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"""
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Generic configuration file output
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"""
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import os, tempfile, shutil
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class Object (object) :
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"""
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An object that can be written to a ConfFile, as multiple lines of text.
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"""
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def fmt_lines (self) :
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"""
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Yield a series of lines to be output in the file
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"""
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abstract
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class File (object) :
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"""
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A single configuration file on the filesystem.
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Configuration files are
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"""
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def __init__ (self, name, path, backup_suffix='.bak', mode=0644) :
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"""
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Initialize the config file, but don't open it yet
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@param name the human-readable friendly name for the config file
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@param path the full filesystem path for the file
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@param backup_suffix rename the old file by adding this suffix when replacing it
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@param mode the permission bits for the new file
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"""
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self.name = name
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self.path = path
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self.backup_suffix = backup_suffix
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self.mode = mode
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def write_file (self, file, objects) :
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"""
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Write out the given config objects into the given file
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"""
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writer = Writer(file)
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writer.write_objs(objects)
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def write (self, objects) :
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"""
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Write out a new config file with the given series of objects using the following procedure:
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* lock the real file
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* open a new temporary file, and write out the objects into that, closing it
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* move the real file out of the way
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* move the temporary file into the real file's place
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* unlock the real file
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"""
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# XXX: how to aquire the lock?
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# XXX: this needs checking over
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# open the new temporary file
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# XXX: ensure fd is closed
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tmp_fd, tmp_path = tempfile.mkstemp(prefix=self.name)
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# ...as a file
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tmp_file = os.fdopen(tmp_fd, "w")
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# fix the permissions
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os.chmod(tmp_path, self.mode)
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# write it
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self.write_file(tmp_file, objects)
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# close it
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tmp_file.close()
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del writer
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del tmp_file
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# move the old file out of the way
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os.rename(self.path, self.path + self.backup_suffix)
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# move the new file in
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shutil.move(tmp_path, self.path)
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class Writer (object) :
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"""
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A conf.Writer is used to write out a new conf.File (as a temporary file)
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"""
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def __init__ (self, file) :
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"""
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@param file the temporary file object
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"""
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self.file = file
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def write_obj (self, obj) :
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"""
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Write a single object to the file
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"""
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# just write out all the lines
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self.file.writelines(obj.fmt_lines())
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def write_objs (self, objs) :
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"""
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Write a series of objects to the file
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"""
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# just write each in turn
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for obj in objs :
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self.write_obj(obj)
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