60 lines
2.1 KiB
Ruby
60 lines
2.1 KiB
Ruby
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# BufferedTokenizer takes a delimiter upon instantiation, or acts line-based
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# by default. It allows input to be spoon-fed from some outside source which
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# receives arbitrary length datagrams which may-or-may-not contain the token
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# by which entities are delimited. In this respect it's ideally paired with
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# something like EventMachine (http://rubyeventmachine.com/).
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class BufferedTokenizer
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# New BufferedTokenizers will operate on lines delimited by a delimiter,
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# which is by default the global input delimiter $/ ("\n").
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#
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# The input buffer is stored as an array. This is by far the most efficient
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# approach given language constraints (in C a linked list would be a more
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# appropriate data structure). Segments of input data are stored in a list
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# which is only joined when a token is reached, substantially reducing the
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# number of objects required for the operation.
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def initialize(delimiter = $/)
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@delimiter = delimiter
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@input = []
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@tail = ''
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@trim = @delimiter.length - 1
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end
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# Extract takes an arbitrary string of input data and returns an array of
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# tokenized entities, provided there were any available to extract. This
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# makes for easy processing of datagrams using a pattern like:
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#
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# tokenizer.extract(data).map { |entity| Decode(entity) }.each do ...
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#
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# Using -1 makes split to return "" if the token is at the end of
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# the string, meaning the last element is the start of the next chunk.
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def extract(data)
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if @trim > 0
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tail_end = @tail.slice!(-@trim, @trim) # returns nil if string is too short
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data = tail_end + data if tail_end
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end
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@input << @tail
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entities = data.split(@delimiter, -1)
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@tail = entities.shift
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unless entities.empty?
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@input << @tail
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entities.unshift @input.join
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@input.clear
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@tail = entities.pop
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end
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entities
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end
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# Flush the contents of the input buffer, i.e. return the input buffer even though
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# a token has not yet been encountered
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def flush
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@input << @tail
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buffer = @input.join
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@input.clear
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@tail = "" # @tail.clear is slightly faster, but not supported on 1.8.7
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buffer
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end
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end
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