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	jonathan	696	# 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	bh	1542	"""Handle resources loaded from files such as projections"""
9
10			__version__ = "$Revision$"
11			# $Source$
12			# $Id$
13
14
15	jonathan	696	import os
16	frank	1132	import os.path
17	bh	1830	import weakref
18	frank	1132
19	jonathan	696	import Thuban
20	jonathan	875	from Thuban import _
21
22	frank	1149	from Thuban.Lib.fileutil import get_application_dir
23
24	jonathan	1161	from Thuban.Model.xmlreader import XMLReader
25			from Thuban.Model.xmlwriter import XMLWriter
26	jonathan	696	from Thuban.Model.proj import Projection, ProjFile
27	jonathan	727	from xml.sax import SAXParseException
28	jonathan	696
29			projdir = \
30			os.path.join(Thuban.__path__[0], os.pardir, "Resources", "Projections")
31
32
33			PROJ_EXT = ".proj"
34
35	jonathan	1161	has_gdal_support = lambda: False
36			try:
37	jonathan	1230	# 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	jonathan	1161	import gdal
44	jonathan	1230
45	jonathan	1161	"""Return True if the gdal library is available."""
46			has_gdal_support = lambda: True
47			except ImportError:
48			pass
49
50	bh	1830	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	jonathan	1161	def read_proj_file(filename):
60	bh	1786	"""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	bh	1830	proj file parser.
65	bh	1786
66	bh	1830	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	bh	1786	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	jonathan	718	"""
75	bh	1830	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	jonathan	696
85	jonathan	1161	def write_proj_file(pf):
86	jonathan	727	"""Write a single .proj file
87
88			Raises IOError if the file cannot be written.
89			"""
90
91	jonathan	696	saver = ProjFileSaver(pf)
92	jonathan	739	saver.write(pf.GetFilename())
93	jonathan	696
94
95	bh	1786	def get_system_proj_file():
96			"""Return the standard projections and a list with warnings
97	jonathan	696
98	bh	1786	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	jonathan	696
104	bh	1786	If the file could could not be opened return an empty projection
105			file object set to store data in the default file.
106	jonathan	696	"""
107	jonathan	727	filename = os.path.join(projdir, "defaults.proj")
108			try:
109	bh	1786	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	jonathan	696
114	bh	1786	def get_user_proj_file():
115			"""Return the user's projections and a list with warnings
116	jonathan	696
117	bh	1786	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	jonathan	727	"""
126	jonathan	1189	usrdir = get_application_dir()
127	jonathan	727	filename = os.path.join(usrdir, "user.proj")
128			try:
129	bh	1786	return read_proj_file(filename)
130	jan	1791	except (OSError, IOError, SAXParseException), val:
131	bh	1786	msg = _('Could not read "%s": %s') % (filename, str(val))
132			return ProjFile(filename), [msg]
133	jonathan	727
134	bh	1786
135	jonathan	709	class ProjFileReader(XMLReader):
136	jonathan	696
137	jonathan	709	def __init__(self):
138			XMLReader.__init__(self)
139	bh	1786	self.projfile = ProjFile("")
140			self.warnings = []
141	jonathan	709
142			XMLReader.AddDispatchers(self,
143			{'projection': ("start_projection", "end_projection"),
144			'parameter': ("start_parameter", None)})
145	bh	1786
146	jonathan	709	def read(self, file_or_filename):
147			XMLReader.read(self, file_or_filename)
148
149	bh	1786	self.projfile.SetFilename(XMLReader.GetFilename(self))
150
151	jonathan	696	def start_projection(self, name, qname, attrs):
152			self.params = []
153	bh	1786	name = self.encode(attrs.get((None, 'name')))
154			if name is None:
155			name = _("Unknown")
156			self.name = name
157	bh	1816	self.epsg = self.encode(attrs.get((None, 'epsg')))
158	jonathan	696
159			def end_projection(self, name, qname):
160	bh	1786	try:
161	bh	1816	proj = Projection(self.params, self.name, epsg = self.epsg)
162	bh	1786	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	jonathan	696
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	bh	1786	return self.projfile
175	jonathan	696
176	bh	1786	def GetWarnings(self):
177			"""Return the list of warning messages that may have been produced"""
178			return self.warnings
179
180
181	jonathan	709	class ProjFileSaver(XMLWriter):
182	jonathan	696
183			def __init__(self, pf):
184	jonathan	709	XMLWriter.__init__(self)
185			self.__pf = pf
186	jonathan	696
187			def write(self, file_or_filename):
188	jonathan	709	XMLWriter.write(self, file_or_filename)
189	jonathan	696
190	bh	1755	self.write_header("projectionlist", "projfile.dtd")
191	jonathan	709	self.write_projfile(self.__pf)
192	jonathan	696	self.close()
193
194			def write_projfile(self, pf):
195
196			self.open_element("projectionlist")
197
198			for p in pf.GetProjections():
199	bh	1816	attrs = {"name": p.GetName()}
200			if p.EPSGCode():
201			attrs["epsg"] = p.EPSGCode()
202			self.open_element("projection", attrs)
203	jonathan	696
204	jonathan	709	for param in p.GetAllParameters():
205	jonathan	696	self.write_element("parameter", {"value": param})
206
207			self.close_element("projection")
208
209			self.close_element("projectionlist")
210
211
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svn:keywords	Author Date Id Revision