile = ProjFile("")
140	self.warnings = []
141
142	XMLReader.AddDispatchers(self,
143	{'projection': ("start_projection", "end_projection"),
144	'parameter': ("start_parameter", None)})
145
146	def read(self, file_or_filename):
147	XMLReader.read(self, file_or_filename)
148
149	self.projfile.SetFilename(XMLReader.GetFilename(self))
150
151	def start_projection(self, name, qname, attrs):
152	self.params = []
153	name = self.encode(attrs.get((None, 'name')))
154	if name is None:
155	name = _("Unknown")
156	self.name = name
157	self.epsg = self.encode(attrs.get((None, 'epsg')))
158
159	def end_projection(self, name, qname):
160	try:
161	proj = Projection(self.params, self.name, epsg = self.epsg)
162	except IOError, val:
163	self.warnings.append(_('Error in projection "%s": %s')
164	% (self.name, str(val)))
165	else:
166	self.projfile.Add(proj)
167
168	def start_parameter(self, name, qname, attrs):
169	s = attrs.get((None, 'value'))
170	s = str(s) # we can't handle unicode in proj
171	self.params.append(s)
172
173	def GetProjFile(self):
174	return self.projfile
175
176	def GetWarnings(self):
177	"""Return the list of warning messages that may have been produced"""
178	return self.warnings
179
180
181	class ProjFileSaver(XMLWriter):
182
183	def __init__(self, pf):
184	XMLWriter.__init__(self)
185	self.__pf = pf
186
187	def write(self, file_or_filename):
188	XMLWriter.write(self, file_or_filename)
189
190	self.write_header("projectionlist", "projfile.dtd")
191	self.write_projfile(self.__pf)
192	self.close()
193
194	def write_projfile(self, pf):
195
196	self.open_element("projectionlist")
197
198	for p in pf.GetProjections():
199	attrs = {"name": p.GetName()}
200	if p.EPSGCode():
201	attrs["epsg"] = p.EPSGCode()
202	self.open_element("projection", attrs)
203
204	for param in p.GetAllParameters():
205	self.write_element("parameter", {"value": param})
206
207	self.close_element("projection")
208
209	self.close_element("projectionlist")
210
211
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