Class: RubyTDMS::Segment

Inherits:
Object
  • Object
show all
Defined in:
lib/ruby_tdms/segment.rb

Overview

Implements the TDMS segment, including a Segment factory and stream parser. TODO: Refactor the parser out? Too much coupling between Segment and Document!

Constant Summary collapse

FLAG_META_DATA = 
1 << 1
FLAG_RAW_DATA = 
1 << 3
FLAG_DAQMX_RAW_DATA = 
1 << 7
FLAG_INTERLEAVED_DATA = 
1 << 5
FLAG_BIG_ENDIAN = 
1 << 6
FLAG_NEW_OBJECT_LIST = 
1 << 2

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(document) ⇒ Segment

Returns a new instance of Segment.



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# File 'lib/ruby_tdms/segment.rb', line 18

def initialize(document)
	@document = document
	@objects = []
end

Instance Attribute Details

#chunk_count ⇒ Object (readonly)

Returns the value of attribute chunk_count.



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# File 'lib/ruby_tdms/segment.rb', line 15

def chunk_count
  @chunk_count
end

#document ⇒ Object (readonly)

Returns the value of attribute document.



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# File 'lib/ruby_tdms/segment.rb', line 14

def document
  @document
end

#length ⇒ Object (readonly)

Returns the value of attribute length.



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# File 'lib/ruby_tdms/segment.rb', line 15

def length
  @length
end

#meta_data_length ⇒ Object (readonly)

Returns the value of attribute meta_data_length.



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# File 'lib/ruby_tdms/segment.rb', line 15

def meta_data_length
  @meta_data_length
end

#meta_data_offset ⇒ Object (readonly)

Returns the value of attribute meta_data_offset.



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# File 'lib/ruby_tdms/segment.rb', line 15

def meta_data_offset
  @meta_data_offset
end

#objects ⇒ Object (readonly)

Returns the value of attribute objects.



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# File 'lib/ruby_tdms/segment.rb', line 15

def objects
  @objects
end

#raw_data_offset ⇒ Object (readonly)

Returns the value of attribute raw_data_offset.



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# File 'lib/ruby_tdms/segment.rb', line 15

def raw_data_offset
  @raw_data_offset
end

#tag ⇒ Object (readonly)

Returns the value of attribute tag.



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# File 'lib/ruby_tdms/segment.rb', line 15

def tag
  @tag
end

#version ⇒ Object (readonly)

Returns the value of attribute version.



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# File 'lib/ruby_tdms/segment.rb', line 15

def version
  @version
end

Class Method Details

.parse_stream(stream, document) ⇒ Object 



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# File 'lib/ruby_tdms/segment.rb', line 25

def parse_stream(stream, document)
	new(document).tap do |new|
		new.parse_lead_in stream
		document.segments << new # TODO: smelly
		new.parse_meta_data stream if new.meta_data?
	end
end

Instance Method Details

#big_endian? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/ruby_tdms/segment.rb', line 68

def big_endian?
	flag? FLAG_BIG_ENDIAN
end

#daqmx_data? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/ruby_tdms/segment.rb', line 58

def daqmx_data?
	flag? FLAG_DAQMX_RAW_DATA
end

#flag?(flag) ⇒ Boolean

Checks if the segment flags have flag set.

Parameters:

  • flag (Fixnum) —

    The flag mask to check, like FLAG_META_DATA or FLAG_RAW_DATA.

Returns:

  • (Boolean) —

    Whether the segment has the flag in question set.



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# File 'lib/ruby_tdms/segment.rb', line 43

def flag?(flag)
	!!(@flags & flag == flag)
end

#interleaved_data? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/ruby_tdms/segment.rb', line 63

def interleaved_data?
	flag? FLAG_INTERLEAVED_DATA
end

#meta_data? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/ruby_tdms/segment.rb', line 48

def meta_data?
	flag? FLAG_META_DATA
end

#new_object_list? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/ruby_tdms/segment.rb', line 73

def new_object_list?
	flag? FLAG_NEW_OBJECT_LIST
end

#parse_lead_in(stream) ⇒ Object

protected



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# File 'lib/ruby_tdms/segment.rb', line 80

def parse_lead_in(stream)
	@tag = stream.read 4
	@flags = stream.read_u32
	@version = stream.read_u32
	@length = stream.read_u64 # Overall length of segment minus length of lead-in, aka "Next segment offset" in NI docs.
	@meta_data_length = stream.read_u64 # Overall length of meta information, aka "Raw data offset" in NI docs.

	@meta_data_offset = @meta_data_length > 0 ? stream.pos : nil
	@raw_data_offset = stream.pos + @meta_data_length # Stream offset at which raw data for this segment begins.
	@raw_data_length = @length == -1 ? stream.length - @raw_data_offset : @length - @meta_data_length # Number of bytes raw data occupies. NI docs say @length == -1 means the entire file, after lead-in and header, is raw data.
end

#parse_meta_data(stream) ⇒ Object 



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# File 'lib/ruby_tdms/segment.rb', line 93

def parse_meta_data(stream)
	@number_of_objects = stream.read_u32

	@number_of_objects.times do
		object = ObjectParser.parse_stream stream, document, self
		@objects << object
	end


	@chunk_length = raw_channels.map(&:chunk_length).reduce(:+) # Length of an individual data chunk (summation of each object's raw data length)
	@chunk_count = @raw_data_length / @chunk_length
	raw_channels.each { |object| object.calculate_offsets }
end

#raw_channels ⇒ Object 



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# File 'lib/ruby_tdms/segment.rb', line 35

def raw_channels
	objects.select { |object| object.is_a? Objects::Channel }
end

#raw_data? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/ruby_tdms/segment.rb', line 53

def raw_data?
	flag? FLAG_RAW_DATA
end