refactored configuration file handling, closes #265

glymur/lib/config.py

@@ -18,6 +18,19 @@ else:
     from configparser import ConfigParser
     from configparser import NoOptionError
 
+# default library locations for MacPorts
+_macports_default_location = {
+        'openjp2': '/opt/local/lib/libopenjp2.dylib',
+        'openjpeg': '/opt/local/lib/libopenjpeg.dylib'
+}
+
+# default library locations on Windows
+_windows_default_location = {
+        'openjp2': os.path.join('C:\\', 'Program files', 'OpenJPEG 2.0',
+                                'bin', 'openjp2.dll'),
+        'openjpeg': os.path.join('C:\\', 'Program files', 'OpenJPEG 1.5',
+                                 'bin', 'openjpeg.dll')
+}
 
 def glymurrc_fname():
     """Return the path to the configuration file.
@@ -42,30 +55,23 @@ def glymurrc_fname():
     # didn't find a configuration file.
     return None
 
+def load_openjpeg_library(libname):
+    
+    path = read_config_file(libname)
+    if path is not None:
+        return load_library_handle(path)
 
-def load_openjpeg(path):
-    """Load the openjpeg library, falling back on defaults if necessary.
+    # No location specified by the configuration file, must look for it
+    # elsewhere.
+    path = find_library(libname)
 
-    Parameters
-    ----------
-    path : str
-        Path to openjpeg 1.5 library as specified by configuration file.  Will
-        be None if no configuration file specified.
-    """
-    if path is None:
-        # Let ctypes try to find it.
-        path = find_library('openjpeg')
-
-    # If we could not find it, then look in some likely locations on mac
-    # and win.
     if path is None:
         # Could not find a library via ctypes
         if platform.system() == 'Darwin':
             # MacPorts
-            path = '/opt/local/lib/libopenjpeg.dylib'
+            path = _macports_default_location[libname]
         elif os.name == 'nt':
-            path = os.path.join('C:\\', 'Program files', 'OpenJPEG 1.5',
-                                'bin', 'openjpeg.dll')
+            path = _windows_default_location[libname]
 
         if path is not None and not os.path.exists(path):
             # the mac/win default location does not exist.
@@ -73,29 +79,6 @@ def load_openjpeg(path):
 
     return load_library_handle(path)
 
-def load_openjp2(path):
-    """Load the openjp2 library, falling back on defaults if necessary.
-    """
-    if path is None:
-        # No help from the config file, try to find it via ctypes.
-        path = find_library('openjp2')
-
-    if path is None:
-        # Could not find a library via ctypes
-        if platform.system() == 'Darwin':
-            # MacPorts
-            path = '/opt/local/lib/libopenjp2.dylib'
-        elif os.name == 'nt':
-            path = os.path.join('C:\\', 'Program files', 'OpenJPEG 2.0',
-                                'bin', 'openjp2.dll')
-
-        if path is not None and not os.path.exists(path):
-            # the mac/win default location does not exist.
-            return None
-
-    return load_library_handle(path)
-
-
 def load_library_handle(path):
     """Load the library, return the ctypes handle."""
 
@@ -119,36 +102,48 @@ def load_library_handle(path):
     return opj_lib
 
 
-def read_config_file():
+def read_config_file(libname):
     """
-    We must use a configuration file that the user must write.
+    Extract library locations from a configuration file.
+
+    Parameters
+    ----------
+    libname : str
+        One of either 'openjp2' or 'openjpeg'
+
+    Returns
+    -------
+    path : None or str
+        None if no location is specified, otherwise a path to the library
     """
-    lib = {'openjp2':  None, 'openjpeg':  None}
     filename = glymurrc_fname()
     if filename is not None:
         # Read the configuration file for the library location.
         parser = ConfigParser()
         parser.read(filename)
-        for name in ['openjp2', 'openjpeg']:
-            try:
-                lib[name] = parser.get('library', name)
-            except NoOptionError:
-                pass
-
-    return lib
+        try:
+            path = parser.get('library', libname)
+        except NoOptionError:
+            path = None
 
+    return path
 
 def glymur_config():
-    """Try to ascertain locations of openjp2, openjpeg libraries.
     """
-    libs = read_config_file()
-    libopenjp2_handle = load_openjp2(libs['openjp2'])
-    libopenjpeg_handle = load_openjpeg(libs['openjpeg'])
-    if libopenjp2_handle is None and libopenjpeg_handle is None:
+    Try to ascertain locations of openjp2, openjpeg libraries.
+
+    Returns
+    -------
+    tpl : tuple
+        tuple of library handles
+    """
+    lst = []
+    for libname in ['openjp2', 'openjpeg']:
+        lst.append(load_openjpeg_library(libname))
+    if all(handle is None for handle in lst):
         msg = "Neither the openjp2 nor the openjpeg library could be loaded.  "
         raise IOError(msg)
-    return libopenjp2_handle, libopenjpeg_handle
-
+    return tuple(lst)
 
 def get_configdir():
     """Return string representing the configuration directory.