Class: Whispr::Archive

Inherits:
Object
  • Object
show all
Includes:
Enumerable
Defined in:
lib/whispr/archive.rb

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(whisper, header) ⇒ Archive 



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# File 'lib/whispr/archive.rb', line 20

def initialize(whisper, header)
  @whisper   = whisper
  @header    = header
  @offset    = @header[:offset]
  @points    = @header[:points]
  @size      = @header[:size]
  @retention = @header[:retention]
  @spp       = @header[:secondsPerPoint]
  @eoa       = @size * @points + @offset
end

Instance Attribute Details

#header ⇒ Hash (readonly) 



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# File 'lib/whispr/archive.rb', line 6

def header
  @header
end

#offset ⇒ Fixnum (readonly) 



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# File 'lib/whispr/archive.rb', line 8

def offset
  @offset
end

#points ⇒ Fixnum (readonly) 



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# File 'lib/whispr/archive.rb', line 10

def points
  @points
end

#retention ⇒ Fixnum (readonly) 



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# File 'lib/whispr/archive.rb', line 14

def retention
  @retention
end

#size ⇒ Fixnum (readonly) 



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# File 'lib/whispr/archive.rb', line 12

def size
  @size
end

#spp ⇒ Fixnum (readonly) 



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# File 'lib/whispr/archive.rb', line 16

def spp
  @spp
end

#whisper ⇒ Whispr (readonly) 



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# File 'lib/whispr/archive.rb', line 18

def whisper
  @whisper
end

Instance Method Details

#each(&blk) ⇒ Object

Retrieve each point from the archive.

If a block is provided each point is read directly from the whisper file one at a time and yielded. If a block is not provided, all points are read from the file and returned as an enum.

Each point is represented as a three element Array. The first element is the index of the point. The second element is the timestamp of the point and the third element is the value of the point.



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# File 'lib/whispr/archive.rb', line 42

def each(&blk)
  return slurp.to_enum unless block_given?
  o_pos = @whisper.fh.pos
  begin
    @whisper.fh.pos = @offset
    points.times {|i| yield(i, *next_point) }
  ensure
    @whisper.fh.pos = o_pos
  end
end

#eoa? ⇒ Boolean

Has the end of the archive been reached?



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# File 'lib/whispr/archive.rb', line 54

def eoa?
  @whisper.fh.pos >= @eoa
end

#fetch(fromTime, untilTime) ⇒ Object

Retrieve values for a time period from an archive within a whisper file

The return value will be a two element Array. The first element will be a three element array containing the start time, end time and step. The second element will be a N element array containing each value at each step period.

See Also:



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# File 'lib/whispr/archive.rb', line 94

def fetch(fromTime, untilTime)
  fromInterval  = (fromTime - (fromTime % spp)) + spp
  untilInterval = (untilTime - (untilTime % spp)) + spp
  o_pos         = @whisper.fh.pos
  begin
    @whisper.fh.seek(offset)
    baseInterval, baseValue = @whisper.fh.read(POINT_SIZE).unpack(POINT_FMT)
    if baseInterval == 0
      step     = spp
      points   = (untilInterval - fromInterval) / step
      timeInfo = [fromInterval, untilInterval, step]
      return [timeInfo, points.times.map{}]
    end

    # Determine fromOffset
    timeDistance  = fromInterval - baseInterval
    pointDistance = timeDistance / spp
    byteDistance  = pointDistance * POINT_SIZE
    fromOffset    = offset + (byteDistance % size)

    # Determine untilOffset
    timeDistance  = untilInterval - baseInterval
    pointDistance = timeDistance / spp
    byteDistance  = pointDistance * POINT_SIZE
    untilOffset   = offset + (byteDistance % size)

    # Reall all the points in the interval
    @whisper.fh.seek(fromOffset)
    if fromOffset < untilOffset
      # we don't wrap around the archive
      series = @whisper.fh.read(untilOffset - fromOffset)
    else
      # we wrap around the archive, so we need two reads
      archiveEnd  = offset + size
      series      = @whisper.fh.read(archiveEnd - fromOffset)
      @whisper.fh.seek(offset)
      series     += @whisper.fh.read(untilOffset - offset)
    end

    points          = series.length / POINT_SIZE
    series          = series.unpack(POINT_FMT * points)
    currentInterval = fromInterval
    step            = spp
    valueList       = points.times.map{}
    (0..series.length).step(2) do |i|
      pointTime = series[i]
      if pointTime == currentInterval
        pointValue     = series[i+1]
        valueList[i/2] = pointValue
      end
      currentInterval += step
    end

    timeInfo = [fromInterval, untilInterval, step]
  ensure
    @whisper.fh.pos = o_pos
  end
  [timeInfo, valueList]
end

#next_point ⇒ Object

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future.

Retrieve the next point from the whisper file.



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# File 'lib/whispr/archive.rb', line 64

def next_point
  return nil if @whisper.fh.pos >= @eoa || @whisper.fh.pos < @offset
  @whisper.fh.read(POINT_SIZE).unpack(POINT_FMT)
end

#slurp ⇒ Array

Retrieve all points for this archive from the whisper file.

Each point is represented as a three element Array. The first element is the index of the point. The second element is the timestamp of the point and the third element is the value of the point.



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# File 'lib/whispr/archive.rb', line 77

def slurp
  o_pos = @whisper.fh.pos
  @whisper.fh.pos = @offset
  data = @whisper.fh.read(@size).unpack(POINT_FMT * @points)
  @points.times.map { |i| [i, data.shift, data.shift] }
ensure
  @whisper.fh.pos = o_pos
end

#to_enum ⇒ Object 



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# File 'lib/whispr/archive.rb', line 58

def to_enum
  slurp.to_enum
end

#update_many(points) ⇒ Object 



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# File 'lib/whispr/archive.rb', line 154

def update_many(points)
  step = spp
  alignedPoints = points.map { |ts, v| [(ts - (ts % step)), v] }
  # Create a packed string for each contiguous sequence of points
  packedStrings    = []
  previousInterval = nil
  currentString    = ''
  alignedPoints.each do |interval, value|
    next if interval == previousInterval
    if previousInterval.nil? || (interval == previousInterval + step)
      currentString   += [interval, value].pack(POINT_FMT)
    else
      numberOfPoints = currentString.length / POINT_SIZE
      startInterval  = previousInterval - (step * (numberOfPoints - 1))
      packedStrings << [startInterval, currentString]
      currentString  = [interval, value].pack(POINT_FMT)
    end
    previousInterval = interval
  end
  if !currentString.empty?
    numberOfPoints = currentString.length / POINT_SIZE
    startInterval = previousInterval - (step * (numberOfPoints - 1))
    packedStrings << [startInterval, currentString]
  end

  # Read base point and determine where our writes will start
  @whisper.fh.seek(offset)
  baseInterval, baseValue = @whisper.fh.read(POINT_SIZE).unpack(POINT_FMT)
  baseInterval = packedStrings[0][0] if baseInterval == 0
  packedStrings.each do |interval, packedString|
    timeDistance = interval - baseInterval
    pointDistance = timeDistance / step
    byteDistance = pointDistance * POINT_SIZE
    myOffset = offset + (byteDistance % size)
    @whisper.fh.seek(myOffset)
    archiveEnd = offset + size
    bytesBeyond = (myOffset + packedString.length) - archiveEnd

    if bytesBeyond > 0
      @whisper.fh.write(packedString[0..-bytesBeyond])
      if(@whisper.fh.pos != archiveEnd)
        raise ArchiveBoundaryExceeded.new("archiveEnd=#{archiveEnd} pos=#{@whisper.fh.pos} bytesBeyond=#{bytesBeyond} len(packedString)=#{packedString.length}")
      end
      @whisper.fh.seek(offset)
      @whisper.fh.write(packedString[-bytesBeyond..-1])
    else
      @whisper.fh.write(packedString)
    end
  end # interval, packedString|

  # Now we propagate the updates to the lower-precision archives
  higher = self
  @whisper.archives.select{|a| a.spp > spp }.each do |lower|
    lowerIntervals = alignedPoints.map{|p| p[0] - (p[0] % lower.spp) }
    propagateFurther = false
    lowerIntervals.uniq.each do |interval|
      propagateFuther = @whisper.send(:propagate, interval, higher, lower)
    end
    break unless propagateFurther
    higher = lower
  end
end