XML::Filter::Sort::BufferMgr 1.01

XML::Filter::Sort::BufferMgr is a Perl implementation class used by XML::Filter::Sort.

The documentation is targetted at developers wishing to extend or replace this class. For user documentation, see XML::Filter::Sort.

Two classes are used to implement buffering records and spooling them back out in sorted order as SAX events. One instance of the XML::Filter::Sort::Buffer class is used to buffer each record and one or more instances of the XML::Filter::Sort::BufferMgr class are used to manage the buffers.

API METHODS

The API of this module as used by XML::Filter::Sort::Buffer consists of the following sequence of method calls:

When the first record in a sequence is encountered, XML::Filter::Sort creates a XML::Filter::Sort::BufferMgr object using the new() method.

XML::Filter::Sort calls the buffer managers new_buffer() method to get a XML::Filter::Sort::Buffer object and all SAX events are directed to this object until the end of the record is encountered. The following events are supported by the current buffer implementation:

start_element()
characters()
comment()
processing_instruction()
end_element()

When the end of the record is detected, XML::Filter::Sort calls the buffer managers close_buffer() method, which in turn calls the buffers close() method. The close() method returns a list of values for the sort keys and the buffer manager uses these to store the buffer for later recall. Subsequent records are handled as per step 2.

When the last record has been buffered, XML::Filter::Sort calls the buffer managers to_sax() method. The buffer manager retrieves each of the buffers in sorted order and calls the buffers to_sax() method.

Each buffer attempts to match the sort key paths as SAX events are received. Once a value has been found for a given key, that same path match is not attempted against subsequent events. For efficiency, the code to match each key is compiled into a closure. For even more efficiency, this compilation is done once when the XML::Filter::Sort object is created. The compile_matches() method in the buffer manager class calls the compile_matches() method in the buffer class to achieve this.