source: sasview/sansdataloader/src/sans/dataloader/loader.py @ d970df9

"""
    File handler to support different file extensions.
    Uses reflectometry's registry utility.
    
    The default readers are found in the 'readers' sub-module
    and registered by default at initialization time.
    
    To add a new default reader, one must register it in
    the register_readers method found in readers/__init__.py.
    
    A utility method (find_plugins) is available to inspect
    a directory (for instance, a user plug-in directory) and
    look for new readers/writers.
"""
#####################################################################
#This software was developed by the University of Tennessee as part of the
#Distributed Data Analysis of Neutron Scattering Experiments (DANSE)
#project funded by the US National Science Foundation.
#See the license text in license.txt
#copyright 2008, University of Tennessee
######################################################################

import os
import sys
import logging
import time
from zipfile import ZipFile
from data_util.registry import ExtensionRegistry
# Default readers are defined in the readers sub-module
import readers
from readers import ascii_reader
from readers import cansas_reader

class Registry(ExtensionRegistry):
    """
    Registry class for file format extensions.
    Readers and writers are supported.
    """
    
    def __init__(self):
        super(Registry, self).__init__()
        
        ## Writers
        self.writers = {}
        
        ## List of wildcards
        self.wildcards = ['All (*.*)|*.*']
        
        ## Creation time, for testing
        self._created = time.time()
        
        # Register default readers
        readers.read_associations(self)
        
        #TODO: remove the following line when ready to switch to
        #the new default readers
        #readers.register_readers(self._identify_plugin)
        
        # Look for plug-in readers
        #self.find_plugins('plugins')

    def load(self, path, format=None):
        """
        Call the loader for the file type of path.

        :param path: file path
        :param format: explicit extension, to force the use
            of a particular reader

        Defaults to the ascii (multi-column) reader
        if no reader was registered for the file's
        extension.
        """
        try:
            return super(Registry, self).load(path, format=format)
        except:
            try:
                # No reader was found. Default to the ascii reader.
                ascii_loader = ascii_reader.Reader()
                return ascii_loader.read(path)
            except:
                cansas_loader = cansas_reader.Reader()
                return cansas_loader.read(path)
            
    def find_plugins(self, dir):
        """
        Find readers in a given directory. This method
        can be used to inspect user plug-in directories to
        find new readers/writers.
        
        :param dir: directory to search into
        
        :return: number of readers found
        """
        readers_found = 0
        temp_path = os.path.abspath(dir)
        if not os.path.isdir(temp_path):
            temp_path = os.path.join(os.getcwd(), dir)
        if not os.path.isdir(temp_path):
            temp_path = os.path.join(os.path.dirname(__file__), dir)
        if not os.path.isdir(temp_path):
            temp_path = os.path.join(os.path.dirname(sys.path[0]), dir)
        
        dir = temp_path
        # Check whether the directory exists
        if not os.path.isdir(dir):
            msg = "DataLoader couldn't locate DataLoader plugin folder."
            msg += """ "%s" does not exist""" % dir
            logging.warning(msg)
            return readers_found
        
        for item in os.listdir(dir):
            full_path = os.path.join(dir, item)
            if os.path.isfile(full_path):
                
                # Process python files
                if item.endswith('.py'):
                    toks = os.path.splitext(os.path.basename(item))
                    try:
                        sys.path.insert(0, os.path.abspath(dir))
                        module = __import__(toks[0], globals(), locals())
                        if self._identify_plugin(module):
                            readers_found += 1
                    except:
                        msg = "Loader: Error importing "
                        msg += "%s\n  %s" % (item, sys.exc_value)
                        logging.error(msg)
                            
                # Process zip files
                elif item.endswith('.zip'):
                    try:
                        # Find the modules in the zip file
                        zfile = ZipFile(item)
                        nlist = zfile.namelist()
                        
                        sys.path.insert(0, item)
                        for mfile in nlist:
                            try:
                                # Change OS path to python path
                                fullname = mfile.replace('/', '.')
                                fullname = os.path.splitext(fullname)[0]
                                module = __import__(fullname, globals(),
                                                     locals(), [""])
                                if self._identify_plugin(module):
                                    readers_found += 1
                            except:
                                msg = "Loader: Error importing"
                                msg += " %s\n  %s" % (mfile, sys.exc_value)
                                logging.error(msg)
                            
                    except:
                        msg = "Loader: Error importing "
                        msg += " %s\n  %s" % (item, sys.exc_value)
                        logging.error(msg)
                     
        return readers_found
    
    def associate_file_type(self, ext, module):
        """
        Look into a module to find whether it contains a
        Reader class. If so, APPEND it to readers and (potentially)
        to the list of writers for the given extension
        
        :param ext: file extension [string]
        :param module: module object
        """
        reader_found = False
        
        if hasattr(module, "Reader"):
            try:
                # Find supported extensions
                loader = module.Reader()
                if ext not in self.loaders:
                    self.loaders[ext] = []
                # Append the new reader to the list
                self.loaders[ext].append(loader.read)

                reader_found = True
                
                # Keep track of wildcards
                type_name = module.__name__
                if hasattr(loader, 'type_name'):
                    type_name = loader.type_name
                    
                wcard = "%s files (*%s)|*%s" % (type_name, ext.lower(),
                                                 ext.lower())
                if wcard not in self.wildcards:
                    self.wildcards.append(wcard)
                            
                # Check whether writing is supported
                if hasattr(loader, 'write'):
                    if ext not in self.writers:
                        self.writers[ext] = []
                    # Append the new writer to the list
                    self.writers[ext].append(loader.write)
                        
            except:
                msg = "Loader: Error accessing"
                msg += " Reader in %s\n  %s" % (module.__name__, sys.exc_value)
                logging.error(msg)
        return reader_found

    def associate_file_reader(self, ext, loader):
        """
        Append a reader object to readers
        
        :param ext: file extension [string]
        :param module: reader object
        """
        reader_found = False
        
        try:
            # Find supported extensions
            if ext not in self.loaders:
                self.loaders[ext] = []
            # Append the new reader to the list
            self.loaders[ext].append(loader.read)

            reader_found = True
            
            # Keep track of wildcards
            if hasattr(loader, 'type_name'):
                type_name = loader.type_name
                
                wcard = "%s files (*%s)|*%s" % (type_name, ext.lower(),
                                                ext.lower())
                if wcard not in self.wildcards:
                    self.wildcards.append(wcard)
                 
        except:
            msg = "Loader: Error accessing Reader "
            msg += "in %s\n  %s" % (loader.__name__, sys.exc_value)
            logging.error(msg)
        return reader_found

    def _identify_plugin(self, module):
        """
        Look into a module to find whether it contains a 
        Reader class. If so, add it to readers and (potentially)
        to the list of writers.
        :param module: module object
        
        """
        reader_found = False
        
        if hasattr(module, "Reader"):
            try:
                # Find supported extensions
                loader = module.Reader()
                for ext in loader.ext:
                    if ext not in self.loaders:
                        self.loaders[ext] = []
                    # When finding a reader at run time,
                    # treat this reader as the new default
                    self.loaders[ext].insert(0, loader.read)

                    reader_found = True
                    
                    # Keep track of wildcards
                    type_name = module.__name__
                    if hasattr(loader, 'type_name'):
                        type_name = loader.type_name
                    wcard = "%s files (*%s)|*%s" % (type_name, ext.lower(),
                                                     ext.lower())
                    if wcard not in self.wildcards:
                        self.wildcards.append(wcard)
                            
                # Check whether writing is supported
                if hasattr(loader, 'write'):
                    for ext in loader.ext:
                        if ext not in self.writers:
                            self.writers[ext] = []
                        self.writers[ext].insert(0, loader.write)
                        
            except:
                msg = "Loader: Error accessing Reader"
                msg += " in %s\n  %s" % (module.__name__, sys.exc_value)
                logging.error(msg)
        return reader_found

    def lookup_writers(self, path):
        """
        :return: the loader associated with the file type of path.
        
        :Raises ValueError: if file type is not known.
        """
        # Find matching extensions
        extlist = [ext for ext in self.extensions() if path.endswith(ext)]
        # Sort matching extensions by decreasing order of length
        extlist.sort(lambda a, b: len(a) < len(b))
        # Combine loaders for matching extensions into one big list
        writers = []
        for L in [self.writers[ext] for ext in extlist]:
            writers.extend(L)
        # Remove duplicates if they exist
        if len(writers) != len(set(writers)):
            result = []
            for L in writers:
                if L not in result:
                    result.append(L)
            writers = L
        # Raise an error if there are no matching extensions
        if len(writers) == 0:
            raise ValueError, "Unknown file type for " + path
        # All done
        return writers

    def save(self, path, data, format=None):
        """
        Call the writer for the file type of path.

        Raises ValueError if no writer is available.
        Raises KeyError if format is not available.
        
        May raise a writer-defined exception if writer fails.
        """
        if format is None:
            writers = self.lookup_writers(path)
        else:
            writers = self.writers[format]
        for fn in writers:
            try:
                return fn(path, data)
            except:
                pass  # give other loaders a chance to succeed
        # If we get here it is because all loaders failed
        raise  # reraises last exception

        
class Loader(object):
    """
    Utility class to use the Registry as a singleton.
    """
    ## Registry instance
    __registry = Registry()
    
    def associate_file_type(self, ext, module):
        """
        Look into a module to find whether it contains a
        Reader class. If so, append it to readers and (potentially)
        to the list of writers for the given extension
        
        :param ext: file extension [string]
        :param module: module object
        """
        return self.__registry.associate_file_type(ext, module)

    def associate_file_reader(self, ext, loader):
        """
        Append a reader object to readers
        
        :param ext: file extension [string]
        :param module: reader object
        """
        return self.__registry.associate_file_reader(ext, loader)

    def load(self, file, format=None):
        """
        Load a file
        
        :param file: file name (path)
        :param format: specified format to use (optional)
        :return: DataInfo object
        """
        return self.__registry.load(file, format)
    
    def save(self, file, data, format):
        """
        Save a DataInfo object to file
        :param file: file name (path)
        :param data: DataInfo object
        :param format: format to write the data in 
        """
        return self.__registry.save(file, data, format)
        
    def _get_registry_creation_time(self):
        """
        Internal method used to test the uniqueness
        of the registry object
        """
        return self.__registry._created
    
    def find_plugins(self, dir):
        """
        Find plugins in a given directory
        
        :param dir: directory to look into to find new readers/writers
        """
        return self.__registry.find_plugins(dir)
    
    def get_wildcards(self):
        return self.__registry.wildcards